England and Wales High Court (Chancery Division) Decisions

IN THE HIGH COURT OF JUSTICE
CHANCERY DIVISION
PATENTS COURT

		Royal Courts of Justice Strand. London. WC2A 2LL
		21 December 2004

Mr Justice Pumfrey :

Introduction

1. This is an action for infringement of European Patent (UK) 0 039 596. It is the second action between the parties, the first having been decided by the Court of Appeal (Aldous, Tuckey and Rix LJJ) on 10 May 2002 ([2002] EWCA Civ 612) in favour of the claimant.
2. The patent in suit is entitled "Pumping Apparatus for delivering liquid at high pressure" and is particularly concerned with pumps for delivering solvent under pressure to high pressure liquid chromatography (HPLC) columns. HPLC is an analytical technique widely used in chemical research and in process and product quality control. In very broad outline, a separation column is packed with a material such as alumina or silica. A small quantity of a liquid sample (or a solution of the sample) to be analysed is introduced in the top of the column. A continuous flow of solvent under high pressure then flows down the column, and the different components of the material to be analysed travel at different speeds depending upon the strength of their adsorption on the surface of the packing material, and emerge (elute) at different times characteristic of the component. Each component is detected at the foot of the column by a suitable detector, commonly an infra-red detector. Obviously, if repeatable results are to be obtained from such an apparatus, the solvent flow must be steady and controllable. The pressures are very substantial.
3. The parties to this action are bound by the judgment of the Court of Appeal in the first action as to the interpretation of the patent and as to its validity. For reasons which I shall enlarge upon when I consider the details of the issue of infringement, this simple proposition gives rise to a number of difficulties. But first I must describe the invention of the Patent in Suit.

The Patent in suit

4. As I have indicated, the patent in suit is entitled "pumping apparatus for delivering liquid at high pressure". The specification begins with a description of the invention which introduces the problem which the invention is intended to solve. Having described the requirements for pumps for use in chromatographic analysis, it makes it clear (column 1 lines 25 to 39) that the first requirement for a pump, is that the flow rate, once determined, should be kept as constant as possible. It is in the nature of a single cylinder pump that it cannot provide a constant flow as its output without additional means, and at column 1 line 40 to column 2 line 14 dual-piston pumps are described by reference to two patent specifications. The second of the specifications is acknowledged to disclose a dual-piston arrangement in which the second, or accumulator, piston is filled during the delivery stroke of the primary piston. The accumulator piston and the primary piston are necessarily 1800 out of phase, and a non-return valve between accumulator piston and primary piston enables the flow to be maintained while the primary piston is drawing fluid in. Such an arrangement was referred to at trial as a series pump, and I am satisfied on the evidence that such a pump was a common general knowledge in the art at the priority date. I shall return to this topic below.
5. At column 2 lines 15 to 33, a patent specification that seems to have tangential relevance at best to the invention to the patent in suit is described and the specification proceeds at line 34 to a discussion of a further problem that arises at the pressures encountered in HPLC. This problem is caused by the compressibility of the solvents. It will be understood that if a solvent is compressible that part of the stroke of the pump which is occupied merely in compressing the solvent will not cause the flow to occur at the appropriate rate. As the specification says:-

"as a consequence thereof, pulsations in the outflow occur at the pump frequency. These flow pulsations are particularly disturbing at low flow rates. The reason is the percent magnitude of pulsations remains substantially constant 'over a wide range of flow rates but that the amplitudes of the peaks in the chromatogram becomes. smaller when the flow rate is reduced, in particular when smaller separations columns are used. So that the influence of the flow pulsations on the chromatographic results is more pronounced at lower flow rates. "

6. The specification then acknowledges (column 2 line 53) US Patent 4,352,636 which discloses the use of shaped cams to compensate for compressibility of the liquid. It continues

"The pre-compression phase is dependant on a variety of parameters like volume at the top dead centre of the first piston, stroke volume, pressure in the pump, compressibility of the liquid, stiffness of the pumping system, closing performance of the valves. Since not all of the parameters can be precisely determined, a remaining pulsation in the outflow is to expected. Furthermore, the known pumping apparatus has a comparatively complex mechanical design requiring precisely machined cams."

