Agilent Technologies Deutschland GmbH v Waters Ltd
Jurisdiction | England & Wales |
Judge | MR JUSTICE PUMFREY,Mr Justice Pumfrey |
Judgment Date | 21 December 2004 |
Neutral Citation | [2004] EWHC 2992 (Ch) |
Docket Number | Case No: HC 04 C 1069 |
Court | Chancery Division |
Date | 21 December 2004 |
[2004] EWHC 2992 (Ch)
IN THE HIGH COURT OF JUSTICE
CHANCERY DIVISION
PATENTS COURT
Royal Courts of Justice
Strand, London, WC2A 2LL
The Honourable Mr Justice Pumfrey
Case No: HC 04 C 1069
Roger Wyand QC and Piers Acland (instructed by Bird & Bird) for the Claimant
Guy Burkill QC and Tom Mitcheson (instructed by Shoosmiths) for the Defendants
Hearing dates: 22, 23 November 2004
Approved Judgment
I direct that pursuant to CPR PD 39A para 6.1 no official shorthand note shall be taken of this Judgment and that copies of this version as handed down may be treated as authentic.
Mr Justice Pumfrey:
Introduction
This is an action for infringement of European Patent (UK) 0 309 596. 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.
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.
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
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 180° 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 common general knowledge in the art at the priority date. I shall return to this topic below.
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 separation columns are used, so that the influence of the flow pulsations on the chromatographic results is more pronounced at lower flow rates. "
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 dependent 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 be expected. Furthermore, the known pumping apparatus has a comparatively complex mechanical design requiring precisely machined cams."
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. "
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 an 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 "
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...
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