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City Technology Ltd v. Alphasense Ltd [2000] EWHC Patents 56 (25th October, 2000)
CHANCERY DIVISION
PATENTS COURT
Before: MR. DAVID YOUNG Q.C.
Sitting as a Deputy Judge of the High Court
B E T W E E N
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CITY
TECHNOLOGY LIMITED
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Claimant
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-and-
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ALPHASENSE
LIMITED
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Defendant
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Mr. Iain
Purvis instructed by Messrs. Walker Morris, Leeds
appeared on behalf of the Claimant
Mr. Mark Platts-Mills Q.C. and Mr. Robert Onslow instructed by Messrs Hewitson Becke & Shaw, Cambridge appeared on behalf of the Defendant
Hearing dates: 10th, 11th, 12th and 13th October 2000
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J U D G M E
N T
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| This is the official judgment of the court and direct that no further note or transcript be made |
David Young Q.C.
DATED: 25 October 2000
1. The Claimants City Technology Limited are proprietors of UK Patent No. 2,094,005 which relates to electro-chemical gas sensors - in particular carbon monoxide gas sensors which were originally developed for the National Coal Board in the early 80s. In this action they claim that the Defendants gas sensors, in particular their carbon monoxide gas sensors infringe claims 1-3, 7-9 and 11-15 of their patent. The Defendants deny infringement and counterclaim for the revocation of the patent on the grounds that the alleged invention is obvious and does not involve an inventive step having regard to US Patent N. 3,755,125 (Shaw) and/or in the alternative common general knowledge.
U.K. Patent No. 2,094,005
2. The patent in suit claims a priority date of 3rd February 1991. Having pointed out that there is an increasing demand for small compact reliable and relatively inexpensive gas sensors for safety monitoring, pollution control, fire detection and flue gas analysis it states that a particular problem with such gas sensors is to ensure an adequate electrolyte connection between the electrodes regardless of the orientation of the instrument and the changes in volume of electrolyte with changes in ambient humidity.
1. An objective
of the invention is stated to be to provide a small compact sensor that
is simple in construction and has a high degree of integrity, reliability
and freedom from the proneness to leakage and the problems of adequate electrolyte
connection.
2. A typical
electrolyte used in such sensors is an acid such as 10-N sulphuric or 50%
phosphoric acid. It is therefore necessary to ensure that in the construction
of the cell, any materials including the electrodes in contact with such
strong acid electrolyte must be compatible. The electrodes as described
are constructed from porous PTFE support tape to which a catalyst/PTFE mixture
is bonded over a smaller circular area. The catalyst in question is finely
divided platinum black and it was common ground that such electrodes were
generally known from their use in fuel cells - indeed it was accepted that
the knowledge of such electrodes would be part of the common general knowledge
in the relevant art.
3. The
porous PTFE support for the electrode allows the gas being sensed to pass
through it but being hyphophobic is impervious to the acid electrolyte.
Thus the electrolyte can be conveniently contained between two electrodes
namely a sensing anode electrode where the carbon monoxide is electrochemically
oxidised and the counter electrode where a reduction process must take place
e.g. the reduction of oxygen by the hydrogen ions produced by the oxidization
of the carbon monoxide. Such electrodes are separated by separators made
from hydrophilic material such as glass fibre paper.
4. The
electro chemical principles as to how such gas sensors function are well
known. Optionally one may have a third reference electrode to control the
base line of the sensor output or the potential of the sensing electrode
(see e.g. Figures 3 and 5).
5. The
subject of the patent in suit is the particular structure of a gas sensor
in the sense of the arrangement of elements which per se are known but which
if arranged in the manner claimed provide a sensor fulfilling the stated
objective.
3. The relevant claims are as follows:
6. Claim 1- A compact and
leak-resistant electrochemical gas sensor in the form of an electro-chemical
cell assembly comprising
(iii) a planar hydrophilic non-conducting porous separator interposed between said first and second electrodes and in contact therewith and being in contact with
(iv) a hydrophilic non-conducting porous wick passing through said opening and extending into
(iv) an electrolyte chamber partially filled with an electrolyte contacting said wick
said assembly permitting access of a gas to be sensed to the sensing electrode and providing an electrolytic connection between the sensing and counter electrodes in all orientations of the assembly.