7. It is by reference to the prior art which is acknowledged that the specification describes the invention. At column 3 line 17 the invention of the patent is introduced in the following words:

"Relative to this prior art, it is an object of the invention to provide a pumping apparatus for delivering liquid at high pressure according to the preamble of claim 1 which has a simpler mechanical design and which substantially avoids over a wide range of flow rates the problems caused by interferences of pulsations of the flow of the delivered liquid with the chromatographic measuring results.

This object is solved by the characterising features of claim one. "

8. It is convenient to set out the entire claim at this point. It is as follows:

"1. A pumping apparatus for delivering liquid at a high pressure at which compressibility of the liquid becomes noticeable, and at a selectable flow rate, comprising

a) a first piston (10) for reciprocation in a first pump chamber (7), the first pump chamber having inlet port and an outlet port,

b) a second piston (20) for reciprocation in a second pump chamber (18), the second pump chamber having an inlet port and an outlet port,

c) a conduit connection (12,14) between the outlet port of the first pump chamber and the inlet port of the second pump chamber,

d) an inlet valve (4) connected to the inlet port of the first pump chamber for allowing flow of liquid into the first pump chamber and for inhibiting flow in the opposite direction,

e) an outlet valve (13) connected to the outlet to the first pump chamber for allowing flow of liquid into the second pump chamber and for inhibiting flow in the opposite direction,

f) drive means (30,34;31,33;32,36) for reciprocating the first and the second piston,

g) wherein the liquid in the first pump chamber is compressed to a high pressure before delivery of the compressed liquid into the second pump chamber,

characterized by

control means (41,42,43,44,35) coupled to the drive means (30,34;31,33;32,36) for adjusting the stroke lengths of the pistons (10,20) between their top dead centre and their bottom dead centre, respectively, in response to the desired flow rate of the liquid delivered at the outlet of the pumping apparatus, with the stroke volume (i.e., the amount of liquid displaced during a pump cycle) being decreased when the flow rate is decreased and visa versa such that pulsations in the flow of the liquid delivered at the output of the pumping apparatus are reduced"

9. The operation of such a device is described in the immediately following passage in the specification at page 3 line 28:

"In order to see how the provision of an adjustable stroke volume leads to a reduction in the flow pulsations, the following is to be considered: in known solvent delivery systems, the flow rate is changed by changing the frequency of reciprocation of the pistons so that the pistons move at a higher frequency when a high flow rate is selected, whereas the stroke volume remains the same when the flow rate is altered. According to the present invention, however, the flow rate is changed by changing both the frequency of reciprocation of the pistons and the stroke volume. In a preferred embodiment of the invention, the stroke volume is decreased with the flow rate. Thus when the stroke volume becomes smaller the volume which has to be compressed to the final pressure before delivery starts also becomes smaller. Since the volume to be compressed is smaller, the compression phase becomes shorter. resulting in smaller pulsations at the outflow of the pump. It is a further consequence of the variation of the stroke volume as a function of the flow rate that, particularly at low flow rates, the frequency of reciprocation of the pistons is higher than in a prior art pump having a fixed stroke for all flow rates. This increase in the frequency of reciprocation leads. to a corresponding increase in the frequency of any remaining pulsations of the pump output which has advantageous effects on the reproducibility of quantitative chromatographic measurements in contrast to low frequency pulsations which may effect the retention times and areas of different peaks in the chromatogram in different ways, high frequency pulsations are more like a uniform background signal which effects the whole chromatogram in substantially the same manner. The increase in the frequency of the pulsations is particularly advantageous when a detector is used which is very sensitive to flow pulsations e.g., a refractive index detector. "

