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	England and Wales Court of Appeal (Civil Division) Decisions
You are here: BAILII >> Databases >> England and Wales Court of Appeal (Civil Division) Decisions >> Seb SA v Societe De'longhi Spa [2003] EWCA Civ 952 (04 July 2003) URL: http://www.bailii.org/ew/cases/EWCA/Civ/2003/952.html Cite as: [2003] EWCA Civ 952

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IN THE SUPREME COURT OF JUDICATURE
COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM THE HIGH COURT OF JUSTICE
CHANCERY DIVISION PATENTS COURT
Pumfrey J.

		Royal Courts of Justice Strand, London, WC2A 2LL
		4 July 2003

SEB SA v SOCIETE DE' LONGHI SPA

Peter Gibson L.J. (giving the judgment of the court):

1. This is an appeal in a claim for patent infringement from the order made by Pumfrey J. on 26 July 2002. The judge dismissed the action on the basis that the patent in suit ("the Patent") was invalid for obviousness, though he held that, had the Patent been valid, it would have been infringed by all of the alleged infringements. The patentee, the Claimant SEB SA ("SEB"), appeals with the permission of the judge against the finding of obviousness. The alleged infringers, the Defendants, the Italian company Société De' Longhi SPA and its English subsidiary De' Longhi Ltd. (whom we shall call "De' Longhi" without distinguishing between them), by a Respondent's Notice ask that the judge's decision be affirmed for additional reasons which had been rejected or not adopted by the judge.
2. The dispute relates to deep fat fryers. SEB is a French company. It is a major manufacturer of kitchen utensils which it sells under the TEFAL, MOULINEX, KRUPS and ROWENTA marks. De' Longhi also manufactures kitchen utensils which it sells under the mark DE' LONGHI.

The Patent

3. SEB applied for the Patent on 11 May 1988 but claims priority from an application made on 11 May 1987. At that date deep fat fryers were well established on the market, but were principally double-walled fryers, the outer wall or skirt of which was metal. As is explained in the Patent, SEB's invention relates to an electric fryer provided with a plastics skirt, a metal vessel and an electrical heating resistance. The draftsman of the Patent explains that in most known electric fryers the vessel is directly exposed to ambient air, which has the drawbacks that (a) the vessel readily reaches a temperature of 150⁰, creating a risk of burning for users who touch the vessel, (b) there are major heat losses affecting electrical consumption, and (c) the bare metal of the vessel makes it impossible to provide the vessel with an attractive appearance. The draftsman then gives two methods which had been used to overcome those disadvantages. One was to surround the vessel by an enamelled metal skirt. The other was to provide a plastics skirt; but given the way the metal vessel is secured to the interior of the plastics skirt and the many heat bridges between the vessel and the skirt, the skirt had to be made from a plastics material capable of withstanding temperatures of more than 150⁰, such as polyamides and polyesters, which were expensive and so not compatible with the mass production of inexpensive fryers.
4. The draftsman then refers to the Spanish Utility Model 290 283 published on 16 November 1983 ("Taurus") as disclosing:

"an electric fryer comprising a metal vessel and an electrical heating resistance, which vessel is adapted to be heated to at least 150ºC and is surrounded by a skirt of plastics material such as polypropylene which does not continuously bear the temperature of the vessel wall since the skirt is spaced from the side walls and base of the vessel by a layer of air. The skirt is completely free with respect to the vessel with the exception of a connection between the top edges of the skirt and the vessel.

This connection takes the form of metal flanges rigid with a metal plate fitted on the top edge of the plastics skirt.

Openings are provided in the base of the skirt and in the metal plates located at the top of the skirt so as to allow air to circulate between the plastics skirt and the metal vessel. This air circulation makes it possible to cool the plastics skirt.

However, the air emerging from the openings in the metal plates located at the top of the skirt is at a high temperature. Given that these openings are disposed in an area which may be touched by users, the latter may receive burns."

5. The purpose of the Taurus invention was said in its specification to be to achieve a significant reduction in the manufacturing cost of the outer body of the fryer and to achieve other potential benefits, in particular the ability to hold the apparatus directly without the danger of getting burnt. The figures in the specification show holes in the edges of the base of the skirt and further holes at the top of the metal plates inserted at the top of the plastic skirt. The purpose of the holes is said to be to establish air circulation by convection between the body (consisting of the skirt and the plates) and the vessel, the air entering at the bottom and exiting at the top; this movement of air contributes to cooling the space between the walls of the body and the vessel, which in use reaches temperatures of about 200⁰C and heats the space by radiation. The material in the skirt is said in the claim to be "moulded synthetic resins, preferably polypropylene."
6. To return to the invention in the Patent, its object is said in the specification to be to provide an inexpensive fryer which simultaneously provides users with effective protection against possible burns and prevents external heat loss. Claim 1, as subdivided by the judge who numbered the features for ease of reference, is as follows:

