England and Wales High Court (Patents Court) Decisions

1.1.1 This action began as an action for infringement of six patents, European Patent (UK) 0,011,493 "Somers", European Patent (UK) 0,011,495 "Dakin", European Patent (UK) 0,052,253 "Cane", UK patent 2,006,666 "Holmes", European Patent (UK) 0,072,378 "Wilkinson I", and European Patent (UK) 0,081,649 "Wilkinson II". Each of the patents is concerned with the manufacture of compact discs, which I shall refer to as CD's. For present purposes, it is sufficient to describe the manufacturing process as follows. A lathe in which the cutting tool is a dot of light produced by a laser is used to mark out the track of the recorded signal on a thin layer of photoresist material coated on a flat, rotating, glass plate. The exposed areas of the photoresist are developed so as to leave a spiral pattern of pits which record the data. A series of metal versions are produced from the glass master. First a "father" is made by evaporating silver or some similar metal onto the photoresist and then electroplating the silver so as to back it with a thin metal layer. A series of "mothers" is produced from the father. From the mothers, "stampers" are produced. The CD's are manufactured by injection moulding in moulds, one wall of which is occupied by a stamper. Somers and Dakin are concerned with the manner in which information is recorded on the photoresist-coated master. Cane and Holmes are both concerned with the mould in which the CD is made, and the manner of its use. Wilkinson I is concerned with the development of the information-carrying photoresist layer on the master, and Wilkinson II is concerned with the conditions under which the master is coated with metal by vacuum deposition.

1.2.1 The Writ in this action was issued in January 1996. Infringement of all six patents was alleged. Directions were given by Jacob J on 30 October 1996, which included directions for Notice of Experiments in the usual form. On 29 July 1997, Laddie J made an order for inspection by the Plaintiff's experts of of the defendants' injection moulds for the manufacture of CD's alleged to infringe and providing for service of reports of expert witnesses by 8 September 1997. On the 3 March 1998, shortly before the trial, Laddie J gave further directions to give both plaintiffs and defendants leave to adduce evidence relating to scanning electron micrographs which had been produced following the inspection of certain CD's. While the defendants gave notice of certain experiments relating to the Cane patent, the patentees gave none.

2. Both these patents are invalid. If valid, they would have been infringed by the defendants.

3. Cane is valid, but is not infringed. Holmes is invalid.

4. Both these patents are invalid.

5. Had any of the patents been infringed, the Plaintiffs would have been entitled to sue in relation to them. No transaction, instrument of event has occurred which would have the effect of depriving the plaintiffs of damages in respect of any relevant period of activities of which complaint was made.

6. This defence fails. The fact that use of the Philips machine was licensed when the machine was owned by Philips does not mean that its use is licensed when used by the defendants, who purchased it from Philips.

3.1.1 Sound has been recorded on discs for many years. The basic structure of the black record is known to everybody. It consists of a spiral groove in the surface of a moulded plastic disc. The sound is recorded as essentially wiggles in the track of this groove, which reproduce the waveform of the recorded sound. Many people will have replayed the sound on a black disc with nothing more sophisticated than a fingernail (the experiment is easier on 78 rpm discs), but the basic modern system is merely the electronic analogue of the old horn gramophone. Where the horn gramophone used a needle and diaphragm for the direct production of sound, the modern system uses a stylus to follow the groove, and a cartridge to turn the movements of the stylus into a varying electrical signal (or pair of signals in a stereophonic cartridge) which are amplified in an amplifier and used to drive loudspeakers. The loudspeakers turn the electrical waves back into sound waves. The use of an electrical signal which is a wave analogous to the sound wave which it represents is called analogue recording. In general the word "analogue" is used of any electrical circuit in which either the amplitude, the phase or the frequency of the signal is varied to be proportional to the instantaneous value of the quantity which it represents, whether that be sound or the colours and intensity of a television signal.

3.1.2 In an old-fashioned record, the disc rotates at a constant angular velocity (33, 45 or 78 rpm). The groove follows a constant pitch. It is a familiar feature of such discs that the quality of reproduction is better near the edge of the disc than it is towards the centre. This is because the speed of the disc as it passes the stylus is greater towards the edge of the disc, and (to summarise) it is possible to record more of the detail in the sound.

3.2.1 The present case is really concerned with digital recording although some of the prior art is concerned with early systems designed for use with videodiscs in which recording of the frequency modulated analogue signal and other analogue techniques were used.

3.2.2 In digital systems, the analogue electrical signal representing the matter to be recorded is sampled at regular time intervals, and its instantaneous amplitude encoded as a number. The numbers are then processed at the sampling rate, and recorded. They are recorded as a series of marks and spaces. In a compact disc, with which this action is concerned, the marks and spaces are recorded by laser on a master disc. The laser leaves pits on the master disc which vary in length. These pits are 0.6µ wide and 0.12µ deep. They may vary from 0.9 to 3.3µ in length. 1µ is one-millionth of a metre, or one-thousandth of a millimetre, or 40 millionths of an inch. The wavelength of visible light varies from 0.4 to 0.8µ. The track has a uniform pitch of 1.6µ. This means that a conventional compact disc, which has a recording surface 35mm wide, has about 22,000 pitches of the spiral groove. It contains sufficient data for about 70 minutes of music or 650 MB of data.

3.2.3 When the compact disc is played, the replaying transducer has to distinguish tracks only a few wavelengths of light apart. The method of ensuring that the reproducing transducer follows this track must, therefore, be capable of a high degree of precision.

3.3.1 In 1973, well before the priority date of the patents with which I am concerned, Philips had announced the VLP system. This was a system in which an analogue frequency modulated colour and sound signal was recorded on a 12-inch disc. The analogue signal was recorded as a series of pits of continuously varying length, and the speed of rotation was fixed so that one frame of a television signal was recorded in each revolution. Thus, for European systems the disc rotated at a speed of 25 revolutions per second, or 1500 rpm. Each disc accommodated 30 minutes of recording in the part of the disc lying between a radius of 5cm and 15cm. The pitch of the spiral track was thus of the order of 2µ. The methods of achieving accurate tracking are described in an article called "Control Mechanisms in the Philips 'VLP' record player" by Janssen & Day annexed to Professor Limebeer's first report.

3.4.1 This system is described in general terms in a July 1974 article by Broadbent, also annexed to Professor Limebeer's report. While this differed in detail from the Philips system, in general terms it was similar. The recording was analogue. The disc rotated at constant angular velocity. The groove was an equally spaced spiral. It is to be noted that the angular velocity of the disc was kept constant by a different arrangement from that used by Philips, and used a so-called phase-locked loop. This is described as follows:

3.4.2 Broadbent describes a leadscrew drive system for moving the playback transducer.

3.5.1 The patents refer to the use of servos. Servos are systems whose response is determined by a drive which is actuated by the difference between a set target and the actual response. A simple form of servo control is that described by Janssen & Day. They drive their turntable using a dc (direct current) motor, whose speed of rotation is (in general terms) proportional to the voltage of its supply. They attach a tachometer (an ac dynamo, or alternator) to the shaft of the turntable. This tachometer produces an alternating current signal whose frequency is proportional to the speed of rotation of the turntable. This ac signal is supplied to a rather simple network of components which produce a voltage which depends on the frequency of the input signal. This voltage is compared with a reference value, and the magnitude of the difference used to adjust the voltage applied to the motor driving the turntable in such a way that the difference is minimised.

3.5.2 The phase-locked loop control referred to in Broadbent was, at the priority date, a well known method of control. Professor Limebeer describes phase-locked loops as electronic gear boxes. In a part of his statement which was unchallenged, he says this.

4.1.1 Dakin and Somers together were referred to at trial as the CLV (for constant linear velocity) patents. They are both concerned with the arrangement of the data recorded on a disc. It is convenient to deal with Dakin first, since it comes first in time. Because of their close relationship, for reasons which will become clear hereafter I shall deal with their validity together, after considering infringement separately.

4.1.2 The priority date of Dakin (which was not challenged) is 16 November 1978. At that date, it had already been proposed to record data other than sound on discs, and the patent is concerned with a particular method of ensuring that the space available on the disc is used efficiently. It is not concerned with what the data on the disk represents: nor is it concerned with any particular type of disk although the preferred embodiment is a video disk, that is, a disk on which signals representing moving pictures are recorded.

4.1.3 In a conventional record player, the disc rotates at a constant angular velocity (angular velocity is conventionally denoted by the symbol ), usually 33 rpm. The cartridge with its stylus is positioned on the end of the tone arm, and moves along a substantially radial path with respect to the record. A moment's consideration will show that the speed of the record's surface past the stylus (its 'linear velocity') on an inner groove is less than its speed past the stylus on an outer groove. This means that on the outer groove the length of groove required to provide say 1 second's worth of music is greater than the length of inner groove required for the same period. If the disc is rotating with constant angular velocity, therefore, the density of the recording falls off towards the periphery of the groove. This is an inefficient use of the groove, since more is being taken up for 1 second's worth of music than is necessary.

4.1.4 In this case, the mathematics are central. I understood from the experts that the mathematical relations are elementary, certainly within the competence of an undergraduate electronic engineer, and I shall do my best to explain them here. If is the angular velocity of the disc, r the instantaneous radius of the cartridge ('transducer') from the centre of the disc and c the velocity of the disc relative to the transducer, then, provided that r is changing slowly (i.e. the pitch of the spiral is small)

where is the total angle through which the point has rotated about the origin (and may therefore be much greater than 360° or 2 radians). This may be visualised in more concrete terms. If I have a turntable, I can place a gear wheel on its spindle. I can use this gearwheel to drive a shaft which rotates a worm shaft to which the transducer is keyed. If the worm shaft has a uniform pitch, then the transducer would mark out an Archimedean spiral on the face of the turntable as the turntable rotates.

4.2.1 The title of Dakin is "Method and apparatus for rotating an information storage disc". The description is deliberately general, and the invention is suggested to be capable of application in any field where it is sought to record data on a disc. The field of the invention is stated to be the "type of drive in which disc rotation drive and transducer carriage drive are only connected electrically."

4.2.2 Underlying the alleged invention of Dakin is a system of recording in which the track of the transducer follows the Archimedean spiral, and the angular velocity is not constant, but is adjusted as the transducer moves outwards so that the linear velocity remains constant. If c is to be constant, then must be inversely proportional to r. If the transducer is moving with speed v away from the centre of the disc, then it follows from the relationship that v is proportional to and so inversely proportional to r also. Thus the condition for a track which follows an Archimedean spiral and which moves past the transducer at a constant linear velocity is that both the angular velocity of the disc and the radial speed of the transducer are inversely proportional to the instantaneous distance of the transducer from the centre of the disc.

4.2.3 Column 1 line 28 sets out the field of application of the invention:

4.2.4 The system so described is closely akin to the Philips VLP system to which I have referred. The emphasis on constant velocity of rotation is to draw the essential contrast with the variation in angular velocity which is required if the signal is to be recorded with constant linear velocity. (It will be seen that if constant linear velocity is used, the simple relationship of 1 frame per revolution is lost, to be replaced by frames equally spaced in distance along the spiral track.)

4.2.5 At column 1 line 56 to column 2 line 9 the specification describes a method of maintaining a constant angular velocity. This describes a phase locked loop method of control.

