England and Wales Court of Appeal (Civil Division) Decisions

IN THE SUPREME COURT OF JUDICATURE CHPCF 96/1775/CMS3

COURT OF APPEAL (CIVIL DIVISION)

(MR JUSTICE JACOB )

Royal Courts of Justice

The Strand

London

Thursday 30 April 1998

B e f o r e:

LORD JUSTICE ROCH

LORD JUSTICE ALDOUS

and

LORD JUSTICE BROOKE

B E T W E E N:

LUBRIZOL CORPORATION & ANR Appellant

and

ESSO PETROLEUM CO LTD & OTHERS Respondent

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(Computer Aided Transcription by

Smith Bernal, 180 Fleet Street, London EC4A 2HD

Telephone 0171 421 4040

Official Shorthand Writers to the Court)

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MR SIMON THORLEY QC and MR RICHARD ARNOLD (instructed by Messrs

Simmons, Simmons, London EC2) appeared on behalf of THE APPELLANT

MR DAVID YOUNG QC, MR GUY BURKHILL and MR DOUGLAS CAMPBELL (instructed

by Messrs Bird and Bird, London WC1) appeared on behalf of

THE RESPONDENT

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J U D G M E N T

(As Approved by the Court )

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LORD JUSTICE ALDOUS: The Lubrizol Corporation were the proprietors of Patent No 1565627 in respect of an invention entitled "Novel Carboxylic Acid Acylating Agents, Derivatives Thereof, Concentrated and Lubricant Composites Containing the Same and Processes for their Preparation". They and their exclusive licensee, Lubrizol Limited, which I will collectively call Lubrizol, sued Esso Petroleum Company Limited, Exxon Chemical Limited and Exxon Corporation which I will refer to as Exxon, for infringement. Exxon denied infringement, alleged the patent was invalid and counterclaimed for its revocation.

The action came before Jacob J. He dismissed the action, held the patent invalid and ordered that it be revoked. Against that judgment Lubrizol appeals.

I need not set out the background technology in full as it was contained in an agreed statement which the Judge reproduced in his judgment with some explanatory additions. I will therefore confine this part of my judgment to a short historical background and an outline of the chemistry needed to understand the patent.

The development of high speed diesel engines in the l930's led to the establishment of the modern lubricating oil additive industry. Such engines were prone to fail with the lubricants available at the time which were refined crude oils. In the late l930's it was discovered that the addition of a detergent made a substantial contribution to the problem. Further advances were made during the Second World War. Even so, the detergents produced as additives had drawbacks in that they left a metallic residue in diesel engines and formed sludge and varnish in petrol engines.

After the war researchers started to look at chemicals with the same basic structure as the existing detergents with a view to obtaining an ashless dispersant. The first ones to be produced were the polymethacrylates. In the late l950's, Dr William LeSuer of Lubrizol discovered and patented a type of ashless dispersant using, amongst other things, a polyamine as the polar head. The succinimide dispersants of that invention had polyisobutene as the tail linked to a head which contained at least one free amine group, the link being formed via a succinic group. Such dispersants were commercially successful. The patent is concerned with a development of that invention.

A basic form of reaction to produce the patented dispersant is shown in the Appendix to this judgment. It was known at the priority date of the patent. The raw material normally used to form the hydrocarbon portion of the patented product is polyisobutene (PIB). It was a commercially available material containing a mixture of polymers and copolymers of isobutene, n-butene and other alkenes. The PIB is reacted with maleic anhydride, C ₄H₂O₃ (MA) to form an acylating agent, polyisobutenyl anhydride (PIBSA). The reaction is a succination reaction which results in formation of a succinic group on the hydrocarbon tail. In practice not all the PIB reacts with MA so the product of the reaction includes unreacted PIB and MA and possibly more complex structures as well as PIBSA.

The next step, 5 and 6 in the Appendix, uses the PIBSA to acylate the polar head. A common form of polar head used in dispersants was a polyamine H ₂N-R-NH (PAM) which when acylated produces a succinimide, in this case PIBSA/PAM. The unreacted PIB will remain, but the MA is stripped out as it has a deleterious action when used as part of a lubricating system. Thus the basic steps of the reaction can be set out in summary form as:

PIB + MA = PIBSA

PIBSA + PAM = PIBSA/PAM (the carboxylic derivative at the heart of the invention).

The patent specification is a substantial document of 4l pages with 36 claims. It contains a detailed description of various chemicals which can be used to carry out the invention and methods of their use. It is not necessary to understand all the various alternatives. Insofar as it is necessary to consider the specification in detail that is best done when considering the submissions of the parties on the construction of claim l. That claim, split up for convenience into features, is in this form:

A lubricating composition comprising

[A] a major amount of oil of lubricating viscosity and

[B] a minor amount of one or more carboxylic derivatives produced by reacting

[C] at least one substituted succinic acylating agent with

[D] a reactant selected from

(a) an amine having within its structure at least one H-N< group,

(b) an alcohol,

(c) a reactive metal or reactive metal compound, and

(d) a combination of two or more of any of (a) to (c), the components of (d) being reacted with said one or more substituted succinic acylating agents simultaneously or sequentially in any order,

[E] wherein said substituted succinic acylating agent(s) consist of

(i) substituent groups and

(ii) succinic groups

[F] wherein the substituent groups are derived from polyalkene,

[G] said polyalkene having

(i) a Mn value of 1300 to 5000 and

(ii) a Mw/Mn value of l.5 to 4,

[H] said acylating agent(s) having within their structure an average of at least l.3 succinic groups for each equivalent weight (as hereinbefore defined) of substituent groups.

The claim is to a product of two ingredients, an oil and one or more carboxylic derivatives. The carboxylic derivative in feature [B] is typically PIBSA/PAM. If so, it is produced according to feature [C] by reacting a succinic acylating agent, a PIBSA, with an amine as required by feature [D](a). Features [E], [F] and [H] relate to the properties of the PIBSA. The Mn value is the number average molecular weight and Mw is the weight average molecular weight.

It follows that features [C], [E] and [H], when read as applying to use of one agent, require the substituted succinic acylating agent (the PIBSA) to consist of substituent groups and succinic groups and to have within its structure an average of at least l.3 succinic groups for each equivalent weight (as defined) of substituent groups. Features [F] and [G] require the substituent groups of the PIBSA to be derived from a polyalkene (PIB) having a M _n value of 1300 to 5000 and a M _w/M_n value of l.5 to 4.

There are three issues which involve construction of the patent. They are different in kind and need to be considered separately.

Feature [H], "Acylating Agent" - Feature [H] of the claim requires that the acylating agent(s) have "within their structure an average of at least l.3 succinic groups for each equivalent weight ... of substituent groups." Lubrizol submitted that the acylating agent referred to denotes the PIBSA which is the substituted succinic acylating agent of features [C] and [E]. Exxon submitted that the acylating agent referred to is the entire mixture produced by the reaction of PIB with MA, but excluding the surplus MA which is stripped out. It therefore consists of both PIBSA and PIB. The difference between those submissions can be illustrated by considering this example.

PIB is produced with units of molecular weight of 336, 448, 1680 and 3920. Therefore the Mn = 1596, Mw = 2898, Mw/Mn = 1.82. The PIB when reacted with MA will produce a variety of PIBSAs. For the purpose of the example it can be assumed that the reaction results in a mixture of monosuccinated, disuccinated PIBSA (PIBSA ₁ and PIBSA ₂), unreacted PIB and MA. The MA is then stripped out leaving behind the PIBSA ₁, PIBSA ₂ and PIB. For the purpose of illustration it is assumed that there are four PIBSA ₁, and four PIBSA ₂ giving 12 succinic groups with two moles of unreacted PIB. According to Lubrizol the succination ratio of feature [H] is worked out by dividing the 12 succinic groups by the 8 PIB substituent groups of PIBSA giving an average of l.5. According to Exxon the 12 succinic groups of PIBSA have to be divided by 10 made up by the 8 substituent groups of PIBSA and the two PIB unreacted groups. The result is an average of l.2.

Patent specifications like other documents have to be construed purposively. That means that not only must the language of the claim be construed so as to ascertain the intention of the patentee as expressed, but also so as to take into account the purpose of the various parts of the specification.

Fletcher Moulton LJ explained in British United Shoe Machinery Company Ltd, v A Fussell & Sons Ltd (1908) 25 RPC 631 at 650 how claims came to be incorporated into a patent specification and their purpose:

"As it is the duty of the inventor to give the fullest practical information to the public he is bound to put in, if, for instance the invention is a process, quantities and times which are the best he knows. But it would be very cruel to hold him to the invention when carried out only with those best quantities and times, because a person could then take his invention in substance if he did not take it in quite the best way, and the value of the grant would be practically nothing. Hence inventors, in their own protection, took to introducing into their specifications language intended to distinguish between that which was there for the practical information of the public, and that which was there for delimitation of the invention. Correct delimitation was of the greatest possible importance to the inventor, because if his Patent covered something which was old the Patent was wholly bad. At the same time there was the danger of confining himself to a mere outline which gave delimitation, but did not tell the public the best way within those limits of performing his invention. The one duty required him to state his invention in its most general form, and the other duty required him to state it in its best and therefore in a very special form. Out of that has arisen the practice, which originally was perfectly optional, of having a separate part of the specification primarily designed for delimitation. That is what we call the Claim."

The Claims have to be construed as part of the whole specification. The correct approach was succinctly stated by Lord Evershed MR in Rosedale Associated Manufacturers Ltd v Carlton Tyre Saving Coy Ltd (1960) RPC 59 at 69:

"It is no doubt true and has been well established (see for example, the speech of Lord Russell of Killowen in the EMI case ( Electric & Musical Industries v Lissen (1939) 56 RPC 4l) that you must construe the claims according to their terms upon ordinary principles, and that it is not legitimate to confine the scope of the claims by reference to some limitation which may be found in the body of the specification but is not expressly or by proper inference reproduced in the claims themselves. On the other hand, it is clearly no less legitimate and appropriate in approaching the construction of the claims to read the specification as a whole. Thereby the necessary background is obtained and in some cases the meaning of the words used in the claims may be affected or defined by what is said in the body of the specification."

Patent specifications are intended to be read by persons skilled in the relevant art, but their construction is for the Court. Thus the Court must adopt the mantle of the notional skilled addressee and determine, from the language used, what the notional skilled addressee would understand to be the ambit of the claim. To do that it is often necessary for the Court to be informed as to the meaning of technical words and phrases and what was, at the relevant time, the common general knowledge; the knowledge that the notional skilled man would have.

Claim l of the patent contains words having a chemical meaning. Their meaning is not in dispute. "Succinic" denotes a succinic group CH(CH ₂COR)COR or a derivative. An acylating agent is a compound which is capable of acylation, namely the substitution of an acyl group R - (C=0) into another compound. The "structure" of a compound refers to its arrangement of atoms and the word "group" denotes a number of atoms forming a part of a molecule.

Lubrizol contend that the ambit of Claim l is clear. The acylating agent referred to in feature [H] is that referred to in features [C] and [E]. It is by definition the PIBSA not the PIB as that is not an acylating agent. Further the mixture of PIBSA and PIB cannot be the acylating agent of feature [H] because of the requirements of features [E], [F] and [G]. Feature [E] states that the acylating agent consists of substituent and succinic groups. That is applicable to PIBSA, but not to PIB. Further the substituent groups have to be derived from polyalkene (PIB). Therefore it would do violence to the language to suggest that the unreacted PIB was a substituent group as in no sense could it be said to have been derived from a polyalkene. Further the acylating agent has to have within its "structure" a particular ratio of succinic groups to substituent groups. PIB does not have any succinic groups within its structure, but PIBSA does.

I have no doubt that, as a matter of language, Claim l cannot be interpreted in the way Exxon suggest. The words "said acylating agent(s)" in feature [H] refer to the PIBSA for the reasons given by Lubrizol. To read them as referring to a mixture of PIBSA and PIB disregards the meaning of the words in features [E], [F], [G] and [H]. The unreacted PIB is a diluent not an essential of the claimed invention.

Mr Young QC, who appeared for Exxon, submitted that when claim l was construed in the light of the common general knowledge and as part of the whole specification, it became clear that what was termed the "acylating agent" in feature [H] was the reaction mixture; the PIBSA and the unreacted PIB with the MA stripped out. That submission found favour with the Judge. It is therefore necessary to consider the teaching of the specification, read in the light of the common general knowledge, to see whether Exxon are correct.

On page l, line 21, the specification states the nature of the invention:

"From one viewpoint, the invention can be regarded as an improvement in the known field of lubricant additive technology which has developed since the l950's around high molecular weight carboxylic acid acylating agents and various acylated derivatives thereof."

It then refers to a number of patent specifications which disclose how such high molecular weight agents can be prepared.

On page 2, line l the basis of the invention is set out in this way:

"This invention is based on the discovery that a novel class of high molecular weight carboxylic acid acylating agents is capable of imparting beneficial properties to lubricant additives prepared therefrom and lubricating compositions containing such acylating agents or such additives while, at the same time, retaining the desirable properties of similar lubricant additives and lubricating compositions prepared from other high molecular weight carboxylic acid acylating agents of the prior art. In addition, the retained desirable properties are themselves not only retained as such but often enhanced or improved. For example, if the similar lubricant additives prepared from high molecular weight carboxylic acylating agents of the prior art are known to function as ashless dispersants in lubricant compositions, the corresponding additive prepared from the novel high molecular weight carboxylic acid compositions often exhibit improved ashless dispersant properties.

The novel class of high molecular weight carboxylic acid acylating agents of this invention and derivatives thereof, especially the latter, impart significant fluidity modifying properties to lubricant compositions sufficient to permit elimination of all or a significant amount of viscosity index improver from multigrade lubricant compositions containing the same, for example, a 10W-30 crankcase engine oil."

The specification goes on to describe in general terms three known approaches to preparing multifunctional lubricant additives. There follows the statement (page 3 line l) that the acylating agents of the invention represent a further distinct and hitherto unrecognised approach for preparing multifunctional lubricating additives. The specification continues (page 3, line 4):

"The substituted succinic acylating agents used in this invention consist of substituent groups and succinic groups, wherein the substituent groups are derived from polyalkene, said polyalkene being characterized by a Mn value of 1300 to 5000 and a Mw/Mn value of l.5 to 4, said acylating agent being characterised by the presence within its structure of an average of at least l.3 succinic groups for each equivalent weight of a substituent group."

That passage would be read by the notional skilled man with knowledge that producers of additives were using PIBSA made from PIB of Mn value in the range of about 900 - 1000. He would therefore realise that the invention was said to produce an improved lubricant additive by using higher molecular weight PIB to produce the PIBSA, with the polydispersity kept within limits and with a significant proportion of oversuccinated PIBSA present. If so, he would not expect the claim to be worded such that it would cover acylating agents which did not have a significant degree of oversuccination.

