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2.8 A purposive approach should always be adopted during the course of examination. Claim construction is a matter of law, and construction is not concerned with what the patentee himself actually meant to say. The patent should be construed in order to determine what the person skilled in the art would have understood the patentee to mean by using the language of the claims.
2.9 It is a convention in infringement and validity actions neither the patentee nor witnesses are consulted on that matter (British Celanese v Courtaulds  52 RPC 171 at 196). The specification is fixed in time and cannot be subject to the possibility that the patentee might change their mind about what he meant by the words he used.
2.10 This was also noted by the Court of Appeal in First Currency Choice Pte Ltd v MainLine Corporate Holdings Ltd  1 SLR 335. As set out by the Court of Appeal, the starting point of construction is what the person skilled in the art would have understood the patentee to mean by the use of the language of the claims. In this regard the Court of Appeal cited Lord Hoffmann in Kirin-Amgen v Hoechst Marion Roussel  RPC 9 and further guidance can be taken from this UK decision.
2.11 Construction is therefore objective in as much as it is concerned with what the person skilled in the art would have understood the patentee to mean by the words he used. The specification is to be read through the eyes of the person skilled in the art attempting to give it practical meaning (Ratiophram v Alza  EWHC 213). Wherever possible the specification should be construed so as not to lead to a “foolish” result (EMI v Lissen 56 RPC 23).
2.12 Generally, a document will destroy the novelty of a claim only if it discloses each and every feature of the claim. If the claim contains equivalent or additional features, then the question normally becomes one of obviousness. However, since a patent specification should be given a purposive construction rather than a purely literal one, the protection conferred may go beyond the literal wording of the claim. One possible consequence of purposive construction is that a term may be construed to encompass variants which the person skilled in the art would have realised to have no material effect upon the way the invention worked, and excluded those which would have been thought to have a material effect. As held by Lord Diplock in the Catnic Components Ltd and another v Hill and Smith Ltd  RPC 183, a claim to a lintel having inter alia a support member “extending vertically” was held to have been infringed by otherwise identical lintels in which the support member was 6o or 8o from vertical, since this produced a negligible reduction in the vertical support provided by the member. Therefore, depending on the facts of the case, a disclosure comprising only variations in “unessential” features from the claimed invention may still fall within the scope of the claims because the person skilled in the art would have understood the patentee had intended to claim these variations by using the language in the claim and reading the specification as a whole.
2.13 Kirin-Amgen Inc v Hoechst Marion Roussel Ltd  RPC 9 made it clear that there is no “doctrine of equivalents” in the UK in the sense that the protection afforded by the patents cannot extend beyond the claims. The purposive construction approach therefore combines a fair degree of protection for the patentee with a reasonable degree of certainty for third parties.
2.14 The purposive construction approach adopted since the Catnic decision was reaffirmed in the case of Improver Corporation v Remington Consumer Products Ltd  FSR 181. The “Improver questions” (subsequently dubbed the “Protocol questions”) provide a guidance for applying the principle of purposive construction in the context of equivalents, which can be used when assessing whether or not a variant falls within a claim (Wheatley v Drillsafe Ltd  RPC 7).
2.15 Improver Corporation v Remington Consumer Products Ltd  FSR 181 involved a consideration of an infringement of claims defining a depilatory (hair removal) device which comprised a rotating spring. In the opposing device the spring had been replaced by a rubber rod that comprised a number of parallel slits. The Court applied the following general questions to the variant:
(1) Does the variant have a material effect upon the way the invention works? If yes, the variant falls outside the claim. If no:
(2) Would this fact (i.e., that the variant has no material effect) have been obvious to the person skilled in the art at the date of publication of the patent? Or alternatively: Would this fact solve the problem underlying the invention by means which have the same technical effect? If no, the variant falls outside the claim. If yes:
(3) Would the person skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention?
Whether it would have been apparent to the person skilled in the art from the wording of the claim that a limitation to exclude the variant could have been intended by the patentee? If yes, the variant is outside the claim. If no, then the variant falls within the scope of the claim.
2.16 The Court determined that the change to a rubber rod had no material effect on the way the invention worked and it would have been obvious to the person skilled in the art that this variant would work in the same way. However, the person skilled in the art would have understood from the patent that the patentee meant to limit the claim to a “helical spring”. Thus, the variant did not meet the third requirement and was considered as not infringing the claims.
2.17 However, the Improver/Protocol questions may not be useful in determining the extent of protection in rapidly-developing, high-technology fields. In these cases, a claim could, on its proper construction, cover products or processes which involve the use of technology unknown at the time the claim was drafted if the person skilled in the art would have understood the description in a way which was sufficiently general to include the new technology.
2.18 Difficulties in applying the Improver/Protocol questions also occur where there is no common understanding of whether a word was being used in a strictly conventional or looser sense. In Kirin-Amgen Inc v Hoechst Marion Roussel Ltd  RPC 9 the Court cautioned that the Improver questions should only be considered as guidelines for applying the principle of purposive construction and not as rules for determining the scope of protection – there is only one compulsory question, namely what would a person skilled in the art have understood the patentee to have used the language of the claim to mean? In this case there was no suggestion that “an exogenous DNA sequence coding for erythropoietin” could have some looser meaning to include “an endogenous DNA sequence coding for erythropoietin”. Rather, the question was whether the person skilled in the art would have understood the invention as operating at a level of generality which made it irrelevant whether the DNA which coded for erythropoietin was exogenous or not.
2.19 It should also be noted that in most cases the Improver/Protocol questions are most relevant in the context of infringement. During examination variants are more likely to be considered under inventive step.