4.2.6 The fact that recording at a constant angular velocity necessarily means that the full information-storing capacity of the disc is not utilised is pointed out at column 2 lines 10-22. The specification then identifies a need in the following terms:

4.2.7 Before turning to the claim, it is helpful to consider the illustrated embodiment (this version of the Figure is from Professor Lawes' report):

13. I have coloured some of the more important signal paths. The basic idea is that a signal representing the radial position of the transducer (red) is fed to an inverting amplifier, which produces a voltage signal inversely proportional to radius (yellow). The inverse radius voltage is supplied to a voltage controlled oscillator, a well-known piece of equipment which produces an ac signal whose frequency is proportional to the input voltage. So the VCO produces a signal whose frequency is inversely proportional to radius (blue) which is divided to a suitable value for driving the lens carriage (transducer) motor which traverses the lense carriage across the disc. It also forms the reference for a phase-locked loop which controls the spindle motor. Both the lens carriage motor and the spindle motor are ac motors whose speed of rotation is proportional to the frequency of the current with which they are supplied. This means that the lens carriage goes across the disc at a speed inversely proportional to the radius of the lens carriage, and the disc rotates at an angular velocity inversely proportional to (and locked to) the radius of the lens carriage.

4.2.8 In this way, the two mathematical relationships which I outlined above in paragraph 0 are satisfied, and the transducer marks out an Archimedean spiral over the surface of the disc while the disc surface moves at a constant velocity past it.

4.2.9 The claim can be set out as follows:

4.3.1 The skilled man through whose eyes this patent has to be read and construed must be familiar with electronic design principles. The plaintiffs accept that he must be capable of understanding block diagrams (for example, figure 1 of Dakin) and be capable of implementing that design in terms of electronic components and circuits. If he did not have this ability, the patent would be hopelessly insufficient. The skilled man must be familiar at least with the general principles of servo control, as applied to frequency and position references. He must be familiar with the principles of phase-locked loops and be able to design them. He will be able to buy, or have made, the appropriate hardware for traversing the motor across the disc. This is a patent which is concerned with underlying principles of operation: it is indifferent to details of implementation. The level of skill of the addressee must be appropriate to the degree of abstraction with which the invention is described. Although I have referred to the addressee in the singular, for simplicity, in fact the skills I have described might well be found in a team of persons seeking to develop such a recording or playback device.

4.3.2 It should also be pointed out that the embodiment depicted has an optical transducer which uses a collimated (i.e. laser) beam of light. A real system using the invention of the patent will be very complicated, and the skilled addressee or addressees of this patent will themselves be part of a larger hypothetical team having the necessary skills.

4.4.1 Some of the issues of construction can only sensibly be understood in the context in which they arise. There are other, more general issues, which I shall attempt to deal with here.

4.4.2 In seeking to encompass both concentric, discrete circular tracks and a single spiral track of comparatively low pitch by the phrase "a plurality of substantially circular and concentrically arranged information tracks" the claim is certainly imprecise, but both plaintiffs and defendants agreed that the claim covered both.

4.4.3 There is no requirement for any feedback loop of any description in the claim. All that is required is that the disc be rotated in synchronism with the frequency of the velocity signal, and the transducer should be driven at a velocity controlled by the velocity signal. It might be added that since the transducer is not required to be driven in synchronism with the frequency of the velocity signal, more complex relationships between the speed of the transducer and its radius, which do not result in an Archimedean spiral, are possible. No doubt this is to encompass the possibility that there are a number of discrete circular tracks spaced apart: but the result is that claim 1 is not limited to an Archimedean spiral.

4.4.4 The most important general question is whether this claim is apt to cover an infringement in which the signals are "digital" in the sense that they are in fact not continuously varying voltages but numbers, represented electronically, which are varied (or updated) at regular intervals to reflect changes in the quantities which they are supposed to represent. In principle, I do not see why this should not be so, given the high degree of generality in the disclosure: see the cross-examination of Professor Lawes (page 181-2):

16. However, Professor Lawes was not optimistic that the addressee he had in mind would be able to derive a digital signal indicative of the reciprocal of radius:

4.4.5 I have quoted this passage in cross-examination at length because it illustrates a particular difficulty which I experienced with Professor Lawes's evidence. While I have no doubt that he was doing his best to assist the court, I do not think that there can be any doubt that he was keeping his eye on the other issues in the case (hence his reference to Somers). He was not particularly consistent, since later on in his evidence at 243 line 17- 244 line 12 he seemed to accept that an engineer confronted with the problem of generating a signal whose frequency accurately depended on 1/R would certainly think of using a programmable divider. Professor Limebeer, on the other hand regarded the substitution as trivial.

4.4.6 I have come to the conclusion that the skilled man would regard the use of digital signals representing the same quantities as the analogue signals specified, and processed in a way appropriate to digital signals, as being within this claim absent some clear indication that this was intended not to be the case. There is no language in the claim or in the specification which drives one to this conclusion, and in my judgment the claim is apt to cover digital signals.

4.5.1 The alleged infringement consists of a so-called lathe, the Philips Laser Beam Recorder ("LBR").

4.5.2 The LBR is a very high precision instrument. The master and its driving motor, the transducer carrier (called the sled) and its driving motor and all the other optical components are mounted on a massive granite slab, which is itself supported on pneumatic supports to insulate everything so far as possible from vibration..

4.5.3 A convenient diagram of the alleged infringement was prepared by Professor Lawes. Marked up with cross-references to Professor Limebeer's explanatory diagrams it is to be found at X9. There was in the end no dispute between the experts as to how it worked. Professor Lawes' diagram is as follows. I have added the colours and the central dividing line to simplify the explanation.

4.5.4 There are two relevant "modules", the Rotation Control Module and the Translation Control Module. The Rotation Control Module is shown generally on the right hand side of the drawing, and is responsible for controlling the angular velocity of the disc to be inversely proportional to the radius of the transducer from the centre of the disc. The Translation Control Module is shown generally on the left hand side of the diagram and is responsible for moving the transducer at a speed dependent on the distance of the transducer from the centre of the disc.

4.5.5 I shall describe the Rotation Control Module first. The basic scheme is that a train of pulses generated by the tachometer (green line) is locked in a conventional phase-locked loop to a signal (blue line) derived from a 25MHz reference signal. The signal on the blue line is obtained by dividing that frequency by a number N in the programmable divider circuit.

4.5.6 The tachometer generates 250 pulses per revolution. The signal on the broken green line is derived by dividing the 250 pulses per revolution by 125, thus obtaining a single pulse every half revolution of the disc.

4.5.7 The number N is computed and changed every half-revolution of the disc. The range of values which it may take up is calculated from the initial rotational speed, the final rotational speed and the number of tracks. It is changed from its initial value to its final value every half revolution, and the size of each change is given by

where L is the number of tracks, s is the initial rotational speed and e is the final rotational speed. Because a CD recording starts towards the middle of the disc and moves towards the edge, the rotational speed slows during the playing of the disc as time elapses.

4.5.8 It will be observed that no signal derived from a measurement of the distance of the transducer from the centre of the disc is used for the purpose of deciding on the value of N. The system is entirely determinate, and so it "knows" that after so many half revolutions N (and so the speed of rotation of the disc) must have a particular value. The transducer is moved so that it is in the right place after that number of half revolutions as well, under control of the Translation Control Module.

4.5.9 The Translation Control Module determines the manner in which the sled traverses the disc. The sled can be thought of as being carried on a threaded rod which is rotated by the translation motor. `It moves very slowly-the confidential service manual for the LBR points out that it will traverse 4 pitches separated by 1.6µ per second towards the outside of an audio CD. This is a speed of about 2.5 centimetres per hour. The required accuracy of positioning is 0.1µ. So the control system must have remarkable precision.

4.5.10 There are two motors which drive the threaded rod. The first is a high speed motor which is used for initial positioning of the sled. The low speed motor is used for data recording. When recording, the sled must follow an Archimedean spiral, and must therefore move by one track pitch (1.6µ) every rotation of the disc. This is achieved as follows. There is again a 25MHz oscillator and a programmable divider. In normal use, the number in the programmable divider is always the same as the number in the programmable divider in the Rotation Control Module, which is called N above, although the number used in this module is produced by a different piece of software from that used in the Rotation Control Module (see the cross-examination of Professor Lawes at 327 line 10, and Professor Limebeer at 1246 lines 9-19). Thus in normal use M and N are required to be equal and change effectively simultaneously every half-revolution of the disc by the same amount. The reference signal (blue) is therefore always the same as that in the Rotation Control Module.

4.5.11 The motor is a dc motor, whose speed of rotation is determined by its supply voltage. There is a digital servo system controlling the motor, and in essence this servo system operates to ensure that the voltage applied to the motor is adjusted 50 times every rotation of the disc so as to ensure that the rate at which the tachometer on the generator provides pulses is precisely in step with the pulse rate of the reference signal. In the result, the speed of the sled is determined by the frequency of the (blue) reference signal.

4.6.1 The defendants admit that all the features of the claim other than (b), (d) and (h) as they are labelled above are present in the alleged infringement. The questions on infringement are therefore

18. It used to be said that it was wrong to construe the claim with one eye on the alleged infringement, but it is not possible to ascertain the correct construction of the claim until a literal meaning of the claim has been arrived at, and, if necessary, any variants from that strict, literal meaning present in the alleged infringement have been identified. The modern law of construction is set out in the judgment of the House of Lords in Catnic v Hill & Smith [1982] RPC 183 at 242 line 44 ff..

4.6.2 The question is whether on a proper construction of the claim in its context in the specification, the patentee intended that strict compliance with any particular descriptive word or phrase was an essential requirement of the invention, so that any variant would fall outside his monopoly, on the assumption that the variant would have no effect upon the way the invention worked and that a skilled man would have appreciated that to be the case. In Kastner v Rizla Ltd [1995] RPC 585, Aldous LJ (with whom the other members of the court agreed) said that the convenient way to approach this question was by way of Hoffmann J's questions in Improver Corp v Remington Consumer Products Ltd [1990] FSR 181 at 189. They are as follows:

4.6.3 The plaintiffs identify the digital signal which sets the value of N in the programmable divider as being the radius signal, which is produced by calculation in the microprocessor in the manner I have indicated above. Dakin undoubtedly describes his radius signal as being a signal derived by measurement of the radius. Does the claim require the radius to be measured, or is it sufficient to navigate by dead reckoning: a certain number of half-rotations have passed, and so we know where the transducer must be, because we have determined the law according to which the radius varies, and programmed it into the microprocessor? As a matter of literal, acontextual, construction, I cannot conclude that a signal produced by counting the rotations of the disc rather than measurement is excluded. So feature (b) of the claim is present.

4.6.4 Feature (d) presents different problems. The radius signal must be used to produce an alternating current velocity signal. The claim identifies the alternating current velocity signal as being the signal in synchronism with which the disc is rotated (feature (e)) and as controlling the means for driving the sled (feature (h)). If one identifies the output of the programmable divider in the Rotation Control Module as being the requisite signal it is not the one that is used to control the means driving the transducer, and if one identifies the output of the programmable divider in the Translation Control Module as being the relevant signal, the disc is not rotated in synchronism with it. But the signals output from the programmable dividers are the same. So the variant is the use of two signals where one would do. The evidence was that the use of the two signals enabled the lathe to perform other tasks not relevant to this judgment. This was put to Professor Lawes in chief at 114:

4.6.5 It was not in dispute that the use of the distinct control signals had no effect on the synchronism between disc and transducer, nor upon the use of a constant linear velocity law in recording the information on the track. The answers to the first and second questions posed by Hoffmann J must therefore be answered in the affirmative. There is no reason appearing either expressly or by necessary inference from the specification itself why this possibility should nonetheless be excluded, and I conclude that feature (d) of the claim is present in the Philips LBR.

