Cartonneries De Thulin SA v CTP White Knight Ltd [2000] EWCA Civ 174 (25 May 2000)

Judgment As Approved by the Court Crown Copyright © LORD JUSTICE ROBERT WALKER: Introduction The principal issues in this appeal are whether the claimant's patent EP 0 430 956 ("the patent in suit") is valid, and (if so) whether it has been infringed by the defendant. The patent in suit relates (in the English language version of the original German) to a `storage case for circular data carriers' but for practical purposes the article in question can more readily be identified as a cassette for storing and protecting compact discs (CDs). The claimant is a Belgian company, Cartonneries de Thulin SA (which trades as Carthuplas and is referred to in this judgment by its trading name). The defendant is an English company, CTP White Knight Ltd (White Knight). By an order dated 21 December Neuberger J dismissed the action by Carthuplas on the ground that the patent in suit, although valid, had not been infringed by White Knight's products. He also dismissed White Knight's counterclaim for revocation of the patent in suit. From that order Carthuplas appeals and White Knight cross-appeals, in each case with the permission of the judge (but limited to the issues of infringement and validity respectively). As Mr Henry Carr QC (for Carthuplas) has said in his skeleton argument, CD cassette boxes are familiar household objects, but most people do not bother to look at their construction. In this case the members of the court have looked closely at a number of exhibits, from which different features of design are more readily apparent than from a written specification. But it is necessary to bear in mind that it is the text of the patent specification, properly construed, which must ultimately be decisive on the issue of infringement (and is of central importance to the issue of validity). The commercial background to this case is that Carthuplas was involved in the design and manufacture of plastic injection moulded products and in 1985 it first became interested in the market for CD cassette boxes. In 1986 it obtained a licence from Polygram (a subsidiary of Philips and a leader in the development of CDs) to manufacture two staple Polygram products, that is the so-called Jewel Box for a single CD and the Multipack for collections of two, three or four CDs. All CDs are manufactured in the same physical format, that is the 120mm disc developed by Philips and Sony in the early 1980's. There is in the witness statement of Mr Filip Lammerant (who is now the managing director of Carthuplas, and has been involved in this part of its business since 1985) a useful summary which provides the technical background to the problems of designing CD cassette boxes (two references to technical drawings have been omitted): "Digital information is stored on a CD as a sequence of "pits" and "flats" within the substrate of the disc. This sequence runs in a spiral track located in what is called the information area between the outside edge and the centre of the disc, where a non-information carrying area is preserved around the perimeter of the centre hole. To recover the digital information, a laser light is directed at one side only of the CD called the program side which is usually identifiable by its shiny, silvery coloured, surface. The laser light reflects differently depending on whether it strikes a "pit" or a "flat", and the digital information is interpreted from the different reflections. The opposite side of the CD is usually only used to carry some form of labelling. Whilst the CD is a reasonably robust medium, it is still good practice to handle or store individual CD's in a way that will minimise the risk of damage or distortion to the program side. The "pits" and "flats" are very small, and a distorted disc can mean that the laser light will not accurately follow the spiral track when the CD spins, and any scratches or abrasions to the program side can produce a false reflection. Circular abrasions (as might occur if the program side of a CD is twisted on a surface) are the most damaging, because they are likely to extend along the line of the spiral track. Apart from setting the optical and electrical standards for the CD format, Polygram also established standards for CD packaging. This helped to ensure basic protection for the CD, and also offered a number of marketing advantages that I shall describe later. An important protective feature of the CD disc is its central hole. This centre hole serves two main purposes; it centres the disc in the CD player when it is being played and it is used to secure the CD to a ring of clamp holders formed in the storage cassette. Some form of clamp holder has always been present in CD cassette boxes that I am aware of, and such a feature is present in all the CD boxes exhibited with this Report. Clamp holders are mounted on a distance ring, which stands above the surrounding surface area. The CD should be placed program side down on the clamp holders to shield the information carrying surface. The non-information carrying part on the program side around the centre hole of the CD rests on the distance ring so that the information carrying part is kept clear from the underlying surface, thereby reducing the risk of contact and damage. The CD should be removed from the clamp holder by pulling it outwards and away from the clamp holder. This reduces the likelihood of damaging the program side of the CD by scuffing it against the cassette." By 1988 there were about ten European companies (including White Knight as well as Carthuplas) licensed by Polygram to manufacture its Jewel Box and Multipack, and millions of these products were being manufactured. They were, as the judge said, in common general use. But the Multipack was perceived as having several disadvantages (though these did not prevent it retaining a substantial market share so long as CDs sold on quality rather than price). It was slightly more than twice as thick as the Jewel Box, it had five plastic parts, it could not be stored and displayed in the same racks, and it could not be packed automatically (packing machines came into use from about 1986). It was wasteful of materials and space, especially if used for only two (rather than three or four) CDs. In 1987 Polygram introduced a third model of a cassette box, the Two Piece. This was a much simpler and cheaper product with only two plastic parts, holding a single CD. Carthuplas took a licence for it in 1987. In January 1991 Mr Lammerant began work on the design of a new product which came to be called the DuoBox (and later the Brilliant Box) and a patent application was filed in May 1991. That did not however lead to the patent in suit. It was acquired by purchase in March 1992, after complaints by patent attorneys acting for a competitor called Posso, which was a licensee of the inventor, Mrs Petra Dunker. By 1991 or thereabouts (some of the evidence on this point was unclear) there were five new products, either on the market or about to be brought onto the market, which had the common features of holding two CDs and being as slim as the Jewel Box. These were the Z-Box, the Pilz Box, the Viva Box, the Posso Box and the Brilliant Box. Their introduction signalled that a huge and growing market was interested in price as well as in quality. The Z-Box (or Twin Box) was not a commercial success, despite having been developed and introduced by Polygram itself (White Knight took a licence from Polygram to manufacture the Z-Box). The Brilliant Box has been a great success, to the extent of achieving almost 90 per cent of the European market for sales (about 150m a year) of twin slim-line CD holders. However a complicating factor is that its success may be due in large part to the excellence of its central disc-holding tenon (also referred to as a clamp holder) for which Mr Lammerant holds a separate patent (not at suit in these proceedings). It is unnecessary to embark on a detailed description of the thirteen exhibits placed before the court (there is a fairly full description of most of them in Mr Lammerant's witness statement). All the cassettes have a base part and a cover part hinged together and made of polystyrene, a hard glassy plastic. The simple Two-Piece has no other component (apart from the inserted card), the tenon being formed in the centre of the base part. All the others have a separate disc-holding part made of a more flexible plastic, with a central tenon for holding the CD (the tenon being surrounded, in most of the products, by finger holes for better contact with the edge of the CD). In the Jewel Box the disc-holding part is clipped into the base part and is not hinged. The Multipack has a disc-holding part in each of the outer compartments and also a further substantial disc-holding part to which the other compartments are hinged, so that it opens like a book. The Z-Box has (as its name suggests) two hinges at opposite sides of the disc-holding part, attached to the base and the cover respectively and opening in a Z-shape, with