10. It should be obvious that in the operation of a pump whose stroke is adjustable, there are two independent variables affecting the pump's ultimate flow rate. These are the frequency of the reciprocation and the volume of the stroke. Obviously also, for a given piston diameter it is possible to obtain a range of flows by adjusting the stroke length at a fixed frequency; and equally it is possible to obtain a range of flows by adjusting the frequency of reciprocation while holding the stroke constant. The specification contemplates the use of any means for driving the pistons that permits the adjustment to the stroke length (see column 4 line 43). The specification points out that if ball-screw drives are used then it is straightforward to programme any desired displacement/time function for the pistons during a pump cycle: the displacement may be linear with time or may include a pre-compression phase during which the piston moves more rapidly - see column 4 lines 50 to column 5 line 1. There was no issue that such cylinder/piston arrangements together with the techniques for programming and driving the piston through the use of a stepper motor would have been well understood by a person skilled in the art at the priority date (26 September 1987).
11. It will be observed that the claim is not explicit as to the manner in which the generation of the frequency, said to be variable in the passage that I have quoted above, is achieved. From this, I draw the inference that when the claim speaks of "drive means ... for adjusting the stroke length of the pistons ... between their top dead centre and their bottom dead centre, respectively, in response to the desired flow rate" it is contemplating a relationship between stroke length and desired flow rate that is not necessarily linear though no doubt it is required to be monotonic. To the extent that it is non-linear, there must be corresponding adjustments in the driving frequency of the pistons, but Mr Wyand Q. C. who appeared on behalf of the claimants accepted that the specification did not explicitly describe any manner in which the frequency might be adjusted.
12. Figure 1 of the specification is a diagram indicating the functional units of the preferred embodiment. There is no description of the manner in which the speed, and hence frequency, of the pump piston is controlled, save only to say that it is so controlled. There is some indication in figures 4,5, and 6 of the nature of the control which is possible. Figure 4 shows the plot of flow rate against stroke volume (i.e. swept volume) in the case of a compressible liquid. It will be apparent that the effect of the dead space, which shows clearly in Figure 4, is to require an increase in the frequency over and above what it would otherwise be for the specified displacement. This is shown in Figure 5, the two figures being described in the passage in the specification in column 11 line 38 to column 12 line 25. It will be observed that in the case of this embodiment the frequency of the pump and so. the frequency of any ripple in its output is higher than would be the case of a given pump with a single stroke volume, at least up to the flow rate of 5 ml/min.
13. Finally, I should refer to Figure 6 and its description in column 12 lines 26 to 51. This is the only example given in the specification of a determination whether "the pulsations in the flow of the liquids delivered to the output to the pumping apparatus are reduced". Obviously, this feature of the claim gives rise to a problem of construction (what is the apparatus the pulsations in the output of which are to be compared with those of the allegedly infringing apparatus?) but for present purposes it may be noted that the pump pulsation is defined as the difference between the pressure in the delivered liquid when the second piston is directly before its top dead centre, and the minimum pressure is taken to be the pressure at the beginning of the compression phase of the first piston. In the patent specification, the comparison is done by reference to the same comparator as is used for Figures 4 and 5, that is, a pump having a fixed stroke volume of 100 µl.
14. Figures 4 and 5 can be derived from each other. For example, taking Figure 4 as relating to a machine which has a maximum stroke volume for the first piston of 100 µl, the designer of the machine fixes the stroke volume of a flow of 2 mls per min as 50 µl. In order to maintain a flow of 2 mls per min with a swept volume of only 50 µl, a frequency of 0.67 Hz is required (a point on curve a). If the swept volume of the first piston had not been reduced, a frequency of only 0.33 hertz would have been required (the corresponding point on Curve b). Thus, both curves a and b of Figure 5 can be derived using Figure 4. To take a further example, the pump of curve a uses a frequency of 0.5 Hz for a flow rate of 1 ml/min. This is because the swept volume for a flow rate of 1 ml/min has been fixed at 35 µl or so and (0.5 x 35 x 10^-6) = 17.5 µl/s or ~ 1 ml/min. It can best be summarised by saying that if the pump is designed to have the swept volume against flow rate characteristic of Figure 4, then the frequency must vary against flow rate in the manner shown in curve a of Figure 5, and the skilled man is assumed to be capable of arranging the 'system controller' of Figure 1 to achieve this result. For this pump, therefore, the only independent variable is flow rate: the system controller takes care of the rest. If the pump characteristic of Figure 4 passed through the origin (so that stroke were proportional to flow) no variation in frequency would be required at all, but that would involve increased pulsation because of the amount of the stroke required to compress the solvent. By having a finite minimum displacement and a flatter stroke/flow rate characteristic frequency must be adjusted as shown in curve 5b.
15. Figure 6, which depends upon a measurement of the pulsation in fact, is not as I understand it a curve that can be derived from the others. As I have indicated, the measurement seems to be made upon the footing that the pump with which the comparison is to made has the maximum available displacement. The comparison is performed with a fixed-stroke pump, and nothing is said about an adjustable-stroke pump working at fixed frequency.