4.6.6 Once it is accepted that the use of two identical velocity signals is irrelevant to the question of infringement and that feature (d) is present, it necessarily follows that feature (h) is also present, since the output of the programmable divider by M indisputably controls the radial velocity of the sled. It follows that the Philips LBR infringes claim 1 of Dakin.

4.6.7 Before leaving this topic, I wish briefly to refer to the series of answers given by Professor Lawes above, since they are relevant quite generally to the common general knowledge to be attributed to the addressee of the specification. I am quite satisfied that in these answers Professor Lawes correctly sets out the understanding of the skilled man at the priority date. I read the answers at page 116 lines 11-20 as indicating that once the use of CLV and a uniform spiral is suggested to the skilled man, then he would have no difficulty in constructing a digital implementation which worked.

4.6.8 Claims 4 and 6 of Dakin were said to be independently valid, and both are alleged to be infringed. The plaintiffs accepted in reply that claim 6 stands or falls with claim 4 and therefore it does not have to be considered separately.

21. Claim 4 of Dakin, which is dependent on claim 1, covers "the use of apparatus as claimed ... to record on a storage disc a plurality of substantially circular and concentrically arranged [t]racks, on which the information is recorded at substantially uniform density". This claim is infringed. Its relevance is more to the allegations of invalidity which I shall consider below.

5.1.1 To all intents and purposes, Somers , which is entitled "Method and apparatus for precisely controlling the angular velocity of an information storage disc" describes and claims a digital version of the Dakin invention. Although it is a separate patent, and must therefore be assessed separately, the underlying concepts are the same as those of Dakin: the implementation of the embodiments described is digital rather than analogue, and the scope of the claims is rather different. This patent gave rise to a serious issue on construction relating to claim 7, which is relied on for independent validity.

5.1.2 Apart from the recital of specific prior art in Dakin at column 1 line 20, the introductory passages of the two patents are remarkably similar. Somers identifies the problems with analogue CLV systems as follows:

24. Before turning to the claim, it is convenient to look at the preferred embodiment. Fig. 1 of the patent shows the actual apparatus in block form, and fig. 2 shows a timing diagram for the various signals. Figure 3 is a reproduction of fig. 1 of the patent, but with certain signal paths coloured using the same scheme as that used by Professor Lawes in his report.

5.1.3 The manner in which this system works is straightforward. The block labelled 25 is the motor control servo, which is again a phase-locked loop which synchronises the motor speed to the frequency of the signal on line 47 (blue). It works in precisely the same way as the corresponding PLL in Dakin. The idea of the system is that the disc rotation motor is driven by the alternating disc velocity signal (blue line) and the carriage drive motor is driven by the alternating lens carriage velocity signal (green line). Both velocity signals are obtained by dividing a constant clock signal (on the line 33, output from the crystal oscillator which is a very stable source of pulses of a prescribed frequency) by a number stored in the radius register 21. A signal whose frequency is the result of this division is output from the magnitude comparator on the red line and its frequency further divided by appropriate factors (N1 and N2) to produce disc and carriage velocity signals having frequencies suitable for the particular motors. This means that both velocity signals are alternating signals whose frequency is determined by the value stored in the radius register.

5.1.4 A number indicating the initial carriage position is stored in the radius register 21. If the system is to be used for constant angular velocity recording, the value stored in this register is never changed, and the angular velocity of the disc and the linear velocity of the lens carriage never change. This is achieved by opening the switch labelled CONSTANT RPM/CONSTANT LINEAR VELOCITY. If the recording is to be made with constant linear velocity, the switch is closed. There is no direct measurement of carriage position, but the value stored in the radius register is steadily increased by pulses derived from the carriage velocity signal. Thus, the system uses dead reckoning, and it is assumed that the actual position of the lens carriage is where it would be if the motor had accurately followed the frequency of the signal supplied to it on the green line.

5.1.5 In the system described, the value in the radius register is not updated with every pulse of the lens carriage control signal, but only at intervals determined by the value of N3 in the divider 69. This is merely to provide a number appropriately scaled for subtraction or addition in the radius register.

5.1.6 While not illustrated, direct measurement of the radius is also contemplated (column 9 line 39):

5.1.7 Four apparatus claims (1, 3, 5 and 7) are relied on as having independent validity. Claims 3, 5 and 7 are said to be infringed and must therefore be considered for purposes of infringement, as must claims 12, 14 and 17 which are method claims. Claim 1 may be divided up as follows:

27. Issues only arise in relation to (d) so far as infringement is concerned. Feature (c) is not admitted to be present on the pleadings, but is accepted by Professor Limebeer in his second report (5II tab 6) paragraph 6.114. Feature (d) calls for means for producing a digital signal indicative of the radius of the particular data track selected. If the preferred embodiment is to fall within the claim this feature must cover the process of counting, comparing and updating the contents of the radius register, which will hold the "signal" referred to. While the claim is clumsily drafted (like Dakin, it also tries to encompass a single spiral and concentric rings in one form of words) it seems to me that all this feature calls for is some digital signal which will be used as an indication of where the transducer has got to in a radial direction. This is undoubtedly present in the Philips lathe if I am right in my conclusions as to infringement of Dakin. It is the value of N in Figure 2 above. I conclude that claim 1 of Somers is infringed.

5.1.8 Claim 3 appears never to have been pleaded as infringed. It is mentioned for the first time as infringed in the reading guide and Professor Limebeer gives no evidence about it. The same goes for claims 7, 13 and 14. No application to amend was made until the beginning of the trial when I gave leave on terms.

5.1.9 Claim 5 is an independent apparatus claim. The allegation of infringement was introduced by re-amendment on 28 March 1998, about 4 weeks from trial. Professor Limebeer accepts that this claim is infringed (see section 4.00 of his supplementary report 5II tab 17). The method claim 12 is merely a counterpart to claim 1, and is infringed by the use of the Philips lathe. Infringement of claim 17 is equally accepted. I can refer compendiously to certain tables which were produced by Professor Lawes in Bundle 4 tab 11. I believe that none of these claims raises a real issue of infringement. The remaining claims (3, 7, 13 and 14) are also infringed.

6.1.1 Before I turn to the pleaded grounds of invalidity, it is necessary to consider the common general knowledge in this field in rather more detail than is necessary to arrive at conclusions on construction. "Common general knowledge" is a phrase which has to be approached with some caution.

6.1.2 The defendants say that at the priority date the use of phase-locked loops for motor control, the use of "ganged" PLL's for motor control, the use of PLL's with voltage controlled oscillators providing the reference frequency and the use of digital frequency synthesisers for a similar purpose were all part of the common general knowledge of the electrical engineer whom I have identified as the addressee of this specification. It is also said that in the disc recording art the constant linear velocity recording law and the Archimedean spiral were both well known, as was the use of PLL's for motor control. They sought to support these contentions by reference to certain pleaded items of prior art, and by a detailed cross-examination of Professor Lawes.

6.1.3 I believe that the real attack on these two patents is that the underlying concepts are common general knowledge, or old and/or obvious, and that their implementation in electronic circuitry is a routine matter. The result of any such implementation will be apparatus which falls within the claims both of Somers and Daikin. At the priority date, it is said that it was common general knowledge to use a phase-locked loop to control the speeds of motors, whether it was intended that the angular velocity should be constant or should vary. Thus it was obvious to use a PLL to control the disc speed. Equally, it is said that it was obvious to use some sort of servo to control the radial speed of the transducer, whether that is constant or varying. One possibility is a PLL. Accordingly, implementation of a lathe which operates according to a CLV law (and lays down an Archimedean spiral) is in principle simply a matter of making both speeds depend inversely upon radius, which any competent control engineer can do.

6.1.4 The objection to an approach of this kind is two-fold. It is said to be based upon hindsight: and to involve an unfair step-by-step decomposition of the invention into a number of stages, none of which of itself involves invention. In Technograph v Mills & Rockley [1972] RPC 346 at 362, Lord Diplock said this:

28. Much the same thing was said by Fletcher Moulton LJ in British Westinghouse v Braulik (1910) 27 RPC 209 at 230:

30. At the same time, it has to be remembered that inventions which are truly obvious can also be broken down into a series of easy steps devoid of ingenuity. It cannot be said that a patent for any alleged invention more than one uninventive step away from the prior art is valid. The real question, it seems to me, is whether the alleged invention is one that would occur naturally to the ordinary skilled man either from the common general knowledge or from the publications relied on considered in the light of the common general knowledge. I shall rely on the principles stated by Oliver LJ in Windsurfing International v Tabur Marine [1985] RPC 59 at 73:

32. I believe that the experts did not in the end disagree that any engineer concerned to stabilise the speed of an electric motor would use some sort of servo system, and that the phase-locked loop was a method of choice for use with ac motors, given that it guaranteed a motor speed as stable as the frequency of the reference frequency. Professor Limebeer at page 1299 while giving evidence about the prior publication called Bringol, said this:

36. Again, Professor Lawes had his eye on the ball, but when he was cross-examined again on this issue the answers were as follows: (page 235)

38. I believe that Professor Lawes accepted that these matters were all part of the mental apparatus of an electrical engineer capable of designing and building control systems at the priority date. It emerged that chips for constructing PLL's were available off the shelf by 1973 from companies such as Texas Instruments and Motorola: Professor Limebeer was cross-examined to establish this at page 1281. In his report he supports his view by reference to the cited article by Moore in IEEE Spectrum, an article which is an example of what is sometimes called "advertorial". Electro-Craft corporation (a manufacturer of electric motors) were responsible for a book published by Pergamon in 1977 which devotes a substantial section to phase-locked servo systems. The opening passage of the relevant section (4.6) represents a useful summary, and it places the phase-locked loop firmly in the field of precise velocity control. I find that the knowledge that a phase-locked loop was one of the best ways of accurately controlling the speed of rotation of an electric motor so as to conform to a supplied frequency was well known to the addressee of this specification at the priority date.

39. For this purpose, the defendants based their arguments on Millar, an item of pleaded prior art. Millar was published in IEEE Spectrum, which is a non-specialist technical publication from the IEEE. I am bound to say that given that one has a standard method of accurately controlling the speed of the motor, it would be surprising if it was not also understood that one could operate two such devices using the same reference, which is what Millar does. Millar gives a number of examples (see page 130). I understood Professor Lawes to accept that 10 years after publication this article would record standard practice (224 line 13 to 225 line 1). He accepted that Miller described use of a PLL in constant speed applications and also in precisely controlled variations of speed in bringing equipment up to a running speed (237 line 15 ff) but he was reluctant to accept that the use of a variable reference for other speed variations was also part of the common general knowledge (238 line 6 ff).

6.2.3 Professor Limebeer said under cross-examination that the use of multiple PLL's to synchronise multiple motors was everywhere in the PLL literature: 1397 line 15 - 1398 line 22. He was challenged in this passage of cross-examination, and in others, as to the fairness of his analysis. He was certainly a formidable witness (as were the others from Imperial College who gave evidence) and I hope that I have guarded myself against being excessively influenced by this. However, I found that his evidence was more cogent because I felt in the end that Professor Lawes was too willing to look for reasons why that which was certainly apparently straightforward might not have been in fact. I think that he was inclined to put the skills of his engineer too low-he (or she) was certainly not capable of designing the whole system (see 256-7), but the specification is directed to all the designers. I do not mean any criticism of Professor Lawes in this: it is merely that I found his approach less convincing. I consider that jointly controlling two synchronised systems by the use of PLL's operating with a common reference was equally part of the intellectual toolkit of the addressee at the priority date.