a tenon in the centre of each side of the disc-holding part. The Brilliant Box has (if placed on a flat surface) a base part to the left-hand side of which is hinged the cover part and to the right-hand side of which is hinged the disc-carrying part (made in transparent polystyrene and with a tenon surrounded by finger holes in the centre of each face of the disc-carrying part). The two parts hinged to the base open out like a triptych. The disc-holding part opens out to an angle of about 180° relative to the base part. All the products have space for the insertion of contents cards and small booklets. It is convenient to say something at this point about the course of the trial. Mr Lammerant gave evidence at the trial not only as a witness of fact but also as an expert. He said in his witness statement that despite his interest in the matter he understood that he should assist the court in an unbiased manner, and that he believed that his report contained an objective appraisal of the issues. Mr Lammerant was cross-examined at length by Mr Alastair Wilson QC (who appeared below, as he has in this court, with Mr Michael Tappin for White Knight). The judge said of Mr Lammerant's evidence, "...while I would certainly not question his honesty, Mr Lammerant was not an entirely dispassionate witness. Mr Wilson was not inaccurate in describing Mr Lammerant as a good salesman, and he did not leave this aspect of his character behind when he entered the witness box. Nonetheless, I am far from saying that his evidence should be discounted entirely, but it seems to me right to approach it with a degree of caution. He seemed to me to be a witness with considerable direct relevant experience, doing his best but not able to be entirely dispassionate." Later the judge referred to him as being inclined to exaggerate, but basically an honest as well as a relevantly expert witness. The patent in suit The patent in suit claims a priority date of 29 August 1988. It was prepared by German patent attorneys and it follows the usual model of setting out the prior art in some detail before moving on to the perceived advantages and inventive concept of the invention. It is convenient to defer reference to the prior art until later in this judgment. The most important passage dealing with the invention's advantages and concept is as follows: "The aim of the invention therefore is to construct a storage cassette of the initially-mentioned kind, which is reliable and space-saving. To this end, a storage cassette having the features of claim 1 is proposed. A storage cassette of this kind can be made extremely flat, can be completely free from tilting when pivoted, and can be provided with a part for receiving two CDs and pivotable through a wide angle. It has been found advantageous to provide end walls, preferably of use as book spines, on opposite edges of the base part. The end walls increase the reliability of the hinge devices and also make it easier to keep the storage cassette free from dust when closed. It has also been found advantageous, for reliable use of the storage cassette, to provide a means for limiting the angle through which the disc-storing part pivots outwards, since this reliably prevents the disc-receiving part turning over completely, resulting in damage to the circular information disc. The invention and the features thereof provide inter alia the following advantages: - The novel hinge arrangement considerably improves the protection of circular information carriers, particularly CDs, against falling out of the cassette when opened or used in an open state; - The protection against falling is further improved by limiting the angle of opening; - The storage cassette is as dust-proof as the known, commercial cassettes for storing single CDs; - The storage cassette consists of only three, easily manufactured parts; - The same cover parts can be used as for known cassettes for storing a single CD; also the base part of the known storage cassette requires only slight alterations, ie two bores serving as hinge parts; - Adjustable furniture for displaying or privately storing the cassettes according to the invention can continue in use without restriction, as hitherto used for individual cassettes; - Two CDs can now be stored in the same space hitherto required for a single CD or other circular information disc, and - In addition, a fourth area available for information is provided in the cassette and is approximately equal to the entire front or rear side of the cassette." The specification then sets out a detailed description of the new cassette, by reference to four figures (which are reproduced in the judgment under appeal). Ten paragraphs of claims follow. Claim 1, which is of greatest importance, is in the following terms, which are reproduced with the integers lettered in the same way as in the judgment. It should be noted that in the official version, while integers (e) to (h), most of (i) and (j) to (m) all are indented, the words "characterised in that" (in the German language version, `dadurch gekennzeichnet') in integer (i) are not indented: "(a) A cassette (1) for storing circular information discs (29) and comprising (b) a base part (2) (c) a cover part (3) (d) and a disc-holding part (4) in which (e) the base part (2) is pivotable relative to the cover part (3) (f) by means of a first hinge device (12,17) (g) provided on a first edge (6) of the base part (h) and the disc-holding part (4) is pivotally received by the base part, (i) both sides of the disc-holding part (4) respectively have clamp holders (24-27) for a central hole of a circular information disc (29) characterised in that (j) The disc-holding part (4) is pivotally mounted on the base part (2) by means of a second hinge device (18,19) (k) which is disposed on the edge (7) of the base part (2) opposite the first edge (6) comprising the first hinge device (12,17), (l) the disc-holding part (4) is pivotable by means of the second hinge device (18,19) by a maximum pivoting angle of at least 80° to an end position in which the disc-holding part (4) comes to abut a pivoting-travel limiter provided in the region of the second hinge device (18,19) (m) and in which both sides of the disc-holding part (4) are freely accessible for removal of one of the two information discs (29) as desired." It should also be noted that claim 7 is the only claim which mentions any specific angle as the largest acceptable angle for the disc-receiving part to pivot through: "A cassette according to any of claims 1 to 6, characterised in that the maximum pivoting angle between the disc-receiving part (4) and the base part (2) is 120°, preferably about 80° to 100°." (In this claim `maximum' must be used in a strong sense as setting a limit as part of what the specification teaches, whereas in claim 1 it must be used in a weaker sense, reflecting the obvious fact that a hinged door which can open to say 135° can also open to any smaller angle.) The only other claim which calls for particular mention is claim 2: "A cassette according to claim 1 characterized in that the cover part (3) and the base part (2), apart from the second hinge device (18,19) are commercial parts of a cassette (1) for storing a single circular information disc." It is common ground that the single-CD cassette referred to is the Jewel Box. The issues The judge dealt first with the issue of infringement (raised in the action) and then with the issue of validity (raised in the counterclaim). The issue of infringement is in the end quite a short (but not necessarily easy) point, because it is and always has been common ground that if Carthuplas was right as to the correct construction of claim 1 of the patent in suit, White Knight had infringed that patent; but that if White Knight was right on the point of construction, it had not infringed the patent. The crucial issue of construction was whether White Knight was correct in arguing that claim 1 applied only to a cassette with a disc-carrying part which opened by pivoting through an angle of not much more than 90° (the judge suggested the figure of 135°, as halfway between 90° and 180°; this may be compared with the figures of 100° and 120° in claim 7). If so, there was no infringement, because in White Knight's Super-2 CD cassette boxes the disc-carrying part opens by pivoting through an angle of about 180° (or in some versions about 165°). That is why the angles mentioned in claims 1 and 7, and the reference to `a pivoting-travel limiter' in claim 1 are important. The other issue, validity, involved an attack by White Knight on the patent in suit as being an obvious derivation from the prior art (and in particular, the Jewel Box). In his approach to this part of the case the judge adopted the well-known test for obviousness enunciated by Oliver LJ in Windsurfing International v Tabur Marine (Great Britain) [1985] RPC 59, 73-4. In this court Mr Carr, in seeking to uphold the judge's conclusion, has relied on the well-known observations of Lord Hoffmann in Biogen v Medeva [1997] RPC 1 , 45. The issue of