So far the specification supports Lubrizol's interpretation. If the acylating agent of feature [H] is only the PIBSA, then a change of succination will be reflected in a change of the ratio required by the feature. That does not necessarily apply if unreacted PIB is also taken into account. For instance, if there were 4 PIBSA ₁, 4 PIBSA ₂ and two unreacted moles of PIB, the ratio calculated according to the Lubrizol construction would be l.5 and according to Exxon l.2. If there were less over-succination, for example 6 PIBSA ₁, 3 PIBSA ₂ and l mole of unreacted PIB that would be reflected in the result obtained by the Lubrizol construction, ie l.33. However according to Exxon's construction the ratio would still be l.2.

On page 4 of the specification there appears the heading "The Substituted Succinic Acylating Agent". There follows this passage:

"The substituted succinic acylating agents of this invention are those which can be characterized by the presence within their structure of two groups or moieties. The first group or moiety is referred to herein, for convenience, as the "substituent group(s)" and is derived from a polyalkene. The polyalkene from which the substituent groups are derived is characterized by a Mn (number average molecular weight) value of from 1300 to 5000 and a Mw/Mn value of l.5 to 4.

The second group or moiety is referred to herein as the "succinic group(s)". The succinic groups are those groups having the structure".

That passage also supports the Lubrizol construction. It there is stated that the acylating agent has two groups. The first, called the substituent group, is "derived" from polyalkene, not as suggested by Exxon derived from and may be a polyalkene.

A similar statement is made on page 5, line 5, where it is stated that:

"The substituted succinic acylating agents are characterized by the presence within their structure of at least l.3 succinic groups (that is, groups corresponding to Formula l) for each equivalent weight of substituent groups. ....

Another requirement for the substituted succinic acylating agents within this invention is that the substituent groups must have been derived from a polyalkene characterized by a Mw/Mn value of l.5 - 4, Mw being the conventional symbol representing weight average molecular weight."

Further teaching as to the degree of succination appears on page 6, line l8:

"From the foregoing, it is clear that the substituted succinic acylating agents of this invention can be represented by the symbol

R₁-(-R₂)_y

where R represents one equivalent weight of substituent group, R ₂ represents one succinic group corresponding to Formula I, Formula II, or Formula III, as discussed above, and y is a number equal to or greater than l.3."

In that passage the specification is again drawing to the reader's attention that a degree of over-succination is required. Nobody reading that passage would believe that the ratio of substituent groups to succinic groups could depend upon the amount of unreacted PIB that was present. That is the consequence of Exxon's construction.

At the bottom of page 9 the specification comes to the procedures that can be used to produce a product of the invention. It describes in outline the known "Two Step Procedure", the direct acylation procedure and other processes. On page ll the process deemed to be the best is described in this way:

"The process presently deemed to be best for preparing the substituted succinic acylating agents of this invention from the standpoint of efficiency, overall economy, and the performance of the acylating agents thus produced, as well as the performance of the derivatives thereof, is the so-called "one-step" process. This process is described in US Patents 3,215,707 and 3,231,587. Both are expressly incorporated herein by reference for their teachings in regard to that process.

Basically, the one-step process involves preparing a mixture of the polyalkene and the maleic reactant containing the necessary amounts of both to provide the desired substituted succinic acylating agents of this invention. This means that there must be at least l.3 moles of maleic reactant for each mole of polyalkene in order that there can be at least l.3 succinic groups for each equivalent weight of substituent groups. Chlorine is then introduced into the mixture, usually by passing chlorine gas through the mixture with agitation, while maintaining a temperature of at least about 140 ^oC."

The Judge accepted Exxon's submission that the passage at page ll, which I have quoted, was inconsistent with Lubrizol's construction. He set out that submission on page 29 of his judgment:

"Most crucially of all, the Lubrizol construction is inconsistent with part of the specification. No purposive construction could lead a claim to have such width. The passages relied upon to establish this are on page ll. I have already quoted them. To summarise, the specification says that there must be at least l.3 moles of maleic reactant for each mole of PIB in order that there can be at least l.3 succinic groups for each equivalent weight of substituent groups, and preferably an excess of maleic is used. Suppose less than l.3 moles of maleic reactant is used to 1 of PIB. The product cannot be within the claim on the Exxon construction. But it may be on Lubrizol's, all depending on how much unreacted PIB is left. So it is simply not true, on Lubrizol's construction, to say that you need at least l.3 moles of maleic.

Consider other possibilities too:

(a) 1.3 moles of maleic reactant to one of PIB are used and it all reacts. On Exxon's construction there is an SR of just l.3. On Lubrizol's construction the SR will be higher: the reaction mixture will contain zero, mono, di and tri-succinated PIB. The skilled man would know this. Indeed the patent itself points out that mixtures of products are inherently present. Thus there is no point in mentioning the initial l.3 on the Lubrizol construction. It is not a lower limit.

(b) l.3 moles of maleic reactant to one of PIB are used and the maleic does not all react, leaving some to be stripped out as the patent contemplates. The product is not within the claim on the Exxon construction, but the statement is true because of the "at least". It is simply that you need more than l.3 maleic to start with, as the specification itself suggests in saying that preferably an excess of maleic reactant is used. It is conventional organic chemistry that if you want to drive a reaction further to completion you add a stoichiometric excess of the reactant concerned. So far as the Lubrizol construction is concerned, you have no idea whether or not you are within the claim: it all depends on how much PIB is reacted. The statement is pointless on the Lubrizol construction."

The Judge was correct that the specification states that to provide the desired substituted succinic acylating agents of the invention "there must be at least l.3 moles of maleic reactant for each mole of polyalkene in order that there can be l.3 succinic groups for each equivalent weight of substituent groups". He goes on to read the passage on page ll as stating that, if less than l.3 moles maleic are used, the resulting product will not fall within the claim. Thus he reasons that the statement is inconsistent with the Lubrizol construction, but not with Exxon's. Therefore Exxon's construction is to be preferred.

This was not the only part of the specification which was relied on to show that Exxon's construction was to be preferred, but it is typical. In my view it demonstrates an attempt by Exxon to put a gloss on the claim using a statement in the specification. That is not permissible (see Rosedale Associated Manufacturers Ltd (supra)). In any case the passage in the specification, when read in context, does not say that if you use less than l.3 moles of maleic reactant you will not infringe the patent. The claim is to a product. The passage on page ll appears in the part of the specification which is describing the preferred process to be used. It correctly states that you must have l.3 moles of reactant to obtain at least l.3 succinic groups for each equivalent weight of substituent groups and therefore is a true teaching as to how to achieve a product falling within the invention. To read the passage as defining the ambit of the claim is to read the claim as a process claim or perhaps a product by process claim. Further the passage does not state that if you do not use l.3 moles of maleic reactant you will not produce a product falling within the claim of the patent. To imply such a statement and then use the implication to modify the plain meaning of the words of the claim is not an appropriate way to construe a claim.

The Judge also accepted Exxon's submission that the examples indicated that the patentee, when referring to a substituted acylating agent, was referring to the PIBSA and the unreacted PIB.

The examples are said to illustrate the preferred embodiment of the invention. Example l informs the skilled reader to take a mixture of PIB and MA and heat to ll0 ^oC. It is then chlorinated and the MA is stripped out. It continues:

"The residue is the desired polyisobutene-substituted succinic acylating agent having a saponification equivalent number of 87 as determined by ASTM procedure D-94."

Similar statements are made in other examples in the same context.

There is no doubt that the residue after stripping out would contain PIBSA and unreacted PIB. But Exxon submitted that the patentee, by using the words he did, was indicating that the residue (PIBSA + unreacted PIB) was the acylating agent of feature [H].

This also shows a wrong approach by Exxon to construction of the claim. The claim is clear and to seek to alter its clear meaning by the statement in the examples cannot be right. The examples are said to illustrate preferred embodiments of the invention and it would be surprising to find in them a definition. A person carrying out the examples should be able to obtain the product of the invention and, as stated, he will use the residue as his additive. The example would have been more happily worded if the word "contained" had been used instead of "is", but the particular sentence in the examples cannot be read as stating that where the words "substituted succinic acylating agent" are used, they denote the residue of the reaction.

Exxon also relied upon the absence of any teaching in the patent of the need to measure the amount of PIBSA after the reaction had taken place and the absence of any indication of how that was to be done. The submission of Exxon accepted by the Judge was set out on pages 26 and 27 of his judgment:

"The patent nowhere speaks of any AI determination. (By AI the Judge is referring to active ingredient, namely PIBSA). To carry out the teaching of the patent all you need to measure (besides initial charge ratio) is the Mn and polydispersivity of the starting PIB and the sap No. of the resulting succination reaction. The patent explicitly mentions the measurements of all these parameters, the first two by GPC (mentioned above) and the latter by "conventional techniques". It would be bizarre for the method of determination of a critical claim limitation not even to be mentioned, even if only by an assertion that it could be determined by conventional techniques.

Further there is uncertainty as to how one would measure AI."

The Judge went on to set out certain passages from the evidence of the witnesses and continued:

"On the basis of this evidence I hold that no standard method of determination of AI was known at the relevant date, that different skilled men would or might use different methods for such determination, that such methods might differ in their result and that the skilled man would know this. I hold that, for this reason, a skilled man would not regard the question of determining compliance with the claim as requiring him to make any determination of the AI - he would expect specific instructions as to the method to be followed if this were to be done. In so holding I do not overlook the fact that parties did make their own determinations of AI before the date of the patent. Organic chemists are always interested in their yields and try to find ways of improving them. But provided they used the same method, any improvement in yield could be established. Absolute determination of yield was not as important for this purpose. It is not shown that anyone prior to the date of the patent used AI to determine charge ratios and the position after the patent is irrelevant (as I ruled at an early stage of the case)."

Mr Thorley QC, who appeared for Lubrizol, submitted that there was no basis for the Judge's conclusion, that the methods of determining the amount of AI "might differ in the result and that the skilled man would know this", as such a conclusion was contrary to his ruling made on the first day of the trial and in any case was not supported by the evidence.

On the first day of the trial Counsel who appeared for Lubrizol objected to evidence being admitted to the effect that different methods for determining AI would give different results and that the skilled man was unable to determine AI for certain polyalkenes covered by the claim. The Judge having heard submissions decided:

"The second allegedly unpleaded point relates to a different dispute between the parties. This is whether or not a certain parameter of the patent claim should or should not take into account unreacted PIB. The defendants say that one takes into account the unreacted material, pointing to the fact that nowhere does the patent suggest any measurement of how much material has reacted and how much active ingredient has been produced by the reaction.

The plaintiffs say that it is implicit in the patent that you measure how much AI you have, to which the defendants seek to respond by saying a number of different things. First, they say there are different methods for measuring AI which will give different results and therefore it is all ambiguous and, secondly, one cannot do it in the case of certain compounds covered by the patent which are not PIBs.

Mr Young accepts that the second point is not pleaded, but he asserts that the first point is pleaded. He relies upon the following passage under the general pleading of insufficiency. Paragraph 3 states as follows: 'The complete specification does not sufficiently and fairly describe the alleged invention and the method by which it is to be performed. Particulars: ... (b) There is no adequate explanation given as to the meaning and determination of the requirement that the acylating agents the subject of claims l and 25 have within their structure an average of at least l.3 succinic groups for each equivalent weight (as defined) of substituent groups.

'In particular if (which is denied) it is an essential requirement that the determination of the said average be carried out on only a part of the product of the reaction of PIB and maleic anhydride, there are insufficient directions for determining the same.'

Mr Young says that covers and fairly pleads the proposition that there can be different methods of measuring AI. All I can say is that I do not think that it does. Again, it is a matter which might have been dealt with both by way of evidence from the plaintiffs and by way of experiments. I think it is just too late to take the point now. I therefore rule it and the relating evidence out."

There was no appeal against that ruling.

Exxon accepted the ruling, but submitted that it was appropriate for the Judge, despite his ruling, to decide that different methods of determining AI gave different results because Lubrizol themselves led evidence on the issue and also cross-examined Dr Brownawell on it. That Lubrizol disputed. They submitted that they were at all times concerned to confine the evidence, as required by the ruling, so that the only issue was whether or not the skilled man would know how to determine the amount of AI.

Dr Gordon, one of Lubrizol's experts, said in paragraph 59 of his Witness Statement - "The experimental techniques used to determine the saponification number and active ingredient ... have been well-known to those persons skilled in the manufacture of lubricating oil additives since before l980". In his statement in reply he gave evidence in answer to the evidence that had been ruled out by the Judge. It therefore could not have formed part of the evidence at the trial. He was cross-examined on his statement in reply (Evidence 5 at page 504). He accepted that he was not aware of any ASTM standard and that different manufacturers of PIBSA would use different tests. He was then asked - "Have you any idea what different values you will get depending on the different ways ...". At that stage Lubrizol objected as the question was seeking to open up matters excluded by the Judge's ruling. The Judge allowed the cross-examination to continue on the basis that Dr Gordon's evidence in reply had been admitted. He should not have done so as that part of his evidence in reply had been ruled out as it was in reply to evidence that had been excluded. The issue was not a live one after the ruling. Mr Young then referred Dr Gordon to a report of a Dr Billmeyer which had been produced for proceedings in the USA. It had also been excluded by the ruling.

MR YOUNG: May we come then, Doctor, back to Tab 7. You have set out in paragraphs ll6 to l20 a number of differing ways of determining AI. You accepted that differing ways would be adopted by differing manufacturers. My next question before the intervention was to be: and that would give you different results, would it not, depending on the way you adopt it?

A. The direct answer to your question is "No", but I would like to explain why. If the methods, whichever ones they are, are proper methods, they would all give the same answer.

Q What is your experience of doing AIs?

A I have little experience in doing AIs. I have done none of them on succinimide. However, I have spent a number of years in ASTM where I was in charge of the committee looking into methods of analysing lubricants. We looked at many different ways of running analyses. Sometimes more than one would be approved because they both gave the same answer. If they did not give the same answer they would not be an approved method.

Q I think you have told my Lord that there is no approved method of AI testing. We have already established that fact.

A That is correct, but any proper method will give the correct answer and there is only one correct answer.

Q I would like you to take bundle l4.4, please, and turn to Tab l9. These are some statements. You know Dr Billmeyer, do you not?

A Yes.

Q He was giving evidence, as you were, in the Ohio One proceedings. He was talking about column chromatography techniques.

A Are you talking about page 236 now?

Q Page 236, yes, you can start there. The gist of his evidence (we can look at it in detail if you wish to) is that depending on the solvent that you elute with, the concentration of the solvent, the type of packing material that you use, these are all critical parameters. His evidence was that even so far as Exxon are concerned, when they made a change in the way they were determining AI - if you look right at the end, page 245 - it gave a difference of 5 per cent even in the way that Exxon had changed their methodology. Do you follow? That is the gist of what Dr Billmeyer is saying right at the bottom of page 245.

A That is what he says, yes, but he also says there is a false weight percent AI increase. In other words, my previous statement can still hold; there is only one right answer. If you change your method and get a different answer, there is something wrong with one of the methods.

Q Which is the right one?

A That is something that has to be determined; I do not know. One of them has got to be wrong, or perhaps both of them are wrong."

The report of Dr Billmeyer was not concerned with the issue as to whether it was possible to carry out an AI determination. It was directed to an issue in the United States proceedings as to whether Exxon had made a colourable change in the method of determining AI after the grant of an interlocutory injunction. It concerned the method used by Exxon which Lubrizol had formally admitted for the purposes of these proceedings as being accurate pursuant to a request to admit being served by Exxon.