6.2.4 Finally, in relation to the electronic skills to be expected of the addressee, the defendants identify the use of a voltage controlled oscillator (which is controlled by an analogue voltage) to provide a varying frequency reference for a PLL used to control a motor. They manage even to identify in the Electrocraft book a PLL chip which incorporates a VCO so that it can be used with either a reference frequency input or an analogue input so that the motor speed follows the analogue voltage. I think that this concept is inherently obvious and Professor Limebeer was not cross-examined on it. This was also part of the common general knowledge of the skilled man.

6.2.5 I now consider the art concerned with recording on disc. Mr Howe's submission was the Archimedean spiral was plainly common general knowledge, being used in every gramophone record there ever was. This is correct. The question is really whether the CLV law was common general knowledge. Professor Lawes was cross-examined:

41. The idea of a moving transducer is obviously part of CLV. The whole idea is that the rotational speed of the disc varies depending upon how far the transducer is across the disc. I think this evidence came close to conceding that a control system using a phase locked loop to control disc rotation and some pick-off of radial position was common general knowledge, or at least completely obvious as a way of implementing CLV. I think that Professor Lawes accepted that the concept of CLV was common general knowledge by 1978. Paragraph 2.42 of Professor Limebeer's first report goes some way to support this conclusion, but he appears to deduce that CLV was well known from the fact that it is mentioned in three of the cited documents only (Schuller, Bringol and Wentzell). Of course, mention of a concept in three patent specifications does not make it well known, let alone common general knowledge, but each of these inventors appears to suggest that he had invented the concept, and I can see in this some support for the view that the concept is obvious. In my judgment, the use of CLV was something which would naturally occur to any man who wished to record as much information as possible on a rotating record in 1978.

6.2.6 The plaintiffs suggested throughout the trial that the Archimedean spiral was in some way a distinct question. They accepted that the addressee would have the mathematical equipment to work out the control laws for CLV and for an Archimedean spiral, but would be incapable of combining these concepts in what they referred to as "imaginative ways". I think that this is a false argument. For a given system, the actual way in which the speed of the disc will have to be controlled is not known until the law by which the transducer will move is known. This follows from equations (1) and (2) above. Of course, an Archimedean spiral is just the simplest case, and is produced if the disc shaft and the transducer leadscrew are directly geared together.

6.3.1 In my judgment, the underlying concept of both Dakin and Somers, the use of a CLV recording law with the standard form of spiral was common general knowledge and obvious to any person seeking to design an efficient method of recording on disc. It is irrelevant that Dakin and Somers apparently made their invention in the context of video discs: their claims are not so limited, and extend to any form of recording on disc. Any invention must lie in the particular apparatus and methods claimed. This analysis must begin with the identification of the inventive concept of the apparatus and method claims. There is a risk of falling into error if the inventive concept is not ascertained from the words of the claims themselves.

6.3.2 In the case of Dakin, it seems to me that there are essentially three components of the system: a radius signal: a velocity signal derived from the radius signal with which the rotation of the disc is synchronised and the use of the velocity signal to drive the transducer as well. The use of a radius signal follows directly from the mathematics. A signal is needed which is a measure of r. No-one suggests that given two quantities each of which depends on 1/r it is ingenious to use a signal proportional to 1/r. There is no doubt that any electronic engineer could generate such a signal. It is common general knowledge to use phase-locked loops where accurate movement of the disc and the transducer are required. Use of a voltage controlled oscillator (available on a commercially available PLL chip by the date) can be used for the purpose of generating the reference for the PLL. The same signal is used to drive the transducer, again using a PLL. I am quite satisfied that such a system would be perfectly obvious, and it is within claim 1 of Dakin.

6.3.3 In the case of Somers, it should first be observed that claim 1 is not concerned with the transducer drive at all. CLV comes in only in claim 2:

43. Movement of the transducer to describe an Archimedean spiral on the moving disc comes in claim 3:

45. A direct digital version of the apparatus which I have already described falls within these claims. It is not suggested that there is any ingenuity in making a digital version of the design to which I have referred. The radius signal is digital and it may be directly measured. The velocity signal is digital, derived from the fixed frequency clock by division by the radius signal. The velocity signal controls rotation. The necessary design techniques and the necessary apparatus are, it is accepted, well known. The programmable divider was well known for this purpose as Professor Lawes accepted (page 243). It follows that in my judgment the invention of claim 1 of Dakin, and of claims 1, 3 and 12 of Somers, are obvious in the light of the common general knowledge of the addressee of the specification. I shall deal with the other claims alleged to be independently valid below.

6.4.1 The defendants rely upon a large number of citations against these patents. I shall leave on one side those which are concerned only with PLL's and their application, to which I have already referred. They are merely illustrative of the common general knowledge. However, shortly before the trial the plaintiffs supplied the defendants with a bundle entitled "Other CLV Art". This was to show that quite apart from the defendants' own pleaded citations (Schuller, Wentzell, and Bringol) there were a number of other attempts to devise a suitable system for recording according to a CLV law, and that there were in the art far too many shots at the target. The plaintiffs relied on a statement by Jacob J in Honeywell v ACL (unreported, 22 February 1996):

46. There is a risk of taking this epigram too literally. While it may be a useful tool for the advocate, it proves too much. Too many shots at the target only make for subject matter when the target is the same, the others have missed it, the common general knowledge is the same for each and the inventors did not have idiosyncratic reasons for doing what they did. As Jacob J said, the court must look at each citation relied on individually. I think also that there is a suggestion in the epigram that the existence of a number of other solutions to a given problem may suggest that the next has subject matter. This is quite illogical, but it is a line of argument which is frequently encountered. The fact that there are a number of ways of approaching a problem does not mean that any one of them is obvious or not obvious. In Brugger v Medicaid [1996] RPC 635 at 661, Laddie J said this:

47. I think this is right. I should add that when the allegation is that the invention is obvious in the light of the common general knowledge, the question of the starting point of the earlier work is still relevant. The enquiry as to obviousness or otherwise is an objective one, and speculation as to why a particular worker went down one path rather than another is unrewarding because the real facts will never be known. Citations for the purpose of obviousness are just that: they represent starting points from which either the invention is obvious or not. A multiplicity of possible starting points is not an indication of non-obviousness.

48. Perhaps unsurprisingly two of the plaintiffs' new documents (Young and Haneji) were added by the defendants to their list of citations. Wentzell, Schuller and Haneji are all in the field of optical disc storage. I shall take them in turn referring also to the documents in the plaintiffs' list where it is convenient to do so.

49. Young is an early publication of CLV (1938). It points out the advantages of using CLV. It was principally used as an anticipation of the principal method claim 6 of Dakin, but in my view it failed, since there is no disclosure in Young of playback in which the transducer is moved at any velocity by any signal. The opening words are of interest:

6.4.3 Young, who is concerned with conventional black audio discs, records an inaudible signal whose frequency is inversely proportional to the distance of the transducer from the centre of the record together with the sound signal, and on playback extracts that signal and uses that signal to control the rotational speed of the disc. His transducer therefore follows the groove, and obeys a CLV law. His disclosure of the recording process is unclear, merely saying that when the signal is recorded, its frequency is varied by gearing the tuning element of the signal generator to the shaft of the recording turntable. He does not explain in terms how he achieves CLV in the recording machine. So far as the Archimedean spiral is concerned, I am bound to say that if he used a conventional lathe for cutting his record, and just varied the speed of the motor, he would cut an Archimedean spiral.

50. Stovall was not put to Professor Lawes and is not pleaded. It discloses a method of recording on magnetic discs used for data storage in a computer, and the method used is not to speed up the disc but to record the data more densely as the recording radius increases. This solution is not feasible where the disc is required to be played back in real time. It is irrelevant and does nothing to show non-obviousness. The problem is a different one. However, this publication does show that the problem of making best use of available space on a rotating disc is one of which skilled men were aware.

51. Wentzell is pleaded prior art. He again is concerned to achieve CLV in the optical disc field. He has two embodiments (Figures 1 and 2) which are not entirely easy to interpret. In his Figure 1 (recording)

he appears to derive a pulse train t from an oscillator 5 which is so arranged to adjust the speed of the motor 7 to give constant tangential velocity at the transducer (stylus 2). The transducer is mechanically coupled to the motor - this will give an Archimedean spiral. So he records a varying frequency signal: just like Young. His second embodiment is curious:

52. During recording, he mounts the stylus 2 and a readback head 9 together. The stylus records clock pulses, and the read head immediately reads them back. The motor speed is adjusted so that the time between the recording of a pulse and the reading back of that pulse is constant. This maintains CLV. He does not describe how the stylus is moved. I do not read Professor Limebeer's report (paragraph 4.13) as suggesting that Wentzell will support an allegation of obviousness, and it was not put to Professor Lawes.

53. Schuller is pleaded prior art. It is to all intents and purposes a more modern version of Young, being concerned with optical discs and playback. His description of the method of recording is rather like the method Young did not like:

6.4.7 Schuller's method of adjusting speed is to use a brake which acts in dependence on a signal recorded on the disc at the video frame rate. This is very like Young's brake. There is really no evidence suggesting that either Dakin or Somers are obvious in the light of Schuller.

55. Bringol is said by the defendants to lead directly to an apparatus and method falling within Dakin if what is sometimes called a "workshop variation" is carried out on it. In this case, the variation is upgrading it from a device suitable for use with a dictating machine to one suitable for recording with standards suitable for optical discs. Bringol discloses a CLV recording system with an Archimedean spiral.

56. Bringol starts out with a clear description of the reasons for the use of CLV. He uses a DC motor 30 in the diagram above. In the diagram, the transducer 3 moves between ri and rd. The transducer moves the wiper of the potentiometer 11, which gives a resistance proportional to radius. Bringol does not describe how he constrains his transducer to move: the only reasonable inference is that his magnetic disc has a groove, but this is only an inference. Bringol's date is 1972. It seems to me that he is dealing with a very specific problem with a cheap piece of apparatus. In order to pass from Bringol to a device falling within Dakin, the DC motor and hyperbolic function generator (cheap and inaccurate) must be replaced by a suitable motor and tacho and a PLL for accuracy. The transducer must be driven, about which Bringol says nothing. While I accept that Professor Limebeer maintained under cross-examination that it was obvious to substitute a PLL and to drive the transducer in an Archimedean spiral (see Transcript 1299 to 1303) this is in the context of evidence which supports the suggestion that the invention of both Dakin and Somers is anyway obvious in the light of common general knowledge. If Dakin and Somers are not obvious in the light of the common general knowledge, then I do not think that Bringol helps the defendants.

57. This was the most interesting of the citations. It was explained by the experts to me in mathematical terms, and I shall do my best to reproduce their explanation. I suspect that there is no other convenient way in which to explain it. Haneji solves the basic CLV equations not with respect to radius but with respect to time. On page 4 of the translation, he says this:

59. So Haneji uses a simple mechanical reduction drive between the disc drive and the transducer to maintain an Archimedean spiral. He writes his equations:

(where v is the constant linear velocity, p the pitch of the Archimedean spiral track and ri the radius of the first track) would be computed directly as the disc rotated and the transducer moved.

61. The plaintiffs object that this is not a radius signal indicative of the radius of the individual track. In fact, it is a velocity signal (and, if produced by a microprocessor, it is a digital velocity signal). It is produced by dead-reckoning, i.e. by a measurement of elapsed time (t in the equation above: all the other quantities are constant). If the claim is to be construed to include the use of signals which are indicative of radius because they represent the number of pulses sent to the motor driving the transducer, as I have held it must, I can see no rational basis on which this signal is not to be said to be "indicative of radius" also. The denominator of the expression for is after all just the radius, as Professor Limebeer explains in X11.