validity also involves a point on section 72(1)(d) of the Patents Act 1977, under which a patent may be revoked if "the matter disclosed in the specification of the patent extends beyond that disclosed in the application for the patent, as filed". The judge, having decided that the patent in suit had not been infringed, and was not invalid on the ground of obviousness, did not find it necessary to say much about the `added matter' point. But Mr Wilson has submitted that if the judge is held to have been wrong on the issue of infringement (and the point of construction on which it turns) then the `added matter' point assumes a new importance. It is best to take the issues in the same order as the judge took them. Construction: relevant principles The court's approach to the construction of a patent specification is not essentially different from its approach to any other text or document which has legal force. But there are two important complicating factors. One is the European dimension. Section 125 of the Patents Act 1977 provides, "(1) For the purpose of this Act an invention for a patent for which an application has been made or for which a patent has been granted shall, unless the context otherwise requires, be taken to be that specified in a claim of the specification of the application or patent, as the case may be, as interpreted by the description and any drawings contained in that specification, and the extent of the protection conferred by a patent or application for a patent shall be determined accordingly. (2) ... (3) The Protocol on the Interpretation of Article 69 of the European Patent Convention (which Article contains a provision corresponding to subsection (1) above) shall, as for the time being in force, apply for the purposes of subsection (1) above as it applies for the purposes of that Article." Article 69 is (as section 125(3) indicates) in terms similar to section 125(1). The protocol on the interpretation of Article 69 provides, "Article 69 should not be interpreted in the sense that the extent of the protection conferred by a European patent is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Neither should it be interpreted in the sense that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and drawings by a person skilled in the art, the patentee has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties." This court has accepted that the well-known speech of Lord Diplock in Catnic v Hill & Smith [1982] RPC 183, although concerned with the Patents Act 1949, correctly states the approach required by section 125(1) and the protocol: see Improver Corporation v Remington Consumer Products [1990] FSR 181 (Hoffmann J) [1989] RPC 69 (CA). The other complicating factor is the special importance of the claims made in a patent specification, and the degree to which the construction of the claims may be influenced by other parts of the specification. (This factor is not wholly distinct from the first, since patent attorneys in different industrial countries adopt perceptibly different approaches to drafting patent specifications: German (and other continental) draftsmen tend to a `central' style which concentrates on the `centre of gravity' of an invention; British (and still more, American) draftsmen tend to a `peripheral' style which seeks to delimit the boundaries of an invention). Although a patent specification must, like any other legal document, be read as a whole in its technical and commercial context, the claims set out in the specification have a special importance: "The function of the claims is to define clearly and with precision the monopoly claimed, so that others may know the exact boundaries of the area within which they will be trespassers. Their primary object is to limit and not to extend the monopoly. What is not claimed is disclaimed. The claims must undoubtedly be read as part of the entire document, and not as a separate document; but the forbidden field must be found in the language of the claims and not elsewhere. It is not permissible, in my opinion, by reference to some language used in the earlier part of the specification, to change a claim which by its own language is a claim for one subject-matter into a claim for another and a different subject-matter, which is what you do when you alter the boundaries of the forbidden territory." That is what Lord Russell said in EMI v Lissen (1939) 56 RPC 23, 40 (that case was not cited by counsel but is very well known). Lord Evershed MR said in Rosedale Associated Manufacturers v Carlton Tyre Saving Co Ltd [1960] RPC 59, 69 "It is no doubt true and has been well established (see, for example, the speech of Lord Russell of Killowen in the EMI v Lissen case) that you must construe the claims according to their terms upon ordinary principles, and that it is not legitimate to confine the scope of the claims by reference to some limitation which may be found in the body of the specification, but is not expressly or by proper inference reproduced in the claims themselves. On the other hand, it is clearly no less legitimate and appropriate in approaching the construction of the claims to read the specification as a whole. Thereby the necessary background is obtained and in some cases the meaning of the words used in the claims may be affected or defined by what is said in the body of the specification." That passage was recently approved by this court in Lubrizol Corporation v Esso Petroleum [1998] RPC 727, 738, a case which illustrates an inadmissible attempt to use other parts of the specification to put a gloss on the clear language of a claim. These, and other authorities to which this court has been referred, provide general guidance as to the task which the court has to undertake. What Viscount Simonds said about statutory construction in A-G v Prince Ernest Augustus of Hanover [1957] AC 436, 461 may also be apposite to the construction of patent specifications, especially since the protocol: " ... it is natural enough that in a matter so complex the guiding principles should be stated in different language and with such varying emphasis on different aspects of the problem that support of high authority may be found for general and apparently irreconcilable propositions." The court has to do the best it can to reconcile the literal meaning of the language of the claims with the context provided by the rest of the specification (as both would be read by the ordinary skilled man) in order to provide both fair protection for the patentee and reasonable certainty for the patentee's competitors. Construction: the problem In some well-known cases the tension between a literal and a purposive construction can be expressed as a question which can be simply posed, even if it is difficult to answer: in Catnic , how vertical? or in Minnesota Mining & Manufacturing Co v Plastus Kreativ [1997] RPC 737, how opaque? The court finds in a claim an expression with a clear "primary, literal or acontextual meaning" and applies appropriate tests (most clearly spelled out by Hoffmann J in Improver [1990] FSR 181, 188-9) to see whether a variant meaning is within or outside the claim. The peculiar difficulty of this case is that the judge had to start with a claim which uses an expression ("freely accessible" in integer (m) of claim 1) which has no clear primary meaning beyond the imprecise notion of being `get-at-able'. This seems to have led at the trial (as it has, to a lesser degree, in this court) to a considerable volume of submissions based on informal demonstrations and experiments in court with the exhibits (which suffered frequent casualties). This may have tended to distract attention from the central problem of construing the specification of the patent in suit. There are two points which increase the obscurity of the requirement (in integers (l) and (m)) of "an end position in which the disc-holding part comes to abut a pivoting travel limiter [PTL] provided in the region of the second hinge device and in which both sides of the disc-holding part are freely accessible for removal of one of the two [CDs] as required" (it was common ground in this court, though it had been in issue below, that both of these expressions "in which" qualify "end position"). The first is uncertainty as to how the user of CDs holds the cassette while extracting a disc. The judge accepted "that there is no reference to, let alone teaching as to, the way in which one might open a cassette, or remove a CD, in the patent in suit." The judge considered, apparently by reference to his own handling of the exhibits, what was the most natural way to open and remove a CD from a cassette held in one's hand. The judge did have some evidence from Mr Lammerant about this, but it seems to have been of limited assistance to the judge, and in the absence of findings by the judge it is of even less assistance to this court, since manual gestures, like nods, do not appear on the transcript. The following extract from the cross-examination of Mr Lammerant gives the flavour: "Q This may be a very trivial point, but if you