" [1] An electric fryer

comprising

[2] a metal vessel and an electrical hearing element,

[3] the vessel readily reaching a temperature of 150ºC and

[4] surrounded by a plastics skirt which does not continuously withstand the temperature of the vessel wall

[5] which skirt is spaced from the side wall and base of the vessel by a layer of air and

[6] is completely free with respect to the vessel except for a connection between the top edge of the skirt and the top edge of the vessel

characterised

[7] in that the skirt completely surrounds the side wall and the base of the vessel and

[8] in that the connection is made by means of a ring which connects the top edge of the skirt to the top edge of the vessel and closes the air filled space between the skirt and the vessel,

[9] the layer of air being thick enough to limit the skirt temperature to a value compatible with the thermal characteristic of the plastics material of the skirt,

[10] the ring being of a thermally insulating material which is continuously resistant to the temperature of the top edge of the vessel which rests freely on this ring.'"

7. Of the other claims we need only refer to claim 9 which only adds the characteristising feature that the skirt and the lid are made of polypropylene.
8. The first six features of claim 1 closely follow the Taurus invention. The final four characterising features are said to constitute invention over the Taurus disclosure. The following advantages are claimed for the invention:

(i) the skirt is not likely to be heated to an excessive temperature, as the ring made of heat-resistant material is the only part in contact with the vessel;

(ii) the ring being of high quality material, the remainder of the skirt can be made from an inexpensive, low quality plastics material which does not continuously withstand a temperature in excess of 80⁰C;

(iii) because of the large layer of air between the vessel and the skirt, external heat losses are very reduced and that makes the appliance economic to use;

(iv) users touching the skirt run no risk of being burnt;

(v) the skirt, being of plastics material, can be moulded into any shape, and so the appliance can be made aesthetically attractive.

9. The specification continues with references to features of the lid with which we are not concerned. The draftsman then refers to features of a preferred embodiment which relate to the ring. The edge of the ring adjacent to the top end of the skirt comprises an annular groove which is engaged on the top edge of the skirt, the top edge of the vessel having a collar bent so as to define a downwardly open groove which is engaged on the adjacent edge of the ring. The vessel is thus suspended from the ring which is fitted on the top edge of the skirt, thereby providing the vessel with a secure fastening within the skirt with no heat bridges other than the contacts between the edges of the vessel, the ring and the skirt. This is illustrated in Figure 1 (a longitudinal section through the fryer) and Figure 2 ( a view on an enlarged scale of detail A of Figure 1).
[Diagram or picture not reproduced in HTML version - see original .rtf file to view diagram or picture] [Diagram or picture not reproduced in HTML version - see original .rtf file to view diagram or picture]
10. After a further description of the preferred embodiment, the draftsman continues:

'The outer plastics skirt 3 separated from the oil vessel 1 makes it possible to insulate the latter and prevent any risk of burns on the part of the user. At the same time the air space 4 which surrounds the vessel 1 substantially limits external heat losses which allows a reduction in electricity consumption.

Given that the skirt 3 is practically free with respect to the vessel 1, i.e. no heat bridge is created between this vessel and the skirt, the latter can be made from plastics material of an inexpensive, widely available quality which does not withstand high temperatures; this means that the fryer can be produced at low cost."

11. The draftsman then returns to commenting on the invention:

"The merit of the present invention lies in particular in that this ring of simple design provides an effective solution to the problem raised. This ring performs all the following functions:

it defines the spacing between the vessel 1 and the outer plastics skirt 3,

it is designed to support and centre the vessel 1 within the skirt 3,

it completely shuts off the air space between the vessel 1 and the skirt 3,

it allows the vessel 1 to expand freely with respect to the skirt 3,

it allows the transmission of heat between the vessel 1 and the skirt 3 to be limited."