6.4.10 If Professor Limebeer is right, and it is obvious to calculate this quantity using a microprocessor in 1978, then features (b), (d) and (e) of claim 1 of Dakin are present. The only question is whether a mechanical reduction drive from the disc to the transducer is sufficient to satisfy feature (h) of the claim ("means for driving a transducer at a radial velocity controlled by the velocity signal"). Literally construed, this requirement is satisfied, since the speed of the disc in Haneji is controlled by the signal via the voltage controlled oscillator, and if the transducer is mechanically coupled to the disc, then so is the transducer velocity so controlled. The plaintiffs say that the specification makes it quite plain that the claim is not that wide. They rely on four passages: column 1 lines 16-19, column 1 lines 23-27, column 2 lines 47-56 and (in the description of the preferred embodiment) column 3 lines 16-22. Leaving aside the reference in the description of the preferred embodiment, which does not have such a connection, the first two passages referred to contain the words "more particularly":

63. The first passage appears to relate to Bringol. In Bringol there is no description of how the transducer is moved at all, and it is not possible to infer that it is driven from the disc. There is, strikingly, no exclusion of such drives. The invention is not said not to include such devices within its scope and feature (h) of the claim does not succeed in its object of excluding them, if that was the intention. I conclude that Claim 1 of Dakin is obvious in the light of Haneji. If I am wrong on the question of construction, I am satisfied that the substitution of an electrical coupling with a second motor driven by the signal is obvious.

6.4.11 So far as Somers is concerned, I am satisfied that the signal produced by the microprocessor which it was obvious to use in 1978 is a digital signal indicative of radius, albeit computed from the elapsed time. Then the only question is whether it was obvious in 1978 to substitute a digital frequency synthesizer (i.e. a clock and a programmable divider) for the VCO of Haneji to drive the motor, in the context of making a digital version of that apparatus. Since the clock and the programmable divider together are the direct digital equivalent of the VCO and are equally part of the common general knowledge (I have referred above to the fact that this was accepted by Professor Lawes), I believe that claim 1 of Somers is obvious in the light of Haneji.

6.4.12 Somers itself only provides an approximation to the CLV law, so the claim must cover approximations as well. Thus, since it must be obvious to provide direct digital equivalents of the circuits described in Haneji, even with his approximations the claim is obvious. Claims 2 and 3 (the CLV law and the Archimedean spiral) are satisfied for the same reason as I have already given in relation to feature (h) of Dakin.

6.4.13 In coming to these conclusions, I have been very mindful of the warnings which I set out at the beginning of this section of the judgment. In any apparatus which has a number of elements, each of the elements must be considered in turn. That is not necessarily a stepwise approach. If it involves taking a consistent approach to each of the elements then in fact it is a single step, and I believe that this is the case here.

6.5.1 The only claim of Dakin which is alleged to be independently valid is claim 4, which is a method for using the apparatus of claim 1 for recording at uniform density. In the light of my finding of obviousness of claim 1 whether for recording or for playback, this claim cannot stand.

6.6.1 Claims 5 and 17 correspond to each other and are independent apparatus and method claims. They are alleged to have independent validity. The only characterising features of these claims to which I need to refer is the explicit mention of a digital transducer velocity signal, derived from a clock signal by division by the radius signal. This is, in fact, the digital equivalent of the final feature of claim 1 of Dakin. It is not suggested that the manner in which this signal is generated involves invention. Professor Limebeer's second supplemental report appears to provide the only evidence in relation to these claims, Professor Lawes saying nothing about their validity. I have no note of Professor Limebeer having been cross-examined in relation to their validity. In any event, it seems to me that it is to the last degree improbable that the use of a common clock, and its division by the radius signal, to provide the signal to drive the disc motor and the transducer motor is anything other than a straight implementation of exactly the same idea as Dakin in digital terms, and is correspondingly invalid.

6.6.2 Claims 7 and 14 were incorrectly referred to as the dead-reckoning claims. As I have said, they were introduced late into the proceedings, and there was no evidence in chief in relation to them. Claim 7 is satisfied by a digital analogue of a radius pick-off, that is, a digital signal directly measuring the distance travelled by the transducer used to update the stored value from time to time. This is obvious, for the reasons I have already given. It also covers a radius signal which is produced by "dead reckoning". This is the technique which I have held to be obvious in the light of Haneji. Evidence relating to dead reckoning alone was given by Professor Lawes, who described it as an important concept, and as requiring some degree of insight, and as an important jump in concept. But he accepted at page 256 the more basic contention that the skilled man knew that he could deduce the radius by counting the rotations of the disc. This is sufficient to satisfy the claim. If the disc speed is derived from the clock the transducer radius can be derived from the disc speed signal. I think Professor Limebeer's view was that if the addressee of the specification had to be capable of implementing Somers at all he would know that he could compute his radius signal: see 1402 to 1404. In my judgment, these claims are not independently valid.

7.1.1 When a CD is played, it is normally placed label up in the player, and is read by a laser shining up from below. The spiral pattern of pits representing the recorded data is moulded into the top surface of the CD, below the label, so that the important part of the pits is the surface which protrudes into the disc, and it is this surface which is responsible for optical effects upon which the reading system depends.. When the disc is moulded, the so-called stamper occupies that side of the mould which corresponds to the label side. After moulding, the top surface is metallised, to make it reflective, and then coated with a protective lacquer.

7.1.2 It is necessary first to set out my understanding of certain terms. I take the following description from Professor Fenner's report, which was not challenged on this point.

7.1.3 In injection moulding, plastic material is driven in a molten state under considerable pressure into a closed mould, where it sets. The mould is opened, and the moulded article removed. An injection mould is made in at least two pieces, the cavity of the required shape to produce the moulding being formed between them. Molten plastic, which is normally supplied by a screw device, is injected into the mould from a narrow nozzle. The direction of injection is typically at right angles to the plane of separation of the two halves of the mould. The channel that conveys melt from the nozzle towards this plane is known as a sprue or sprue port. The material that may eventually solidify in this channel is also known as a sprue. From the sprue port, material flows in the plane of separation towards the mould cavity. It enters the cavity via the gate, which is very narrow in at least one direction normal to the direction of flow, and which creates a restriction in the flow path. The gate provides a position at which the moulding can be readily detached from its sprue when the moulding process is complete. When the mould is finally opened, removal of the moulding may have to be assisted by ejector pins, which are rods whose ends are flush with the surfaces of the mould cavity when the mould is closed, but which protrude when it is open. Removal of the solidified sprue may have to be assisted in the same way.

7.1.4 This patent is concerned with a "hot sprue valve assembly for an injection moulding machine". A hot sprue is a sprue maintained at such a temperature that the material within remains injectable when the mould is opened and the moulded article removed. Necessarily there is always a region of transition between the moulded article on the one hand and the molten plastic in the sprue on the other, and the distinction between a hot sprue and a cold sprue lies in the location of that region of transition.

7.1.5 A mould is kept sufficiently cool for the article moulded in it to set. When molten plastic material is introduced into a mould through the gate, it comes into contact with the comparatively chill walls of the mould, where it immediately begins to solidify (I shall deal with the solidification process below). -

7.2.1 There are a number of properties of the relevant materials which need to be borne in mind in the ensuing discussion. The first is that while the claim of the patent is not limited to any particular polymer, those of interest in the moulding of compact discs (and optical discs) include polycarbonate. This material does not have a well defined melting point. On cooling from the completely molten, it passes through a number of stages, as its viscosity increases. There is a generally recognised point called the glass transition temperature and generally abbreviated Tg. This is described as the temperature at which the shear modulus of the material collapses and below which it becomes brittle. Polycarbonate has a Tg of 130°C, but is injected at 300°C or thereabouts, at which temperature it is runny. Its viscosity steadily increases as it is cooled to the glass transition temperature. It will be extremely viscous above Tg: Dr Crofton said it would be rubbery, and then leathery gradually becoming less viscous, becoming liquid at about 270°C or so. These materials are non-Newtonian and their viscosity decreases with the rate of shear (crudely, how vigorously they are stirred or forced through narrow orifices). Accordingly the material can increase in viscosity as it leaves a narrow orifice and enters a region of low shear. These properties are illustrated in the manufacturer's data sheet for one grade of polycarbonate used in the manufacture of CD's at X28. The dependence of viscosity on shear rate is shown in Fig 1 of this document and the dependence of shear modulus on temperature in Fig 5, which clearly shows the glass transition temperature where the modulus falls away.

7.2.2 There seems to be a difference of view between those concerned in this art as to when a material of this type may be said to be solid. An obvious candidate is any temperature below Tg, but Dr Bacon, one of the plaintiffs' experts, suggested that this is a matter of some doubt: see page 712 lines 12-22. There was no doubt, however, that the material shrinks substantially on cooling; from 300°C it shrinks about 15% on cooling to below Tg.

7.3.1 The patent is concerned with an improved mould assembly for making record discs, in which the disc production rate is substantially independent of the solidification time of molten plastic material in the sprue bushing region of the injection moulding machine. The mould has a central sprue, located in a so-called sprue bush. When the mould is closed, the gate region is a circular slit surrounding the sprue bush. The idea is that the molten plastic flows under pressure through the sprue, and enters the mould through the gate. There is a valve member which advances to "valve off" the molten plastic material by engaging with the sprue bush when the mould is full. It simultaneously forms the central aperture in the disc. The specification says (column 1 line 48) that it is a particular advantage that the valve member remains in the closed position during solidification of the plastic material in the mould cavity to isolate the hot sprue region of the mould assembly from the mould cavity (in which the disc is formed). The advantage lies in the fact that a cooling fluid can be circulated round the mould cavity, so accelerating cooling and solidification of the plastic of the disc, and the disc can be ejected without waiting for the material in the sprue region to solidify. It is not suggested that one of the advantages of the invention is that the plastic in the sprue region does not solidify at all, as is made clear by the passage at column 1 line 64-column 2 line 32. What is aimed at is a limited degree of solidification near to the end of the sprue.

7.3.2 In the preferred embodiment, the sprue bushing is heated, so as to limit solidification (column 4 line 20). The description of the operation of the preferred embodiment suggests that the stages of operation of the device are:

(a) filling the mould cavity with molten material through the sprue (column 5 line 60);
(b) when the mould cavity is full, closing the valve member to shut off the flow of molten material to the mould and isolate the material within the sprue bushing and the valve itself from the material in the mould cavity (column 6 line 4);
(c) permit the material in the mould cavity to solidify sufficiently to be ejected from the cavity (column 6 line 34-59);
(d) eject such material as may have solidified in the sprue bush.

64. Thus far, it seems to me that the invention is straightforward: it consists of providing some means to permit the disc material to solidify sufficiently for ejection while not permitting the solidification to spread back into the sprue, which is a hot sprue.

7.3.3 The claim is as follows:

(a) A valve assembly for controlling flow of molten disc-forming material

(b) said valve assembly comprising:

(c) said valve means (62, 100) being

(d) said valve means (62, 100) including means (68, 168) for forming a central aperture in the record disc formed within the mould cavity (25, 125)

(e) and means (80, 100) for ejecting from the machine the portion (92, 192) of the disc-forming material displaced from said central aperture upon at least partial solidification of said portion.

65. The real issues on construction turned on two features of the claim only, (c)(ii) and (iii), requiring the valve means be movable into "bearing engagement" with the sprue bushing, and that such engagement be "for preventing the flow of the molten disc-forming material through the sprue bushing into the mould cavity".