take one of the products which was in issue until the Lesley Garrett products were introduced into the case ... MR JUSTICE NEUBERGER: 1 to 5. MR WILSON: I do not know if there are any which still survive. Your Lordship may still have number 1. MR JUSTICE NEUBERGER: All mine have come to bits. A I have a survival here. MR WILSON: Mr Lammerant, it is a very simple point. If you have this box opening, as many of them do, by more than 180°, and you keep the lid at its end point, that is to say the point set by the hinge mechanism ... A Yes. Q ... when you remove the disc at 90° to the mechanism, it will in fact hit the case. A No, not with this one. Q You have not got it fully opened. If you have it fully opened by 190°, or so, it just files the edge of the case. A But you never take a CD out like that; you do it like this. Q We are now moving into the area of construction. The relevance of this question may not be apparent to you, but in due course we will be arguing about the meaning of the end position in which both sides of the disc holding part are freely accessible for removal of one of the two information discs. A That is exactly one of the two. The first one you take it here. When you need the second one, you do it like that. Q We are talking about construction, so I do not want to do that with you. A Eventually you can take it like this." What that amounts to, it seems, is that Mr Lammerant thought that the normal user would not in practice remove both CDs at the end point, at any rate if the PTL allowed movement through more than 180°. Mr Wilson has relied on this as evidence that the normal user does not access CDs from below. The other factor tending to obscurity is the absence of clear teaching about the PTL. In the specification of the patent in suit there is (in the passage already quoted) a reference to its being advantageous "to provide a means of limiting the angle through which the disc-storing part pivots outwards, since this reliably prevents the disc-receiving part turning over completely, resulting in damage to the [CD]." The description of a preferred embodiment of the invention, by reference to the figures, shows the vertical end wall of the base part acting as a PTL at an angle of 90° or thereabouts (that is, very much in accordance with the figures in claim 7). Mr Carr has submitted, no doubt correctly, that the PTL does not have to be the end wall of the base part and has criticised the judge's reference to the possibility of the teaching being deficient (since there is, as Mr Carr has pointed out, no pleading of insufficiency). Nevertheless it may be said that if the PTL is an essential part of the invention, the specification is not very generous in its teaching about it. Construction: the judge's decision After a full description of the patent in suit and after identifying the construction issue, the judge summarised Mr Wilson's contention as to the effect of integers (l) and (m): " ... this involves the disc-carrier having a minimum pivoting angle of around 80° as taught in terms by the claim (because any lesser angle would mean that the second disc was too close to the inside of the cover part) and a maximum angle of around 135°, because if the disc-carrier opened to any greater angle, the first disc would cease to be `freely accessible'. On any view, it would certainly cease to be anything like as `freely accessible' as the second disc, because it would be significantly more difficult to remove, and, indeed, to replace." In his skeleton argument in this court Mr Carr has assumed that the last sentence presents the judge's own view. That seems an unlikely reading. It is more natural to take it as continuing the summary of Mr Wilson's argument. Mr Wilson was in effect saying that a maximum angle for the PTL, although not specified in claim 1, could (within reasonable limits) be inferred from the `both sides ... freely accessible' requirement. The judge went on to consider, and rejected, Mr Carr's opposing arguments. He noted that integers (l) and (m) plainly required both sides of the disc-holding part to be freely accessible for disc-removal in the end position, whether or not the normal user would wish to remove two CDs at the same time. After referring to some observations of Jacob J in Minnesota Mining & Manufacturing Co v Plastus Kreativ [1997] RPC 737, 747, he noted that twin slim-line cassettes have proved more marketable if the disc-holding part can swing through 180° (as is true of the Brilliant Box), but that at the priority date there was no reason to foresee that. The judge then referred to Mr Carr's argument that it should not be assumed that the cassette would be opened when it was lying on a flat surface such as a table. He mentioned his own observations about what was natural in handling a cassette. He concluded that Mr Carr's arguments had not displaced Mr Wilson's: "In other words, it seems to me that the draftsman of Claim 1 had in mind that the "pivoting-travel limiter" would limit the angle through which the disc-carrier would travel relative to the base part to around 130°. It is true that there is no specific limitation to any particular angle in Claim 1, but it appears that the draftsman was content to limit himself in the teaching of Claim 1, at least, to identifying the maximum angle by reference to what had to be capable of being done, namely in feature (m), rather than by reference to arithmetical precision." The judge then found confirmation of this conclusion in certain parts of the specification preceding the claims. These points are, in brief summary: (1) The prior art discussed included patent DE 34 14 903 ("903"), which the judge found difficult to understand. The specification of this patent identified a risk of CDs falling out and being damaged. (2) The perceived advantages of the patent in suit included that "the protection against falling is further improved by limiting the angle of opening". (3) The preferred embodiment depicted in the figures limited the angle of opening to 90° by using the vertical end wall as the PTL. (4) The reference to "turning over completely" meant rotation through 180°, not 270° or (almost) 360°. (5) The expression "pivotable through a wide angle" could refer to any angle other than an acute angle. (6) The skilled reader would naturally have the Jewel Box in mind as some sort of point of departure (compare claim 2). The Jewel Box cover opened through 180° and the reference to "a means for limiting the angle" would naturally suggest a comparison with the Jewel Box. The judge did not attach any weight to a further point relied on by Mr Wilson, that is a statement in patent EP O 515 342 ("342"): "The arrangement of the pivoting access of the disc-holder tray does not allow it to open completely, that is to say through 180°." That was part of the description of the patent in suit contained in the discussion of prior art in 342, deposited on 17 February 1992. The judge, relying on Glaverbel v British Coal Corporation [1995] RPC 255, 270-1, declined to look at a later patent for the purpose of construing an earlier patent. Construction: conclusions In this court Mr Carr has submitted that the judge's maximum figure of 130° or 135° is arbitrary and mistaken. He has submitted that for both sides of the disc-holding part to be freely accessible means no more than that there is no obstruction to removal of the discs in the normal manner (that is, by pulling at right angles to the plane of the disc-holding part). He has criticised the judge for relying on his own observations and for making an assumption, which is described as speculative, as to what the patentee's belief may have been at the priority date. Mr Wilson, in seeking to uphold the judge's conclusion, has concentrated on the risk of a CD falling off the disc-holding part before the user wants to remove it. There was ample evidence before the judge that some tenons were badly designed and others became less effective through wear and tear. Where a disc-holder carried a CD on each side, rotation of the disc-holder through 90° made each freely accessible, and continued rotation carried an ever-increasing risk (through the operation of both static and dynamic forces) of the CD being dislodged prematurely and suffering damage. The furthest that Mr Wilson got with Mr Lammerant on this aspect of the case seems to have been in the following exchange: "Q Let me put to you another possibility, Mr Lammerant. The greater the angle beyond 100°, the greater the effect of gravity on the disc held by the clips; is that not right? It may not be an effect that makes the disc fall off so long as the clips are working properly but the greater the angle the greater the effect of gravity. A You have gravity, yes. Q Therefore the greater the angle at which it stops the more the force of gravity tending to pull the disc off the clips. A No, but this has to see with the clip construction. Q So long as you have your clip construction working properly that will not be a problem. A It has to work properly otherwise you do not have a CD case. The