The hearing before the judge

12. SEB alleged that 21 different models of deep fat fryer produced by De' Longhi infringed claims 1 and 9. It is common ground that they can be divided into five classes, known as F2, F2 – E9, F7, F7 – E9 and FP. De' Longhi denied infringement, arguing that on the true construction of the Patent their fryers did not infringe. They also challenged the validity of the Patent on the basis of obviousness in the light of the common general knowledge and in the light of the prior art, originally relying on four disclosures including Taurus but in the event relying only on one, the disclosure of a rice-boiler in Japanese Patent Application no. 52 – 132964 ("Toshiba"). They further challenged the Patent on the ground that the specification does not disclose the invention clearly and completely enough for it to be performed by a man skilled in the art. SEB resisted De' Longhi 's challenges and initially relied on commercial success as negating obviousness, but did not persist in that point.
13. The judge received written and oral evidence from two experts, Mr. Wassall for SEB, and Mr. Robben for De' Longhi . Mr. Wassall in 1984 became Quality Manager and Engineer of Moulinex Swan Holdings Ltd. ("Swan"), responsible for the design of new domestic appliances. In 1987 Mr. Wassall was part of the design team of Swan which produced a new fryer. Mr. Robben in 1984 became Director of Research and Development at Nova Electro International NV ("Nova"), a manufacturer of small electrical appliances including deep fat fryers and waffle irons. The judge described Mr. Robben as being of an inventive turn of mind. The judge said that both experts had relevant experience, and he found assistance in their evidence. The judge considered the issue of infringement first.
14. The judge had no doubt that all the features of claim 1 other than feature 8 were present in the allegedly infringing fryers. He noted the fact that the rings in the alleged infringements were not simple but had spacers and other features moulded into them. The features of the rings were set out in para. 30 of the judgment in this fashion:

"•    F2 The ring has 8 vertical spacers of approximately 3mm in height around its circumference which support and raise the metal vessel and decrease the heat conduction between the vessel and the ring. The fryer also has air vents on each side of its base.

•    F2-E9 The spacers are increased to 3.5mm (thereby producing a larger gap between the vessel and the ring). The fryer also has air vents on each side of its base.

•    F7 The F7 fryers are larger in capacity than the F2s and the design of the ring is different to the F2 and F2-E9 series and includes both spacers above the ring as well as "feet" between the base of the ring and the skirt. The eight spacers are 1mm high. As in all fryers there is a slot in the lower front of the skirt through which air can enter.

•    F7-E9 Corner gaps have been introduced by means of indentations in the top of the skirt below the ring. The skirt has been cut down slightly and the rim of the skirt pulled back at the corners. The spacers remain at 1mm high. The fryer also has vents introduced to its base.

•    FP The spacing elements have been placed on the underside of the vessel collar at regular intervals. These spacers are 0.8mm high. The fryer has vents in its base and skirt. There is a screw between the ring and the vessel."

15. De' Longhi had conducted a smoke experiment designed to show some convection by the injection of smoke into the skirt. The judge accepted that this demonstrated some flow of air but said that it "appeared to be practically negligible".
16. SEB had also conducted power consumption experiments designed to show the steady state temperatures of the vessel and the upper and lower skirt with and without the ventilation louvers in the base of the machine open. The judge found the results difficult to interpret and compare because of the slight differences and also the difference in the ambient temperature for different runs. He said that the best the experiments could be taken to show was a slight reduction in temperature, probably caused by the airflow.
17. De' Longhi 's case was and is that on the correct construction of the Patent, in which a ring of "simple design" "supports" the skirt and "closes the air-filled space", its fryers cannot infringe, because the presence of the spacers (and the corner gaps in the F7 – E9 version) means that the rings in its fryers are not of a simple design and do not close the air-filled space. The correctness of that case largely depends on the construction of feature 8 of Claim 1 and in particular on the meaning of the word "closes".
18. The judge said that "close" is a word with a considerable penumbra of meaning, capable of meaning anything from a hermetic joint to a general closure as may be achieved by closing a door. He pointed out that the meaning of the word necessarily had to be ascertained in its context, giving it a purposive construction which would satisfy the requirements of the Protocol on the Interpretation of Article 69 of the European Patent Convention ("the Protocol"). That requires that the meaning to be placed on the claim combines a fair protection for the patentee with a reasonable degree of certainty for third parties. The judge referred to the disadvantage of Taurus in that air emerges from the upper holes at a high temperature, which might burn users, and contrasted that with the invention of the patent in that hot air is not to emerge in such a way as to heat the skirt or otherwise imperil users. He stated that it was in that sense that the word "closes" was to be understood. He noted the description in the specification of one of the functions of the ring as being that "it completely shuts off the air space between the vessel 1 and the skirt 3" (see para. 11 above), but said (in para. 21):

"I do not think that the use of the word 'completely' here qualifies the meaning of 'closes' in the claim. Indeed, it is difficult to see how it could do so. Construed strictly, it would require the space to be sealed, but that is not possible and is not described. I conclude that the purpose of the word is practically to exclude convective cooling with the associate risk of the escape of hot air where the user may put his or her hand. The air in a device according to claim 1 is to act as an insulating layer."