Dr Brownawell, an expert witness called by Exxon, was cross-examined about measuring AI. At Evidence 8, page 922, he agreed there was no ASTM standard of testing. He was then asked:

Q It is right, is it not, that Exxon were internally doing AI determinations and producing results which they considered to be satisfactory?

A We had a number of active ingredient tests that changed over time. They were the best results we had. I would note that on many of these tests there was the notation from the Analytical Department that they could not guarantee the accuracy.

He was reminded in re-examination of the tests done by Exxon to determine AI and he said that it was his understanding that there had been no verification of the tests.

Dr Gordon's evidence that the skilled man would know how to carry out a determination of AI was not contradicted. It was supported by evidence that Exxon and Lubrizol had done the determinations albeit for different reasons. Following the ruling given by the Judge there was no admissible or cogent evidence that persons carrying out determinations would arrive at different results depending upon the method used. That being the evidence; does the absence of any statement in the specification about determining AI lead the Court to construe Claim l as suggested by Exxon?

The Judge believed it was "bizarre" for the method of determination of a critical feature in the claim not to be mentioned. I disagree. If, as was the evidence, the skilled man would know how to carry out the determination, there could be no reason for stating that in the patent or even mentioning that he could do so. It is only if the patentee believed that a particular method of determination was appropriate or that the skilled man would not know how it was to be done, would the reader expect to be given appropriate instructions. The absence of information as to how to determine the amount of AI is consistent with the view that the skilled man would know what to do or at least the patentee believed he would. The absence of any statement as to the method to be used, throws no light on the meaning of the words "acylating agent" in Claim l.

I conclude that the meaning of the words "acylating agent" in feature [H] are clear. They denote the PIBSA, not the mixture of PIBSA and PIB as Exxon contend.

FEATURE [H], "1.3" - Lubrizol supported the Judge's conclusion that the figure of l.3 meant "l.3 to two significant figures". Exxon in their Respondent's Notice did not dispute that conclusion, but Mr Young when asked by the Court submitted that the words "at least" meant that the figure of 1.3 was the lower limit so that 1.28 or 1.29 would not fall within the ambit of the claim.

I agree with the conclusion reached by the Judge for the reasons he gave. The notional skilled man would read the claim and the specification using conventions adopted by scientists, one of which was that numbers are given to the number of figures that are significant. It follows that in giving the ratio in two figures, the patentee was indicating that only those two figures were significant.

FEATURE [G] - This feature requires the PIB to have a Mn value of 1300 to 5000. Exxon submitted that it was not possible, from the claim nor from the specification, to decide upon a particular way of determining Mn which would give one value. It followed that the patent was invalid as the scope of the claim was "not sufficiently and clearly defined" (see Section 32(1)(i) of the Patents Act 1949). That was the conclusion reached by the Judge.

Lubrizol submitted that the specification should be read through the eyes of the skilled man and, when so read, it taught one method of determination which would, when carried out, give appropriate results.

The specification does give guidance at page 5, lines 20 - 38 as to how Mn and Mw values are to be determined.

"Before proceeding, it should be pointed out that the Mn and Mw values for polyalkene, for purposes of this invention, are determined by gel permeation chromatography (GPC). This separation method involves column chromatography in which the stationary phase is a heteroporous, solvent-swollen polymer network of a polystyrene gel varying in permeability over many orders of magnitude. As the liquid phase (tetrahydrofuran) containing the polymer samples passes through the gel, the polymer molecules diffuse into all parts of the gel not mechanically barred to them. The smaller molecules "permeate" more completely and spend more time in the column; the larger molecules "permeate" less and pass through the column more rapidly. The Mn and Mw values of the polyalkenes of this invention can be obtained by one of ordinary skill in the art by the comparison of the distribution data obtained to a series of calibration standards of polymers of known molecular weight distribution. For purposes of this invention a series of fractionated polymers of isobutene, polyisobutene being the preferred embodiment, is used as the calibration standard."

There was no dispute between the witnesses that as of l980 the most accurate method to determine Mn was by VPO. That was time consuming and annoying to carry out. No doubt that was why GPC was used by Lubrizol when the invention was made and was the method required by the specification for determining values of Mn and Mw.

Exxon accept that the specification requires the value of Mn to be determined by GPC. They accept that GPC was a well-known technique by l980. Even so, they contend that the claim is ambiguous (the scope is not sufficiently and clearly defined) on two grounds. First there is no indication as to whether or not a refractive index (RI) correction should be made. That being so, some skilled men would make such a correction and some would not, with the result that different Mn values would be obtained depending on whether the correction was made. Second, even if the skilled man would not use RI correction, he would not derive consistent values as the passage in the specification set out above does not contain sufficient directions on calibration. Lubrizol submitted that when the specification was construed through the eyes of the notional skilled man, it was clear that GPC was to be used and that RI correction was not indicated. The skilled man would know that he should take trouble to calibrate his apparatus and provided that he adopted well-known techniques appropriate results would be obtained. In essence there was no ambiguity when the specification was read through the eyes of the skilled man.

The specification is written so as to be understood by the notional skilled man. The notional skilled man is deemed to be possessed of the relevant common general knowledge. That, as the Court of Appeal made clear in General Tire (1972) RPC 457 at 483 must be distinguished from what is public knowledge.

"The common general knowledge imputed to such an addressee must, of course, be carefully distinguished from what in patent law is regarded as public knowledge. This distinction is well explained in Halsbury's Laws of England , Vol 29, para 63. As regards patent specifications it is the somewhat artificial (see per Lord Reid in the Technograph case (1971) FSR 188 at 193) concept of patent law that each and every specification, of the last 50 years, however unlikely to be looked at and in whatever language written, is part of the relevant public knowledge if it is resting anywhere in the shelves of the Patent Office. On the other hand, common general knowledge is a different concept derived from a commonsense approach to the practical question of what would in fact be known to an appropriately skilled addressee - the sort of man, good at his job, that could be found in real life."

It is for the Court to construe the specification, but to do so it must adopt the mantle of the notional skilled man. In this case, that is particularly important as RI correction is not mentioned in the specification. If it did not form part of the common general knowledge, it could not form part of the way of determining the value of Mn indicated in the specification.

The Judge made certain findings of fact, but did not decide whether RI correction was part of the common general knowledge. It is therefore necessary to review the evidence on the matter.

Lubrizol's expert on GPC was Professor Dawkins. He said that by l980 it was possible, by GPC, to obtain values of molecular weights of good accuracy and from them to calculate the Mn. He also gave evidence as to whether RI correction was part of the common general knowledge in l980. He said:

"67. In l980 I was aware of the possible variation in refractive index increment in some polymers of low molecular weight and the potential effect of this on GPC results, but in my experience it was not usual to attempt to make any adjustment for this. It was certainly not my own practice to do so. At that time to adjust for refractive index effects would have been considered a refinement which was difficult and uncertain to undertake. Furthermore the effect was not thought significant in the context of other relevant sources of error such as band broadening. Even today it is not usual to make such an adjustment and I do not do so. In my research group at Loughborough, I currently have three research students and one postdoctoral research assistant working on polymers of molecular weights of between about 1000 to 5000. It is not and never has been our practice to apply any refractive index adjustment in our study of these polymers by GPC. Indeed, I had not heard of anyone making this adjustment in practice until I became involved in this case."

Professor Dawkins went on to review the textbooks that were available as of 1980. As he pointed out, there was mention in them of refractive index distortion that occurred and in one, Yau, two paragraphs dealt with the subject, one of which suggested a method of correction.

Having reviewed the literature, it was Professor Dawkin’s view that it was not part of the common general knowledge "that an adjustment for variation in refractive index increment should be made. As for those who were aware that some adjustment might be desirable, how it should be done was (and remains) far from common general knowledge." He did not resile from that view in cross-examination.

Mr Baumanis worked for Lubrizol as a research chemist in the Dispersant Group. His job involved making and evaluating new dispersant additives which involved molecular weight analysis. He had never heard of the question of RI adjustment before about l985. He said it was not an issue in l980.

Exxon's GPC witness was Professor Bartle. For the purpose of the action he was asked by Exxon's solicitors to measure the molecular weight of certain PIBs according to the instructions given in the patent. He used GPC with RI correction because he thought that to get an accurate result proper account needed to be taken of the fact that the responses of the detector could be inaccurate for low molecular weights, a fact that he knew by l980. From his reading of the literature, carried out for the purpose of completing the task he had been set, he concluded that it was well-known by 1980 that to arrive at an accurate determination of Mn, a RI correction had to be made. He believed that there was ample disclosure of how it could be done.

In cross-examination Professor Bartle accepted that the book by Billingham was a primary reference at the relevant time. He was shown the passage which stated that RI correction was a very difficult and normally neglected procedure. He was asked (Evidence 6, page 721):

Q .... Can you comment from your own knowledge, do you have enough knowledge from how GPC was being done in l977 to comment on whether it was normally neglected or not?

A No, I cannot.

Professor Bartle knew the Yau book which he used as a definitive work for the purpose of the task set by the solicitors. Having decided to make an RI correction, he had to decide how to do it. He outlined what he did at Evidence 6, page 686:

Q You must have been doing this search with something in view. You just told his Lordship by that stage you realised that you were going to need a refractive index. The question I ask you is: How long did it take you to reach that stage?

A Perhaps I could think of the steps. I knew I needed to always consider detector response. I knew the DRI was particularly problematical, partly from my own work, partly from general knowledge, Professor Knox's book for example, and then I read in Yau that I needed to have data corresponding to the refractive indices of polymers and low molecular polymers and oligomers. I do not think that probably took me more than a few days.

Having reached that position Professor Bartle did a literature search of publications between l970 and l980 which produced a paper by Rhein and Lawson which was not mentioned in Yau. From that paper and with the help of his assistants he produced the necessary RI corrections and the computer program as none was commercially available. It took him many months to do.

Exxon did not in the ordinary way use RI correction. Only one determination using RI correction was referred to in the evidence and that was done to satisfy the Federal Drug Authority that a material was satisfactory for packaging.

Mr Sims was employed by BP. In about l97l he helped to build a GPC machine. He realised from measuring the refractive index of different grades of polybutene produced by BP that the refractive index of the low viscosity low molecular weight materials was less than that of the high materials. From that he concluded that a RI correction was necessary. He and his colleagues carried out research and came up with a method of RI correction. In l985 their home-made GPC machine broke down and they purchased a commercial unit. At Evidence l0 page ll40 he explained why they then abandoned use of the RI correction factor which they had derived.

A .... In order to talk to other people in different parts of BP, we agreed that when we got our new GPC with the same solvent as everybody else, we would adopt their procedure. It was a step change. We recognised that it would make a difference to the answers but we had the view that we had defined our technique and that is the answer that we get by that method, recognising that it was going to be different than before.

MR PUMFREY: Is it right that none of the other parts of BP

did use such a refractive index correction?

A Our research department, did not, no.

MR JUSTICE JACOB: Your research department did not use a

refractive index correction?

A With their Waters GPC, they did not. They acknowledged that there was a refractive index effect but they just said "Our method says that we ignore it." In the end, the need to adopt a common procedure really overrode the question of which is more accurate.

MR PUMFREY: Did the commonality extend beyond BP's research

department to other BP plants as well?

A No. At this time there was only us, the works laboratory and the PIB research project, the research department, carrying out these analyses that I was aware of.

Q Do you remember when you stopped using the refractive index correction?

A When we bought the new machines. What we have on this table is the computer method of calculating the result which was already in place before we bought the new machine. When we bought to the new machine we used to set the factors to one in that column so that we could carry on using the same program.

Dr Bergmann explained what was done at Amoco. He knew that different grades of PIB had different refractive indices and because the GPC unit used a refractive index detector there was, in his words, obviously a problem. He solved the problem in three to four weeks by producing a formula which took account of RI divergence. That formula was not published. In cross-examination he said that if you were wanting a single number for Mn, then the appropriate way to obtain it was by using VPO; but in practice the output of plants at Amoco was monitored using viscosity measurements not GPC analysis. It was his view that if a GPC machine was to be used in an analytical sense for PIB, it was necessary to make a RI correction. However his answers at Evidence 7, page 802 indicate that his knowledge and experience were not typical of those operating GPC machines.

MR PUMFREY: If refractive index correction was such a

trivial and well-known matter, did you consider it surprising that Mr Chandler or Enjay needed to be written to, to tell them that was the reason for your different results?

A I have a feeling that in many laboratories the GPC was not part of the analytical laboratory; it was somewhere else. I do not know about Exxon but I know of cases where the people that were operating them were not extremely knowledgeable from an analytical point of view as to what needed to be done. So Waters would sell these things and people just used them. Most people used them in a qualitative sense and that was perfectly fine. But when you started to use them in an analytical sense, lots of people got into trouble.

Dr Bergmann did not know whether Amoco plants used RI correction.

The evidence established that Professor Dawkins would not have made an RI correction whereas Professor Bartle would. In practice, Exxon and Lubrizol did not correct for RI divergence. BP did not correct, but Mr Sims devised a method which was used in the Analytical Department between the late l970's and l985. Amoco may not have used GPC in their plants but Dr Bergmann had done so. The methods of correction used by Mr Sims, Dr Bergmann and Professor Bartle differed in detail.

The evidence did not establish that RI correction formed part of the common general knowledge at the time. In fact I believe the evidence established the contrary. Review of the text books showed no evidence of any acceptance of the need to carry out correction. Billingham stated that it was a difficult and normally neglected procedure and Yau only explained it in two paragraphs. In general, persons who knew how to use GPC machines never corrected for RI divergence and it would not immediately have sprung to their mind that there was any need to do so. If they needed an accurate Mn measurement, VPO would be used. If GPC was to be used to obtain a measurement equivalent in accuracy to that derived using VPO then a correction, perhaps RI correction, would be considered. However as Dr Sims pointed out a GPC determination without RI correction produced an answer which was considered to be sufficient for the purposes of BP. That I believe was the stance taken by the specification. I believe the passage on page 5 of the specification, construed through the eyes of the notional skilled man, teaches that Mn and Mw values should be obtained using standard GPC techniques. RI correction is not mentioned and there is nothing to suggest that a person, determining the values, was required to carry out something which would require the sort of literature search and analysis carried out by Professor Bartle nor to carry out the research done by Mr Sims. The reader, if he thought about the effect of RI divergence, was entitled and right to conclude that the patentee must have known that the way to determine Mn using RI correction would not be known to the notional skilled man and therefore the patentee would have included appropriate instructions if he intended it to be carried out.

The Judge came to the wrong conclusion because he approached the issue incorrectly. The correct approach was to ask - What is the specification teaching? To answer that question it was necessary to put on the mantle of the notional skilled man and, having done so, to construe the passage on page 5 of the specification. The Judge did not do that. He concluded, relying on the evidence of the witnesses called, that some people who were skilled in the art would use RI correction and some would not. Such people differed in experience and would have particular reasons which would cause them to act in a particular way. They would be skilled in the art, but not necessarily equivalent to the notional skilled addressee who only possessed common general knowledge. Further the Judge wrongly assumed that the specification was teaching the need of the absolute Mn value. If that had been the requirement, VPO would have been advocated. It was not. The specification said that the value should be determined by GPC. There could be nothing wrong with that, even if it differed from the VPO value, provided it was sufficiently reliable.