CDs have always to be clamped with the clamp elements. If you do not have clamping elements you do not have a CD case." Mr Lammerant resisted the suggestion that the proposed improvement of the invention's disc-carrying ability must involve a PTL at less than 180°, and put forward three different problems which he perceived. In this court Mr Wilson has described those as hypothetical difficulties devised by Mr Lammerant in order to support a claim for a much wider maximum angle. The judge does not appear to have made any findings about this part of the cross-examination of Mr Lammerant, except so far as it may have contributed to his view that the witness could not be wholly dispassionate. Nor would I criticise the judge for not making findings about these rather obscure points as to the details of the design of a hypothetical product. His task was, after all, to construe the language of the specification of the patent in suit. That task was far from easy but I feel that the judge may, with great respect to him, have made his task still more difficult by starting with Mr Wilson's proposed construction and seeing whether Mr Carr's arguments dislodged it. That was, I think, not the right place from which to start. The plain fact was that although claim 7 specified numerically both a minimum and a maximum angle for the PTL, claim 1 specified only a numerical minimum; and it was to be supposed that there was some reason for that. Mr Wilson accepted that claim 1 imposed a functional rather than a numerical maximum (and in this context he referred to a decision on a now repealed ground of invalidity, No-Fume v Frank Pitchford (1935) 52 RPC 231). But he proceeded to try (by submissions to which I have already referred) to translate that functional limitation into a numerical limitation. Mr Wilson's attempt to make that translation does gain some support from the preceding text of the specification, in the form of the six points already enumerated. But some of them can be understood as directed principally to the preferred embodiment depicted in the figures, or to the variant described in claim 7. Moreover it seems to me that the judge may have attached too much weight to his own observations. These seem to have been based on the unspoken assumption that any cassette would (whether or not placed on a flat surface like a table) be handled in such a way that the base part remained horizontal. (That may be reflected in the qualification "in the absence of any further re-handling of the cassette" which the judge added to what he said about his own observations.) Mr Wilson says that Mr Lammerant accepted that in practice no user takes out a disc from below. It is not clear from the transcript what the witness intended to say about this, and the judge made no finding. But assuming that Mr Lammerant did say that, I derive very little assistance from it in the construction of integers (l) and (m). The point is in the end a short one, though far from easy. On the whole I consider that the judge was wrong in concluding that there must be read into claim 1 a numerical maximum angle (less than 180°) for the PTL. Such a maximum could easily have been expressly included, but was not in fact included. The requirement for free access to both sides of the disc-holding part at the end point does no doubt involve there being some maximum which could be roughly quantified, but it would be in excess of 180° (and probably in excess of 270°). It follows that in my judgment the judge should have found that the patent, if valid, was infringed. Obviousness: relevant principles There was no significant difference between the parties as to the principles to be applied. Under the Patents Act 1949 section 32(1)(f) obviousness was a ground for revocation of a patent. The same result is arrived at under the Patents Act 1977 by the combined operation of section 72(1)(a) (revocation because an invention is not a patentable invention), section 1(1)(a) (a patentable invention must involve an inventive step) and section 3: "An invention shall be taken to involve an inventive step if it is not obvious to a person skilled in the art, having regard to any matter which forms part of the state of the art by virtue only of section 2(2) above (and disregarding section 2(3) above)." The effect of the latter part of section 3 is to exclude material in certain other patent applications; it is not relevant in this case. The burden of proving obviousness lies on the party which alleges it. In Windsurfing International v Tabur Marine [1985] RPC 59 Oliver LJ, giving the judgment of the court, said at p.71, "The question to be decided when an objection is made on the ground of obviousness is, as Jenkins LJ observed in Allmanna Svenska Elektriska A/B v The Burntisland Shipbuilding Co Ltd (1952) 69 RPC 63 at page 70: "in the end of all ... as it were a kind of jury question". But it is one which has to be answered, not by looking with the benefit of hindsight at what is known now and what was known at the priority date and asking whether the former flows naturally and obviously from the latter, but by hypothesizing what would have been obvious at the priority date to a person skilled in the art to which the patent in suit relates, who is assumed to have access to what was known of the art in the United Kingdom immediately before the priority date." At pp.73-4 he said, "There are, we think, four steps which require to be taken in answering the jury question. The first is to identify the inventive concept embodied in the patent in suit. Thereafter, the court has to assume the mantle of the normally skilled but unimaginative addressee in the art at the priority date and to impute to him what was, at that date, common general knowledge in the art in question. The third step is to identify what, if any, differences exist between the matter cited as being "known or used" and the alleged invention. Finally, the court has to ask itself whether, viewed without any knowledge of the alleged invention, those differences constitute steps which would have been obvious to the skilled man or whether they require any degree of invention." That was a decision on the Patents Act 1949 but it provides guidance in cases under the Patents Act 1977 also: Molnlycke v Procter & Gamble [1994] RPC 49, 115. In the latter case Sir Donald Nicholls V-C (giving the judgment of the court) said at p.112, after referring to sections 1,2 and 3 of the Patents Act 1977, "Under the statutory code (which is further confirmed in its completeness by sections 74 and 72) the criterion for deciding whether or not the claimed invention involves an inventive step is wholly objective. It is an objective criterion defined in statutory terms, that is to say whether the step was obvious to a person skilled in the art having regard to any matter which forms part of the state of the art as defined in section 2(2). We do not consider that it assists to ask whether the patent discloses something sufficiently inventive to deserve the grant of a monopoly. Nor is it useful to extract from older judgments expressions such as "that scintilla of invention necessary to support a patent". The statute has laid down what the criterion is to be: it is a qualitative not a quantitative test. The warning against coining phrases given by the Court of Appeal in General Tire & Rubber Co v Firestone Tyre & Rubber Co Ltd [1972] RPC 457 at 497 to 498 is even more apt under the 1977 Act." The Vice-Chancellor said at p.113, "In applying the statutory criterion and making these findings the court will almost invariably require the assistance of expert evidence. The primary evidence will be that of properly qualified expert witnesses who will say whether or not in their opinions the relevant step would have been obvious to a skilled man having regard to the state of the art. All other evidence is secondary to that primary evidence. In the past, evidential criteria may have been useful to help to elucidate the approach of the common law to the question of inventiveness. Now that there is a statutory definition, evidential criteria do not form part of the formulation of the question to be decided. In the nature of things, the expert witnesses and the court are considering the question of obviousness in the light of hindsight. It is this which may make the court's task difficult. What with hindsight, seems plain and obvious, often was not so seen at the time. It is for this reason that contemporary events can be of evidential assistance when testing the experts' primary evidence." He went on to comment on the difficulties of evaluating secondary evidence as to commercial needs, the search for solutions to problems, and ultimate commercial success and said (also at p.113), "Secondary evidence of this type has its place and the importance, or weight, to be attached to it will vary from case to case. However, such evidence must be kept firmly in its place. It must not be permitted, by reason of its volume and complexity, to obscure the fact that it is no more than an aid in assessing the primary evidence." Since