6.1. General principles

According to the established case law, the skilled person should try, with synthetical propensity, i.e. building up rather than tearing down, to arrive at an interpretation of the claim which is technically sensible and takes into account the whole disclosure of the patent. The patent must be construed by a mind willing to understand, not a mind desirous of misunderstanding (see inter alia T 190/99, T 920/00, T 500/01, T 1023/02, T 749/03, T 405/06, T 2480/11, T 2456/12, T 383/14, T 1477/15, T 448/16, T 111/22).

A considerable number of decisions have held that the skilled person, when considering a claim, should rule out interpretations which are illogical or which do not make technical sense (see inter alia T 190/99, T 552/00, T 920/00, T 1023/02, T 749/03, T 859/03, T 1537/05, T 1204/06, T 383/14, T 681/15). Some decisions (T 1408/04, T 1582/08, T 493/09, T 5/14) have emphasised that this is understood to mean only that technically illogical interpretations should be excluded. A mind willing to understand does not require that a broad term need be interpreted more narrowly (even if, as in the case underlying T 1408/04, the narrower interpretation would refer to a structure which is very common, but not exclusive, in the technical field concerned). In T 1514/14 the board noted that when a claim requires interpretation, the skilled person will endeavour to interpret it in a technically sensible manner and in the overall context. However, this of course did not mean that only those interpretations which fulfil the requirements of the EPC can be considered technically sensible.

It is a well-established principle laid down in the boards' case law that a non-specific definition in a claim should be given its broadest technically sensible meaning in the context of that claim (see e.g. T 79/96, T 596/96, T 1266/19). T 1553/19 applied this rule of claim construction to a feature defined in a negative manner ("in absence of […] metal organic catalyst"). The board explained that the broadest scope of the claim corresponded to the narrowest (i.e. most limited) technically sensible definition of the element to be excluded.

In T 1354/18 the board pointed out that patent claims conveyed a technical teaching and were directed at a reader with technical knowledge in the field of the application. The correct interpretation of claim features must therefore always be based on their technical literal meaning in the overall technical context of all features from the perspective of a person skilled in the art and not on a purely linguistic analysis of the wording of individual terms. The terms used in patent documents should therefore primarily be given the meaning they usually conveyed in the relevant state of the art. This could easily lead to a situation where the skilled person in the relevant technical field understood certain terms differently on the basis of her/his general technical knowledge than on the basis of a purely linguistic analysis. Moreover, the patent specification itself could attribute a specific meaning to individual features that deviated from a purely linguistic understanding; in this respect, a patent document could be its own dictionary. The interpretation must lead to a technically sensible result, whereby the claims should normally be attributed the broadest technically sensible meaning. The linguistic analysis of a feature could at best complement or confirm the analysis of the technical meaning, but could not replace it. See also T 2007/19, T 1382/20.

In T 42/22 the board considered whether an independent product claim 1 was to be interpreted in the context of method claim 6. In the board's view, the interpretation of product claim 1 could not be dependent on whether or not method claim 6 was present in the claim set. Instead, each claim should be interpreted independently. The board did not find in Art. 84 EPC support for the contention that all claims needed to be interpreted together. In addition, there was a technically sensible interpretation of claim 6 which was also compatible with the selected interpretation of claim 1. The board pointed out that in line with the case law, a technically sensible interpretation could not be disregarded even if additional interpretations were possible.

On the consultation of the description and drawings to interpret the claims, see in this chapter II.A.6.3. "Using description and drawings to interpret the claims".

In T 1513/12 the board noted that an interpretation of a claim agreed by the parties to the proceedings was not to be regarded as binding on the board: the "principle of party disposition" was not to be understood as meaning that the parties to the proceedings could choose an interpretation of the patent which, although it might be satisfactory for them, might have implications for others not party to the proceedings. Confirmed in T 2319/18 and T 1024/19.

In T 1473/19 the board pointed out that claim interpretation is overall a question of law which must as such ultimately be answered by the deciding body, and not by linguistic or technical experts. It does, however, involve the appraisal of linguistic and technical facts which may be supported by evidence submitted by the parties. In T 450/20 and T 1494/21 the board concurred with this statement and it stressed that a board of appeal is not limited to the claim interpretations advanced by the parties but may also adopt a claim interpretation of its own. Relying on documentary evidence is not a precondition for the adoption of a certain claim interpretation by a board of appeal. In this context evidence can only be relied upon to prove facts, such as how the person skilled in the art understood a certain technical term in a certain prior-art document at a certain point in time, but not to ultimately ascertain whether a certain claim interpretation is correct or not.

See also chapter I.C.8.1.3c) "Interpretation of process claims".