11. Claim 2 - A sensor according
to claim 1, wherein the wick passes through a hole or slit in the counter electrode.
12. Claim 9 - A sensor according
to anyone of claims 1 to 8 wherein the sensing electrode is an anode for the
detection and measurement of oxidisable gases.
13. Claim 11- A sensor according
to claim 9 wherein the counter electrode is an oxygen reduction cathode receiving
its oxygen from ambient air.
14. Claim 13 - A sensor according
to claim 11 or 12, wherein one or both of the counter electrode and reference
electrode comprises a hydrophobic porous support which extends to the surface
of the assembly and permits oxygen to diffuse to the electrode.
15. 4.
The novelty of the cell assembly claimed in claims 1 and 2 lies in arranging
a wick to pass through an opening (hole or slit) in the counter electrode
and its support and thereby allow electrolyte to be drawn up from a reservoir
or chamber and by capillary action to continuously wet a hydrophilic separator
which is in contact with both electrodes. It is stated that such an arrangement
provides a compact and leak-resistant sensor that allows electrolytic contact
between the electrodes in all orientations.
16. 5.
At page 2 line 21 to page 3 line 3 it is stated that the wick may be integral
with the separator and that the wick arrangement ensures an adequate supply
of electrolyte to the space between the electrodes independently of any volume
change or attitude of the cell and also permits close spacing of the electrodes
with consequent reduction in size of the sensor.
17. 6.
Whilst there was evidence as to the meaning of the word wick, such evidence
was neither admissible or helpful and I propose to give the word its ordinary
meaning namely as a bundle of fibres (or woven material) which allows liquid
to be drawn up through it - such as a wick for a lamp.
18. There
was also a dispute as to the meaning of claim 13. At page 5 lines 17 to 21
the counter electrode is stated to be an oxygen reduction electrode receiving
its oxygen supply from the ambient air "by radial diffusion inwardly through
the porous PTFE tape from the perimeter of the tape".
19. 7.
Again at page 8 line 27 to page 9 line 6 it is stated that ingress of oxygen
to the perimeter of the counter electrode occurs via the clearance between
the current collectors 6 and 7 and the slots in the O-ring retaining ring
12. To ensure good distribution around the perimeter a narrow, shallow annular
channel may be cut in the bottom plate 17 with an outside diameter the same
as the inside diameter of 13. From the perimeter the oxygen diffuses radially
inwardly along the porous PTFE support of the counter electrode to the counter
electrode catalyst, the PTFE tape retaining sufficient diffusibility for this
purpose even when compressed by the O-ring 12
20. 8.
Reading these passages which provide the only basis for claim 13, I have
no doubt that applying a purposive construction to claim 13 it requires
the hydrophobic porous support to extend to the surface of the assembly
to permit oxygen to diffuse to the electrode from the outside surface
or perimeter of the support radially inwards as at least a route for the
required oxygen at the counter electrode. That is the whole purpose of
extending the support to the surface of the assembly.
Infringement
21. 9.
A product description of the Defendants carbon monoxide sensor is to be
found in Core Bundle Part C TAB 7 and various photographs of its parts
in Part F.
22. The
exploded drawing below illustrates the sensor which has three electrodes,
namely sensing electrode (8), reference electrode (13) and counter electrode
(15) - all three electrodes consist of a platinum black PTFE mixture supported
on a porous PTFE tape. The counter electrode has an opening in its centre
facing downwards i.e. in the opposite direction to the sensing electrode.
Sandwiched between the electrodes are various separators (9), (11), (12)
and (14) which when assembled are all in contact with each other to allow
electrolyte to be held between them. Below counter electrode (15) is a
separator (16) which is in contact with a wick (9) threaded through a
slot in the reservoir cup top. The wick (19) which has two legs extending
into the reservoir co-operates with the centre of separator (16) to form
a wick arrangement which when the sensor is assembled passes through the
opening in the counter electrode (15) and forms an electrolytic connection
with the electrolyte held by the separators sandwiched between the electrodes.