With leave of this Court, Exxon amended their Respondents' Notice to allege that the claim was ambiguous, even if the passage on page 5 of the specification was directing the reader to use standard GPC techniques. They alleged that the passage was devoid of detail and in particular failed to indicate whether calibration should be carried out using narrow fractions or broad fractions with curve shifting.

The allegation appears to be an after thought. If right, it would normally have been pleaded as an insufficiency (section 32(l)(h) of the Act). It was not. It appears to have been introduced as a ground of ambiguity because that allegation was sufficiently wide to enable it to be argued. In any case I believe that the evidence does not establish this ground of ambiguity.

The specification informs the reader that the GPC apparatus should be calibrated using fractionated polymers, PIB being preferred, but otherwise leaves it to the notional skilled man to carry out his calibration using conventional techniques that were available at the time. As of l980 the skilled man would probably have calibrated his GPC machine using narrow fractions of PIB if he could obtain or produce them. A calibration curve would be obtained by plotting molecular weight of each standard against elution time or elution volume. If narrow fractions were not available, then it would be possible to use broad fractions and curve shift. In this technique polymers of relatively high polydispersity having known Mn and/or Mw values, and structurally similar to the sample under investigation, would be used with the reference materials for the purpose of calibration. A first approximation of the calibration curve for each reference would be adopted. Trial values of Mn and/or Mw, derived from chromatograms of the reference material, would be compared to the known values. The trial calibration curves are then shifted and the values of Mn and Mw recalculated. This procedure is repeated until the calculated Mn and Mw values match the known values as closely as possible. This curve shifting technique was developed in the late l960's.

It is common ground between the parties that even after calibration the result obtained would to some extent differ from that determined by VPO. The issue between the parties concerns the degree of accuracy of the two calibration methods. According to Exxon the evidence established that the use of broad fractions with curve shifting gave a more accurate result than calibration using narrow fractions without RI correction. It follows that the skilled man, adopting different calibration techniques would, for the same PIB, get different results of Mw and Mn. Thus the scope of the claim was not sufficiently and clearly defined.

Lubrizol submitted that there was no evidence which showed that the results obtained using the two methods of calibration differed materially. Thus adopting the teaching of the specification acceptable Mw and Mn values could be obtained. There was no ambiguity.

Professor Dawkins set out in his Witness Statement the possible methods of calibration. He said that if a person, seeking to carry out the instructions on page 5 of the specification, was unable to obtain sufficiently narrow fractions a curve shifting method could be applied. He did not suggest that comparable results would not be obtained by use of the two methods. He said that by l980 it was known that even if the GPC instrument was carefully calibrated, there was the possibility of some deviation from the true value of the Mn obtained.

Exxon's case was based on deduction and upon the cross-examination of Professor Dawkins. They submitted that because curve shifting was a sort of reverse engineering a value close to the real value, derived by VPO, would be achieved. Such accuracy, they say, is unlikely to be obtained by using narrow bands as the calibrant. That may or may not be right. I suspect the true answer is that it all depends upon how good the narrow fractions are and how well the curve shifting is done. However it would be wrong to come to any conclusion on this without evidence directed to the issue and there was none.

Answers given by Professor Dawkins in cross-examination did not support Exxon's submission. The questions asked presupposed that a more accurate result would be obtained by curve shifting. Professor Dawkins did not agree that different values would be obtained after calibration using narrow fractions and by using broad fractions with curve shifting.

It follows that Exxon have not made out their case that claim l is ambiguous.

INFRINGEMENT - Experiments were carried out upon the Exxon's additives alleged to infringe. The results adopting the correct construction of the claim, were set out by the Judge on page 32 of his judgment. They are:

Mn SR

ECA 7474 1401 l.63

ECA 10444 2452 1.58

ECA 12819 2452 l.29

It follows that the products alleged to infringe fell within claim l. Therefore there has been infringement, if the claim is valid and the Section 64 defence fails.

VALIDITY

The appeal on validity was confined to allegations that the patent was invalid because the claim was ambiguous and not fairly based (Section 32(1)(i)); the invention was obvious (Section 32(1)(f)); the invention had been prior used (Section 32(1)(e)), alternatively secretly used (Section 32(1)(l)).

I have already decided that there is no substance in the allegation that claim 1 is ambiguous.

FAIR BASIS - Mr Young drew our attention to this statement of the law by Oliver LJ in Van der Lely NV v Rushtons Engineering Co Ltd (1985) RPC 461 at 474:

"Whatever may be the precise ambit of the words it is in my judgment clear from the decision of this court in Stauffer Chemical Co's Application (1977) RPC 33 that in order to find that a claim is fairly based on the disclosures in the specification, one has at least to find that that invention for which monopoly is claimed is disclosed as an invention in the specification. The inventor is, in fairness to the public, entitled only to monopolise that which, fairly read, he has disclosed as his invention."

Mr Young submitted that the claim, construed as Lubrizol suggest it should be, covered dispersants produced with less than l.3 moles of MA for each mole of PIB. Relying upon passages of the specification, such as that appearing on page ll lines l3 - l6, he submitted that there was no fair basis for a claim of such a width.

That submission would have some force if the claim was a process claim or a product by process claim. It is not. It is a claim to a product and the ambit of the claim is not defined by details of the process put forward as preferred processes. The patent, when fairly read, describes as the invention the product which is claimed. This allegation of invalidity has no substance.

OBVIOUSNESS - Exxon submitted that claim l was obvious having regard to the disclosure in US Patent No. 3576 743 and US patent No 3632 510. US Patent No 3576 743 was published in l97l and was named after Robert Widmer, one of its inventors. The other patent was published in l972 and was called LeSuer because he was the inventor.

Before the Judge, both Widmer and LeSuer were said to have prior published the invention claimed in the patent in suit. The Judge rejected that allegation, but found that the invention of the patent was obvious having regard to LeSuer. He made no finding on obviousness having regard to Widmer. Before us, Exxon confined their case to obviousness. Thus the sole issues before us were:

1. Was claim l obvious having regard to the disclosure in LeSuer and in particular the disclosure in example 32 of that patent?

2. Was claim l obvious having regard to the disclosure in Widmer and in particular to the disclosure in example 5 of that patent?

LeSuer - LeSuer relates to an invention entitled "Mixed Ester Metal Salts and Lubricants and Fuels Containing the Same." The invention is a lubricant comprising a major amount of oil together with a minor portion of an ester derivative of a hydrocarbon-substituted succinic acid. Example 32 states:

"Following the general procedure set forth in US Patent No 3215 707 or 3231 587 a polyisobutylene-substituted succinic acid anhydride is prepared by heating a mixture of polyisobutylene having an average molecular weight of about 2100 with maleic anhydride in a mole ratio of polyisobutylene to anhydride of about l:2 while passing chlorine through the reaction mixture. The resulting polyisobutenyl-substituted succinic acid anhydride is mixed with mineral oil to produce a 42.5% oil solution of the anhydride, the solution being characterized by an acid number of about 52."

The example goes on to describe how the PIBSA is reacted to produce the acid ester which is then changed into the ester salt.

The Judge had to decide what example 32 disclosed before he could decide whether the claim of the patent was obvious having regard to the disclosure. Two matters of dispute were raised.

First, Exxon submitted that when the example said that the PIB had "an average molecular weight of about 2l00", it was referring to Mn. Lubrizol submitted that it was likely to be Mv. In any case there could not be certainty as to what was meant. Second, if the figure of 2100 was Mn, was the PIB that was used within the polydispersity of claim 1?

The Judge held:

"Again the question arises: what is meant by 'average MW'? Here Exxon are on firmer ground. Other examples of LeSuer, namely l, 33, 35 and 36, it is accepted, must refer to Mn. It is said that to be consistent all other MW's must be the same. I think this is essentially a matter of construction and I think it right to assume that LeSuer is using MW consistently throughout the document."

The Judge went on to decide that it was not inevitable that the PIB used in the example fell within the range of l.5 to 4.

Before us Lubrizol submitted that the Judge was wrong to conclude that the figure of 2l00 in example 32 was to be understood to be Mn. As before they submitted that at the very least it was uncertain what was being referred to. Exxon supported the Judge's reasoning.

In my view the Judge was right to come to the conclusion that the words "an average molecular weight of about 2100" in example 32 would be understood as Mn. That would be consistent with usage at the time and the way those words were used in LeSuer. LeSuer uses the expression average molecular weight in respect of PIB without stating whether it is Mw, Mn or Mv. However there is no doubt that in examples l, 33, 35 and 36 Mn is meant. That would be apparent to the notional skilled man from the information given in those examples. It would therefore be very unlikely that the same words would be understood to be used in a different sense in example 32. LeSuer uses the same words in example 3 in respect of polyethylene glycol and it is clear that they denote an Mn value. Further all the witnesses who were asked about the matter, except Dr Gordon, were quite clear that what was being referred to was Mn. Dr Gordon at Evidence 5, page 532 accepted that the examples to which I have referred were referring to Mn. He was taken to example 32 and it was suggested to him that the same words must have the same meaning and therefore the 2100 must be a Mn value just as in the other examples. His answers were:

A It is possible that that relates to Mn values but when it is not spelled out you simply do not know for sure.

Q Even with other examples you would be sure?

A The other examples you would be relatively sure, yes. It is possible that it is Mn but it is not spelled out as Mn so you simply do not know for certain.

I accept that there cannot be certainty, but on the balance of probabilities it appears to me that the skilled man would understand that the words "average molecular weight" in example 32 were referring to Mn.

Mr Thorley seemed at times during his submission to suggest that the or part of the inventive step of the patent in suit was selection. However he made it clear that the patent was not a selection patent. No doubt that was because the specification did not meet the requirements of a selection patent recognised by Maugham J in the I G Farbenindustrie case. Such requirements were summarised by Lord Diplock in Beecham Group Ltd v Bristol Laboratories International SA (l978) RPC 52l at 579:

"The inventive step in a selection patent lies in the discovery that one or more members of a previously known class of products possess some special advantage for a particular purpose, which could not be predicted before the discovery was made. (In re I G Farbenindustrie AG's Patents (1930) 47 RPC 283 per Maugham, J at pp 322/3) The quid pro quo for the monopoly granted to the inventor is the public disclosure by him in his specification of the special advantages that the selected members of the class possess. So there can be no invention to support a selection patent until the would-be patentee is in a position to define with adequate precision what those special advantages are."

As the patent is not a selection patent, the issue of obviousness is best considered using the structured approach suggested by Oliver LJ in Windsurfing International Inc v Tabur Marine (GB) Ltd (1985) RPC 59 at page 73:

"There are, we think, four steps which require to be taken in answering the jury question. The first is to identify the inventive concept embodied in the patent in suit. Thereafter, the court has to assume the mantle of the normally skilled but unimaginative addressee in the art at the priority date and to impute to him what was, at that date, common general knowledge in the art in question. The third step is to identify what, if any, differences exist between the matter cited as being "known or used" and the alleged invention. Finally, the court has to ask itself whether, viewed without any knowledge of the alleged invention, those differences constitute steps which would have been obvious to the skilled man or whether they require any degree of invention."

The parties agree that the inventive concept of the patent in suit is set out in features [G] and [H] of the claim. Stated in general terms, it is an additive made from a PIB of relatively high Mn, with the polydispersity kept within limits and there being over-succination. Dr Gordon said (Evidence 4 page 479) that the inventive step was to go to a higher molecular weight value for the PIB compared with what was used in l977 and to over-succinate.

On this part of the case there is no dispute as to the common general knowledge. I can therefore go next to the third Windsurfer step.

LeSuer is principally concerned with a range of esters used as additives. As the Judge held it does not contain any general teaching that would lead the skilled man to the invention of the patent in suit. Without example 32 LeSuer could not provide a starting point for an attack of obviousness. However, as was made clear in Windsurfer, the notional skilled addressee is taken to have read LeSuer with care. Thus he would understand, for the reasons I have given, that example 32 disclosed use of a PIB having an Mn of 2100 and therefore the succination ratio would be about 2.1. There is no disclosure as to the polydispersity of the PIB. That is the only difference between example 32 and claim 1.

The fourth step requires the Court, without recourse to hindsight, to decide whether or not it would be obvious to the skilled man to use a PIB having a polydispersity between l.5 and 4 when carrying out example 32.

Mr Thorley submitted that it was not obvious to carry out example 32 with a PIB of the appropriate polydispersity. To conclude that it was involved knowledge of the invention. Anybody who had the idea of performing LeSuer would use PIB of a Mn below 1000. Example 32 was the exception. Thus selection of example 32 would only happen once the idea of the invention was known and to do that selection and to use a PIB of a particular polydispersity was not obvious.

Exxon accepted that the general teaching of LeSuer did not point towards the invention. But example 32 was obvious. Further the most obvious way to carry out the example was with a commercially available PIB. If so, you would use a PIB with a polydispersity within the range 1.5 - 4.

With one exception all the witnesses who gave evidence on the subject accepted that the PIB that was commercially available at the priority date fell within the range l.5 - 4. That was supported by trade literature of such companies as Amoco and BP. The one exception was Mr Baumanis who produced a record of a few analyses done by him of PIB with a polydispersity exceeding 4. They were few and were exceptions. In my view, on the balance of probabilities, anybody seeking to perform example 32 would select a commercially available PIB having a polydispersity with the range l.5 - 4: to do so could not involve invention. The likelihood of falling outside the range was minimal.

I reject Mr Thorley's submission that there could be anything inventive in what he called "cherry picking" (I understand him to mean selecting) example 32. This is not an invention based on selection. A person practising LeSuer would be likely to try the examples. All of them were obvious. When carrying out the teaching of example 32, it would be obvious to use a commercially available PIB. If so, a product within claim l would be produced. It follows that claim l includes within its ambit a product which it was obvious to produce and is invalid. No scintilla of invention was required.

It may be that the patent could have been framed as a selection patent and that there could be an inventive step in selecting a class of additive from those disclosed in the prior art. The reason, perhaps, why the patent was not so framed was that the whole class which was claimed did not give the special advantage which had to form the basis of the inventive selection.

I agree with the Judge. Claim l was invalid as it was obvious over example 32 of LeSuer.

WIDMER - Widmer is concerned with an invention for making improved additives. In example 5 there is disclosure of use of a PIB having an average of two succinic anhydride substituents per PIBSA group prepared by reacting PIB having an average molecular weight of about 2000 with maleic acid in a mole ratio of about 1:2.

Again there arose a difference of opinion between Dr Brownawell and Dr Gordon as to whether the molecular weight referred to was Mn or Mv. Dr Brownawell concluded that it was Mn for three reasons. First, he believed that the skilled man would so read it. Second, the calculation of the ratio of SA:PIB given in example 5 required the use of Mn. Further the example states that the average equivalent weight of the acylating agent was 550. Adopting the method of calculation suggested by Widmer in column 6, the PIBSA would have four equivalents. As the equivalent weight was stated as 550, the molecular weight had to be 2200 and the number average molecular weight would be about 2000 as stated.