66. Although this claim is in form an apparatus claim, it was treated on both sides as being in effect a claim for a particular piece of apparatus operated in a particular way. I think that this was the right approach. It was not contended that the claim would be infringed by a piece of apparatus which was merely capable of acting in the specified manner, if it did not do so in use. Thus the timing diagrams and indications of the state of the material in the mould in use were investigated for the purpose of considering infringement. The patentees approached the question of construction by considering first the inventive concept of the patent, relying on Mr Bartholdtsen's identification of the inventive concept of the patent, which was in the following terms (transcript page 420).

68. I think that this analysis is unhelpful, and coloured by wishful thinking, for the following reasons.

7.4.1 There is no teaching in Cane which deals with birefringence. Birefringence is a property of all transparent polymer materials and is essentially the consequence of anisotropy in the transmission properties of the material, which depend upon the polarisation of the incident light. When a beam of unpolarised light is incident upon a birefringent material two beams emerge, polarised at right angles to each other and displaced from each other. Because of the extremely tight optical tolerances which are required in the reading of an optical disc, the degree of birefringence exhibited by the transparent material must be reduced as much as possible. It was the patentees' case that the problem of birefringence was common general knowledge in this art by the priority date in 1981. Then they submitted that the skilled man would understand that Cane was concerned with birefringence; that it was also common general knowledge that birefringence would be exacerbated by small flows in a material near Tg and that it followed that Cane was concerned with preventing such flows. This is a wholly illegitimate approach to construction. The cross-examination of Mr Bartholdtsen revealed the basis on which he was proceeding (pages 451-2):

70. A patent is not to be construed by guessing what the patentee has deliberately concealed. I do not accept that it is possible to construe Cane so as to relate the word "flow" in its context in the claim to microscopic flow of material near Tg. The patent is concerned merely with the filling of the mould, and not with microscopic phenomena occurring during cooling.

7.4.2 It was also said that Cane gave a relevant teaching in relation to birefringence by reason of a cross-reference (column 1 line 5) to the US patent equivalent to Holmes. This is not so. There is no cross-reference for the purpose of discussing birefringence, but merely for recognising certain apparatus features disclosed in Holmes. Furthermore, reference to Holmes shows that the relevant passage at page 7 lines 45 to 81 has nothing to do with birefringence caused by microscopic flow of material.

7.4.3 In fact, Cane is extremely simple minded in the way in which it deals with the flow behaviour of the plastic material as it enters the mould. By the time of Mr Bartholdtsen's second report, it was common ground between the parties that on entry into the mould the plastic near the walls of the mould immediately began to set. Thus, as the plastic advanced into the mould there would always be a solid skin near against the wall of the mould, and the plastic would be progressively cooling. The diagram of the mould filling process advanced by Professor Foyer in his report (figures 3 and 4, and 6 and 7) and the accompanying text is in this respect misleading. It does not reflect what is occurring in the mould, and the diagrams themselves were rejected by Mr Bartholdtsen (431-433) as more confusing than helpful. Cane is silent as to all this. It does not recognise that in the region of the gate there will be layers of cooling material.

7.4.4 Having referred to these passages in the evidence of Mr Bartholdtsen and Professor Foyer, I should say a word about them as witnesses. I did not find either of them satisfactory. Mr Bartholdtsen had undoubted experience in the field, and would have been a most valuable witness had he not been so plainly concerned to advance the patentee's case. His evidence on the issue of infringement changed sharply between his first and second reports, in respects which are not to be explained by the undoubted inadequacies of the defendants' product description. Thus, he said this in his first report of the allegedly infringing mould:

73. He said under cross-examination (504-506) that he had omitted all reference to the presence of skins and so to the presence of solidified material because their presence was obvious to him. This is not an explanation, and is plainly inconsistent with what is said on page 17 of this report. I believe that Mr Bartholdtsen did not mention skins and their rate of formation in the mould, which is cooled, because it served to detract from the clear view as to infringement which he was seeking to give.

7.4.5 I was left in considerable confusion by Professor Foyer's evidence. I have already referred to the misleading nature of his evidence on the manner in which the CD mould filled. He also advanced evidence directed to certain measurements of allegedly infringing CD's carried out by using a Talysurf machine. His colleague Dr Bacon had also carried out some scanning electron micrographs which I shall discuss below. His evidence was that "both of these types of examination are standard and necessary methods used to diagnose what has happened inside a closed mould during a moulding or casting operation. I have used similar approaches for this purpose on many occasions in the past". In fact, it became clear that the Talysurf measurements were wholly unreliable. Not only was the method inappropriate, but it had been performed in a manner which seemed to contravene all rules for performing measurements of small distances accurately, and it was subjected to trenchant criticism by Dr Crofton in paragraphs 16 to 45 of his second supplementary report, which was not effectively challenged. Professor Foyer himself submitted a third report, which for some reason included most of the operator's handbook for the Talysurf machine, seeking to refute Dr Crofton's criticisms, but in the result, Mr Watson did not seek to rely on the measurements using the Talysurf machine. Finally I must record that Professor Foyer's reports seemed to be cast in a rather tendentious form. Thus, although he knew that the movable member in the defendants' mould was said to act not as a valve for liquid material but as a punch, he referred to it as the "Valve Means" throughout his report. He also referred to "Bearing Engagement" in the defendants' moulds, where he knew that there was a dispute as to whether such engagement took place. Taken as a whole, I regret that I found his evidence unhelpful.

7.4.6 The question of "bearing engagement" is more difficult. The word "bearing" implies some sort of support. The figures are not consistent, Figure 3 suggesting that the valve means 62 touches the front face of the sprue bush 56 while Figure 4 suggests a clearance, the valving action in fact taking place by the sliding engagement between the valve means and the cylindrical die bushing 59. In fact, the word "bearing engagement" is far more naturally used of the interrelationship between the valve means 62 and the cylindrical die bushing 59 than of the abutting relationship of the valve means 62 and the sprue bushing 56. However that may be, there is no clear suggestion that there must be metal to metal contact, and it seems to me that the engagement must be such that the flow referred to is effectively prevented.

7.4.7 In my judgment, the claim is not concerned with the prevention of microscopic movement in the plastic material in the gate region of the mould during cooling. The claim is entirely straightforward: it requires there to be molten material in the sprue region, whose flow from the sprue region into the mould is prevented by the valve. The valve must operate by engaging with the sprue bushing so as to prevent such flow.

7.5.1 Three models of mould are now alleged to infringe, one having been dropped in Mr Bartholdtsen's first report. These were called the Husky, the Axxicon CAV, the Axxicon HC and the Axxicon HCA. The allegation of infringement was withdrawn in relation to the Axxicon CAV, and there is no material difference between the Axxicon HC and the Axxicon HCA, to which I shall refer collectively as the Axxicon. The Husky falls into two subtypes: the one I illustrate below and which was used for the production of the sample discs supplied to the patentees and the one which was used for the manufacture of the "Uno Clio" disc. This mould was more symmetrical, and is illustrated at X14 Figures D1, D3 and D4.

7.5.2 There is no dispute that apparatus features are present in the moulds which would be capable of operating in the manner called for by the claim. The issues are whether there is "bearing engagement" and whether the sliding member in the defendants' mould operates to prevent flow from the sprue to the mould cavity.

7.5.3 In each case, it is necessary to show as a minimum that the material in the gate region of the mould is above Tg when the sliding member operates. If the material is below Tg there is no possibility of there being any flow to prevent. In both cases, it was accepted that some of the material in the gate (that closest the walls of the mould and the sliding member) was below Tg. The general approach taken by the patentees after Mr Bartholdtsen's first report was to say that in operation, the two more or less solid skins formed over the mould components operated to "squeeze off" the flow when they moved together as the sliding member moved. Thus, the fact that in neither mould did the sliding member touch the sprue insert bush was irrelevant: the effect of "bearing engagement" was provided between the two skins, which came together to prevent the flow.

7.5.4 The reason why I say that at a minimum the patentees must show that the material in the gate was above Tg is that the evidence of the flow properties of polycarbonate above that temperature did not establish with any clarity at what temperature it could reasonably be said that the material was flowable: Dr Crofton's evidence was that above Tg polycarbonate was rubbery, and his evidence in paragraphs 18-55 was not really challenged.

7.6.1 It is convenient to set out sectional drawings from X13 showing the Husky mould open and closed.

7.6.2 The starting point of the allegation of infringement is a straightforward observation which the patentees made on the sample discs, sprues and discs-with-sprues which had been supplied to them. This observation was that the thickness of separated discs and sprues at the region corresponding to the gate was less than the corresponding thickness of the discs-with-sprues that had been made without use of the separating means. This meant, so the patentees said, that there had been liquid material in the region where the cutter operated which had been displaced by the cutter. The measurements the patentees relied on were the Talysurf measurements, and although I have rejected these measurements as unreliable, it was accepted by the defendants that there was, or might be, a reduction in the thickness in the case of discs made using the Husky mould.

7.6.3 The patentees' contentions may be seen clearly from X14 figures C1, C2 and D. They show the cross-section of the mould marked to show what are alleged to be corresponding regions on certain discs of which scanning electron micrographs (SEM's) were taken by Dr Bacon. A great deal of the trial was taken up with the analysis of the SEM's, particularly the one known as plate 4 (Bundle 4 page 145) which is reproduced also on X14 figure C1. Figure C2 is an edge-on SEM of a sprue which is said to correspond to the corresponding regions on the sprue side. In each case, the area marked liquid is said to show a region which, when the cutter operated, was sufficiently liquid to flow.

7.6.4 Before I analyse the evidence, I should deal with the manner in which the evidence of the SEM's was given. Until July 1997, there had been no provision for an inspection of the allegedly infringing moulds. In July 1997, Laddie J made an order for inspection of the moulds used for the production of the 26 CD's mentioned in the particulars of infringements. The inspection took place on 26 October 1997, and on that date, the mould was inspected and two sample discs from the mould were supplied to the patentees' representatives, who also took a number of discs with the sprues still attached and some sample sprues. The idea of taking SEM's of these discs did not occur to the patentees until mid-January, and the results were annexed to Professor Foyer's report which was produced on 24 February 1998. They were not annexed to a Notice of Experiments as they should have been. The defendants waived the requirement for a Notice of Experiments and asked for a repetition, at which Dr Crofton was allowed to take additional micrographs at different angles. In the result, there was never any proper indication of the facts which the patentees sought to prove by the use of the SEM's . For example, an attempt was made to use measurements taken from the SEM's in the course of the trial to suggest that the patentees had been provided with atypical sample discs and an application was made for a further inspection of the defendants' moulds and moulding process, which was rejected by me on 11 May 1998.

7.6.5 The SEM evidence was objectionable because it was disorganised; because there was no attempt to photograph a number of samples; because photographs of part only of the bores of the sample discs were used and because Professor Foyer, who did not in fact have the relevant expertise gave the evidence in relation to them, whereas Dr Bacon should have done. In particular, Professor Foyer gave evidence relating to the interpretation of SEM's (see for example paragraphs 3.2.3, 3.2.4 and 3.2.5 of his report on the SEM's) which he was not qualified to give. The late admission, by consent, of evidence which should have been the subject of a Notice of Experiments led to confusion and a substantial waste of costs.

7.6.6 In support of the allegation that the liquid was capable of flowing, the patentees relied on the evidence of the micrographs, upon deductions which they said could be drawn from the operating conditions of the moulds, and from the defects which the defendants identified in their internal documents as occurring in the moulded discs when those operating conditions were departed from. They also relied upon the Talysurf measurements to which I have already referred and which I have rejected.

