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UK – Kwikbolt v. Airbus / Applying the “inventive concept” to the doctrine of equivalents

20 Apr 2021

Further to the UK Supreme Court introducing a doctrine of equivalents into UK patent law in the summer of 2017 (see here), the UK courts are gradually coming to terms with the various approaches that have to be applied in deciding whether to apply the doctrine in the absence of “literal” infringement of a claim. Since Actavis v Eli Lilly, a court in the UK will use three questions as guidelines in deciding whether there is infringement by equivalents. The first of these three questions is to decide whether the “variant” achieves the same result in substantially the same way as the invention. In this context the “invention” is not just the wording of the claim but the “inventive concept” revealed by the patent.

The notion of “inventive concept” is used in various contexts in relation to patents, but strangely the phrase has not been not defined anywhere in the legislation. It has been described as “the clever bit”. In the context of equivalents, its meaning arose in a recent case in the Intellectual Property Enterprise Court – Kwikbolt Ltd v Airbus Operations Ltd [2021] EHWC 732 (Pat). The patent concerned a fastener used in the construction of aircraft. In that case, the inventive concept was said by the judge to be the “new technical insight” revealed by the invention as claimed, in the context of the specification as a whole, as it would have been perceived by the skilled person at the priority date.

The patent itself was actually of no assistance in determining the “inventive concept”. In fact, it contained an inaccurate statement of the problem which the invention was said to solve. That was simply a broad statement of the general field of the invention. It therefore fell to the parties to argue what was the correct “inventive concept”. The judge observed that each party will necessarily know what is the integer which is missing from the claim (i.e. the “variant”) and will tend to tailor its definition of inventive concept accordingly. The integer in issue is liable to be irrelevant to the inventive concept which is advanced by the patentee, but will be central to the inventive concept advanced by the alleged infringer – effectively a sort of game in which the winner gets to move on to the other questions posed in the Actavis case.

Clearly, a correct assessment of the inventive concept cannot be achieved with the variant in mind. It is only after the inventive concept has been identified that the variant, and with it the integer(s) in issue, come into play, so that the relevant questions can be considered

The alleged infringement had one integer missing from claim 1, so the “inventive concept” needed to be identified. The court took the view that the new technical insight of the patent was that a fastener having the features of claim 1 will be an improvement over those of the prior art in a particular manner, namely that a certain surface of the fastener be substantially flush with the surface of the workpiece. This was not achieved in the alleged infringement. The court decided that the variant did not achieve the result of the inventive concept, in which case the scope of claim 1 was not extended by the doctrine of equivalents.

The patent was found valid but not infringed.

A copy of the judgment can be read here.

Headnote: Gregor Grant, Marks & Clerk Law LLP