The First Alleged Infringement

16. Before turning to the interpretation placed upon the claim by the Court of Appeal, and the findings of the Court of Appeal in relation to the common general knowledge, I should briefly describe the first alleged infringement. In the first alleged infringement, which I shall refer to as the automatic version, the displacement of the piston was adjusted not continuously but in a stepwise manner. 'Thus, the increase of displacement with flow rate was not linear but was monotonic. At first instance, I held that such an adjustment was not within the contemplation of the words of the claim. My determination as to the scope of the words of the claim was reversed by the Court of Appeal who held that the words did not require that the displacement be varied in a continuous manner in response to the desired flow rate.
17. The machine in issue in the Court of Appeal also had a semi -automatic mode of operation. In that mode of operation, the machine did not fix the stroke volume in reliance upon the value of flow rate input by the operator. It permitted the operator to specify both flow rate and displacement, and, if the desired flow rate could not be obtained using the stated displacement it automatically provided a displacement which would permit such a flow rate. This mode of operation was not the subject of a complaint of infringement by the claimants but it was nonetheless discussed in the witness statement of the defendants expert, Herr Riggenmann, who expressed the view that it possessed none of the features called for by the characterising portion of the claim. There was no cross-examination on this evidence and it did not form any part of the determination either at first instance or in the Court of Appeal.
18. I extract the following propositions from the judgment of the Court of Appeal.

1. The invention involves a series dual piston pump which seeks to overcome the difficulty of variation in flow rate and pressure pulsations in the outflow of the pump by reducing the stroke length of the piston and hence the stroke volume with reducing flow rate. (paragraph 15).

2. The claim requires there to be control means coupled to the drive means. In the Waters automatic apparatus, that was present. The control means was for adjusting the stroke lengths of the pistons in the sense that it was configured to do so. The adjustment was in response to the desire flow rate when a change was made from within one range to within· another range. (paragraphs 32 and 34).

3. The claim does not state that every change in flow rate has to be accompanied by a change in stroke volume and it would be wrong to imply such limitation into the claim by importing a word such as "continuously" (paragraph 35).

19. The section of the judgment of Aldous LJ. In the Court of Appeal entitled "The Background" (Paragraphs 2 to 8) represents, as I understand it, the common general knowledge in the art. There is no criticism of my determination (paragraph 7 of my judgment) that the book called "Colin" represented the common general knowledge in the art.

Manual Mode

20. The pump and control system with which I am concerned in this action operates in what was referred to as "manual mode". In manual mode, flow rate and stroke length are, in principle, independently selected by the operator. The machine is described in detail by Professor Smith in his report and in the Product and Process description served in the current action. The key feature is that the pump has four preselectable pump volumes. The flow rate is independently specified. If the machine cannot deliver the specified flow rate at the volume specified, then the operator is informed-but there is no automatic change of range as there was in the semi-automatic mode of the machine the subject to the first action. The result is that the machine no longer maintains any predetermined relationship between stroke length and flow rate other than that necessarily imposed by the maximum and minimum possible frequencies and the maximum and minimum possible stroke lengths. Any flow rate that is possible for a given stroke volume is permitted by the machine. There is no suggestion, as I understand it, that the machine does anything to suggest to the operator a change in stroke volume so as to use an optimum volume for a given flow rate. There is, however, a series of instructions for the use of the machine when it is used in substitution for the automatic machine which do certainly contemplate that the user should take care to select manually the displacement which would have been fixed by the automatic machine for the specified flow rate.
21. The question is again how to construe the characterising portion of the claim. It is superficially astonishing that a claim which is based upon a description which only contemplates automatic tracking of the desired flow rate by the displacement should be capable of covering a device in which there is no such automatic tracking. But that is Agilent's contention and it must be considered as a matter of the meaning of words in their context.
22. The claim can be analysed as follows:

"Control Means

a) coupled to the drive means

b) for adjusting the stroke length of the pistons between their top dead centre and their bottom dead centre respectively

c) in response to the desired flow rate of the liquid delivered at the outlet of the pumping apparatus,

d) with the stroke volume (i.e., the amount of liquid displace during a pump cycle) being decreased when the flow rate is decreased and visa versa,

e) such that pulsations in the low of the liquid delivered to the output of the pumping apparatus are reduced."