7.6.7 I can consider the interpretation of the micrographs first. Dr Bacon gave all the relevant evidence for the patentees, and Dr Crofton gave it for the defendants. I should emphasise at the outset that the interpretation of SEM's is not straightforward and I should be unwilling to place any weight at all upon my own view as to what they showed. Dr Bacon gave evidence that the crucial SEM, plate 4, identified a region of material which could flow and which did not come into contact with the valve, being withdrawn into the disc moulding, by the process of shrinkage. I do not understand why the areas which are allegedly capable of flow although very viscous, did not contact the cutter. Dr Bacon was not familiar with fracture patterns in polymers or hot polymers (see pages 601-2, 652-3). He was not consistent about where the solid-liquid boundary was in plate 4: see 700 line 22 to 704 line 8. In the result, I believe that Dr Bacon's evidence was that there was material in the part of the edge of the disk which corresponded to the gate region of the mould which looked as though it was above Tg when the cutter operated. How far above, and how capable of flowing, I do not think in the end he could say. Nor could he identify it with precision.

7.6.8 Dr Crofton had direct experience in interpretation of SEM's of hot polymers. He was an impressive witness. He is criticised for being combative by the patentees, who rely as an example on the cross-examination at 1165-1172. I do not think that this criticism is justified. Dr Crofton was undoubtedly somewhat curt, but I did not have the impression that he was arguing the defendants' case. He was left unshaken by cross-examination and his conclusion in relation to the SEM's exhibited by Professor Foyer, that "there is absolutely no evidence of any liquid layers having been present in any of the samples considered at the time when the sprues were cut out" was not, in my judgment, shown to be incorrect.

7.6.9 There is one further matter to which I should refer. Dr Crofton is said by the patentees to have failed to follow the logic of his own explanations, where the answer would favour the patentees. He said that certain control tests which he had done indicated that the magnitude of shear-cut regions increases, and the magnitude of brittle fracture regions decreases, as temperature increases and the material becomes tougher even before Tg is approached. It is said that he was inconsistent with this in his intepretation of plate 4, which, it is said, must have been cut at a higher temperature than his control tests, which were carried out on uniformly warmed disks with their sprues attached which had been moulded on a previous occasion. This is merely a failure by the patentees to compare like with like. Dr Crofton did not attempt quantitative measurement. He said that SEM's were not suitable for it, and in any event the temperature distributions in his samples and in the disc during the moulding process must have been quite different.

7.6.10 I conclude that the SEM's showed no evidence of flowable material present when the cutter operated but did show material which had fractured (as opposed to cut) at temperatures below Tg.

7.6.11 The next matter on which the patentees relied was the process conditions, and particularly the so-called "hot hold". The sequence of operations is as follows. Material is injected through the sprue and the gate into the mould. The material is continuously cooling. The cavity eventually fills, but the pressure of molten plastic is maintained for a brief period, so that the cavity remains fully packed as the material within contracts on cooling. This was common ground. However, Mr Allan's evidence is that the hot hold is released before the cutter advances - see his evidence of the gate cut delay 1413 lines 1-10 and 1459 line 4 to 1461 line 11. I accept this evidence, and accordingly in the Meiki presses in which the Husky moulds are installed there is a generally a delay between the end of the hot hold and the beginning of the cut. The point is obvious: if the holding pressure has come off, there is no reason for the material to be flowable at this point, and it will certainly not be flowing. So there is no flow to be prevented.

7.6.12 The patentees rely on the fact that there may be no gate cut delay. It seems to me that this is irrelevant. If there is a substantial quantity of material which is molten in the mould when the gate cutter operates, the main way of accommodating the shrinkage of that material is taken away, since there is no more supply of molten material. That shrinkage will have to be accommodated by other means, such as breathing of the mould (this is the term used to describe an expansion of the entire mould assembly under pressure, and its contraction as the pressure comes off). It was the patentees' case that in the Husky mould breathing would not compensate for more than a small part of the shrinkage. It was established on the evidence that any underfilling of the mould would result in a defective disc. It seems to follow from this that it is essential not to cut off the supply of material until the mould and the material in it is sufficiently cooled that shrinkage is no longer a problem. Thus, it seems to me that the gate will not be operated until there is substantially no flow to cut off. If at this stage the material in the gate is frozen or so viscous or rubbery that it cannot sensibly be said to flow at all but merely to deform, there is no infringement.

7.6.13 The defendants adduced evidence from Professor Fenner who performed elaborate calculations which demonstrated to his satisfaction that the material in the gate froze at a comparatively early stage in the hot hold. Professor Fenner is the Professor of Engineering Computation at Imperial College. His research interests include the application of computing and numerical analysis techniques to the solution of engineering problems including thermal conduction problems. He has experience in the past in the investigation of polymer melt flow in extrusion and injection moulding equipment. His abilities are not characteristic of the man skilled in this art, who is represented by someone of Mr Bartholdtsen's general level of attainment. I believe that his evidence as to what is going on in the mould is something which I should take into account.

7.6.14 Professor Fenner's evidence was that the gate in the Husky mould froze during the hot hold period. An extensive cross-examination was devoted to his general level of knowledge (938 to 944) and to establishing that his assumptions in relation to the material were incorrect; that the geometrical approximations which he made in relation to the shape of the mould were incorrect, and that these approximations which were necessary to produce an analytical result (i.e. one that did not have to be solved by numerical analysis) were unsafe. The validity of his assumptions was of course crucial to the validity of his calculation. The whole of the cross-examination (961 to 975 on ignoring inflow during the hot hold, 975 to 979 on his analytical approach, 980 to 981 on his approach to assumptions, 981 to 992 on frictional heating of material as it passes into the mould, 993 to 995 on the figures used for thermal diffusivity) failed really to shake him. Professor Fenner was very confident in his results, and he was also reasonable in his discussion of the breathing mechanism. He realised that if the breathing mechanism compensated for all the material shrinkage, there did not need to be any inflow and there could be no criticism of him for ignoring inflow in his calculations. He noted (correctly) that Mr Bartholdtsen had suggested that the breathing mechanism was adequate to compensate for shrinkage (second report paragraph 3.9). Professor Fenner did not think this was right (page 1062) and thought that the shrinkage had to be compensated for by a number of effects and that there was thus an assumption built in to his calculations in this regard. This point was revisited (1064-1073). In the end I was satisfied as to the general correctness of his approach, and I was satisfied that his conclusions in his third report were correct.

7.6.15 The patentees rely heavily on Mr Bartholdtsen's evidence. His evidence was, as I have indicated, a series of deductions from his experience. It was common ground that nobody can know what happens inside a mould, and it was not clear to me why extensive experience of moulding discs would enable anyone, whatever his experience, to say that the material in the gate region was liquid when the cutter operated, when he had never himself operated the process of which he was speaking. The cogency of his evidence was not helped, I regret to say, by the obviously incorrect evidence which he had given in his first report in relation to the basic issue of how plastic flows into the moulds in question. In the end I consider that the weight of the evidence was that the material was frozen in the gate when the cutter operated.

7.6.16 I conclude that the Husky moulds used by the Defendants in the manner complained of do not infringe.

7.7.1 I set out a diagram of the Axxicon mould in suit, taken from X13. It is rotated so that the parts of the mould correspond to those in the two Husky diagrams.

7.7.2 The issue in relation to the Axxicon mould is obviously different from that in the Husky moulds. There is always a clearance between the "valve means" and the fixed mould half, and also between the "valve means" and the sprue bush. It is difficult on the face of it to suggest that there is a pinch-off involving the skins of plastic formed on these components. It was conceded that there was no evidence that the thickness of the gate region of the sprue in the Axxicon mould is reduced on valving from what it would have been if the valving had not taken place (the difference in the measurements of the gate regions of the disc, separated sprue, and unseparated disc-with-sprue), and this means there is no evidence of any pinching effect at all. The evidence in relation to infringement was weak. The interpretation of the SEM's again gave rise to uncertainty. The only real evidence is that of Mr Bartholdtsen and that of Professor Fenner, and for the reasons which I have already given I prefer that of Professor Fenner. There is no evidence of any capacity for flow, and no evidence of any bearing engagement. The allegation of infringement fails.

7.8.1 The patent is attacked on the ground of obviousness only. The documents relied on are US patent 3,937,779 (Simmons) and US patent 4,085,178 (McNeely). The other documents pleaded were not persisted with.

74. Simmons discloses an injection/compression method of moulding conventional records. The material is injected into a separated mould, which is then closed after the injection has ceased (column 2 line 34-46). There is therefore no suggestion of a valve, or of injection moulding as such at all. It seems to me that this document is dealing with a different problem from that of the patent in suit, and that the solution proposed is unrelated to the alleged invention of the patent in suit. In my judgment it requires an unacceptable degree of hindsight to see anything of relevance to hot sprue injection moulding in this document at all. The evidence from Professor Fenner and Mr Bartholdtsten did nothing to suggest to me that I am wrong in this view.

75. McNeely is concerned with the injection moulding of optical discs. It discloses a cold sprue system in which the sprue is separated from the disc as part of the opening of the moulds. Figure 2 shows the relevant movement. At page 1108 Professor Fenner was asked the following questions:

77. The defendants' contention was that it was obvious to speed McNeely up, and in doing so it would inevitably mean that material above Tg would be cut. This is correct, but unless the material is in Mr Bartholdtsen's words "sealed in" the disc would be bound to be unsatisfactory. This seems to me to be right, and the set of questions and answers I have quoted above makes any approach to obviousness on the basis of McNeely very difficult. I was unimpressed by the whole argument, and in my judgment Cane is valid.

8.1.1 Holmes is no longer alleged to be infringed, but I have still to consider its validity. Holmes is concerned with an injection mould for moulding "centrally apertured parts" and in particular videodiscs. The invention is best seen from looking at Figure 9 and its accompanying text (page 6 line 69), and is said to lie in providing a smoothly tapered sprue passage between the sprue and the gate. This is said to promote uniform filling of the mould and to avoid variation in the birefringence of the material (page 2 line 22). The claim is as follows:

(1) An injection moulding apparatus
(2) for moulding centrally apertured parts, said apparatus comprising
(3) a port through which molten material is injected, and
(4) an annular cavity formed by first and second mold halves
(5) and having an inner entrance region into which the molten material is injected
(6) and an injection gate
(7) including an annular injection gate passage positioned intermediate said port and said cavity
(8) said injection gate passage having an inner entrance region and an outer exit region through which said molten material flows
(9) said outer exit region of said passage communicating with said inner entrance region of said cavity
(10) the height dimension of at least a radially extending section of said annular passage taken parallel to the major axis of said annular passage decreasing with increasing radius
(11) to regulate the pressure of said molten material along said injection gate passage
(12) and thereby effect a uniform flow of molten material into said cavity
(13) with minimum disturbance to material flow.

78. This is a lot of words to describe the simple concept of a mould with a central sprue and a tapering passage from the sprue to the gate.

8.2.1 The patentees suggest that there is an issue whether the taper of feature 10 is required to be a gradual taper or merely to include a stepwise reduction. It seems to me that only part of the passage is required always to decrease in height with increasing radius, but the precise dependency on radius may change: thus there may be discontinuities and even zones where height increases with radius provided that there is always one zone where there is decrease in height with radius, and provided always that the "functional requirements" of features 11, 12 and 13 are satisfied.

8.3.1 There are two attacks on this patent: obviousness of claim 1 and added matter. I shall deal with added matter first.