Dr Gordon did not dispute the mathematics nor the logic. He said at Evidence 5, page 511, that he did not believe that what was stated in Widmer was true. What had happened was that the example had been performed with a bottle labelled 2000 molecular weight. It probably was an Mv value. The experimenter had treated the figure as an Mn value, but the true Mn was about 1200. That meant that a l:l charge ratio had been used, not the 2:1 as stated.

Dr Gordon's hypothesis is interesting, and it may be that he did not believe what is stated in example 5. However what has to be decided is what would example 5 teach the notional skilled addressee. I have no doubt that it teaches the use of PIB with an Mn of about 2000 for the reasons given by Dr Brownawell. That being so, the disclosure in example 5 is similar to that of example 32 of LeSuer. The reasoning, upon which I concluded that claim l was invalid as being obvious having regard to example 32 of LeSuer, applies to example 5 of Widmer. Claim l is obvious having regard to Widmer.

PRIOR USE - Under the l949 Act a patent could be invalidated by public or secret prior use. Exxon allege public prior use alternatively secret use.

Although we were taken at length through the facts, I believe this precis of the Judge fairly sets out the relevant facts:

"7474 was developed by Exxon in the US. They were excited by the product which represented an improvement over earlier dispersants. After successful bench testing, the product parameters were finalised in December l975. The first batch, on a pilot plant scale, was made in March l976. This is called "Batch Zero". It was made using an Amoco PIB, H-300. Samples of H-300 were kept for future use as a reference standard to compare with any subsequent PIBs that Exxon might use. 7474 was given a technology endorsement on 7 July l976. This meant that the product could be "commercialised", first in the US and then in other regions. At the time the product was called 7474X. The X meant the product was to some extent still not regarded as having finally passed all tests, but nothing turns on this.

All activity thus far took place in the US. The extent to which there was use or disclosure in the US of 7474 before the priority date does not matter: this is an old Act patent and s.64 relates to acts done in the UK.

So far as the UK is concerned, the first event was the importation of a small quantity (20 gallons) of Batch Zero by Exxon Chemical (the 2nd defendant) in April l976. This was used to make some trial adpacks which were supplied to Shell and BP as potential customers. The purpose of the supply was so that those customers could test the product. This they did by making up lubricating oils and testing these oils in hack cars. The results of these tests were confidential to the customers and Exxon. Up until the priority date the relationship between Exxon and its two customers was confidential, save that there was no secret that adpacks were under test. Neither Exxon nor either customer made an "offer" in the sense that acceptance would give rise to a concluded contract. However there were tentative indications as to price given by Exxon and as a practical matter they would have found it difficult to quote to a higher price later.

Exxon contemplated European manufacture from the outset. Two plants were potentially involved, at Fawley in the UK and Vado in Italy. In relation to Fawley a Mr Sutton prepared an "Action Programme for ECA 7474X production at Fawley" in November l976. This involved consideration of all that was involved, including any necessary plant modifications (particularly to deal with the use of the chlorine process for PIB manufacture). He had "to completely assess the impact on our plant from start to finish." This included what plant trials would be needed. A senior scientist, Dr Anson, went to the US in December l976, inter alia, to discuss 7474 and inspect its pilot plant production.

A meeting to discuss the project further took place on ll February. The minutes of that meeting are, I think, important as accurately recording the position just before the priority date.

'Fawley are currently at a very preliminary stage in the development of this project.'

I think this is a fair summary of the position. It is noteworthy that no decision actually to manufacture at Fawley was made even by July l977, as Dr Anson acknowledged in saying:

'I do not think there is a decision point at this time.'

And even by then no plant modifications had been made, though it was technically possible to manufacture on a small scale without any such modifications: a batch was made in that June with a view to providing data for full-scale manufacture."

The parties agreed that Batch Zero had been imported into this country by Exxon prior to the priority date and had been supplied to two customers for trial. There the agreement ended. Lubrizol submitted, as is the case, that the onus was upon Exxon to establish that Batch Zero was a product falling within the claim. That, they submitted, had not been done. In any case what had happened did not amount to use as would invalidate within Section 32(1)(e) or (l). Exxon submitted that Batch Zero was the same as ECA 7474; a product that I have held to infringe. If they are right, then Batch Zero must fall within claim l and it will be necessary to decide whether what happened amounted to public or secret use. I turn first to consider whether Batch Zero had an Mn of l300 to 5000. If it did, it is accepted it fell within the ambit of claim 1.

Batch Zero does not exist so it is not possible to analyse it. Exxon submit that there are three reasons taken together which prove that the Mn for Batch Zero fell within the range of the claim. First, the material used to produce Batch Zero was supplied by Amoco as being within the agreed specification. As Dr Brownawell made clear Exxon ordered PIB from Amoco with a specification of 1275 to 1375 Mn determined by VPO and monitored it. It follows that the H-300 used to make Batch Zero would have been rejected if it did not fall within the specification. If so, the Mn, determined according to the patent, was likely to be higher than that determined by VPO and therefore would have been within the claimed range. Second, Batch Zero was measured in l976. The Mn by VPO was 1379, by GPC 1024; the Mw by GPC was 2150 and therefore the ratio Mw to Mn by GPC was 2.1. At the time the GPC measurements were made, the apparatus had not been calibrated for PIB. Thus the Mn value was inaccurate. The best value was that determined by VPO which would have been lower than the Mn determined by the method of the specification and therefore the Mn would have been within the claim if it had been determined in the way laid down in the patent.

Before coming to the third reason, it is convenient to set out Lubrizol's objections to the first two. Lubrizol sought to show that there had been no agreement between Amoco and Exxon as to the specification for H-300, but that was rejected by Dr Brownawell in cross-examination. He said that they had agreed an Mn of 1275 to 1375 by VPO and that they had monitored it. Lubrizol also challenged the accuracy of the VPO measurement made in l976. They said there was no evidence as to whether it was carried out using the multipoint or single point techniques and without that knowledge it was not possible to estimate whether the Mn by GPC would be higher than the VPO value. Dr Brownawell did not know what method was used, but confirmed in his evidence that Exxon regarded the measurement by VPO as correct. Lubrizol also referred to the Puskas paper. That gave the Mn of H-300 as determined by VPO as ll76. They submitted that was the best evidence of what the Mn of H-300 was when determined by VPO. Dr Bergmann of Amoco accepted in cross-examination that would have been a pretty reliable VPO result. That paper was never put to Dr Brownawell. If it was a correct value, then the sample tested would not have been within the agreed specification.

The third reason relied on was that the Parapol 1300 used to make 7474 was required to have the same Mn as the H-300 used to make Batch Zero. Further that was checked against a sample of H-300 that had been retained as a reference sample. It followed that if 7474 infringed, Batch Zero must have also fallen within the claim.

Dr Brownawell gave evidence that 7474 was produced using a PIB from Koln in Germany. He said "It was soon established that Koln PIB was the same as our reference PIB for ECA 4600 which was in fact a sample of Amoco H-300". That sample was the same as that used for Batch Zero. Mr Scherzer was employed at Koln by Exxon. In paragraphs 12 - 14 of his Witness Statement he explained that on 2 to 4 June l980 Koln produced the first batch of PIB which was later called Parapol 1300. It met the specification used in the USA for H-300 and was judged to be equivalent based on reference to the reference sample of H-300 from Amoco. He was not cross-examined.

Dr Brownawell was cross-examined on his evidence. After being taken to a number of documents he was asked: (Ev 8 page 89)

Q Is this right, that we cannot really say whether Parapol 1300 ever had the same molecular weight by VPO as H-300 at any time?

A I do not know how to respond to that. We set up a set of specifications based on the initial sample of H-300 and it was our intention and we made every effort to only purchase or use PIB that met those specifications in all our production of 7474 worldwide. The fact that on occasions we may have used PIB that was at one end or the other of those specifications could very well have occurred.

Q The next point is this. Every piece of data we have looked at suggests that the Koln PIB had a higher number average molecular weight than the Amoco H-300, is that not right?

A That would so appear, yes.

Lubrizol emphasised that there were doubts as to the true value of the reference sample. Further they submitted that no reliance could be placed upon a comparison with 7474 as the Mn value could and probably did have a higher Mn than that of Batch Zero.

The Judge held:

"I am not satisfied that the particular batch of H-300 used to make Batch Zero did have an Mn within the claim. The fact that one has no details of the experiment involved means one just cannot know how reliable it was. It is no good saying that the figure is the "best evidence" if the "best" is not good enough. For what it is worth, my earlier conclusion, that the later 7474 does not fall within the claim because its Mn (by GPC with RI correction) is too low is consistent with Batch Zero having too low an Mn, though of course the batches and measurements involved are entirely different."

Exxon submitted that the Judge had applied the wrong standard of proof. He should have resolved the dispute using the normal civil standard and should have held on the balance of probabilities that the Mn of Batch Zero fell within the range l300 to 5000. In any case he was applying his construction of the claim, namely that the Mn value had to be determined using RI correction. If so, he could have been right as the Mn value determined in that way would have been lower than the value determined without RI correction.

The standard of proof must be the civil standard. Thus the Court has to decide whether Exxon established, on the balance of probabilities, that Batch Zero had an Mn of l300 to 5000. I would not have expected this experienced Judge to have applied a different standard of proof and believe it right to assume that he did not. However I am unclear as to what meaning he was ascribing to the claim. He had held that the directions in the specification as to how to carry out the Mn determination were unclear in that some people would carry out RI correction and some would not. On his preferred construction, namely with RI correction, the Mn of 7474 was 1271, below the l300 figure of the claim. Whereas without RI correction it was 1401: well above it. I am not sure which figure the Judge had in mind, nor whether he was comparing like with like. Therefore I believe that this Court should weigh the evidence and decide whether Exxon have discharged the onus on them.

In my view Exxon have discharged the onus on them. 7474 had an Mn of 1401 well above the l300 limit in the claim. It was made using Parapol 1300 from Koln in Germany. It was made to the same specification as H-300 used to make Batch Zero and was checked against it. The measured GPC value of H-300 was done at a time when the GPC apparatus had not been calibrated for PIB. However the VPO value would be a reliable indicator of the true Mn. If so the GPC measurements without RI correction would have been higher. Lubrizol rightly criticised the lack of evidence as to how the VPO measurement were made. They rightly drew to the Court's attention the Puskas paper, but nothing is known about the sample that was measured save it was H-300. Taking the evidence as a whole I conclude, on the balance of probabilities, the Mn of Batch Zero was above 1300. All the indicators were to that effect. It follows that Batch Zero fell within claim l. I therefore turn to consider whether the events that took place before the priority date amounted to an invalidity prior use.

The relevant provisions of the l949 Act dealing with prior use are as follows:

"32 - (l) Subject to the provisions of this Act, a patent may, on the petition of any person interested, be revoked by the court on any of the following grounds, that is to say, -

(e) that the invention, so far as claimed in any claim of the complete specification, is not new having regard to what was known or used, before the priority date of the claim, in the United Kingdom;

(l) that the invention, so far as claimed in any claim of the complete specification, was secretly used in the United Kingdom, otherwise than as mentioned in subsection (2) of this section, before the priority date of that claim.

(2) For the purposes of paragraph (l) of subsection (l) of this section, no account shall be taken of any use of the invention -

(a) for the purpose of reasonable trial or experiment only;

....

and for the purposes of paragraph (e) or paragraph (f) of the said subsection (1) no account shall be taken of any secret use."

Exxon rely upon their dealings with Shell and BP. Trial adpacks were made up which were supplied for testing to Shell and to BP as customers. As found by the Judge, the results of the tests were confidential to those companies and to Exxon. The relationship was also confidential save that there was no secret that the adpacks were being tested. There was no concluded contract, but indications as to price had been given. Exxon in effect were inviting Shell and BP to purchase after trials at a price to be agreed, but around the indicated price.

Lubrizol accept that there was use, but submitted that it was secret use because both customers were bound by an obligation of confidence not to use the samples supplied for any purpose other than the trials for which they had been supplied and also because there was no contractual relationship between the parties. They also submitted that the use was not an invalidating use as it was for reasonable trial and experiment only.

It follows that there are two matters to be decided:

1. Was the use public or secret?

2. If the use was secret, was it for reasonable trial and experiment only?

What is public and what is secret use can be difficult to determine. That is clear from the split in the opinions given in the speeches in the House of Lords in Bristol-Myers Company (Johnson's) Application (1975) RPC 127. That case involved manufacture of ampicillin trihydrate, the product claimed as the invention, by an opponent; but without recognising that it was the trihydrate. The House of Lords had to decide whether that amounted to public use as secret use was not a ground of opposition. They held that it did amount to public use. Lords Diplock and Kilbrandon held that it was not secret as there had been no intention to conceal the composition of what was sold. Lords Reid and Morris dissented. They believed the use was secret as the users were unaware of the use. Lord Cross concluded that the use was public because the opponent had put it out of his power to prevent a purchaser from discovering that it was the trihydrate.

In the present case, I do not believe it necessary to differentiate between the views expressed in Bristol-Myers as the use relied on is the dealing between Exxon and its customers. What is said is that there has been commercial dealing in the patented product before the priority date. That dealing was public in the sense that it was not intended to be secret and was apparent to both parties.

There is no doubt that Exxon was seeking to interest both BP and Shell in their new adpack and that the samples were provided as a first step towards a sale. Further the fact of the supply and the relationship was not confidential although the results of the tests were confidential between them. Did that amount to a use of the invention and was it public?

Lord Diplock in his speech in Bristol-Myers, agreed with by Lord Kilbrandon, set out the historical background to the ground of invalidity of prior use. At page l55 he pointed out:

"Both as a noun and as a verb the word "use" has, in its ordinary significance, a very wide meaning. In relation to the grounds on which a claim to a patent for an invention may be invalid it appears not only in section l4 dealing with opposition to the grant of a patent in proceedings before the Comptroller as in the instant appeal, but also in section 32 dealing with revocation of a patent as a result of a full trial in the High Court. "Used", the past participle of the verb, and "use" the noun, appear in similar contexts in both these sections and must bear the same meaning in each."

He went on to point out at page 156:

"From earliest times it had been taken for granted that by that phrase it was intended to declare unlawful the grant of any patent which would put it into the power of the grantee to prevent any other trader from doing whatever he had done before in the course of his trade. In the earlier cases one often finds the prior use by others which rendered a patent invalid described as "public use"; but where the invention claimed was a new product it was never doubted that any dealing with that product by the way of trade, whether by buying it or selling it with a view to profit or making it for the purposes of sale, constituted such "public use".

At page 157 he explained how an inventor could "prior use" himself:

"If the inventor, after discovering how to make it, had himself dealt with the substance commercially before applying for a patent for it, he would be disqualified from obtaining a grant; but this was not because of any prior use of it by others, but for the different reason that the invention having been put by him to "public use" was no longer a manner of new manufacture within the meaning of the Statute of Monopolies. For the other mischief against which that Statute was directed was that even monopolies of new manufactures should not extend beyond fourteen years. If the inventor had already reaped commercial benefit from a de facto monopoly in his discovery owing to his concealment from all other traders of the way in which the new substance could be made, he was not to be permitted to prolong his monopoly for an additional fourteen years. So "public use" in the sense of commercial dealing in a product claimed as an invention, by any trader even though it were by the inventor himself, rendered invalid any patent for the product claimed.