23. As I have indicated, the crucial point of construction for the Court of Appeal arose in relation to features (b) and (d). Feature (d) of the claim plainly explains the nature of the response (feature (c)) which underlies the adjustment referred to in feature (b). There can be no doubt that feature (b) requires the control means to be suitable for adjusting the stroke length in response to the desired flow rate, and the .control means must, it seem to me, accordingly be capable of, or suitable for, responding to the desired flow rate by achieving an adjustment of the stroke length through the coupling to the drive means. If the control means do not themselves respond to the desired flow rate then it seems to me that the apparatus is outside the claim. This view is certainly consistent with a brief passage in the description of the patent in the passages dealing with the so called isocratic operation. Isocratic operation is the mode of operation in which only one solvent is delivered by the machine from beginning to end of a procedure; It is thus the basic mode of operation of the machine. In the context of the preferred embodiment, the specification describes normal operation in the following words (column 10 line 2 ff) :-

'After this start up procedure, the pump starts with its normal operation. The inlet valve 4 is opened by the solenoid 5 under the control of the inlet controller 46 and the piston 10 moves down from the top dead centre thereby sucking solvent into the first pump chamber. According to the present mode of operation, the stroke length, i.e. the distance the piston travels between the top dead centre and its bottom dead centre is dependent on the flow rate which a user has selected at the user interface 42. From the information about the desired flow rate passed from the user interface 42 to the system controller 41, the system controller 41 computes the corresponding stroke length using a predetermined mathematical relationship between flow rate and stroke length (or stroke volume which is proportional to the stroke length). An example of such a predetermined relationship between flow rate and stroke volume is explained below with reference to figure 4 [a passage which I quoted above]. Although in the present mode of operation there is a predetermined relationship between the flow rate and the stroke volume the control circuitry of the present invention yet permits to put the coupling between flow rate and stroke volume out of action so that a free selection of the stroke length or volume becomes possible. [my italics].

24. In such an arrangement it seems to me clear that the machine is required to fix the pumping frequency having regard to the flow rate and stroke volume specified by the user. Accordingly, the response called for by feature (c) of the claim is not present. Such a mode of operation, if the only mode of operation of the machine would not infringe the claim. I read the words 'free selection' as being deliberately chosen in antithesis to the adjustment called for by the claim. The machine described by reference to Figure 1 of the specification permits operation in which the element of response is present, and thus embodies the invention and the fact that the invention does not have to be used is irrelevant to the question of infringement.
25. Furthermore, in the manual mode which I have described, it seem to me clear that while the stroke volume may by intervention of the operator be decreased in proportion to flow rate that is necessarily a consequence of providing independent manual control of both flow rate and stroke volume.
26. I asked Mr Wyand QC during the course of the hearing whether it was a consequence of the interpretation which he sought to place upon the claim that any machine in which it was possible both to specify stroke volume and flow rate. independently would infringe. It seems to me that this must be the case, since if the apparatus permits the frequency to be reduced by an amount less than the desired decrease in flow rate would require at a fixed stroke, and also permits the stroke to be reduced so as to compensate for the otherwise insufficient reduction in frequency, the pulsations will be of higher frequency than they would otherwise have been and thus reduced, at least so far as the patent is concerned (cf Figures 3, 5 and 6). S.O on this construction the claim would appear to be satisfied, and Mr Wyand accepted that this was so. As there are only two independent variables among flow rate, stroke volume and frequency it seem to me that Mr Wyand must be correct. I shall return to this issue when I come to consider the relevance of the prior art to the question of construction.
27. However, taking what I consider to be an orthodox approach to the problem of construction, and arriving at what seems to be the proper meaning of the words viewed through the eyes of the skilled person in their context in the specification as a whole, I consider that the characterising portion of the claim can be read only as requiring apparatus which is capable of operating automatically in the manner described at length in the specification. The claimants repeatedly asserted that the claim specified an apparatus which was capable of performing the required adjustment. That is absolutely true, but in my view the capability must extend to automatic operation. Otherwise substantially the whole of the description would relate to an optional feature of the machine described in effect in three lines in at column 10 line 23, a possibility which I think the skilled man would reject:

"The control circuitry of the present invention yet permits to put the coupling between flow rate and stroke volume out of action so that a free selection of the stroke volume becomes possible. "

Another way of viewing it is that he method of operation disclosed must be built into the machine itself, and not left to the whim of the operator.