the judge found that the invention disclosed in the patent in suit was not obvious, Mr Carr understandably relied heavily on a passage in the speech of Lord Hoffmann in Biogen v Medeva 1997 RPC 1 , 45, with which all their lordships agreed, "The question of whether an invention was obvious had been called "a kind of jury question" (see Jenkins LJ in Allmanna Svenska Elektriska A/B v The Burntisland Shipbuilding Co Ltd (1952 RPC 63 70) and should be treated with appropriate respect by an appellate court. It is true that in Benmax v Austin Motor Co Ltd [1955] AC 370 this House decided that, while the judge's findings of primary fact, particularly if founded upon an assessment of the credibility of witnesses, were virtually unassailable, an appellate court would be more ready to differ from the judge's evaluation of those facts by reference to some legal standard such as negligence or obviousness. In drawing this distinction, however, Viscount Simonds went on to observe, at page 374, that it was "subject only to the weight which should, as a matter of course, be given to the opinion of the learned judge". The need for appellate caution in reversing the judge's evaluation of the facts is based upon much more solid grounds than professional courtesy. It is because specific findings of fact, even by the most meticulous judge, are inherently an incomplete statement of the impression which was made upon him by the primary evidence. His expressed findings are always surrounded by a penumbra of imprecision as to emphasis, relative weight, minor qualification and nuance (as Renan said, la vérité est dans une nuance ), of which time and language do not permit exact expression, but which may play an important part in the judge's overall evaluation. It would in my view be wrong to treat Benmax as authorising or requiring an appellate court to undertake a de novo evaluation of the facts in all cases in which no question of the credibility of witnesses is involved. Where the application of a legal standard such as negligence or obviousness involves no question of principle but is simply a matter of degree, an appellate court should be very cautious in differing from the judge's evaluation." This court must however consider how to give effect to that guidance in a case in which (if my lords take the same view as I do on the issue of construction) the judge misunderstood the patent in suit. Obviousness: the judge's decision The judge began this part of his judgment by considering the state of the art (within the meaning of section 2(2) of the Patents Act 1977) at the priority date (29 August 1988). The Jewel Box and the Multipack were common general knowledge. The prior art also included 903, which the judge found difficult to understand. It was for a packing unit for disc-like articles. One of its special features was that the hinge mechanism used elongated holes, so that the cassettes (as it is put in the patent in suit) "have to be opened not by simple pivoting but by pivoting and sliding". That gave rise to a risk of jerks and accidents. The last paragraph of 903's specification, and some of its figures, refer to the possibility of mounting two discs, one on each side of a disc-carrier. The judge then referred to the four-stage Windsurfer test and proceeded to apply it. He noted that it was not in dispute that the inventive concept was the use of separate hinge devices at opposite ends of the base part, together with a PTL in the region of the second hinge device (and, under claim 2, the use of the commercially available base and cover parts of the Jewel Box). He referred to the state of the art and analysed the differences between known material and the alleged invention. He then set out the six inventive steps proposed by Mr Carr, while reminding himself of the warning given by Lord Diplock in Technograph Printed Circuits v Mills & Rockley (Electronics) [1972] RPC 346, 362, "The cross-examination of the respondents' expert followed with customary skill the familiar "step by step" course. I do not find it persuasive. Once an invention has been made it is generally possible to postulate a combination of steps by which the inventor might have arrived at the invention that he claims in his specification if he started from something that was already known. But it is only because the invention has been made and has proved successful that it is possible to postulate from what starting point and by what particular combination of steps the inventor could have arrived at his invention. It may be that taken in isolation none of the steps which it is now possible to postulate, if taken in isolation, appears to call for any inventive ingenuity." That was a case in which infringers had called no expert evidence and (see at pp.360-1) it had "been left to their counsel alone to make the best bricks that he can with such sparse straws as can be gleaned from the cross-examination of the [patentee's] expert witness". On a step-by-step approach the steps most relied on were (in line with the inventive concept as already identified) the decisions to hinge the disc-carrier at the other side of the base part, opposite to the hinge of the cover part, and to provide a PTL in the region of the disc-carrier's hinge. The judge noted that Mr Lammerant had stuck to his view that these steps were inventive, despite powerful cross-examination by Mr Wilson who pointed out (i) that a hinged disc-carrier for two CDs had to be hinged on one side or the other and (ii) that the vertical wall of the base part at the disc-carrier hinge end was bound to act as some sort of PTL. The judge added (and this is a point of some importance in this court), "However, as [White Knight] accepts, [Carthuplas's] case on [non-] obviousness is rather stronger if ... [Carthuplas] loses on the issue of construction." That is because a PTL with a numerically defined end point at much less than 180° is more obviously different from the Jewel Box, and more likely to be inventive, than a PTL with only a vague functional limitation. The judge then mentioned some general points made by Mr Carr: that simplicity is not to be equated with obviousness; that Mr Lammerant had been the only expert witness, and had not in the course of cross-examination changed his view that the invention was not obvious; and that the invention satisfied a need (for a slim cassette for two CDs) which had existed since 1987 at the latest, and satisfied it in a way which was a great commercial success. The judge amplified this third point by reference to the commercial background summarised in the first section of the present judgment. He concluded that Mr Lammerant's evidence about the demands of the market at the priority date was exaggerated but that it had some substance. He also accepted that the Brilliant Box had been a commercial success (but did not mention, at that point, the undisputed evidence that much of its success was due to its improved and separately patented tenons). The judge said that he had found the issue of obviousness difficult (a view with which I readily sympathise). He decided the issue in favour of Carthuplas for reasons which are set out in nine numbered paragraphs, of which the most significant are the following (paragraphs 1 and 2 were introductory, paragraph 8 dealt with the burden of proof, and paragraph 9 referred to `long-felt want' in terms which gave no great comfort to either side): "3. This is a case where the alleged invention is simple and elegant, and it is therefore particularly easy to fall into the trap of thinking it obvious with the benefit of wisdom of hindsight; 4. The expert evidence of Mr Lammerant, while challenged by cross-examination, and while weakened by the fact that he was not impartial, was not controverted by any other witness, and was in general credible, and supports the provisional conclusion that the alleged invention was not obvious; 5. Although some of the five or six steps involved in the alleged inventive aspect were plainly not of themselves inventive (because they were obvious over the Jewel Box and the Multi-pack and because they were effectively disclosed by the 903 Patent) other steps were at least arguably inventive, and were certainly original so far as CD boxes were concerned as at the priority date; 6. In any event, one should not be beguiled by the step by step analysis; in this case, as in many cases, it makes the alleged invention look more likely to be obvious than is justified. 