The Claims are Construed as a Legal Document

Date Published

The claims have a special function in the patent specification, as they alone define the monopoly. Consequently, the claims will be scrutinised with as much care as any other document defining a legal right (Decor Corp v Dart Industries 13 IPR 385).

The addressee of the specification is the person skilled in the art, whereas claims are frequently the province of persons trained in law. Thus, a standard of clarity which may be adequate for the body of the specification is not necessarily adequate for the claims. The description has the practical purpose of instructing the person in the art how to perform the invention when able to do so, i.e. after the patent has expired, whereas the claims define the monopoly, i.e. what must not be infringed during the term of the patent (British United Shoe Machinery Co. Ltd. v A. Fussell and Sons Ltd. (1908) 25 RPC 631). In the body of the specification, the words used may be adequate to enable the invention to be performed, whereas the same words used in the claims may leave competitors uncertain as to the overall scope of the monopoly.  In AMP v Utilux (1971) 45 ALJR 123 McTiernan J stated:

"... the degree of particularity of the language required in the claims should not be expected in the body [of the specification]."

Thus, general terms of uncertain ambit may be objectionable in the claims, even when they are terms which the addressee might be expected to be able to interpret for purposes of performing the invention. In British Celanese Ltd.'s Application (1934) 51 RPC 192 at page 195, it was stated:

"It is certainly dangerous for a patentee to seek to obtain a monopoly by reference to such general terms as "known methods" or "general methods", or equivalent phrases of that kind. I think that puts a burden on the public which should not be put upon them; it must necessarily lead to ambiguity and doubt ...".

Note also the comments in Virgin Atlantic Airways Ltd v Premium Aircraft Interiors UK Ltd [2010] RPC 8 at page 200 where it was stated:

“So the skilled reader is taken to suppose that the patentee knew some patent law – that his claim is for the purpose of defining the monopoly and that it should be for something new.  Knowledge of that may well affect how the claim is read – for instance one would not expect the patentee to have used language which covered what he expressly acknowledged was old.”