23. When
fully assembled plastic top cap (2) and the plastic body (22) are welded
together so that ambient air can only enter the system from the top downwards
or the bottom upwards.
10. (a) Infringement of claims 1 and 2
24. The
only issue is whether feature (iv) of claim 1 is taken which requires
the hydrophilic non conducting wick to pass through the opening in the
counter electrode support (or the counter electrode itself).
25. The
Defendants contend that the wick is to be construed as a unitary item
which extends from the reservoir through such opening and does not include
the wick (19) and a separator (16).
26. It
is contended that separator as used in the patent is distinct from the
wick having a different function. The wick supplies the electrolyte to
the separators which maintain the electrolyte in contact with the electrodes
and also separate them to create the necessary electrolytic path. Reliance
is placed on claim 6 where the wick is required to pass through an opening
of a separator. The Claimants rely on the reference that the wick and
separator may be integral to indicate that the roles of the wick and separator
are not distinct and that both are made from the same or similar hydrophilic
porous material. Whether therefore a separator (so called) is a wick or
part of a wick will depend on its function i.e. whether it is supplying
electrolyte to the separator sandwich.
27. 11.
Section 125(3) requires the Protocol on Interpretation of Article 69 of
the EPC to be applied. It states:
"Article 69 should not be interpreted in the sense that the extent of the protection conferred by a European Patent is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Neither should it be interpreted in the sense that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and drawings by a person skilled in the art, the patentee has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties".
28. The
Protocol outlaws what can be termed strict literal and also liberal interpretation
using the claims as a guideline. The correct approach is to achieve a position
between those extremes "which combines a fair protection for the patentee
with a reasonable degree of certainty for third parties".
12. In Improver Corporation v. Remington Consumer Products Limited [1990] FSR 181 Hoffmann J. suggested at page 189 that the court when applying the Protocol should ask these questions:
"(1) Does the variant have a material effect upon the way the invention works?
If yes, the variant is outside the claim. If no-
(2) Would this (i.e. that the variant had no material effect) have been obvious at the date of the publication of the patent to a reader skilled in the art. If no, the variant is outside the claim. If yes -
(3) Would the reader skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention. If yes, the variant is outside the claim.
On the other hand, a negative answer to the last question would lead to the conclusion that the patentee was intending the word or phrase to have not a literal but a figurative meaning (the figure being a form of synecdoche or metonymy) denoting a class of things which included the variant and the literal meaning, the latter meaning, the latter being perhaps the most perfect, best-known or striking example of the class".
29. Hoffman
J went on to explain that the first two questions involved considerations
of fact, but the last was a question of construction.
30. 13.
Assuming in the Defendants favour that on a literal construction of the
word wick there must be a unitary tape a bundle of fibres which extends
from the reservoir through the opening in the support, I have no doubt
that both the requirements of the Improver questions and the Protocol
to Article 69 are satisfied. Thus assuming the variant in this case is
the combined use of a single wick (19) and the centre of the separator
(16) which allows the electrolyte to be transported from the reservoir
to the separators sandwiched between the electrodes, such arrangement
clearly has no material effect upon the way the invention works as it
will allow electrolyte to be maintained within the separators at all orientations
of the sensor (Question 1 of Improver). As to whether such a fact have
been obvious at the date of publication of a patent to the reader skilled
in the art. I have no doubt that the close contact of the hydrophilic
wick (19) with the hydrophilic separator (16) when assembled will allow
electrolyte to be so transported to the separators just as a single wick
would do so as described in the patent (Question 2 of Improver). Finally
as to whether from the language of the claim it was to be understood that
the patentee intended that it was an essential requirement that the wick
should be a unitary piece extending from the reserving through the support
opening. I consider there is no good reason why the claim should be so
narrowly construed particularly in the light of the teaching that the
wick may be made integral with the separator. (Question 3) The essence
of the invention seems to be how the electrolyte is conveyed to the separators
sandwiched between the electrodes, namely by means of a hydrophilic wick
arrangement which transports the electrolyte from the reservoir to the
separators through an opening in the counter electrode support. This seems
to me precisely how the Defendants wick (19) and separator (16) function.