7. [Carthuplas's] case against obviousness is strengthened by its having lost on the construction issue: the fourth, fifth and sixth steps are more inventive if confined to cases where the disc-carrier [is] made to stop at a point where "both sides ... are freely accessible" as I have interpreted that expression than if the disc-carrier is effectively free to rotate." Obviousness: conclusions I have summarised this part of the judgment in a rather detailed and pedestrian way because it is important, in view of Lord Hoffmann's guidance in Biogen v Medeva , to see how far the judge's conclusion depended on the nuances of the oral evidence which he had heard, and how much an appellate tribunal's disinclination to differ from the trial judge on a jury question may be weakened if this court takes a different view on the question of construction. It is clear from paragraph 4 of the judge's reasons that he did attach a good deal of weight to Mr Lammerant's evidence, and in view of Mr Lammerant's lack of disinterestedness the judge's careful assessment of his primary evidence about inventiveness must be entitled to a great deal of respect. His secondary evidence on the subject of `long-felt want' was regarded by the judge as exaggerated and in view of the Vice-Chancellor's warnings in Molnlycke (and the importance of the improved tenon to the commercial success of the Brilliant Box) the judge rightly gave it little weight. How far was the judge's decision on obviousness influenced by his view that the teaching of the specification was that the PTL must limit rotation of the disc-carrier to an end point at a maximum angle of 135°? Mr Wilson has submitted that if that view is held to be wrong, the issue of obviousness is again at large, and must be resolved in favour of White Knight. Mr Carr has submitted that it would make no difference, and that the judge was wrong (in his paragraph 7) to regard the alternative to his own preferred construction as being that "the disc-carrier is effectively free to rotate". I prefer Mr Carr's submissions on this point. It is agreed that part of the inventive concept claimed was a PTL, the purpose of which is said by the claimant to be to prevent uncontrolled rotation by stopping it at some end point. In the absence of any clearer teaching about the purpose and position of the PTL (and I need not repeat what I have already said about that) the attack based on obviousness is not appreciably stronger if the PTL is at 120° or 135° rather than at 180° or some larger angle. It is slightly stronger because of the comparison with the Jewel Box. In relation to the judge's paragraph 6 (not being beguiled by step-by-step analysis) Mr Wilson has submitted that there was no more to the invention than the hinging of the disc-carrier (in one of two possible positions) and the PTL, and that pointing that out should not be condemned as mere step-by-step analysis. Moreover that type of analysis can sometimes make an alleged invention seem more recondite and less obvious, by an unrealistically complicated subdivision of a thought process. (The judge himself made that point, with which I respectfully agree, in his discussion of Technograph .) On the whole I do not think that it is of decisive importance whether or not obviousness is tested on a step-by-step approach. I consider that the judge, who saw and heard Mr Lammerant cross-examined at length, was entitled to accept the witness's evidence (`primary evidence', in the Vice-Chancellor's phrase in Molnlycke ) as to the inventiveness of the hinging arrangement and the PTL, simple and obvious as they may have appeared with hindsight. The judge's view as to the correct construction of integers (l) and (m) of claim 1, from which I differ, does not appear to me to have a very significant effect on that conclusion. I consider that this court would not be justified, either by a different view on the construction issue or on any other ground, to depart from the answer which the judge gave to the jury question. Added Matter Section 72(1)(d) of the Patents Act 1977 gives the court power to revoke a patent on the ground that "the matter disclosed in the specification of the patent extends beyond that disclosed in the application for the patent." This provision gives effect to Article 138 of the European Patent Convention. By section 130(3) of the Patents Act 1977 matter is to be taken to have been disclosed in an application or a specification "if it was either claimed or disclosed (otherwise than by way of disclaimer or acknowledgement of prior)." So it need not actually be claimed but it must be referred to as a positive element in the application or specification. In Bonzel v Intervention [1991] RPC 553,574 Aldous J described the court's threefold task in applying s.72(1)(d): "(1) To ascertain through the eyes of the skilled addressee what is disclosed, both explicitly and implicitly in the application. (2) To do the same in respect of the patent as granted. (3) To compare the two disclosures and decide whether any subject matter relevant to the invention has been added whether by deletion or addition. The comparison is strict in the sense that subject matter will be added unless such matter is clearly and unambiguously disclosed in the application either explicitly or implicitly." The amended particulars of objections relied on by White Knight raised three points, one of which was abandoned at trial. The other two were (i) the substance of integer (m) of claim 1 (this is raised in a late respondent's notice to which Mr Carr did not object) and (ii) a passage in the patent which discusses patent GB 2 132 588 ("588"), but only "if and so far as the comments in the patent concerning 588 contain matter which teaches the person skilled in the art about the subject matter of the invention". That no doubt reflects the effect of s.130(3), as did the judge's comment that an added reference to prior art would be impermissible only if the way in which it was described resulted in a different construction of a claim in a patent. 588 was not referred to at all in the original application (PCT / EP 89/00741) made by Mrs Dunker. That is not entirely surprising since it relates to a container, to be manufactured from a single flat piece of plastic, for storing a quite different product, that is floppy discs for computers. The reference to 588 in the specification did not in my judgment alter the construction of any of the claims in the patent in suit. The other point raised, as to integer (m) of claim 1 in the specification, is more formidable. In the original application the content of claim 1 was substantially the same as claim 1 in the specification down to integer (h) of the specification. That is the point at which the words `characterised in that' appeared, and the application then continued, "d) the disc-receiving part (4) and the base part (2) are pivotally connected through a second hinge device (18,19) and the disc-receiving part (4) has on both sides holders (24,27) for a circular data information carrier (29), e) the second hinge device (18,19) is disposed on the edge (7) of the base part (2) opposite the (first) hinge device (12,17) which is intended to be situated between the base part (2) and the cover part (3) f) the disc-receiving part (4) comes to abut a pivoting-travel limiter when fully pivoted." So there was an explicit reference to a PTL, but no specific reference to a maximum pivoting angle of at least 80° to the end point, or to both sides of the disc-receiving part being freely accessible at the end point. The figure of 80° was mentioned in the original version of claim 3 and it is the latter omission which Mr Wilson has relied on. He has submitted that the introduction of the notion of both sides being freely accessible was new not just as a matter of language but also as a matter of substance. He said the claim was not so much being broadened as changed in its character. Mr Carr dealt with this matter quite briefly in his written and oral submissions. He referred to Aldous J's formulation in Bonzel and contended that the application implicitly disclosed the concept of both sides of the disc-holding part being freely accessible when it was fully pivoted (the expression used in paragraph (f) of the original claim 1). He said that the skilled man would necessarily appreciate that both CDs can be removed from the tenons by pulling outwards, and that there is no restriction on doing this. However I do not consider that the objection can be disposed of so easily. Mr Wilson was right to say that this point becomes much stronger if Mr Carr's argument on construction is successful, as in my view it has been. The user's free access to both sides of the disc-holding part at the end point is then seen as an important functional element of the claim, even if the user would not normally wish to remove both CDs at the end point. I cannot find that implied or even hinted at in the original application even if seen through the eyes of a skilled addressee. I can see no answer to Mr Wilson's objection on this point. The court has under s.72(1) power to revoke a patent on the ground of added matter. It has not been suggested that there is any reason why that power ought not to be exercised, if the ground of added matter is made out. Conclusion I have to acknowledge a feeling of considerable unease that this difficult case, which may have large financial implications, should in the end be decided on a point which was not dealt with by the judge, and on which this court has heard only fairly brief argument. However that outcome reflects the fact that the patent in suit is, on any view, a very unsatisfactory patent, embodying