....

So I would hold both on principle and in accordance with the main stream of authority prior to l949 that where in section l4(l)(d) of the Patents Act, l949, it is provided that one of the grounds of opposition to the grant of a patent shall be: "that the invention, so far as claimed in any claim of the "complete specification, was used in the United Kingdom before the priority date of that claim" any commercial sale by any trader before the priority date of a claim to a product as an invention is "use" of that invention within the meaning of that paragraph and, unless it falls to be disregarded as "secret use" under section l4(3), constitutes a bar to the grant of a patent for that product. To sell the product by way of trade is to "use" it, notwithstanding the seller's ignorance of its identity or his lack of knowledge of its composition or his uncertainty as to how and where further supplies of it could be obtained."

Lord Cross agreed that there was a use. At page l63 he came to consider whether the sale was secret use on the basis that nobody could analyse the product and find out that it contained trihydrate. He concluded that the sale was a "public use" because it was:

"...more satisfactory to hold that if a man by selling the article in question puts it out of his power to prevent a purchaser from discovering, if and when he can, the presence in it of the substance in question he has made a "non-secret" use of the substance whatever he his own state of mind and whether or not analysis is, in the existing state of knowledge, possible. For this reason I agree with my noble and learned friend, Lord Diplock, that this appeal should be dismissed."

In the present case there is no evidence as to whether BP and Shell could have ascertained what the sample adpack contained, but Bristol-Myers makes it clear that that is not material.

As submitted by Lubrizol, Bristol-Myers can be distinguished on the facts. In the present case there was no concluded sale and tests needed to be done, the results of which would be confidential. However the reasoning of Lord Diplock is of interest. In particular where he looks at the historical background. If it be right that it was a principle of law that a patent should not be granted to prevent a man doing what he had done before the priority date, it would be odd for Lubrizol to have a patent which would prevent Exxon continuing to supply 7474.

Further guidance was given by the Court of Appeal in Wheatley's Application (1985) RPC 91. In that case the applicant for the patent had, before the priority date, made a prototype switchgear, demonstrated it in confidence and had accepted an order for l0 devices, the subject of the application. They were not supplied until after the priority date. The Court of Appeal held that the agreement to sell was a non-secret use of the invention.

Lawton LJ said at page 100:

"It remains to be considered whether in this case the use was secret. The applicant opened his negotiations with Mr Stevenson on a confidential basis. When he demonstrated the pull-keys he was using them secretly, but his object in doing so was to bring about a sale. There was no term in the agreement that the National Coal Board should use them for experimental purposes for the benefit of the applicant. By agreeing to sell, the applicant had used his invention to achieve his commercial object. He had dealt in the products of his invention before he had obtained any patent rights. This was doing one of the things which the Statute of Monopolies l623 was intended to prevent, namely, getting a monopoly after having already dealt commercially with the invention. It follows, in my judgment, that the applicant's dealing with the National Coal Board, when looked at as a whole, did not constitute a secret use of his invention."

Oliver LJ was of the same view. At page l0l he said:

"It is not, in my judgment, in any event necessary in the instant case to consider the older cases because, whether the word "use" in the Act of l949 be taken at its face value or regarded as embodying the interpretation put upon it in the l9th century cases, I have no doubt that a commercial dealing for profit of the type with which the instant case is concerned constitutes a use. To hold otherwise would, as it seems to me, be to enable an inventor to reap the benefit of his monopoly for a period longer than the Act prescribes (see the speech of Lord Diplock in the Bristol-Myers case at pages 680 to 681B) albeit in the instant case not for very much longer. That, no doubt, makes the instant case a hard one, but it cannot affect the principle."

Dillon LJ concluded that the use was not secret as "there was no concealment of the offer or its acceptance."

Lubrizol distinguished Wheatley on the facts. In Wheatley there was a concluded contract when in the present case there was only an invitation to treat. I accept that difference, but it is not sufficient to lead me to the conclusion that the use in the present case was secret. In the present case there was an ordinary commercial dealing between Exxon and BP and Shell. Samples were supplied for test. Prices were discussed. The fact that a contract had not been concluded was in my view irrelevant. The dealing between the parties was a use which was not secret. It was an ordinary commercial use.

The conclusion can be tested by assuming that the use had been by Lubrizol. If so, it would have been a commercial exploitation of the invention prior to the date of the patent. It would have had the effect of prolonging the patent monopoly.

I conclude that Exxon had prior used the invention and that the patent is invalid upon this ground as well. Having regard to that conclusion there is no need for me to go on to consider whether the use was for reasonable trial and experiment only.

SECTION 64 OF THE PATENTS ACT l977

Exxon submitted that having regard to the provisions of Section 64 of the Patents Act l977 they were entitled to continue to manufacture 7474. At the relevant time that section had not been amended. It was in this form:

"64 - (1) Where a patent is granted for an invention, a person who in the United Kingdom before the priority date of the invention does in good faith an act which would constitute an infringement of the patent if it were in force, or makes in good faith effective and serious preparations to do such an act, shall have the rights conferred by subsection (2) below,

(2) Any person shall have the right -

(a) to continue to do or, as the case may be, to do that act himself; and

(b) if it was done or preparations had been made to do it in the course of a business, to assign the right to do it or to transmit that right on his death, or in the case of a body corporate on its dissolution, to any person who acquires that part of the business in the course of which the act was done or preparations had been made to do it, or to authorise it to be done by any partners of his for the time being in that business;

and the doing of that act by virtue of this subsection shall not amount to an infringement of the patent concerned.

(3) The rights mentioned in subsection (2) above shall not include the right to grant a licence to any person to do an act so mentioned."

That section has been considered in two previous cases. In Helitune Ltd v Stewart Hughes Ltd (1991) FSR 171 at page 206 I said:

"Section 64 gives what can be called a statutory licence to a person who in good faith either does an infringing act or makes effective and serious preparations to do such an act. The infringing acts referred to are set out in section 60 of the Act and include, where the invention is a product, making, disposing of, offering to dispose of, using and importing the product. Where the invention is a process, infringing acts include using the process and disposing of, offering to dispose of, using or importing a product made by the process.

Section 64(2) confines the statutory licence to the right to continue to do or to do "that act," namely the act which the person had done or had made effective and serious preparations to do. Thus, the right is limited to the particular act of infringement done or for which effective and serious preparation had been made. That conclusion can be illustrated by considering a person who had in good faith imported an infringing product. The section enables him to continue to import the product but not to sell it unless the importation amounted to an effective and serious preparation to sell it.

Section 64(l) relates to acts which constitute an infringement and not to any particular product or process. As I have stated the acts are those covered by a patent as set out in section 60. Thus, provided a person has carried out an infringing act before the priority date, he can continue to carry out that act even though the product or process may be different to some degree. This can be illustrated by considering a person who uses an infringing process. The fact that he alters that process after the priority date does not matter. The section states that the doing of that act, namely using an infringing process, shall not amount to an infringement."

The other case was Lubrizol Corporation v Esso Petroleum Co Ltd (No l) (1992) RPC 281. Mr Laddie QC as he then was considered my judgment in Helitune. He said:

"However, I think it is only right to say that I have some doubts, with great respect to Aldous LJ, as to whether Helitune is correct. The act which the alleged infringer is entitled to continue to conduct by virtue of section 64(2) is the act which he was committing before the priority date. It was not an infringement then. It was an act of commerce. It is that specific act of commerce which he is entitled to continue. I have difficulty in accepting that by, for example, manufacturing product A before the priority date, he was thereby given a right to manufacture any product after the priority date. In my view, section 64 is intended to safeguard the existing commercial activity of a person in the United Kingdom which is overtaken by the subsequent grant of a patent. It is not meant to be a charter allowing him to expand into other products and other processes."

It seems that the words used by me in Helitune have been read in a way not intended. Clearly the right given by Section 64 cannot be a right to manufacture any product nor a right to expand into other products. However I do not believe that identicality is required. I believe that the Judge was right in this case when he said:

"If the protected act has to be exactly the same (whatever that may mean) as the prior art then the protection given by the Section would be illusory. The Section is intended to give practical protection to enable a man to continue doing what in substance he was doing before."

The Judge in my view rightly held Exxon had not made "effective and serious preparations." The word 'effective' qualifies the word 'preparations'. It follows that there must be something more than preparations to do an infringing act. What more will depend upon the nature of the product and all the surrounding circumstances, but in all cases the preparations must be so advanced as to be about to result in the infringing act being done. That was not the position in this case. There had been manufacture in the USA and a program of technology transfer to the United Kingdom. Batch Zero had been shipped into the United Kingdom and samples had been supplied. Management had started to plan for manufacture, but interim site approval was delayed until March l977. First production was in June l977.

By the priority date manufacture was contemplated. But as the Judge said:

"By the priority date nothing effective had been done at all."

"A very preliminary stage with no decision yet made is not sufficient to fall within the words."

It follows that if the patent had been valid, Section 64 would not have provided a defence.

CONCLUSION

I am of the view that the patent is invalid and the appeal should be dismissed.

LORD JUSTICE BROOKE:

Because we are differing in a number of ways from the judge, although concurring in the eventual result, I am venturing to add a short judgment of my own in which I will express in my own words my conclusions on those aspects of the case I found most difficult to resolve. These relate to the measurement of Mn by GPC; the question whether the Patent in Suit is invalid for “obviousness”; and the question whether the patent should be revoked on the grounds of prior user. I will also say a little about the meaning of the words “effective and serious preparations” in Section 64 of the Patents Act 1977.

I have nothing I wish to add to those parts of the judgment of Aldous LJ which are concerned with the succination ratio and the challenge to the claim on “fair basis” grounds. In particular, I am completely satisfied that the judge was wrong, for the reasons given by Aldous LJ, to fasten on words (which could have been more carefully chosen) used to describe preferred methods of implementing the invention or examples illustrating the preferred embodiment of the invention, as the foundation for his conclusion that the Patent in Suit was bad for ambiguity in this respect, instead of construing Claim 1 itself, which makes it abundantly clear that unreacted PIB forms no part of the acylating agent.

I will start, therefore, with the issues relating to the measurement of Mn. Commercially produced polyisobutene (PIB) is made from a refinery stream which consists of a mixture of olefins, in which the main one is isobutene. It is a mixture of molecules of different molecular weights. Close to the centre of this case are two different methods of measuring the molecular weight (MW) of the polymer as a whole.

The first is called number average molecular weight (Mn). This is obtained by dividing the total weight of a sample of PIB by the number of molecules contained in it. A PIB containing a large number of short (and, therefore, lighter) molecules will have a low Mn when compared with one in which there are not so many short molecules present.

The other method is called weight average molecular weight (Mw). This method gives greater weighting to the longer molecules in the sample. This weighting is achieved by squaring each molecular weight that is present, multiplying the ensuing total by the number of molecules present in the sample, and then dividing by the total weight.

The ratio of Mw/Mn of a sample is referred to as its polydispersity, or dispersivity, and this is a measure of the spread of different molecular weight species in a given sample.

A third method, called Mv, measures viscosity molecular weight. It is very close to Mw. It only features in this case at all because it used to be the standard method in use, and there was evidence before the judge that about 30 years ago any reference to the average equivalent weight of a sample might be expected to be expressed in terms of its Mv. This method, which was simple, rapid and inexpensive, was established in the early 1930s and continued as one of the most widely-used techniques for measuring molecular weights of polymers in industrial laboratories up to the 1970s.

The traditional method of measuring Mn was Vapour Phase Osmometry (VPO). This was also the preferred method if the accuracy of the measurement was what was being aimed for. Two different techniques of obtaining VPO measurements feature in the case, and it is quite important to know which of these techniques, single-point or multi-point, was used on any given occasion. Multi-point VPO was regarded as much more accurate.

VPO cannot be used for measuring Mw, and for this purpose a different measuring method known as Gel Permeation Chromatography (GPC), which was first introduced in 1964, was often used. It is also possible to measure the Mn of a sample by this method, although the answer is likely to be not so accurate as that obtained by VPO. After a very short description of GPC, I will go on to discuss the different ways in which some people tried from time to time to adjust the GPC measurement of Mn to bring it closer to the result which would have been produced by recourse to VPO.

In GPC a solvent is pumped at high pressure through a chromatographic column packed with a microporous gel. A solution which contains the polymer being measured is introduced at one end of the column, and this solution then passes through the column. Smaller particles may enter the gel more easily than larger ones, so that they spend more time in the column. The largest molecules emerge first, and the smaller ones emerge more slowly.

At the other end of the column there is a detector (known as a differential refractive index (DRI) detector) which senses changes in refractive index at the outlet stream. Detector response is recorded by a suitable data collection device, either as a function of elution time or as a function of elution volume. From each of these measures it is possible to derive the concentrations of molecules of given molecular weight. Mn and Mw can then be obtained. The essence of the GPC technique, therefore, is to measure the concentration of polymer eluting through the column.

The GPC apparatus has to be calibrated by using samples which have been characterised by some other method, such as VPO. In 1980, polystyrene was the only polymer for which a series of commercial standards of different molecular weight and narrow molecular weight distribution was available for calibration purposes. The evidence showed that it was a long drawn out and expensive business to fractionate whole polymers of a different substance, such as PIB, and that this was rarely done in practice because of the high cost involved. Column fractionation methods for producing PIB fractions had been described in the literature, however, as long ago as the 1960s. If this method was adopted, the preferred technique was to use narrow fractions of PIB. Broader fractions could, however, also be used.

Because GPC is a relative technique, the accuracy of the results depends very much on the accuracy of the calibration. Provided that the standards are of sufficiently narrow distribution and are well characterised, a reliable calibration curve can be obtained when the molecular weight of each standard is plotted against elution time or elution volume. For polymers of a relatively high molecular weight, experience has shown that there is a linear relationship between the concentration of the polymer coming through the column, as detected by the DRI monitor at the far end, and its response.

For polymers of a low molecular weight, however, it was reasonably well known that this relationship was no longer a linear one. There would be under-readings at that end of the graph, which would lead to higher Mn values being recorded than the likely “true” values. Although the knowledge of this phenomenon was fairly widespread, what was less well known was what, if anything, had to be done about it. There was a small school of thought which favoured making an adjustment (known as a Refractive Index (RI) adjustment) although there was no common agreement as to how this adjustment was to be made. The evidence showed, however, that most people were content to use GPC values for Mn and Mw/Mn without making any adjustment at all.

As I have said, in addition to using narrow fractions of PIB for GPC calibration purposes, it is also possible to use broad fractions, ie polymers of relatively high polydispersity which have known Mw and/or Mn values (obtained by some other method of measurement) and which are structurally similar to the sample which is to be investigated.

In this method, once the first calibration curve is obtained, the results are compared with the known values of the material, and the trial calibration curves are then shifted, the values of Mn and Mw being then recalculated. This procedure is repeated until the calculated Mn values match the known Mn values as closely as possible. This process is known as curve-shifting.