Applying the Protocol, such an interpretation combines a fair protection
for the patentee with a reasonable degree of certainty for third parties
- a narrowed interpretation would be unfair to the patentee.
14. (b) Infringement of claim 13
31. Initially
there was a dispute as to precisely what reduction reactions take place
at the counter electrode. However it is now common ground that the principal
reduction reaction is that of oxygen and the Defendants accept that there
are in fact two ways the oxygen will arrive at the counter electrode.
Firstly the oxygen that is dissolved in the acid electrolyte will provide
sufficient oxygen to monitor levels of up to 100 to 200 ppm of carbon
monoxide. However the Defendants sensor is guaranteed to monitor up to
1000 ppm of carbon monoxide.
32. 15.
The second way it is accepted by both parties oxygen will reach the counter
electrode is by a route that was referred to as inside the O ring route;
namely some of the air being monitored will diffuse through an outer annulus
portion of the sensing electrode support (8) it will flow past the outer
periphery of separator (9) and diffuse through PTFE washer (10), then
it will flow past the outer pheriphey of separator (12), reference electrode
(13) and separator (14) to finally diffuse through the support of counter
electrode (15) where it will contact the counter electrode itself.
33. This
second route was not appreciated by the Defendants until the Claimants
expert witness (Dr. Wykes) had referred to the same and calculated that
such a route would indeed provide sufficient oxygen to monitor carbon
monoxide levels up to 1000 ppm.
34. Neither
of such routes would fall within claim 13 which (on my construction) requires
oxygen to be transported radially inwardly from the surface of the assembly
to the counter electrode via its hydrophobic porous support.
35. 16.
As regards the claimed route, whilst it is accepted by the Defendants
that it is one which is theoretically possible, they contend that given
the existence of the first two routes it is highly improbable that significant
levels of oxygen will diffuse radially inwardly given that the oxygen
will have to pass through the porous support which has been compressed
by the O ring. The evidence was that as assembled the downward pressure
exerted via the O ring is in the region of 200 and 400 psi. Precisely
what effect such pressure will have on the porous support will depend
on the nature of the support prior to being compressed. Dr. Safell the
Technical Director of the Defendants states that the porous supports in
the Defendants' sensor are made from Mupor hydrophobic porous tapes having
similar morphology and structure to Goretex and Zitex. However the precise
porosity of the tape before it is compressed is not known and the Claimants
chose not to carry out what were described by Prof. Williams (the Defendants
expert) as a relatively simple experiment to determine whether indeed
oxygen does indeed diffuse radially from the surface of the assembly to
the counter electrode via its support. That such an experiment could have
been conducted is clear from similar earlier experiments conducted by
Chan Henry which are referred to in a report dated July 1983 which forms
part of a thesis he submitted to the City University - see Table 3.1 of
CH Vol part 14 pp 15 & 16. Dr. Wykes in part D of his Supplemental
Report contends that even applying pressure some twelve times greater
than that applied to the Defendants sensor, oxygen will still diffuse
through a porous PTFE tape. Prof. Williams in answer to this relied on
micrographs of cross-sections of the electrode support under pressures
that he understood to be closely similar to that under the O ring seal
in the Defendants device. The micrographs illustrate that the pore structure
appears to be substantially closed up. However as is clear from the micrographs
themselves the pressure applied to such tapes was of the order of 7000
psi and therefore as was accepted by Prof Williams could not be relied
upon. Prof Williams also criticised Dr. Wykes approach in applying the
wrong diffusion coefficient on the grounds that as the pores became smaller
a different diffusion known as Knudsen diffusion occurs. What one is left
with therefore is pure speculation as to how much, if any, oxygen will
diffuse radially inwardly from the perimeter of the support of the counterelectrode.