28. I have focused on the essentiality to the claim of automatic operation in the context of an purely non-automatic infringement, and I accept that this question was not directly before the Court of Appeal. But their reading shows that automaticity is the feature of the invention which explains the wording of the claim. Thus paragraph 15 of the judgment:

'As appears from claim 1, the invention involves a series dual piston pump which seeks to overcome the difficulty of variation of flow rate and pressure pulsations in the outflow of the pump by reducing the stroke length of piston, hence the stroke volume with reducing flow rate. '

Or paragraph 48:

'In contrast, the characterising part of claim 1 of the Agilent patent requires alteration in response to a flow rate to the column. '

29. Mr Burkill also relies, quite fairly, on Agilent's Notice of Appeal:

'The true position is that the user selects the flow reate required. In response to the selection of the flow rate via the user the controls system automatically adjusts the volume delivered during a pump cycle, as the claim requires. The control system [of the Waters automatic pump] adjusts the stroke volume step-wise so that there is a range of flow rates corresponding to a particular stroke volume bu this is a function of the control means and not a "selection" made by the user.'

30. In my view this is an entirely natural reading of the claim in its context, and for this reason alone there is no infringement.

Pulsation reduction

31. Where the adjustment of volume and flow rate is entirely manual it is always possible, it seems, to use an adjustment at which pulsation will be less than it would be at some other volume but the same flow rate. It follows, say the claimants, the apparatus is capable of achieving the stated result even though it does not necessarily do so. It is thus 'suitable for' achieving the result. I think that this is probably based on a misinterpretation of the claim. The words' such that' qualify the word 'adjusting'. The Court of Appeal have held that the sense of the 'adjusting' feature of the claim is that the adjustment of the stroke length does not have to take place with every adjustment of flow rate: but they do not suggest that when the adjustment does take place the reduction in pulsations is an optional extra. Reduction in pulsation according to the claim's criterion must take place when the adjustment called for by the claim takes place. There was not any evidence that this was the case. For this reason also, there is no infringement.
32. There is, moreover, a serious difficulty with the comparison which has to be made. In the preferred embodiment of the patent it is clear enough: it is the lOOll1 pump, run a the rate appropriate to give the desired flow rate. But what is the comparator when the user is free to choose from more than one combination of volume and frequency to give the desired flow? It is not possible to say that the user adjusting the pump manually will be able to alight on a characteristic like curve c in Figure 6, but unless he does so he may not achieve the desired improvement. In my judgment, this consideration reinforces the construction that I have placed on the claim. Without automaticity, there is no way of ensuring that this feature of the claim is satisfied, there being no proper comparator or means of ascertaining whether what is selected is better or worse than the· comparator.

Infringement by virtue of sub-section 60(2) of the 1977 Act

33. Sub-section 60(2) provides that

'(2) Subject to the following provisions of this section, a person (other than the proprietor of the patent) also infringes a patent for an invention if, while the patent is in force and without the consent of the proprietor, he supplies or offers to supply in the United Kingdom a person other than a licensee of other person entitled to work the invention with any of the means, relating to an essential element of the invention, for putting the invention into effect when he knows, or it is obvious to a reasonable person in the circumstances, that those means are suitable for putting, and are intended to put, the invention into effect in the United Kingdom. '

34. When the operator has decided upon a particular combination of flow rate and stroke, this 'method' can be stored electronically. The handbook for the Waters firmware in issue contains the following recommended ranges of flow and volume, which are closely similar to those that were selected automatically by the software in the automatic version:

Flow		Stroke
Range		volume
(ml/min)	(µl)	(µl)
0.010	-	25
0.530
0.531	-	50
1.230
1.23 1	-	100
3.030
3.031	-	130µl)
5.000

35. The upper limits of the flow ranges are also reflected in the range of possible settings:

Stroke volume (µl)	Flow Range
130 (default value)	Up to 10,0 ml/min
100	Up to 3.03 ml/min
50	Up to 1.23 ml/min
25	Up to 0.53 ml/min

