The invention for which the patent was granted is was summarized by Lord Justice Vos at paragraph  by reference to the following drawings:
"the Patent concerns an apparatus for frying food, particularly chips, that involves the use of only a small quantity of oil, by automatically stirring and turning (or "mingling" in the terminology of the Patent) the food so as to coat it in a thin film of oil or fat and cooking it (at least in the preferred embodiment) by a directed flow of heat. The main features of the apparatus that accomplish this, which are relevant to this case, according to the Patent, are:-
i) "the main body 2" which is provided with a "lid 2C", forming a closed box in co-operation with "the side skirt 2B", and "the base 2A";
ii) "a receiver means 5" or receptacle, which is substantially sealed against liquids, designed to contain both the food and the fat;
iii) "a stirrer means 6" with "a blade 16" designed to move with respect to the receiver means, so as to mingle and stir the food and fat;
iv) "a main heater means 24" to generate a "flow of heat 25" orientated so as to strike the food directly."
The AppealJarden contended that the judge misinterpreted the term "the main body" as including the lid of the fryer. It argued that the judge had wrongly made use of identifying numerals in the patent to construe its meaning. It submitted that its Halo fryer did not infringe the patent when properly construed because the Halo's heater was entirely located in the lid, whereas the specification shows only the ducts directing heat in the lid. Jarden also contended that the judge was wrong to hold that claims 10, 11, 13 and 15 were not obvious over German Patent no. P 21 02 062.2 entitled "Method and device for cooking food" filed on 16 Jan 1971 and published on 27 July 1971 ("Vogt"). Jarden alleged that its fryer did not infringe, because claim 3 (and thus claims 10, 11 and 13) required that "the lid together with the main body form a substantially sealed chamber" whereas the Halo fryer has a 2.3 mm gap around its circumference between the body and the lid, and was therefore not "substantially sealed".
At paragraph  Lord Justice Vos summarized the issues as follows:
"As the case was ultimately argued, only two main issues arose. The first was whether the words "mounted on the main body" in claim 9 should or should not be construed as including the lid, and the second was whether the judge ought to have held that claims 10, 11, 13 and 15 were obvious over Vogt. The second issue would not arise if Jarden were right as to construction, so that claim 9 did not cover a fryer where the main heater means was not mounted on the lid."Rules on Construction
Lord Justice Vos referred to the following extract from Lord Justice Jacob's judgment in Virgin Atlantic Airways Ltd v Premium Aircraft Interiors UK Ltd  EWCA Civ 1062,  RPC 8 for the rules of construction in relation to the use of reference numerals:
"The task for the court is to determine what the person skilled in the art would have understood the patentee to have been using the language of the claim to mean. An abbreviated version of [the principles] is as follows:His Lordship cited art 69 of the European Patent Convention and rule 43 (6) and (7) of the Implementing Regulations and para  of Lord Justice Jacob's judgment in Virgin Atlantic:
(i) The first overarching principle is that contained in Article 69 of the European Patent Convention.
(ii) Article 69 says that the extent of protection is determined by the claims. It goes on to say that the description and drawings shall be used to interpret the claims. In short the claims are to be construed in context.
(iii) It follows that the claims are to be construed purposively - the inventor's purpose being ascertained from the description and drawings.
(iv) It further follows that the claims must not be construed as if they stood alone - the drawings and description only being used to resolve any ambiguity. Purpose is vital to the construction of claims.
(v) When ascertaining the inventor's purpose, it must be remembered that he may have several purposes depending on the level of generality of his invention. Typically, for instance, an inventor may have one, generally more than one, specific embodiment as well as a generalised concept. But there is no presumption that the patentee necessarily intended the widest possible meaning consistent with his purpose be given to the words that he used: purpose and meaning are different.
(vi) Thus purpose is not the be-all and end-all. One is still at the end of the day concerned with the meaning of the language used. Hence the other extreme of the Protocol - a mere guideline - is also ruled out by Article 69 itself. It is the terms of the claims which delineate the patentee's territory.
(vii) It follows that if the patentee has included what is obviously a deliberate limitation in his claims, it must have a meaning. One cannot disregard obviously intentional elements.
(viii) It also follows that where a patentee has used a word or phrase which, acontextually, might have a particular meaning (narrow or wide) it does not necessarily have that meaning in context.
(ix) It further follows that there is no general 'doctrine of equivalents.'
(x) On the other hand purposive construction can lead to the conclusion that a technically trivial or minor difference between an element of a claim and the corresponding element of the alleged infringement nonetheless falls within the meaning of the element when read purposively. This is not because there is a doctrine of equivalents: it is because that is the fair way to read the claim in context.
(xi) Finally purposive construction leads one to eschew the kind of meticulous verbal analysis which lawyers are too often tempted by their training to indulge."
"In particular, we do not think that numerals should influence the construction of the claim at all – they do not illustrate whether the inventor intended a wide or narrow meaning. The patentee is told by the rule that if he puts numerals into his claim they will not be used to limit it. If the court subsequently pays attention to the numbers to limit the claim that is simply not fair. And patentees would wisely refrain from inserting numbers in case they were used against them. That is not to say that numbers are pointless. They help a real reader orient himself at the stage when is trying to get the general notion of what the patent is about. He can see where in the specific embodiment a particular claim element is, but no more. Once one comes to construe the claim, it must be construed as if the numbers were not part of it. To give an analogy, the numbers help you get the map the right way up, they do not help you read it to find out exactly where you are."Judgment
The Court of Appeal allowed the appeal on the construction point, and declared that the claims that Mr Justice Arnold had found to be valid were not infringed by the Halo fryer. The Lord Justices had no doubt that Mr Justice Arnold fell into legal error by allowing the reference numerals to influence his construction of the claim. In their view the trial judge was not simply using the reference numerals to identify which parts in fig 2 were being referred to in the claims or the specification, but was relying on the use of the particular identifiers "2", "2A", "2B" and "2C" (referring to the main body, the base, the side flank and the lid respectively) to conclude that the lid was to be regarded as part of the main body.
The Lord Justices then proceeded to construe the patent following Lord Justice Jacob's rules set out above and came to a very different conclusion at para  from that of the trial judge:
"First, claim 3 says that the "lid together with the main body form a substantially sealed chamber". If the lid were construed to be part of the main body, that formulation would have been different. Claim 4 then provides that the hinge is "for connecting the lid and the main body". If it had been intended to communicate to the skilled reader that the lid was to be regarded as part of the main body, the Patent would have used separate words to describe the body without the lid on the one hand and the body with the lid on the other hand. Moreover, all parties accept that the term "main body" has to have a uniform meaning throughout the Patent, though [SEB's counsel] submits that it only includes the lid where there is a lid on what is being described."It followed that Mr Justice Arnold had been wrong to conclude that the main heater means mounted on the main body referred to in the claims could include a "main heater means" mounted in the lid. As that was sufficient to dispose of the appeal it was unnecessary to consider the second ground of appeal. However, their Lordships seemed to think that the judge below was justified in his conclusion.
It is not often that Mr Justice Arnold is successfully appealed. His judgments are well documented and well argued which us why they are so long and detailed. Should anyone wish to discuss this case or patent law generally he or she should call me on 020 7404 5252 during office hours or get in touch through my contact form.