On the basis that sufficient amounts of oxygen can reach the counter electrode
by other routes which provide less resistance to oxygen diffusion - in
particular via the inside of the O ring which seems the most likely route
for the oxygen - I consider that the Claimants have not established claim
13 is infringed by the Defendants device. The Claimants did not contend
that the inside of the O ring route was an immaterial variant to the radial
route via the outer periphery of the support.
Validity
36. 17.
The patent in suit is addressed to persons interested in the design and
manufacture of gas sensors. Such a person (or group of persons) would
have knowledge in the basic principles of electrochemistry and in general
the operation of electrochemical cells.
37. 18.
Professor Williams (the Defendants Expert) who is Professor of Chemistry
at University College London and is clearly someone of considerable distinction
in the field of electrochemistry had no or little knowledge about electrochemical
cells used as gas sensors prior to being retained by the Defendants. He
had never constructed or used electrochemical gas sensors. Therefore his
knowledge was gained solely from literature searches of Chemical Abstracts
and patent literature which he conducted for the purposes of this case.
He was not aware of electrochemical gas sensors on the market as of the
priority date or indeed who were the main players in terms of their production.
38. 19.
Dr. Wykes (the Claimants Expert) worked for the Mining Research and Development
Establishment of the National Coal Board from 1974 to 1983 at the time
they decided to commission the Claimants to produce the electrochemical
gas sensor which became the subject of the patent in suit. Dr. Wykes describes
himself as at that time as having knowledge of electrochemical sensing
of gasses somewhere between that of the informed user and that of a cell
designer. In Appendix A to his Report Dr. Wykes states that public sources
of information whilst good on basic electrochemistry and on engineering
applications were much poorer on industrial sensors - sensor manufacturers
literature was generally unhelpful and patents were often a better source
of constructional details - however how well any particular cell would
perform could only be reliably obtained by direct testing.
Common General Knowledge
39. 20. Whilst there was
some debate as to what constituted the relevant common general knowledge which
the skilled person would possess, in the end there was a considerable measure
of agreement. Mr. Purvis for the Claimants referred me to the recent case (as
yet unreported) of Davina Wheatley v. Drillsafe Ltd 5th July 2000
(C.A) where Aldous L.J. (para 42) recites a passage from his earlier judgment
in Beloit Technologies Inc. v. Valmet Paper Machinery Inc. (1977)
RPC 489 at 494. In particular Mr. Purvis relied upon the following passage as
being apposite to this case, namely:
"It follows that evidence that a fact is known or even well known to a witness does not establish that that fact forms part of the common general knowledge. Neither does it follow that it will form part of the common general knowledge if it is recorded in a document …."
40. Citing
the well known indeed "common general knowledge" passage of Luxmoore J.
from British Acoustics Film 53 RPC 221 at 250
41. … "A piece of particular
knowledge as disclosed in a scientific paper does not become common general
knowledge merely because it is widely read and still less because it is widely
circulated. Such a piece of knowledge only becomes general knowledge when
it is generally known and accepted without question by the bulk of those who
are engaged in the particular art; in other words when it becomes part of
their common stock of knowledge relating to the art."
42. 21.
Aldous L.J. expressed some doubt as to whether "accepted without question"
set too high a test and substituted for it the words "generally regarded
as a good basis for further action". The following matters were accepted
by the parties to be part of the common general knowledge, namely:
(1) that electrochemical cells may be constructed having planar parallel electrodes
(2) that by 1981 platinum black PTFE electrodes supported on a porous PTFE support had been accepted in fuel cell technology and would be considered a suitable electrode for a gas sensor
(3) hydrophilic separators between electrodes were an accepted way of maintaining the electrolyte between the electrodes
(4) that some form of wick could be used to supply electrolyte to separators between the electrodes.
43. 22.
The Defendants also contended that the use of electrodes with holes passing
through them was part of the common general knowledge. This was disputed
by the Claimants.