36. Agilent submit that if the machine is programmed so as to have (for example) a flow of 0.04ml/min for a stroke volume of25~1, a flow of 0.7ml/min for a stroke volume of 50~1, a flow of 2.0ml/min for a stroke volume of 100~1 and a flow of 4ml/min for a stroke volume of 130~1. then a change from pre-programmed method to pre-programmed method cannot be distinguished from the mode of operation stigmatised by the Court of Appeal as infringing. The change in stroke length is entirely automatic. Since there are directions to use the machine in this way, it must be considered to be "means relating ... " for the purposes of section 60(2).
37. I reject this argument for the following reasons. As Mr Wyand QC was at pains to point out, the claim is directed to an apparatus, not a method. While it is no doubt possible to pre-program the pump in this way, it is not necessary to do so. Moreover, it is quite unclear what the comparator for the final feature of the claim is. But the principal answer is that this mode of operation can have nothing to do with the control means. It would not be responsive to the desired flow rate, but to the desired method. There is no feature of the pump which determines whether the pump operates in this way or not: indeed, the pump may be programmed so that all operations take place at a single volume setting. As Mr Burkill observed, you cannot turn a manual gearbox into an automatic one by giving the driver instructions as to the points at which to change gear.

The Prior Art

38. There are many cases of higher authority establishing that a defendant who has been unsuccessful in challenging the validity of a patent is estopped from raising the issue of validity again. Stated so broadly, this may require a slight degree of qualification but in general the proposition is as I have stated it.
39. In the present case, the defendant was sued upon a machine which had an automatic mode and which had a semi-automatic mode possessing all the features the present machine but which added to the present machine the feature that if a wholly unsuitable stroke volume were selected the stroke volume would be automatically "bumped up" to one that would accommodate the specified flow rate. On the previous occasion, it was not contended before me or before the Court of Appeal that the existence of the semi-automatic mode was relevant to the question of infringement. Had it been so contended, Mr Burkill QC submits that it would have been open to him to challenge validity on a broader basis that was available against a claim which required automaticity. There are two arguments.
40. First, pumps, both single and dual headed, having manual stroke adjustment using a micrometer, are part of the state of the art-see Professor Smith's report paragraph 43 and his exhibit RS 7, although this is not a series pump. The Waters LC/500A pump (exhibit RS 11 )used series heads with stroke adjustment to vary flow: see the manual dealing with flow rate adjustment. The adjustment in the case of the LC/500A is in effect purely mechanical depending upon the use of a swash plate whose movement changes the effective pitch of the drives to the pump pistons.
41. Thus, the Waters LC/1500A pump has all the pre characterizing features of the claim. It has control means coupled to the drive means for adjusting the stroke lengths of the pistons (the wobble plate carrying the fibre gearwheels and the motor that drives the wobble plate in response to the desired flow rate-see the top view of the pump which is moved to position the plate in response to the desired flow rate through the 'coupling flow rate drive'). The stroke volume is certainly decreased when the flow rate volume is decreased, since it is the only determinant of flow rate. What this pump may be said to lack is the final feature of the claim, 'such that pulsations in the flow of the liquid delivered to the output of the pumping apparatus are reduced when the output .. .is reduced'. This feature can only serve to avoid anticipation if the result of maintaining frequency would not be the reduction in pulsations. The frequency is, of course, fixed in the case of the LC/1500A. This raises in an acute form the comparison called for by the last feature of the claim, since it seems to me that is must refer to a pump in which the stroke is not decreased: but that comparison is not possible with this pump. There is clearly a strong argument of anticipation based on this pump if automatic adjustment is not a required feature of the claim.
42. The same goes for an argument of obviousness on the basis of the common general knowledge. Given a pump with an adjustable stroke, flow rate must be fixed either by adjusting the stroke or by adjusting the frequency of the pump or by adjusting both. To provide a pump with an adjustable stroke and an adjustable frequency is, he says, plainly obvious, and, as I have indicated, Mr Wyand QC submits that such a pump will fall within the claim construed as he contends it should be construed. Mr Burkill submits that it is plain from Colin that twin-cylinder pumps with interchangeable heads are within the contemplation of the man skilled in the art and a number of them are specified in table 4 in that book. To substitute a stepwise-adjustable stroke for an interchangeable head is, Mr Burkill says, obvious: indeed, they are true mechanical equivalents. Since as he contends it is obvious to keep the frequency up so as to damp the pulsations in the flow (and the reason for providing interchangeable heads is to allow the frequency to be maintained at usable levels at which pulsations are low) then it would follow that feature ( e) of the claim would be satisfied. So he says the claim is invalid for obviousness.
43. These are powerful arguments, which could have been addressed at the first trial had the claimants suggested that the semi-automatic mode infringed. They are arguments of type usually called 'squeezes': if you construe the claim so that the defendant infringes, it is invalid, but if a reasonable construction is placed on the claim it is not. It is a particularly important consideration in the present case because the case advanced on validity at the first trial was directed only to automatic adjustment and had to be advanced on the basis of a publication of some obscurity. As the judgment of the Court of Appeal demonstrates, the objection did not even work as a squeeze, the document failing to provide the basis for a successful objection whether or not the claim covered stepwise automatic adjustment
44. Mr Burkill submits that it is now unfair to permit the claimant to rely on a construction not considered by the Court of Appeal when an allegation of invalidity was open to him, and according he submits (1) that the claimant is now estopped from alleging that that construction of the claim is different from that placed on it by the Court of Appeal and that (2) this issue of construction was one which might have been considered in the first proceedings and accordingly is not now open to the claimants by reason of the rule in Henderson v Henderson (1843) 3 Hare 100.