19. The judge noted the argument for De' Longhi that the ring should as nearly as possible close off the air space between the vessel and the skirt, but rejected that as giving rise to further questions as to the degree of closure. The judge accordingly concluded that all the De' Longhi fryers infringed claim 1, and, being made of polypropylene, infringed claim 9 as well.
20. The judge then turned to validity. De' Longhi's primary argument was that the alleged invention was obvious to the skilled person in the light of the common general knowledge. The judge (in para. 6) identified the skilled man as being a team of people responsible for the design of new domestic appliances, with more than one set of skills represented: there would be a design engineer, a production person and a marketing person. In the same paragraph he also identified the matters of common general knowledge for such a team. He found (in paras. 39 and 40) that the scope of the common general knowledge was established in the cross-examination of Mr. Wassall, whose evidence on this point, the judge said, established that without any particular design in mind the skilled addressee, setting out to design a fryer in 1987, would bring to that exercise the knowledge that the skirt can be made of metal, and that the vessel can rest on the skirt, through (if need be) an insulating ring. The judge said (in para. 46) that what was established to be common general knowledge was the general idea of a double-walled fryer, both walls of metal, with the features identified in paras. 39 and 40 of the judgment. He noted (in para. 47) the acceptance by Mr. Wassall that by 1980, there was a strong emphasis on the use of plastics where possible and that there was a general trend, driven in part by safety considerations, to enclose heated appliances in plastics casings. He said (in para. 48) that if he was to find invention in Claim 1, it must be on the basis that there was a sufficiently strong prejudice against the use of plastics in such a high temperature application that their use would not be obvious to the skilled man, but he found that that view could not be supported on the evidence. He referred to the continued production of non-infringing fryers, including metal-skirted fryers. He also referred to what he called "contraindications to obviousness" and to the secondary evidence of what was going on in the market in 1987. Among the fryers mentioned was Mr. Wassall's own design for Swan. Mr. Wassall's evidence was that his first thought had been to use plastics, but he found that they either melted or were too expensive. The judge said (in para. 52):

"This evidence is strong confirmation that the use of plastics material for the skirt is per se obvious. So the only question is whether the use of an insulating ring to protect it is obvious. There is no doubt that such insulating rings are used in kettles and in electric irons."

21. The judge observed that in this respect there was disagreement between Mr. Wassall and Mr. Robben, which he said:

"comes down to the former's belief that knowledge of techniques such as insulating rings and gaskets, or of materials such as more or less heat-resisting plastics, would be more compartmentalised among designers working in a particular field than the latter considered right."

He continued:

"I must say that I am surprised by the suggestion that it was not obvious to use the insulating ring in Mr Wassall's fryer, but one was not used or considered. I prefer Mr Robben's evidence on this point. My reason is that his approach seems to me to be more consonant with what I would expect in a modern designer. I think that the notional skilled man would have considered an insulating ring, and that this would have given success."

22. Accordingly, the judge found the invention in claim 1 to be obvious and that claim 9 added nothing because the skilled man wanted to use plastics like polypropylene for the skirt.
23. The judge then referred to De' Longhi 's argument based on Toshiba. He said that because of the different temperature at which it operates, the retention of the ring and of the plastics skirt, if it were used to inspire the design of a deep fat fryer, depended on almost the same considerations which he had considered when considering the obviousness of the invention in the light of the common general knowledge alone, the argument in effect being the same. The judge held that if the invention was not obvious in the light of the common general knowledge, it was not obvious in the light of Toshiba and that he did not need to consider it further.
24. Finally, the judge considered the further objection by De' Longhi of insufficiency in that there was no adequate description of the ring and its function to enable the skilled man to produce a fryer within the claim. The judge rejected that objection, saying that it was not a properly formulated objection, but merely argumentative, and that on the evidence the skilled man would have no difficulty in constructing a fryer in which the air flow was sufficiently low that the user's hands were not at risk.

The appeal

25. On this appeal we have had the considerable benefit of skilful and knowledgeable argument from each of Mr. Henry Carr Q.C. for SEB and Mr. Andrew Waugh Q.C. for De' Longhi.
26. Mr. Carr in his skeleton argument submitted that in reaching the conclusions on obviousness the judge made errors of law and principle in seven different respects:

(i) in reaching his finding of obviousness based on common general knowledge, the judge failed to assume the mantle of the normally skilled but unimaginative addressee of the Patent at the priority date;

(ii) having stated that it was helpful to follow the approach in Windsurfing International Inc. v Tabur Marine (GB) Ltd. [1985] RPC 59, he failed to analyse the question of obviousness in accordance with the four stages therein set out;

(iii) he disregarded primary evidence from both experts that the invention would not have been obvious to the normally skilled but unimaginative addressee of the Patent at the priority date; he was not entitled to reach his conclusion in the absence of primary evidence;

(iv) he reached a conclusion based on the application of hindsight to a non-obvious combination of different features found in different types of device;

(v) he wrongly identified matters as common general knowledge;

(vi) he failed properly to test his conclusions against the secondary evidence;

(vii) if and insofar as he decided that the Patent was obvious in the light of Toshiba,

(a) he was manifestly wrong in his conclusion that the argument was the same as in relation to common general knowledge;

(b) he failed in his duty to give reasons to support his conclusion;

(c) alternatively he committed the same errors of law and principle as in relation to common general knowledge.