a very vague concept (free accessibility on both sides of the disc-holding part at an otherwise undefined end point) which seems, on the evidence of Mr Lammerant, to be of little practical utility. The introduction of this concept into the specification after the making of the original application may be the underlying reason for the specification's basic incoherence. But for the added matter point I would have allowed the appeal on the linked issues of construction and infringement, and dismissed the cross-appeal on the issue of obviousness. But for practical purposes the outcome must in my view be determined by allowing the cross-appeal on the issue of added matter, and ordering revocation of the patent in suit. LORD JUSTICE BROOKE: I agree. LORD JUSTICE PETER GIBSON: This appeal and cross-appeal give rise to three questions. (1) On the true construction of claim 1 is the maximum pivoting angle of the disc-carrier limited to around 130° or 135°? (2) Was the invention disclosed in the patent in suit obvious? (3) If the answer to (2) is in the negative, should the patent be revoked on the ground of added matter? I agree with the conclusions reached by Robert Walker L. J. on each of those questions. But as we are differing from the judge on the first question and as the judge did not consider a point taken by White Knight in relation to the third, and ultimately decisive, question and in deference to the skilful arguments of counsel, I add a few words of my own. (1) Construction At first blush the meaning given by the judge to claim 1 is very surprising. It is not in dispute that what is expressed as "a maximum pivoting angle of at least 80°" is in fact a minimum pivoting angle expressed arithmetically as 80°. Claim 1 contains no arithmetically expressed maximum pivoting angle. In contrast claim 7 does contain a maximum pivoting angle (120°) and an optimum range (about 80° to 100°). Claim 7 as a claim subordinate to claim 1 must be taken to be narrower in scope than claim 1, so that one would expect the maximum pivoting angle in claim 1 to exceed 120°. But what stands out from the wording of claim 1 read in its context is that an arithmetically expressed maximum pivoting angle, though it would have been simple to insert, is conspicuous by its absence. Instead the upper limit of the pivoting angle is described as the "end position". Only two characteristics of that end position are identified. One is that in that position the disc-holding part comes to abut a pivoting-travel limiter provided in the region of the second hinge device. The other is that in that position both sides of the disc-holding part are freely accessible for removal of one of the two information discs as desired. The first characteristic does not limit the maximum pivoting angle to 130° or 135°. That is said to be derived from the second characteristic of free accessibility. But unless one posits that the box must be placed on a table - and that is not a teaching of the specification - it is hard to see why both sides of the disc-holding part are not fully accessible between a minimum pivoting angle of 80° and a maximum pivoting angle of, say, 280° (though the pivoting-travel limiter may not permit so great an angle). In so saying, I would give the words "freely accessible" for the stated purpose of the removal of a disc their ordinary meaning that one should be freely able to get at both sides to remove the disc by pulling the chosen disc outwards and away from its clamp holder without obstruction. If the angle between the disc-holding part and the case is too acute, it would not be possible to perform the exercise freely. That being, as it seems to me, the ordinary meaning of the words used in claim 1, what is there to indicate a narrower construction? Mr. Wilson Q. C. for White Knight sought to imply some limitation from the specification. First, he points to the criticisms of the prior art, the cassette the subject of patent 903 having the disadvantage of the risk of a jerk to counteract a tilt and the falling out of the discs in consequence. Second, in relation to a storage cassette having the features of claim 1, it is said in the specification: "It has also been found advantageous, for reliable use of the storage cassette, to provide a means for limiting the angle through which the disc-storing part pivots outwards, since this reliably prevents the disc-receiving part turning over completely, resulting in damage to the circular information disc." Third, the specification claims the advantage that "the novel hinge arrangement considerably improves the protection of circular information carriers, particularly CDs, against falling out of the cassette when opened or used in an open state." Fourth, the specification claims the further advantage that "the protection against falling is further improved by limiting the angle of opening". I acknowledge that some assistance can be obtained from those points for Mr. Wilson's construction favoured by the judge. But I do not see that they are anywhere near clear enough to limit the natural meaning of claim 1. The specification claims as an advantage that the disc-holding part is "pivotable through a wide angle." I would not have thought a range of from 80° to 135° or 135° would naturally be described as a wide angle. True it is that the danger of discs falling is a recognised disadvantage and that the greater the maximum pivotable angle, the greater the risk of falling if the tenon fails to perform its function. But it is "the novel hinge arrangement" that is said to reduce the risk, and the function of the pivoting-travel limiter is to limit the angle of opening. Although the judge thought the natural meaning of "turning over completely" meant turning through 180° rather than 360°, I have to say that I am not persuaded that that is so. Nor am I persuaded by the judge's reliance on the reference on page 6 of the patent in suit to the disc-holding part being pivotable by about 90° relative to the base part. That was said in relation to Figure 1, which is "a preferred embodiment of a cassette, as an example of a storage or disc-holding part according to the instruction" (my emphasis). As one would expect, claim 1 puts the claim at its widest. I conclude therefore that the judge's construction of claim 1 should not be supported. I am the happier to reach that conclusion for two reasons. First, there seems little practical purpose in the limitation found by the judge, as he himself apparently accepted (see p. 22 of his judgment). Second, on no footing can it be said to be easy or obvious to spell out of claim 1 the limitation found by the judge. In this context it is relevant to bear in mind that by the protocol on the interpretation of Article 69 of the European Patent Convention, a meaning must be sought which combines a fair protection for the patentee with a reasonable degree of certainty for third parties. It follows that in my judgment on the true construction of claim 1 White Knight, by its cassettes opening to 180°, infringed Carthuplas' patent if it is valid. (2) Obviousness The judge acknowledged the difficulty he had in determining this question and Mr. Wilson subjected the judge's reasons to powerful criticism. But like Robert Walker L. J. I do not think that this court should interfere with the conclusion reached by the judge, based as it was on the evidence of M. Lammerant as an expert. The economic success of Carthuplas' product, which has taken a hugely preponderant share of the market, lends some practical support to this conclusion that the invention was not obvious, although I recognise that the effective tenon used by Carthuplas is likely to have assisted in that success. (3) Added Matter In White Knight's amended particulars of objection two points were taken as to additional matter in the patent in suit extending beyond what was disclosed in the application for the patent as filed. I agree with Robert Walker L. J. that the late addition to the specification of the discussion of patent 588 is not a material disclosure rendering the patent in suit invalid. But like my Lord I can see no answer to the point taken by Mr. Wilson on the late addition made to feature (m) in claim 1. I do not see how we can say that that addition was already implicitly disclosed in the original application. It follows that the patent in suit was invalid under s. 72 (1)(d) Patents Act 1977. Conclusion For these as well as the reasons given by Robert Walker L. J. I would allow the cross-appeal and order that the patent in suit be revoked. Order: Cross appeal of Def allowed and patent suit revoked. Defendant pay half the costs of the Claimant. Permission to appeal to House of Lords refused. Stay granted on Claimant's undertaking to prosecute with due dilligence a petition to appeal. Stay to continue until 1 month from the determination of the petition with liberty to both sides to appeal to vary the order of the court. (Order does not form part of the approved judgment) BAILII: Copyright Policy | Disclaimers | Privacy Policy | Feedback | Donate to BAILII