There was a certain amount of evidence about curve-shifting at the trial, but Exxon did not call the expert on whose evidence they had originally relied, and Mr Thorley maintained, correctly in my judgment, that Professor Dawkins’s evidence on the topic did not go as far as Mr Young suggested that it did. Since it represented an empirical approach, by which it was sought to adjust the calibration curve to take into account the actual values obtained from a different method of measurement, there was no need to include the correction factors (such as RI adjustment) which were used by some in relation to narrow fractions.

The judge was given by the parties the thankless task of sifting through a number of disparate strands of evidence to ascertain what a person skilled in the art would have made of the references in the Patent in Suit in relation to Mn values to be obtained by GPC in 1980, and how meaningful it was to translate into a common language the different values of Mn which were being recorded for different purposes prior to 1980.

He heard from two witnesses who seem to have been in a comparatively small band of those who made adjustments to the Mn values they obtained by GPC to allow for the RI factor at low molecular weights.

The first of these witnesses, Dr Bergmann, used to work for Amoco, which was one of the largest PIB producers in the world. He had been involved in GPC work as an analytical chemist at his company’s works at Naperville, Illinois, from 1964 onwards, and he had been aware from the outset that there was a difficulty in calculating Mn values because of RI variations in PIB of low molecular weight. His method of combating this problem was to use a sliding scale correction factor to adjust the measured heights of PIB fractions in this category. His approach was entirely pragmatic. The judge was shown a 1963 Amoco bulletin which included Refractive Index among the 12 typical properties of different grades of Indopol PIBs (“Indopol” being a name Amoco used for some of its products) which ranged from a mean molecular weight of 300, measured by VPO, to one of 1900.

The correction factors used by Dr Bergmann were not used at either of Amoco’s two other major plants in the United States, which do not appear to have used GPC for calculating Mn, and they were eventually abandoned in 1991 when all Amoco’s plants installed GPC. There was then a need to use the same numbers for MW distribution for communications between the different plants. In 1966 Dr Bergmann had told one of the Defendants’ plants in the United States about the need to make an RI correction in order to obtain GPC results for Mn which accorded with results produced by VPO, but there was no evidence that his advice was ever followed. His own aim was to match the VPO result within 5%. He told the judge that if he had read the Patent in Suit at the date of publication, he would have applied an RI correction.

Mr Sims’s experience on this side of the Atlantic was rather similar. He had been employed in the works laboratory at BP’s Grangemouth works since 1968, and his job there was to set up analytical techniques for product quality control. In 1971 BP built its own GPC apparatus at Grangemouth. They used polystyrene standards as the calibrants, and alkenes at levels lower than 2100 Mn. He, too, had realised the dependency of the RI of PIB on its molecular weight. He would correct for it at low levels by measuring the RIs of various commercial grade PIBs of known Mn and determining their elution times and elution volumes. This exercise enabled him to calculate an appropriate correction, or scaling, factor, and he told the judge that the corrected values, which he used between 1971 and 1985, were closer by far to the VPO value.

BP Research, on the other hand, did not use an RI correction with their GPC machine, which they had bought from the manufacturers, Waters, and when Grangemouth bought its own Waters GPC machine in 1985 and had to communicate with BP Research it stopped using RI. Mr Sims told the judge that in general they were using GPC to examine the dispersion index of PIB, and they were not interested in obtaining absolute values of Mn, which could be obtained through the use of VPO.

There was no evidence that Exxon had ever used GPC to determine Mn values. They produced one letter, written in 1974 by Dr Schulz, who worked for their analytical and information division at Linden, New Jersey, to a representative of their Chemicals Specialities Technology Division, which drew attention to the phenomenon that the GPC RI detector had a tendency to underestimate very low molecular weight material below 1000 MW. Dr Schulz had suggested that in the case of the lab-synthesised polymers he had examined the error amounted to about 20%, and he said that appropriate corrections were needed. Ten years later, in 1985-6, Exxon started to use GPC to determine Mn and Mw values for PIB, and when they did so they used broader fractions of PIB for calibration purposes, together with curve-shifting. A memorandum written in January 1985 records that Dr Schulz was then of the opinion that because there were several potential sources of error in GPC calibration (including the RI problem) it would be better to use this different form of calibration based on known MW standards.

For Lubrizol’s experience the judge heard from Mr Baumanis, who had responsibility for PIB quality control. He told the judge that although PIB samples were nominally of the same grade, in his experience there was considerable variability between them as between different plants, and even between samples of the same grade coming from the same plant at different times. He said that the main reason for this was that commercial PIBs were made from C4 refinery streams which were variable in composition. If problems were being experienced by Lubrizol in processing a particular batch of PIB, a sample would be sent to him for analysis by GPC to see if there were problems with the MW distribution.

Mr Baumanis had never heard of any issue concerned with RI adjustment before 1984. In that year a computer program was written which took into account an RI correction, as did a replacement program written in 1988. In 1990, when this program was rewritten, Mr Baumanis took the opportunity to ask for the RI adjustment routine to be omitted. So far as he was concerned, it was only the uncorrected figures which mattered. He had never used the corrected figures, which only caused confusion.

He told the judge about the GPC measurements he had made over the years for a single reference sample of H1500 PIB which Lubrizol had bought from Amoco in January 1984. This sample had been analysed by GPC over 200 times between 1984 and 1992, and he said that the average Mn from these analyses was about 2300, which he always considered to be the value on which he could rely. On one occasion, in August 1988, this sample had been subjected to analysis by multi-point VPO, which had produced a Mn value of 2164, but Mr Baumanis had never relied on this value.

The judge was referred to two textbooks and a few learned articles in the course of the parties’ search for evidence as to how GPC was used to measure Mn and Mw values of PIB in the 1970s.

The two textbooks were Molar Mass Measurements in Polymer Science , by Dr Billingham of Sussex University, which was published in 1977, and Modern Size-Exclusion Liquid Chromatography , by Yau, Kirkland and Bly, of Wilmington, Delaware, published in 1979.

Dr Billingham described the usual method of plotting detector response h(V) against retention volume V. He used c(V) to represent the weight fraction of polymer eluted up to retention volume V, and observed that the relation between h(V) and c(V) was normally very simple, since the detector response was directly proportional to the weight concentration of polymer in the eluting solution. He added:

"However, many condensation polymers have significant contents of low molar mass components; for such samples it may be necessary to derive the relation between h(V) and c(V) experimentally - a very difficult and normally neglected procedure."

The book by Yau et al , described by witnesses as the GPC practitioner’s bible, was scarcely more forthcoming. It, too, drew attention to the problem at low molecular range, and said that molecular weight errors from this source might be significant for samples with low molecular weight fractions. It suggested an equation, known as the Gladstone-Dale equation, which might be used to make an appropriate RI correction, but it did not explain what data might be used in connection with this equation. The Gladstone-Dale equation is an approximation derived from an empirical observation made in 1850, based on experimental results.

It was against this unpromising background that Professor Bartle, who is a Professor in Chemistry at Leeds University, was instructed by Exxon’s solicitors in 1993 to perform experiments to measure by GPC the Mw and Mn of a number of samples of PIB which they provided to him. For the particular purposes of this litigation he had to try to produce absolute values of Mn. Claim 1 in the Patent in Suit referred to polyalkenes with an Mn value of between 1,300 and 5,000, and Exxon was concerned to find out whether certain samples of PIB did or did not fall within the bottom end of this range. Faced with this task, it is hardly surprising that Professor Bartle decided that he had to make an RI adjustment for molecules of PIB of low MW, since he would have known that at that level GPC was known to throw up values of Mn which are higher than the “true” value. He decided to use narrow fractions of PIB for calibration purposes, and he used Yau’s book, with which he was very familiar, to guide him on what to do. In paragraphs 23-27 of his statement he described the painstaking work he had to undertake in order to prepare the GPC apparatus for his experiments.

He found that neither of the English commercial sources he was accustomed to use provided a facility for RI correction in the GPC software they supplied, and since Yau did not provide him with direct guidance, he had to search through the literature to find the data to use for the RI and density of PIB oligomers. He eventually ran this to earth on a paper published by Rhein and Lawson in 1971 (which was not concerned with GPC, and was not mentioned in Yau), and it was with the help of this data, and with the use of the Gladstone-Dale equation, that Professor Bartle produced his first results incorporating an RI correction. He then applied this approach to data he derived from three other sources (including a 1972 article by Menin & Roux, who worked for Shell) and found that he was achieving consistent results.

By including an RI correction factor Professor Bartle found that his results compared very closely with the Mn values attributed to the samples he was using, although he was not told of these values when he was carrying out his experiments. For example, for Lubrizol PIB sample 875-19600 (which was the reference sample tested so many times by Mr Baumanis), his mean uncorrected value for Mn was 2345 (compared with Lubrizol’s mean value of 2335), and his mean corrected value 2061 (compared with Lubrizol’s mean value of 2054). Professor Bartle compared this corrected value of 2061 with the figure of 2060 quoted in a 1981 Amoco brochure for the “average MW by VPO” and with the single measurement of 2164 which Lubrizol had obtained using multi-point VPO in 1988. He was also pleased to see that other measurements he had obtained by GPC using his RI correction compared quite closely with the Mn values attributed by Amoco to those samples in their sales literature.

This virtuoso achievement by Professor Bartle demonstrated, perhaps more clearly than ever before, the difference which an RI correction will make when GPC is used for measuring the Mn of PIB of low molecular weight. But it does not answer the question which needs to be answered if the Patent in Suit is to be declared invalid for ambiguity.

Because of the special rules relating to pleading ambiguity in patent cases, which were explained by counsel at the hearing, the relevant issue was not very fully defined in the pleadings. Paragraph 3 of Exxon’s Amended Particulars of Objections contains a plea that the complete specification does not sufficiently and fairly describe the alleged invention and the method by which it is to be performed, and one of the particulars of this plea contains the following averments:

"(i) there are insufficient directions in the specification for properly determining the said number average molecular weight; and

(ii) by reason thereof a skilled person would be unable to tell whether such material fell within or outside the scope of the invention as claimed."

These averments are also relied on in support of Exxon’s contentions in Paragraph 4 that the scope of each claim was not sufficiently and clearly defined.

The judge held that this plea was made out because the skilled man would not know whether or not to use an RI correction. He did not refer at all to an alternative argument which Mr Young had urged on him, and since Mr Young wished to renew this argument before us we granted him leave to amend the Respondent’s Notice in order that he could formulate clearly the point he wished to advance. When he did so, the argument was advanced in these terms:

"(2) Insofar as the Appellants contend (contrary to their Notice of Appeal at paragraphs 16 and 17) that the skilled man, in seeking to apply the GPC method described in the patent in suit, would not be concerned with obtaining an accurate or precise result, then the scope of the claims of the patent is not sufficiently and clearly defined in that:

(a) the patent fails to teach whether such an inaccurate, or alternatively an accurate, result is desired;

(b) there is no teaching as to whether calibration using narrow fractions, or calibration using broad fractions and curve shifting, is to be used; these may give materially different answers in that narrow fractions without RI correction would give a result significantly higher than that obtained by VPO, whereas broad fractions with curve shifting, or narrow fractions with RI correction, would give a result in conformity with that obtained by VPO."

It was common ground that the only details vouchsafed in the Patent in Suit itself about how the GPC was to be performed related to the solvent to be used and to the fact that fractionated polymers of isobutene (preferably PIB) should be used as the calibration standard. After reviewing the evidence the judge said that it was by no means clear what a skilled man would do. If he had to choose between the one and the other he preferred the evidence of Dr Bergmann and Mr Sims, but he rested his judgment on his conclusion that some skilled men would use an RI correction and some would not. Since the patentee had chosen to give an instruction which in fact misled a significant proportion of the relevant addressees, then the judge did not think he had “sufficiently and fairly” described his invention.

Mr Thorley submitted that the judge had adopted the wrong approach. He should have made a specific finding as to the common general knowledge of a hypothetical man skilled in the art, and should not have been diverted because he had heard from two very untypical practitioners in Dr Bergmann and Mr Sims. If he had done so, he would have found that although there was common general knowledge that the RI of PIB varied with molecular weight at low molecular weights, there was no common knowledge about the extent of the variation, and hence the potential inaccuracy of the Mn value (when measured, perhaps, against the mean value of a number of readings taken by multi-point VPO). It was also common knowledge that RI correction was not routine practice in GPC: there was no approved or accepted way of measuring for it (whether with polyalkenes in general or PIB in particular), and there was no commercial software available for making an RI correction to a GPC reading. In other words, the common general knowledge was that people using GPC treated RI in a pragmatic way as being invariant with molecular weight. Mr Thorley relied in part on the evidence of Professor Dawkins, whose effect has been summarised in the judgment of Aldous LJ.

In my judgment this is the correct approach to this question. It is clear that the Patent in Suit was not calling for precise readings or absolute values. So long as the Mn was somewhere between 1,300 and 5,000, measured by GPC, this would be sufficient for the purposes of the patent. I am satisfied that in the absence of any specific instructions (such as an instruction to perform a RI correction or to do curve-shifting), the skilled man would have interpreted the teaching of the patent as instructing him to use the normal routine method of taking GPC readings, which was with narrow fractions (of PIB, if PIB was the polymer of choice). He would have known that there were different theories suggesting different adjustments that might be made to achieve greater accuracy - a need to adjust for an error called band broadening also featured in the evidence - but unless he had been instructed to use any of them he would have steered clear of them. If there had been any doubt as to whether a competing product infringed the patent, then because there was a 5% margin of error on either side of a reading, a number of GPC readings would have to be taken and a mean value adopted.

For these reasons I consider that the judge was wrong to hold the patent invalid for ambiguity in this respect. In particular, since he was concerned with a question of construction he was wrong to place any reliance on what Dr Bergmann told him he would have understood the patent to mean. Dr Bergmann and Mr Sims were unusual practitioners who were trying to achieve a measure of accuracy in GPC readings which the industry eventually decided it did not need or want. If the Patent in Suit had been seeking this measure of accuracy, it would have prescribed that Mn values should be ascertained by the use of multi-point VPO.

I turn now to the question whether “the invention, so far as claimed in any claim of the complete specification, is obvious and does not involve any inventive step having regard to what was known or used, before the priority date of the claim, in the United Kingdom” (Patents Act 1949, s 32(1)(f)). The judge held that the patent should be revoked on this account because of Example 32 in Le Suer. Exxon also rely in their cross-notice on Example 5 in Widmer. Since Widmer was first in time, I will consider it first.

In Widmer, which was filed in April 1969 and patented in April 1971, Example 5 in Table 1 is the only one out of 12 examples which teaches the value of the starting PIB. A footnote reference to this example reads:

"This is a [PIB] having an average of about two succinic anhydride substituents per [PIB] group prepared by reacting [PIB] having an average molecular weight of about 2000 with maleic acid in a molar ratio of about 1:2 in the presence of chlorine according to the general procedure described in [the Rense Patents]."

The acylating agent in this example was “[PIB]-substituted succinic anhydride” with an “average equivalent weight” of 550.