In his oral submissions he drew attention to three errors of principle: the failure to adopt the mantle of the ordinary but unimaginative person skilled in the art, the failure to appreciate that the combination of known factors may not be obvious, and the identification of matters known in the art with common general knowledge.

27. Mr. Waugh submits that the judge was right to find the Patent obvious in the light of common general knowledge. He refutes each of the claimed errors of law and principle. By a Respondent's Notice he submits that the Patent is separately obvious in the light of Toshiba. Further he submits that there was no infringement by De' Longhi , whose fryers differed from the teaching in the Patent in that the space between the vessel and the skirt in their appliances is not closed. Finally, he submits that the judge was wrong to reject De' Longhi's claim of insufficiency, the Patent providing no guidance as to how to determine whether there is the relevant closing.
28. There are therefore four questions raised on this appeal:

(A) Is the Patent invalid for obviousness in the light of common general knowledge?

(B) If not, is the Patent obvious in the light of Toshiba?

(C) In the light of the true construction of feature 8 of claim 1, do De' Longhi's fryers infringe the Patent?

(D) Is the Patent invalid for insufficiency?

(A) Obviousness and common general knowledge

29. The statutory provisions relevant to this issue are the following sections of the Act (so far as material):

"1 (1) A patent may be granted only for an invention in respect of which the following conditions are satisfied, that is to say –

(a) the invention is new;

(b) it involves an inventive step ....

2 (1) An invention shall be taken to be new if it does not form part of the state of the art.

(2) The state of the art in the case of an invention shall be taken to comprise all matter (whether a product, a process, information about either, or anything else) which has at any time before the priority date of that invention been made available to the public (whether in the United Kingdom or elsewhere) by written or oral description, by use or in any other way.

....

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 ...."

30. In Allmanna Svenska Electriska A/B v The Burntisland Shipbuilding Co. Ltd. (1952) 69 RPC 63 at p. 70 Jenkins L.J. said that the question whether an the invention was obvious was a kind of jury question. If it was so obvious, the Patent is invalid.
31. Despite the apparent simplicity of the question, the authorities show that to arrive at the answer, a number of points must be teased out. The guidance given by this court in Windsurfing [1985] RPC at pp. 73,4 per Oliver L.J. has been followed repeatedly:

"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."

The reference to the matter cited as being "known or used" is to wording in s. 32(1)(e) and (f) Patents Act 1949 no longer to be found in the 1977 Act. But it is common ground that the four Windsurfing steps are appropriate to be taken when the question of validity under the 1977 Act arises, the third step being understood as to identify the differences, if any, between the matter forming part of the state of the art and the alleged invention. However, there is no requirement that in every case the court should be seen to take those steps to answer the question of obviousness, though there are dangers in failing to do so.

32. In considering the question of obviousness, we bear in mind what Mr. Carr rightly acknowledged at the outset, that the assessment of obviousness is the application of a legal standard to facts found by the judge and that this court is very reluctant to interfere with such a decision. In Designers Guild Ltd. v Russell Williams (Textiles) Ltd. [2002] 1 WLR 2416 the House of Lords cautioned against interfering with the trial judge's assessment in applying a not altogether precise legal standard to a combination of features of varying importance, unless it can be seen that the judge erred in principle. In Biogen Inc. v Medeva plc [1997] RPC 1 at p. 45 Lord Hoffmann observed that the question whether an invention was obvious should be treated with appropriate respect by an appellate court, and went on to explain that 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. He continued:

"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."

33. We start with Mr. Carr's criticism that the judge failed to adopt the mantle of the skilled person. He drew attention to what the judge said at the commencement of para. 46:

"When obviousness in the light of the common general knowledge is concerned, the risk[s] of failing to look at the problem through the eyes of the skilled person are perhaps diminished. There is no clearly defined starting point in the sense of a single publication."

Mr. Carr says that this is wrong and diminishes the importance of step 2 of Windsurfing.