Abuse of process

45. As I have indicated, the authorities appear to be clear that the defendant is estopped from again challenging validity. As between the same parties, I do not see why this principle should not be capable of extending to issues affecting the interpretation of the claim, but the present case presents a feature which seems to me to render a general discussion entirely inappropriate. This feature is the presence of the non-automatic mode in the apparatus in suit in the original action. Mr Wyand QC says that there was no point in investigating the manual mode in the previous action, because the claim is an apparatus claim and it was only necessary to demonstrate infringement by one mode. This is no doubt true, but there is a general principle that a litigant is not to have two bites of the cherry where one only is possible. The second action runs the risk of being considered an abuse of process-see Johnson v Gore Wood [2001] 1 All ER 482. It cannot be disputed that the allegation of infringement in this case opened up a whole range of considerations concerning validity which would not have been relevant, or foreseeable, in the earlier proceedings unless the contention that the semiautomatic mode infringed, when they would have been directly in point. For what it was worth, the matter was indeed referred to in passing by the defendants' expert, but only to dismiss the possibility of infringement. Nobody bothered to challenge him because not attention was given to the possibility that automatic operation was not intrinsic to the requirements of the claim.
46. I think that in such circumstances it should in principle be possible for the defendant to re-open the question of validity to the extent that the claimant's contention on infringement is different from, or additional to, that which it has previously made, and makes possible grounds of invalidity not previously arguable. Alternatively, the claimant might be constrained to interpretations of his claim that do not raise new issues. I am less attracted to this possibility since a fresh infringing machine or method from the defendant may raise entirely fresh issues requiring a fresh examination of features of the claim which did not give previously give rise to difficulty. Either case is likely to be rare, and I am relieved from the duty to resolve this question by my primary conclusion on construction.

Estoppel

47. Finally, I should deal with a final point, which is that Agilent are estopped from alleging that the version 2.02 firmware infringes by reason of their conduct since judgment in the Court of Appeal in the first case. In my view this defence must fail, for a reason that can be shortly expressed. Two matters only are relevant: on 20 September 2002 Waters sought an acknowledgment of non-infringement in the United Kingdom in relation to the version 2.01 (modified) software, the corrected version of which, in all material respects identical, was released on 30 October 2002. Agilent never replied to this request for an acknowledgment of non-infringement.
48. There is no duty to reply to a request for an acknowledgment: the remedy is an action for a declaration under section 71 of the 1977 Act. A recipient of a request for an acknowledgment who does not reply can scarcely be taken to be representing by his silence that there is no infringement and that the acknowledgment should, therefore, have been given. But in the present case, M Ayache's evidence demonstrated that Waters did not rely upon the lack of an acknowledgment in releasing version 2.02. Whatever mayor may not be the essential ingredients of an estoppel by representation, reliance certainly is, and there was no reliance here. In my view the allegation of estoppel fails.

Conclusions

49. This action fails and is dismissed.