44. In
support of their contention, reliance was placed on Prof Williams' First
Report (para 6.2.4.- conclusion 3) - "the use of electrodes with holes
passing through them was generally known".
45. This
statement was supported by reference to the following matters
(i) making an electrode in the form of a ring
(ii) production on an industrial scale of chlorine e.g. the Billiter diaphragm cell which had a flat cathode electrode with holes in it filled with asbestos fibre immersed in brine which percolates through the holes - (Bundle E2/19, Fig. 5-7).
(iii) a polyelectrolyte cell for the electrolysis of organic reagents as illustrated in a book edited by N.L. Weinberg called Techniques of Chemistry (see Bundle E2 17 Fig 2.34) holes cut in a cylindrical anode allow electrolyte to pass from the central reservoir radially therethrough to be absorbed by the polyelectrolyte which because of its ion exchange properties allows current to flow. Such cells have been used in the hydrodimerization of acrylonitrile to adiponitrile. An industrial version of this cell is illustrated in Industrial Electrochemistry by D. Pletcher (1982) Fig 6.4 (See Bundle E2/18).
47. 23.
Such industrial applications all relate to the synthesis of chemicals
by some form of electrolytical method which are far removed from the sort
of compact gas sensor cells the subject of the patent. In addition the
Defendants (Prof. Williams) relies on the following patents to illustrate
that holes in electrodes were well known:
(iv) US No. 3,132,972 (Ludwig) (1964) Fig. 5: which relates to an energy conversion cell which may be operated to generate electricity or as a fuel cell. Pairs of annular electrodes are separated by a porous non conducting bed which retains sufficient electrolyte to provide the necessary conducting paths between the electrodes. There does not appear to be any reservoir for electrolyte.
48. There was no evidence
that such a cell was ever put into practice.
(v) US 3,239,444 (Heldenbrand) (1966): relates to a polargraphic oxygen sensing cell in which the counter electrode is a stack of consumable anode discs having a central hole which is immersed in electrolyte Again there was no evidence such a cell has ever been put into practice.
(vi) UK 1200595 (Bergman) (1970) Fig 6 illustrates as one construction an electrical cell having a cylindrical silver anode. It does not relate to a planar electrode with a hole or slot in it.
(viii) US 3,767,552 (Lauer) (1973) relates to an electrochemical gas sensor having a consumable porous lead anode in the shape of a cylindrical block having a central hole which is filled with electrolyte. There is no evidence that such a sensor has ever been put into practice.
49. 24.
Apart from the Bergman patent there is not only no evidence that any of
the cell devices have ever been put into practice but there is no evidence
that any of such patents would be familiar to the notional skilled team
of addressees. Whilst there was some evidence that the Bergman cell would
have been familiar to persons such as Dr. Wykes (See Wykes First Report
para 46) such cells were not constructed using a planar electrode with
an opening in it.
50. None
of such prior art has been pleaded as rendering the patent in suit obvious
and apart possibly from the Bergman and Belliter cells none of the prior
art referred to by Prof. Williams constitutes common general knowledge.
51. 25.
It follows that when designing an electrochemical gas sensor cell at the
priority date of the patent in suit (3rd February 1981) the assumed notional
skilled person or persons would have no particular reason to consider
constructing a cell having an opening in the counter electrode support
and/or the counter electrode itself yet alone to provide such an opening
to allow a wick to pass through the opening in order to transport electrolyte
from a reservoir to the hydrophilic separator located between the electrodes.
52. 26.
I consider the Defendants approach based on common general knowledge is
one which the courts have consistently condemned. Starting with the well
known fuel cell electrodes and hydrophilic separators sandwiched between
them it is contended that there is only one way to construct the cell
if it is to be compact, namely to locate the reservoir underneath the
counter electrode and provide a wick which can only be located either
to pass around the counter electrode and its support or through an opening
in it.