34. Mr. Carr contrasted what the judge said with what in Panduit Corporation v Band-It Co. Ltd. [2003] FSR 8 Aldous L.J. (with whom Mance and Latham L.JJ. agreed) said:

"The second step of Windsurfing requires the judge to adopt the mantle of the skilled person. This is particularly important where, as in this case, the attack upon the patent is based upon what was generally known in the art"

35. Mr. Carr points out that the cases are littered with warnings about the danger of being misled by a hindsight analysis of a combination of steps from the common general knowledge, particularly in the case of an apparently simple invention.
36. The difficulty with this argument is that the judge showed himself to be well aware of the necessity to view the invention through the eyes of the skilled person. In para. 5 of the judgment he said:

"The patent in suit is to be construed through the eyes of the notional addressee of the specification, the skilled person. The teaching of the prior art, and the obviousness of the differences between the alleged invention and the prior art is to be ascertained from the perspective of the skilled person. The common general knowledge in the art, the possession of which distinguishes the skilled person from the general run of humanity is ascertained from the evidence of expert witnesses."

The judge thereby correctly adopted the approach laid down in Mölnlycke AB v Procter & Gamble Ltd. [1994] RPC 49 in which this court said that the primary evidence will be the opinion evidence of properly qualified expert witnesses, all other evidence being secondary to that primary evidence. His conclusion was based on the evidence of Mr. Wassall and Mr. Robben, though on some points he had to choose between them.

37. The judge was also well aware that the skilled man is a person lacking imagination. The quotation from Windsurfing which the judge cited and which we have cited in para. 30 above expressly so stated. He was well aware too that Mr. Robben was not the embodiment of the skilled man: he expressly states that Mr. Robben was of an inventive turn of mind. But that does not prevent the judge from being able to obtain assistance from Mr. Robben's evidence as to the characteristics of the skilled man, as to common general knowledge and as to what would have been obvious to the skilled man. When the judge described the skilled man as the legal counterpart of the persons at Nova or Swan responsible for the design of new domestic appliances, he was not saying more than that the skilled man was a team of persons with the different skills which he identified as possessed by the members of the team, such as might have been found at Nova or Swan. With much of Mr. Robben's evidence Mr. Wassall agreed. Mr. Carr criticised the judge for preferring Mr. Robben's evidence to that of Mr. Wassall on the question of the obviousness of using the insulating ring in the Patent, but we do not see any real basis for believing that the judge, in weighing that evidence, was not aware of the danger of Mr. Robben applying his inventive approach to answering the question.
38. Mr. Waugh submits that the judge's remarks in para. 46 of his judgment, which we have cited in para. 33 above, are merely judicial comment that the court may be less likely to fail to remember to look at the problem through the eyes of the skilled person in a case such as this where the court is looking to see if the invention is obvious in the light of the common general knowledge. We agree with Mr. Waugh. We draw attention to the use by the judge of the word "perhaps" in his remarks. Mr. Carr submits that in fact the risk of the court failing to look through the eyes of the skilled man is greater when obviousness is based on common general knowledge. We incline to think that the judge was right in his comments, but, whether he was right or not, we do not see that the judge was failing to adopt the mantle of the skilled man, nor that he was diminishing the importance of step 2 of Windsurfing nor that he was not applying that guidance. The judge expressly stated (in para. 41) that it was often helpful to follow that guidance, which he set out, and went on to direct himself as to the dangers of viewing the question of obviousness with hindsight. In our view on a fair reading of the judgment the judge did not overlook any of the Windsurfing steps.
39. We consider next Mr. Carr's criticism of the judge's findings on common general knowledge.
40. The judge accepted Mr. Waugh's identification, based on Mr. Robben's evidence with which Mr. Wassall substantially agreed, of the following matters of common general knowledge for a design team:

"a) the properties of the standard metals and plastics used in domestic appliances and the processes used for shaping them, their cost and availability;

b) the increasing trend (at the priority date in May 1987) for plastics to be used in domestic appliances and the increased stress on aesthetic considerations in the marketing of domestic products;

c) the greater versatility of plastics in shaping compared with metals;

d) the requirements for plastics used in the manufacture of domestic appliances including their surface characteristics (i.e. whether glossy, resistant to staining and cleanable) their stiffness and feel, the effects of temperature on those characteristics and also on their rates of degradation and discolouration, the ease with which they can be moulded and the expense of tooling for them;

e) the plastics suitable for use in domestic appliances and the low cost, chemical resistance and advantages in manufacture of polypropylene compared to other plastics usable for the outer covers of heated appliances and the heat resistance advantages of glass filled polybutylene terephthalate (PBT), nylon or similar polymers if direct contact with heated parts is required….;

f) familiarity with the range of available electrical household appliances that include heating elements, such as fryers, irons, kettles and toasters including polypropylene kettles and cool wall toasters;

g) the range of temperatures to be expected in such devices;

h) the use of insulating gaskets to separate hot metal parts from plastics components of low temperature resistance."