There were two rival methods of interpreting this information. Dr Brownawell, for Exxon, interpreted “average equivalent weight” as meaning Mn. He then proceeded, quite simply, to start with 2,000 grams of PIB and react them with 2 x 98 grams of maleic acid (water from the maleic acid splitting off in the reaction). Each mole of PIBSA product will then contain 2,000 grams of PIB and 2 x 98 grams of maleic acid (assuming a 100% reaction). The resulting 2,200 grams of PIBSA will contain four acid groups (two from each SA group), and the equivalent weight of the acylating agent will be 550.

Dr Gordon’s approach was altogether more complicated. He postulated that a worker would obtain a bottle of 2000 Mv from his PIB supplier and treat it as though it was 2000 Mn. He, too, would react 2,000 grams of PIB with 2 x 98 grams of maleic acid (with the same water loss). In fact, on the basis that Mv is about twice as large as Mn, 2,000 grams of PIB will then contain 2 moles of PIB.

Each mole of PIBSA product will contain 1,000 grams of PIB and 2 x 98 grams of maleic acid (a 1:1 ratio), or in other words about 1,100 grams of PIBSA, which contains two acid groups (from a single SA group). This will result in the same equivalent weight of the acylating agent, namely 550.

Dr Gordon reached this conclusion because of the widespread use of Mv values in the industry at that time. He said that the authors of the example were assuming a charge molar ratio of one mole of PIB to 2 of maleic anhydride because they wrongly believed that the Mn value of the PIB they were handling was 2,000. If, in truth, its Mn value was 1,000, the true charge molar ratio would be 1:1.

The judge expressed himself willing to accept Dr Gordon’s evidence that a skilled man might have followed the instruction by using Mv. This was one of the reasons why he held that Example 5 of Widmer did not anticipate the invention in the Patent in Suit.

Example 32 of Le Suer (which appeared first in February 1970 in a continuation-in-part of a 1966 patent application) prescribes a mixture of PIB having an “average molecular weight” of about 2100 with maleic anhydride in a mole ratio of PIB to anhydride of about 1:2. The parties repeated the same arguments as they had used for Widmer, but on this occasion the judge preferred the Exxon approach. He was influenced by the fact that it was accepted that other examples in Le Suer must refer to Mn (he mentioned Examples 1, 33, 35 and 36) and he considered it right to assume that Le Suer was using MW consistently throughout the document.

Mr Young deployed before us another reason for preferring the judge’s approach to Example 32 of Le Suer. He observed that Le Suer taught (at column 3, lines 49-50) that olefin polymers having average molecular weights of about 700-5000 were the preferred source of the substantially saturated hydrocarbon substituent to which reference had been made. Most of the examples of Claim 1 were based on PIB in the 900-1080 Mn range. In some the value of the starting PIB was not known, and Example 32 was the only example in which PIB closer to the middle of the range preferred by Le Suer was to be used. So far from standing out as an inexplicable exception, as Mr Thorley had maintained, Mr Young submitted that Example 32 was naturally included to demonstrate the use of a polymer of a rather higher Mn value than the others.

So far as Le Suer is concerned I can find no reason to fault the judge’s approach, buttressed as it was by Mr Young’s supplementary argument. I agree with the judge that it would be surprising if different meanings could be attributed to the expression “average molecular weight” within the same set of examples.

I also agree with Aldous LJ that Widmer Example 5 teaches the use of PIB with an Mn of about 2000 for the reasons he gives, but I will add a few words of my own because we are differing from the judge. I am very conscious that in this court we did not have the advantage the judge enjoyed of seeing and hearing Dr Gordon giving evidence, and in relation to Widmer the judge was clearly influenced by what Dr Gordon had told him. In Wilsher v Essex Area Health Authority [1988] 1 AC 1074 Lord Bridge said at p 1091G:

"Where expert witnesses are radically at issue about complex technical questions within their own field and are examined and cross-examined at length about their conflicting theories, I believe that the judge’s advantage in seeing and hearing them is scarcely less important than when he has to resolve some conflict of primary fact between lay witnesses in purely mundane matters."

Dr Gordon was 50 in 1970, and he told the judge that it was his experience that many industrial chemists, even those working directly with polymers, often failed to make the necessary distinction between Mn, Mv and Mw until well into the 1970s, and that frequently such chemists would use whatever “average molecular weight” they had been given for a particular material (which might well be an Mv) as if it were an Mn. He referred to two Esso patents from this period which referred to PIB in the context of a stoichiometric reaction but which were clearly based upon viscosity average molecular weights. His view was that without knowledge of the method used to determine the “average molecular weight” of a polymer, one could not know whether the value quoted in any document relating to the 1960s or early to mid 1970s was an Mn, Mv or Mw.

Dr Gordon’s approach was based on the thesis that the authors of Widmer Example 5 had made a mistake, and the judge was impressed by his reasons for holding this belief. However, as Aldous LJ points out, what matters is what the skilled man would have made of the teaching of the example, and I have no doubt he would have interpreted it as teaching him to use PIB with an Mn of 2,000, well within the range of Claim 1 in the Patent in Suit. It was common ground between Dr Brownawell and Dr Gordon that anyone reading this example would say to himself that he needed to know what Mn value the PIB has, because he needed to know how much PIB he had got to obtain to add to his maleic acid. Dr Brownawell gave unchallenged evidence that in all the brochures issued in the 1970s by manufacturers of dispersant grade PIB, the molecular weight which was specified for a product was measured in Mn. The skilled man must be assumed to have read the example carefully, if unimaginatively, and the teaching is that he should use a 1:2 charge ratio.

The accuracy of recorded measurements of Mn is important when one comes to consider the issues relating to Exxon’s product known as ECA 7474. I have considered with great care the evidence which Exxon deployed in order to prove that on the balance of probabilities the Mn of Batch Zero fell within the parameters of the Claim: indeed, I prepared my own draft of the detailed reasons why I concluded that they had succeeded in this task. Having now had an opportunity to consider in draft the judgment prepared by Aldous LJ, I can see no value in going over the same ground again. I am content to say that I agree with him, for the reasons he gives. This is not simply a case of being willing to give some weight to a single reading of Mn which may have been taken by single-point VPO. It is a question of examining carefully the totality of the evidence, as Aldous LJ has done, and I share his view that Exxon has proved its case in this regard.

I do wish, however, to give my own reasons for concluding that this use fell within Section 32(1)(e) of the 1949 Act, and was not excluded by the closing words of Section 32(2). Aldous LJ has set out in his judgment the judge’s description of the history of the development and early marketing of EC 7474, and I need not repeat it here, except to reiterate the judge’s finding that there was no secret that adpacks were under test, although up until the priority date the relationships between Exxon and Shell and BP respectively were confidential, as were the results of the tests they were conducting.

If he had been satisfied that the particular batch of H-300 used to make Batch Zero did have an Mn within the claim, the judge held that it would have constituted a use within the meaning of Section 32(1)(e) and (f) of the Patents Act 1949 which was not a secret use within the meaning of Section 32(2). If he had been wrong about the second part of this conclusion, he would have held that the use of the invention in the United Kingdom before the priority date was for the purpose of reasonable trial or experiment only. However, he derived from the judgments of this court in Wheatley’s Application [1985] RPC 91 clear indications that any commercial putting to use of the invention was enough to constitute a non-secret use. He concluded this passage of his judgment:

"Exxon was dealing with its would-be customers for future profit. Exxon commenced the marketing of 7474 when they gave the customers samples for customer trials. They were using 7474 to build up a market demand for it. A later patent should not stand in the way of the continuation of that marketing. After all a patentee is not obliged to start test programmes with his customers before filing his patent - and it was not part of the then patent system that a patentee should be able to find out from his customers if there is a market for his product before deciding whether or not to patent it."

In order to consider whether the judge was right, I have found it necessary to go back to the 1949 Act itself.

The scheme of that Act was to provide that the grant of a patent could be successfully opposed on evidence of prior user (Section 14(1)(d)), but that in this context no account should be taken of any secret use (Section 14(3)).

The rules relating to an application for the revocation of a patent, once granted, were rather different, as Lord Reid pointed out in Bristol-Myers Company (Johnson’s) Application [1975] RPC 127 at p 141, when he said:

"Section 32 sets out the grounds on which a patent can be revoked. Subsection (1)(e) and (f) refer to prior user. Subsection (2) provides that ... for the purposes of paragraph (e) or paragraph (f) ... ‘no account shall be taken of any secret use’. And then section (1)(l) makes it a ground for revocation that the invention was secretly used otherwise than as mentioned in subsection (2)."

The types of secret use, therefore, which might save a patent from revocation, are those set out in Section 32(2) which provides that:

"For the purpose of paragraph (l) of subsection (1) of this section, no account shall be taken of any use of the invention-

(a) for the purpose of reasonable trial or experiment only; or

(b) by a Government department or any person authorised by a Government department, in consequence of the applicant for the patent or any person from whom he derives title having communicated or disclosed the invention directly or indirectly to a Government department or person authorised as aforesaid; or

(c) by any other person, in consequence of the applicant for the patent or any person from whom he derives title having communicated or disclosed the invention, and without the consent of acquiescence of the applicant or of any person from whom he derives title ..."

It follows that in this case there are three questions to be answered:

(1) Was there a prior use?

(2) If there was a prior use, was it a secret use?

(3) If there was a secret use, was it a use for the purpose of reasonable trial or experiment only?

If the answer to Question (1) is “no”, there are no grounds for revocation under s 32(1)(e) or (f). If the answer is “yes”, and the answer to Question (2) is “yes”, the only grounds for revocation in this part of the case would fall under s 32(1)(l), and they would only be available if the answer to Question (3) was “no” (none of the other uses mentioned in s 32(2) being relevant in this case).

I should say at once that since the House of Lords in Bristol-Myers was divided on the meaning of the word “secret”, we are bound by the decision of this court in that case to give it a subjective meaning and to hold that it means conscious concealment of the use (see Wheatley’s Application [1985] RPC 91 per Dillon LJ at p 102).

It needs to be remembered, however, that Bristol-Myers, like Wheatley, was an opposition case, so that the result turned crucially on the question whether the prior use, if proved, was secret ( ibid, per Lord Reid at p 141). In the present case, provided that a “use” is proved, the nature of the use will only have to be considered if it is a secret use, and if it is, then the third question will have to be answered, an issue which could not have arisen in the two earlier cases.

I turn therefore to the first question. Counsel showed us three cases which gave examples of the approach of the English courts to the meaning of the word “use”. The first was Bristol-Myers itself. A patent application relating to the antibiotic ampicillin trihydrate was opposed on the ground that the opponents had already sold to the public a product derived from batches of ampicillin trihydrate, blended with other batches of ampicillin to an extent that was not de minimis . The House of Lords held unanimously that the sales constituted a prior use. Both Lord Morris of Borth-y-Gest (with whom Lord Reid agreed) at pp 144-148 and Lord Diplock (with whom Lord Kilbrandon agreed) at pp 155-160, although subsequently differing on the meaning of the word “secret”, were satisfied that commercial sales of a product to the public constituted a use of the product, and Lord Cross of Chelsea briefly agreed with them at p 162.

In Wheatley’s Application [1985] RPC 91 the use relied upon arose out of the events leading up to and including the agreement for sale to a purchaser of a small order for the product following a demonstration of it to him in confidence, in circumstances in which delivery did not take place until the priority date itself. All three members of the court held that there had been a use. Oliver LJ observed at p 100 that the 1949 Act was not to be read as if there should be a gloss on the word “use” requiring the use to be “public” or “in a public manner”, simply because prior to 1932 the courts had been constrained to inquire into the question of public use when construing Section 6 of the Statute of Monopolies. Lawton LJ was satisfied at p 100 that when he was demonstrating the pull-keys the inventor was using them, albeit secretly, in order to bring about a sale. Oliver LJ agreed with Lawton LJ. He added that there was nothing in Lord Cross’s speech in Bristol-Myers that could be relied on as authority for the proposition that an inventor cannot be said to “use” his invention unless he puts it out of his power to prevent a purchaser from finding out how it works and copying it. Dillon LJ also agreed, although in his short judgment he focused his attention on the agreement for sale as constituting the relevant use.

The final case we were shown was Vax Appliances Ltd v Hoover plc [1991] FSR 307. In that case the use relied on consisted of demonstrations of the cleaning head (the subject of the patent) which were performed by appointment at the premises of Hoover plc and Electrolux for the sole purposes of offering those companies licences to make a device according to the invention.

In holding that these demonstrations did not constitute “use” of the invention, Aldous J said at p 316 that in his view the word “used” in Section 32 related to commercial dealing with the invention, namely the product of the invention, but not to the right to use the monopoly right. He said at p 317:

"I have come to the conclusion that, where an inventor does not publish his invention so that it becomes known, then he will not have used his invention in the way the word “used” should be construed in Section 32, if all that he does is to demonstrate it for the purpose of obtaining finance or to seek licences."

In my judgment, there can be no doubt that the judge was right when he held that Exxon used this invention in this country when 20 gallons of Batch Zero were supplied to Shell and BP for the purpose of seeking a commercial sale of the product. He was also right in holding that these supplies did not constitute a secret use, because Exxon made no deliberate attempt to conceal the supply of these adpacks, even though their customers were to keep the results of their testing confidential to themselves and Exxon. It would have been different if Exxon had told them confidentially that they wished them to test the product and not to allow anybody else to know that they were doing so. If those had been the facts, the use would have been secret and for the purposes of reasonable trial or experiment only, and I agree with the judge that in that context it would not have mattered whether the trials or experiments were being conducted for Exxon’s purposes or for the customer’s purposes. The samples were not, however, being supplied secretly, so that that further question does not arise.

Finally, Mr Burkill submitted to us that the judge was wrong in holding that Exxon’s activities in relation to EC 7474 and Batch Zero in the United Kingdom before the priority date did not show that they were making in good faith effective and serious preparations to manufacture EC 7474 in this country, an act which would have constituted an infringement of the patent if it had been force at that time, and that his clients were therefore entitled to the rights available under Section 64(2) of the Patents Act 1977 (as originally enacted).

I have no doubt that Exxon was acting in good faith and that they were making serious preparations to do an act of the type described. To come within the words of the statute, however, the preparations in question must be both serious and effective. The primary meanings of the word “effective” are “having an effect” or “powerful in effect”. It will of course be a matter for a court to determine in any given case whether the serious preparations in question properly warrant the additional epithet “effective”. I reject Mr Burkill’s submission that it is sufficient to show that the serious preparations, if pursued to finality, will have the requisite effect. Their effectiveness must be measured immediately before the priority date, and in my judgment it would be an abuse of language to say of a project that was then in its preliminary planning stages that preparations to manufacture which were both serious and effective had already been made.

For the reasons given in this judgment, in addition to the reasons given by Aldous LJ, with which I agree, I would also dismiss this appeal.

LORD JUSTICE ROCH: I agree, the appeal is dismissed.

ORDER: Appeal dismissed; applications and issue of costs adjourned; sequential skeleton arguments to be provided by each side within ten days; the matter to be relisted before the court as soon as possible but not sooner than ten days; one fresh core bundle containing all necessary documents to be prepared; any suggested corrections to the draft judgment to be notified by close of business on Friday 1 May 1998.

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