53. As
can be seen from the prior art referred to, electrochemical cells may
have electrodes which are cylindrical (either hollow or solid with a hole
in the centre) or planar - hence a sensor could be constructed using electrodes
having any one of a number of configurations and the question of whether
or where a reservoir for the electrolyte will be required will depend
on the choice of configuration of the electrode. Likewise the question
of whether or where a wick will be required will depend on (1) the electrode
configuration (2) the requirement and location of the reservoir.
54. 27.
Mr. Platts-Mills Q.C. for the Defendants contended that the claimed integers
the subject of claim 1 of the patent in suit are a mere collocation of
integers each integer being part of a cell designer's common general knowledge.
I do not accept the claimed integers are a mere collocation as each of
the integers interact with each other to provide the claimed cell.
55. To
assume one is going to design a gas sensor cell using planar platinum
black/PTFE electrodes on a porous PTFE support and end up with the requirement
of separators, a reservoir and a wick all of which items are individually
well known items and to so arrange them to provide an opening in the counter
electrode and/or its support through which the wick will pass is the hindsight
approach which depends on first knowing that those are the required items.
US 3,755,125 (Shaw)
56. 28.
The Defendants contend that claims 1 and 2 are obvious in the light of
Shaw.
57. As
best seen from Figs 2 and 3 hereunder Shaw relates to an electrochemical
gas sensor which is constructed by forming a stack of hydrophilic non-conducting
disc-like separators 42 and 44 which are sandwiched between two wire mesh
electrodes 41 and 46. Located below this assembly is a reservoir 11 which
is filled with an absorbent sponge like material 39 which retains the
electrolyte and prevents it sloshing about. Integral with the four lower
disc separators 42 are wicks 43 which are spaced circumferentially at
90o and depend downwardly so that they are in contact with
the absorbent filler 39 - the four wicks are accommodated in four notches
in the body which retains the assembled unit.
FIG 3
FIG 4
58. 29.
It is common ground that the novelty of the construction of the sensor
the subject of claim 1 of the patent in suit resides in two features namely:
(1) that the counter electrode comprises a hydrophobic support having an opening therein and
(2) that a wick passes through said opening.
59. 30.
Thus applying the four steps advocated by Oliver LJ in Windsurfing
Inc. v Tabur Marine (Great Britain) Ltd (1985) RPC 59 at 73 the
question is whether when viewed without any knowledge of the alleged invention
those differences over Shaw constitute steps which would have been obvious
to the skilled man or whether they require any degree of invention.
60. I
bear in mind in particular the warning against ex post facto analysis
of Lord Russell in Non-Drip Measure Company Ltd v. Strangers Ltd
60 RPC 135 at 142. Quoting the well known words of Moulton LJ from British
Westinghouse Co. v. Braulik he stated that "nothing is easier
than to say, after the event, that the thing was obvious and involved
no invention".
61. 31.
The Defendants case was that by taking a series of simple modifications
to the Shaw device one could arrive at the device the subject of claims
1 and 2.
62. The
first step is to substitute the wire mesh electrodes with the fuel cell
type electrodes comprising a PTFE mixture and catalyst on a PTFE support
particularly at the sensing electrode due to their higher activity and
efficiency. Such electrodes were part of the skilled persons common general
knowledge and Dr. Wykes accepts an improvement to the Shaw device would
be to use such an electrode as the sensing electrode (See para 70 of Dr.
Wykes First Report).
63. However
it was clear from the cross-examination of Prof. Williams (Day 3/288)
that the substitution of the wire mesh counter electrode 41 by a platinum/PTFE
fuel cell type electrode is not a simple matter. The counter electrode
does not rest on the reservoir itself but is merely supported at its periphery
on a shoulder in the body of the device. For reasons not explained by
Shaw there is a substantial gap between the counter electrode and the
reservoir and whilst a wire mesh electrode of the type described by Shaw
is structurally self supporting, a platinum/PTFE electrode on a PTFE porous
tape support would not be. Thus to accommodate such an electrode the device
would require a shelf underneath it to give it support. In addition because
the PTFE support is non conducting, gold conductor ring 40 would only
function if the electrode was inverted and this would lead to problems
of how to maintain electrolyte at its face with a separator underneath
for electrode. Alternatively the gold conductor ring could be placed on
top of the PTFE/platinum electrode which would mean altering the location
of the electrical wire 38.