The judge also accepted that the skilled man could be expected to understand conduction and convection, and he added that the skilled man had the safety of the device which he designs very much in mind. We did not understand Mr. Carr to challenge this list, provided that it was borne in mind that para. h) had not been shown to be applicable to fryers.

41. Mr. Carr rightly stressed the distinction between cited prior art and common general knowledge. But the judge cannot be accused of ignoring that distinction. In para. 38 he had cited the observations of Aldous L.J. in Beloit v Valmet [1997] RPC 488 at p. 494 on the difficulty in differentiating between common general knowledge and what is known only by some, and the need to bear in mind that the notional skilled addressee is the ordinary man who might not have the advantages possessed by some employees of large companies. In para. 39 the judge said that where an item of prior art is not specifically relied on to support an allegation of obviousness, it is essential that all material which cannot fairly be described as common general knowledge are excluded. He acknowledged that the evidence of Mr. Robben did not make that easy, as he had wrongly regarded a number of catalogues and fryers, including the one called Grossag and the Taurus, as commonly known.
42. However, the judge regarded the evidence of Mr. Wassall in cross-examination as establishing the scope of the common general knowledge, when Mr. Wassall accepted that what was known in 1987 was –

(a) the basic design of electric fryers with a metal skirt serving to support the vessel which rested on the skirt;

(b) the use of an air-filled gap between the vessel and the skirt to insulate:

(c) the use of plastic outer casings in other domestic appliances;

(d) the use of polypropylene;

(e) the preference of plastics to metal for manufacturing and aesthetic reasons;

(f) the properties of plastics; and

(g) the use of insulating rings and spacing elements in irons, coffee makers and toasters.

43. The judge (in para. 40) summarised what was established by that evidence as that "without any particular design in mind the skilled addressee setting out to design a fryer in 1987 would bring to that exercise the knowledge that the skirt can be made of metal, and the vessel can rest on the skirt, through (if need be) an insulating ring." Mr. Carr, with some justification, criticised the last seven words as not established by that particular evidence. But the passage in the cross-examination of Mr. Wassall was a recapitulation of other evidence of Mr. Wassall. He had accepted that the skilled designer would be interested in other electrical appliances with whose basic features he would be familiar, whether (as in the catalogue of a Spanish manufacturer, Ufesa, which was put to him) irons, electric fryers, coffee makers or kettles, that the notion of heat-insulating rings, gaskets and spacers would be commonly known to a design team and that they were examples of a basic design approach of insulating a weaker plastic from another material by the use of a more resistant material (see the Transcript for 23 April 2002 pp. 130 – 140).
44. Mr. Wassall accepted, as the judge noted in para. 47, that by the 1980s there was a strong emphasis on the use of plastics where possible. Mr. Wassall also accepted, again as noted by the judge, that there was a general trend, driven in part by safety considerations, to enclose heated appliances in plastics casings.
45. Mr. Robben in his evidence was clear that the application of basic design concepts from one appliance to another was a basic part of engineering. In cross-examination he made plain his view that it was not just his role but everybody's role to look at that (Transcript for 24 April 2002 p. 321). He said that rings and spacers were such basic design options that they would naturally spring to mind to any design team faced with the need to connect a heated part to another part which had to be kept relatively cool.
46. We conclude that there was material before the judge on which he could properly conclude as he did on common general knowledge. The criticisms made of him on this count have not been made good.
47. We now come to the criticism of the judge that he failed to appreciate that the combination of known features may not have been obvious. Mr. Carr points to the evidence of Mr. Wassall that the Swan team in 1987 had confronted the problem of improving on the then established design of a fryer with a metal skirt, the high temperature of which was a safety concern. They had considered manufacturing the skirt from plastics, but those with a high melting point were prohibitively expensive, while cheaper plastics like polypropylene could not withstand the temperature of the vessel and the temperature inside the skirt. He relies on Mr. Wassall's evidence that when the Swan team found that polypropylene was melting on contact with the vessel rim, they never considered putting an insulating ring on top and did not consider applying their knowledge of gaskets and insulating materials used in other appliances, but instead abandoned the idea of a plastics skirt and used metal instead. When the SEB fryer came on the market, the design team were asked why they had not come up with it. That, Mr. Carr submits, was a powerful indication that the step of using an insulating ring as taught by the Patent was an inventive step and not obvious. He adds the consideration that the Nova team were asked at the end of 1986 to solve the same problem, but came up with a solution completely different from the Patent, as Mr. Robben accepted. He asks why, if what SEB did was obvious, it had not been done before.
48. We readily acknowledge the considerable force in those submissions, particularly when advanced as persuasively as they were by Mr. Carr, and we can see that another judge trying the case might have come to a conclusion different from that reached by the judge. However, we are not persuaded that the judge, with all his experience in the field of patents, was unaware that there may be invention in combining well known features, established as that is by several well-known authorities. Nor are we persuaded that the judge's conclusion that the incorporation of an insulating ring into the design to enable cheap plastics such as polypropylene to be used for the skirt was not properly open to him on the evidence and in the light of the identified features of the common general knowledge. We have already referred to those features and to salient parts of that evidence. There was clear evidence from Mr. Robben, supported by Mr. Wassall, that design teams working on such appliances as fryers went from designing one appliance to designing another type of appliance, and knew the structures of such appliances, and it was Mr. Robben's opinion, unshaken in cross-examination, that there was no inventive step taken by SEB.
49. True it is that Mr. Wassall was of a different view. He was asked by the judge:

