9.5.2 Claim construction
The provisions of Section 60 of the Act refer to “the invention.” Section 125 defines an invention as follows:
(1) For the purposes 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.
[…]
(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.
The “Protocol on the Interpretation of Article 69 EPC” in the EPC provides as follows:
Article 69 should not be interpreted as meaning 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. Nor should it be taken to mean 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 patent proprietor has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patent proprietor with a reasonable degree of legal certainty for third parties.
For the purpose of determining the extent of protection conferred by a European patent, due account shall be taken of any element which is equivalent to an element specified in the claims.81
Until 2017, U.K. courts did not recognize a doctrine of equivalents. Instead, U.K. courts have determined the extent of protection of a patent by applying “purposive construction.” This involved determining what the skilled person would have understood the patentee to be using the language of the claims to mean, and, in that process, account could be taken of equivalents. A person could only infringe a patent if the product or process fell within the claims on a purposive construction.82 In 2017, the Supreme Court held that the interpretation of the language of the claims was only the first stage in determining whether there was infringement. The court also held that a product or process that did not fall within the claims on a normal interpretation could nevertheless infringe if it differed in a way that was immaterial, and proposed questions to assist in determining whether the variation was immaterial.83