64. 32.
Having made such substitution of PTFE electrodes for wire mesh electrodes
it was Prof. Williams evidence that he had no reason to believe it would
not work (Day 3/298, 300) so that there would appear to be no reason to
consider further modifications to the device.
65. In particular
Prof. Williams accepted there was good reason to have four wicks spaced
around the periphery to allow a uniform supply of electrolyte from all sides
of the sensor. Prof. Williams would not have used a single tab at one edge
(See Day 3/30312-30426),
66. 33.
As regards the idea of placing a wick through an opening in the counter
electrode Prof. Williams' evidence under cross examination (Day 3/3059-20)
was as follows:
67. Q. …
the skilled man … is highly unlikely to think (without ingenuity)
of abandoning Shaw's carefully provided slots and his carefully
provided four wicks round the side in favour of something which,
on your own evidence, he has never seen before in the field of gas
sensors, namely a wick cut through the middle of the counter electrode.
68. A. If
you started rigidly from Shaw then you are correct.
69. In
re-examination (Day 3/3548) in response to what he meant by
"rigidly" Prof. Williams evidence was:
70. A. If
you did not allow yourself any flexibility in altering anything
in the design of Shaw other than the use of the PTFE electrodes.
So you were not allowed to alter the wicks. That is my interpretation
of the question.
72. A. Then
you might have punched a hole through the electrode.
74. A. Then
you had only one wick rather than four and it might be easier to
make. That would be my guess. You might not necessarily consider
in Shaw's design, with his electrode on the side and all that kind
of stuff, that that was worth doing, but you can see that if you
punched a hole through the middle of the electrode you might ask
yourself why Shaw had this wacking great big reservoir on the side.
In fact you would ask yourself that anyway - why he had such a huge
reservoir on the side.
Q. Sorry?
75. A.
I am being confusing but Shaw shows this rather large reservoir
on the side of the sensor coming down underneath the sensor. You
might ask yourself why do you have this thing sticking out on the
side. If you cut that off you have a design like the patent in suit.
If you want to ask how would you get from Shaw to the patent in
suit, then what you would have to do is say "Well, why on earth
do we need this bulge sticking out the side. Let's chop that off.
I have got a reservoir underneath and why should I be bothered with
four wicks. Let's just have one". But you could equally well
have four".
76. 34.
This evidence is precisely the sort of ex post facto analysis referred
to by Lord Russell and Moulton L.J. The idea of having a wick passing
through an opening in the counter electrode is an idea which is novel
per se. Prior to the patent in suit, wicking arrangements in electrochemical
cells in so far as cells had such arrangements were via the side of the
electrodes i.e. through the natural gap caused by the electrode separation
- see Dr. Wykes First Report para 43 and the Hersch cell. Dr. Wykes' evidence
(First Report para 70) was that even if he thought of reducing the Shaw
wicking arrangement to one wick it would not have occurred to him to cut
a hole in the electrode or its support unless one had appreciated the
benefits of doing so.
77. 35.
One such benefit of a wicking arrangement in which the electrolyte passes
through an opening in the support of the counter electrode is that the
electrolyte footprint is confined to the centre of the cell due to the
hydrophobic nature of the support - thus proneness to leakage of electrolyte
is improved - one of the principal objectives of the patent in suit.
78. 36.
Having considered the evidence, I consider the concept of a wick arrangement
through an opening in a hydrophobic support for the counter electrode
is a clever solution to providing a compact leak-resistant sensor and
is not obvious in view of Shaw. Hence I conclude claims 1 and all claims
appendant thereto are valid.
37. Conclusions
1. I find the Defendants device infringes claims 1 and 2, but not claim 13. Although no separate argument was addressed on the other subsidiary claims, it seems to me that from my findings at least claims 3, 7-11 and 14 are also infringed.
2. I find claim 1 and all appendant claims to be valid.
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