"Once you knew that some plastics are tougher than others, …. once you know that you used a tougher plastic to protect a more vulnerable plastic, it is your view that you would as it were compartmentalise that knowledge by application, so if you moved away from the designing of irons to designing something which runs at a higher temperature, you would not employ the knowledge that you gained with irons. Is that right?"

His answer was:

"Not necessarily my view. I think the difference I have when I am trying to approach the two products is that one, that the other basic difference with an iron everything is clamped together and you have a sole plate and basically clamped between the upper PB7 whereas with a fryer you would have to support a ring as well, which would have different properties."

That is an equivocal answer, and the judge was entitled to prefer Mr. Robben's clearer and more logically coherent evidence on "compartmentalisation".

50. The fact that particular design teams did not come up with the same solution as SEB does not prove that the alleged inventive step was not obvious. The question, "If it was obvious, why was it not done before?" is a familiar one, but we accept Mr. Waugh's submission that the answer is tied up with many other questions, such as whether there is a long-felt want, before it can provide guidance. The judge said, in respect of the abandoned plea of commercial success, that this could not be established. Metal-skirted fryers in 1987 and now continue to sell well. As Mr. Waugh said, there can be many commercial or social reasons why a solution has not been commercialised before, but for patent purposes what is important is whether any technical reasons exist.
51. We conclude that the judge has not been shown to have made any error of principle, and it follows that his conclusion on obviousness must be upheld.

(B) Toshiba

52. In the light of our decision on question (A), the question whether the Patent is invalid as obvious in the light of Toshiba does not need to be answered. The judge did not consider it further, and in the circumstances we prefer to say nothing on this question.

(C) Construction and Infringement

53. Whilst it is not necessary for the outcome of this appeal to determine whether the judge was right in his construction of feature 8 of claim 1 and in his conclusion that the De' Longhi fryers would have infringed the Patent, if valid, as the point has been fully argued, we shall deal with this question shortly.
54. It was De' Longhi 's contention that by reason of feature 8, requiring the air-filled space between the vessel and the skirt to be "closed", as emphasised by the adverb "completely" in the further comments in the specification which we have quoted in para. 11 above, any fryer which allows air in that space to escape is not within the reach of the Patent. Mr. Waugh submitted that the judge failed properly to consider "closed" in the context of the specification as a whole, and failed to apply the Protocol in that his construction did not provide a reasonable degree of certainty for third parties.
55. In our judgment the judge's approach to the question of construction cannot be faulted. "Closed" has to be construed in its context and having regard to the function which it is intended to perform. It is plain that a purpose of the invention is to improve on the Taurus invention by preventing the risk of burning from hot air emerging from the opening at the top of the skirt in Taurus. It is immaterial that, as Mr. Waugh contends, there is in fact little risk of being burnt by Taurus. The word "closed" is used in the claim to distinguish the prior art and to prevent the risk of burning. Both sides accept that it does not connote that there should be hermetic sealing. We are of the opinion that the judge was right in para. 27 of the judgment to answer the question "How closed?" with the answer, "closed enough practically to prevent connection between the skirt and the vessel and the consequent escape of hot air, with the associated risk of burning." We believe that as a practical matter third parties are left in no uncertainty, whereas De' Longhi's interpretation, that the ring should as nearly as possible close off the air space between the vessel and skirt, would appear to allow deliberate avoidance to succeed, to the prejudice of the patentee.
56. In the light of that construction, and of the fact found by the judge that the flow of air in De' Longhi 's fryers was "practically negligible", it is apparent that De' Longhi would infringe by its fryers, if the Patent were valid.

(D) Insufficiency

57. This point was taken very shortly by Mr. Waugh and it is sufficient to say that in our judgment the Patent adequately discloses the invention clearly and completely enough for it to be performed, as the judge's reasons on construction show.

Conclusion

58. For the reasons given in answer to question (A) on obviousness, we dismiss this appeal.