8.4.1 The A specification of Holmes (as well as the application as filed) contains a figure corresponding to Figure 9. The annular sections are said to lead into one another (page 6 line 87-92) and four annular sections are described. The corresponding description is the same as that in the granted patent. What the granted patent does not have is any description relating the taper of the tapered annular sections to the attainment of the functional features which can best be summarised as requiring smooth, uniform filling. What is disclosed (page 6 line 86) is that the shape of the passage is determined so that the injected material advances across the stamper surface at a uniform rate. This is related to the particular 4-zone construction to which I have referred. It is not related to any more general concept of the spacing of one part only of the passage decreasing with radius. The passage at page 7 line 20 relates the various annular regions to the achievement of the desired fill:

80. There is no disclosure of any general relationship between a taper in some part of the passage and uniform flow. Nor is this provided by claims 12 and 13: claim 12 is concerned merely with the provision of different, unspecified, zones and claim 13 corresponds to the passage which I have quoted.

8.4.2 This is a case of what can be called intermediate generalisation: that is a generalisation of one feature of a detailed disclosure (the tapered region 304) so as to deprive it of its context. In my judgment this amounts to added matter unless the skilled man would immediately understand that the purpose of any taper at any point would be to achieve smooth uniform fill. But if this is the case, it would be common general knowledge that such a taper would achieve such a fill.

8.4.3 The law is that matter is added unless clearly and unambiguously disclosed in the application either expressly or implicitly (see Bonzel v Intervention [1991] RPC 553 and many other cases). While this rule does not extend to a mere different way of describing something disclosed, nonetheless all the features identified in the new description must have been disclosed with all their attributes in the application.

8.4.4 I think that there is here a real dilemma for the patentees. To make good the deficiencies of the disclosure of the application, they must appeal to the common general knowledge, but in so doing they must show that the feature in question is common general knowledge. Since this feature is the only feature of the claim which can give subject matter, the claim must then be obvious. On the whole I prefer the view that this is added matter, since I was not otherwise completely convinced by the evidence that use of a taper in the sprue passage was the application of common general knowledge to achieve the desired result. But I believe that it is one or the other.

8.4.5 It follows that the patent is invalid and must be revoked.

9.1.1 Wilkinson 1 is concerned with the development of the photoresist on the glass master. This is the master which is exposed by the laser beam in a device such as the Philips LBR which I have considered above. The chemical nature of the photoresist is changed in the regions where the laser light has fallen upon it so as to make these regions susceptible to removal by a chemical, called the developer. This will create the first pattern of pits recording the data, which will then be reproduced. The claim is as follows.

81. There is no dispute that the outline of the process (features (a) to (g) of the claim) were conventional. The invention lies in the substitution of three steps (wet with water alone, part develop with dilute developer, complete development with undiluted developer) for the old two-step process involving prewetting and development with dilute developer alone. No significance is attributed to the steps of this process by the specification, which are described only in the passage at column 5 lines 34-57, the remainder of the specification being taken up with a rather detailed description of the preparation of the photoresist layer on the glass master.

82. No points arise on construction.

9.2.1 Professor Lawes gave a witness statement on this subject, but it was withdrawn. The patentees advanced no evidence to support this patent. I need to consider the evidence that Professor Lawes gave under cross-examination and that of Mr Sykes, who was called by the defendants. He was a man with extensive experience in the oldest application of photoresist development, the making of printed circuits. He had no experience of compact disc development. His area of expertise is thus somewhat off the area of the invention, since in the manufacture of printed circuit boards it is the shape of the exposed metallic layer which matters not the shape of the edge of the photoresist itself. He had no experience of semiconductor fabrication where the shape of such edges is important, but he had experience of a particular application (in the microwave field) where edge shape had been important. He gave evidence that staged development (dilute followed by more concentrated development) was well known in his field.

9.2.2 There is one cited document, referred to as Palermo. Palermo is a general description of videodisc mastering and replication. There are only two passages of relevance:

85. The developer is in fact one that was well known to Mr Sykes who used it as well for his printed circuits.

9.2.3 Professor Lawes also accepted that staged development was known in the semiconductor fabrication field, and he was cross-examined on the use of this knowledge in the performance of the process described by Palermo:

9.2.4 There is no evidence that Wilkinson I gives any technical advantage over the method described in Palermo, and there is no evidence that the two-stage method has any general advantage over one-stage methods, although both experts agreed that the reason for the two stage step is to sharpen the development of features. It is right that evidence of an advantage does not make it non-obvious: but it does not follow that lack of evidence of any advantage is not relevant to the question of obviousness, since it tends to suggest that there is no contribution to the art and to reinforce the impression that this is merely a workshop expedient which might or might not occur to any skilled man, but requires no ingenuity.

9.2.5 Mr Sykes confirmed under cross-examination that photoresist development is an empirical matter, and when considering X56 (a document published 3 years after the priority date) he accepted that optimising development was an extraordinarily tedious task. However, there is no suggestion that the process of Wilkinson I is optimised in any relevant sense. In the end, I have come to the conclusion that this is a mere workshop variation without advantage, and claim 1 is invalid.

10.1.1 This patent is concerned with the deposition of metallic vapour on the glass master coated with the photoresist which has been developed to create the spiral pattern of pits recording the data. The coating of such layers by the process known as vapour deposition had been disclosed (for example, in Palermo), and of course the general field of vapour deposition is very wide, going all the way from mirrors for telescopes to metallisation layers for microcircuits. The essence of such a coating process is that metal is evaporated and is deposited on the surface to be coated, and the procedure takes place at high vacuum, to prevent contamination of the deposited layer of metal, principally by oxides of the metal. The field is generally described in the cited book by Ward & Bunn, which represents the common general knowledge in the field of vacuum deposition as at 1967.

10.1.2 The invention is said to reside in coating at a vacuum of 1.33 10-4 Pa (Pascals, or newtons per square metre) rather than the prior art pressure of 1.33 10-3 Pa. In the field of high vacuum technology, these pressures are better known as 10-6 torr and 10­5 torr respectively, where 1 torr is the head of 1mm of mercury, and named for the inventor of the mercury barometer, Torricelli. No issues arise on the construction of the claim, and the only issue is whether it was obvious to coat CD glass masters at the lower pressure at the priority date.

10.1.3 The patentees' evidence came from Mr Slaten, and the defendants' evidence from Professor Edgar Andrews. Professor Andrews was attacked as being an expert expert, and he acknowledged that he had given evidence or had been consulted in many patent actions. But he had directly relevant experience. He gave evidence, which is in my view convincing, that in fact the idea of carrying out the depositing step at the prescribed pressure is simplistic. The pressure will rise as the metal to be vapour-deposited is outgassed as it is heated. The pressure will then substantially reduce as the metal is vapour-deposited, the so-called gettering effect. This reduction in pressure occurs because the deposited metal traps molecules of gas underneath it as it is deposited. So the claim must be talking about the starting point, and Professor Andrews expressed the view, in effect, that one gets what one pays for. The lower the pressure, the lower the degree of potential contamination and so the higher the chance of a high quality evaporated layer of metal. It is clear from Ward that this was the basis for the selection of the appropriate coating pressure in 1967. The book by Berry, to which Professor Andrews also referred, also makes this point.

10.1.4 The defendants submit that the cross-examination of Mr Slaten established that pressure was always one of the variables which was to be adjusted in adjusting the deposition process; that it was conventional to monitor signal to noise ratio of the resultant metal discs as a means of quality control; and that deposition imperfections were a principal cause of poor signal to noise performance. A pressure of 10-6 torr is not out of the way, as all the evidence established, and Professor Andrews gave good reasons for using it as a starting point (see page 1157). There is really no answer to this, and accordingly I find that the alleged invention of this patent is obvious, and the patent must be revoked.

11.1.1 Mr Howe reserves his contention that the first plaintiff is not capable of suing in its own name for future argument in the light of the unreported decision of the Court of Appeal in Oxnard Financing v Rahn (unrep Nourse & Mummery LJJ and Sir John Vinelott, 1 April 1998). In this I am sure he is right. But he relied on a point under section 68 of the Act.

11.1.2 Section 68 of the Patents Act 1977 restricts recovery of damages by a person when a relevant transaction instrument or event by virtue of which that person becomes the proprietor or one of the proprietors of a patent has not been registered within 6 months of its occurrence. In this case the plaintiffs are Discovision Associates ("DVA"), which is a general partnership under Californian law, and its two present partners. DVA is, and has at all material times been, the registered proprietor of the patent.

11.1.3 In about November 1989, the partners in Discovision Associates changed. This occurrence was never registered (the registered proprietor remaining DVA). The defendants say that the change in the partners was a relevant transaction, instrument, or event, and that accordingly they are entitled to take the benefit of section 68.

11.1.4 There is no doubt that a California partnership has a limited degree of legal personality, and, in particular, it has the power to own property in its own name. On dissolution, this property is applied to the discharge of the partnership's liabilities before it can be distributed. Professor Hillman, of the University of California at Davis, gave helpful and clear evidence on this issue. His evidence was that DVA is a partnership governed by the California Uniform Partnership Act and capable of owning property in its own name, the rights of the partners inter se depending upon the terms of the partnership agreement.

11.1.5 By section 30 of the Act, a patent is personal property without being a thing in action. So the only question is, can a Californian partnership own personal property in the United Kingdom, or is such personal property correctly to be viewed as the property of the partners. In Lazard Brothers & Co. v. Midland Bank Ltd. [1933] A.C. 289, 297, Lord Wright said:

11.1.6 Whether or not a partnership is a corporation for the purposes of this rule is to be decided accordingly to the law of the country in which it is formed. I have already referred to the evidence of Professor Hillman.It seems to me that it would be wrong not to accord to DVA the right which it has under its own law of formation of owning property unless I am obliged to do so, since to do so would serve no good purpose and might serve to disrupt established titles. Mr Howe was unable to point to any rule of law obliging me to take this course. It is inherent in the recognition of foreign corporations that they may be corporations of a type which would not be recognised by English law and which have no parallel in English law. That does not mean they are not to be recognised. Mr Howe's submissions were based on a number of fallacies. In particular, he was concerned that if "California partnership law applied" English creditors of the plaintiff would be deprived of their normal remedies of seizure and sale. But this cannot be right: the remedies for debt are a matter for the lex fori (See Dicey Rule 17 and the commentary under (1) Nature of Remedy) not for the law of incorporation of the debtor.

11.1.7 In my judgment, DVA holds the patent in suit independently of its two partners for the time being, and is to that extent to be recognised as a corporation. There has been no transaction, instrument or event affecting DVA's title, and this point must be rejected.

12.1.1 This is a short point. It relates to the Dakin and Somers patents. The defendants purchased their LBR from Philips. Philips enjoyed a licence to use it from the patentees. The defendants say that the patentees have no right to sue in relation to the use of the LBR, having exhausted their rights therein by virtue of what was Article 30 of the Treaty of Rome.

12.1.2 The only licence granted to Philips was a use licence and a licence to sell, with no right to sublicence third parties. The patentees are not alleged to have consented to the sale of the LBR to the defendants, and they are not alleged to have consented, expressly or impliedly, to the use of the equipment by the defendants. Consent is the cornerstone of the doctrine of exhaustion - see Advocate-General Jacobs' summary of the case law under old Article 30 in Case C-10/89 Hag GF [1990] ECR 3711 at 3729. Absent putting the LBR on the market with the consent of the patentees express of implied, to its use, there can be no question of exhaustion. The point is a bad one and must fail.