d) Ambiguous claim features 

In T 1946/10 the board held that according to established jurisprudence the skilled person interprets a claim with a mind willing to understand, so as to arrive at an interpretation which is technically sensible and takes into account the whole disclosure of the patent. Though the skilled person strives in principle to understand a claim within the wording and terms of the claim itself, it may, where it encounters ambiguities, need to consult the description and drawings to gain a better understanding. Based on the understanding of the added feature gained by this claim interpretation, the board arrived at the conclusion that adding the feature to claim 1 as originally filed in isolation from its structural and functional context presented a new teaching not originally disclosed. In the same vein, see T 2350/15 with reference to T 1592/14.

In T 516/18 the board recalled that the claim must be read and construed by a person skilled in the art with a mind willing to understand, thereby giving the words the meaning and the scope that they have in the technical field relevant for the invention, including in view of the technical content of the claim. However, according to established case law of the boards of appeal, using the description and the drawings to interpret the claims was considered admissible and even necessary if the person skilled in the art, in an attempt to construe the claim with a mind willing to understand, was confronted with obscure and/or inconsistent features. In the view of the board, this was presently the case.

In T 1127/16, however, the board held that the fact that a claim of a patent was to be construed by a mind willing to understand (T 190/99) did not mean that the description and the drawings had automatically to be consulted when an "ambiguous" feature (i.e. a feature which at least theoretically allows more than one interpretation) occurred in the claim, or where the claim as a whole included one or more inconsistencies, in order to resolve that unambiguity or inconsistency. Rather, the claim should essentially be read and interpreted on its own merits (T 1018/02, T 1279/04, T 1404/05, T 197/10). The board underlined that otherwise an applicant (patent proprietor) could arguably dispense with providing a clear and unambiguous formulation of claim features, e.g. during the grant proceedings, in order to be able to fall back on a more description-based interpretation at will during subsequent opposition proceedings. Analysing claim 1 of the main request on a linguistic level, the board decided that the feature at issue would be read in a certain way. On a technical level, the skilled person would also conclude that this interpretation was entirely clear, coherent, and consistent with the other features of claim 1. This interpretation of the feature at issue led, however, to the infringement of Art. 123(2) EPC, since no such feature was disclosed in the application as filed.

In T 1473/19 the board pointed out that although Art. 69(1), second sentence, EPC generally required that the description and drawings be taken into account when interpreting a claim, the primacy of the claims according to Art. 69(1), first sentence, EPC limited the extent to which the meaning of a certain claim feature may be affected by the description and the drawings. The established case law that limiting features which were only present in the description but not in the claim could not be read into a patent claim was thus fully compatible with Art. 69 EPC in conjunction with Art. 1 of the Protocol as a legal basis for determining a patent claim's subject-matter. T 1473/19 was endorsed in T 367/20, where the board explained that the interpretation and determination of the subject-matter of the same claim in the same opposition (appeal) proceedings before the EPO should be uniform and consistent, including for the purpose of Art. 123(2) and Art. 123(3) EPC. After G 1/24 was issued, in the context of added matter, the primacy of the claims was also endorsed in T 2001/23, T 1071/23, T 873/23 and T 981/23.

In T 981/23 the board noted that according to the Order in G 1/24, the description and drawings are always to be consulted to interpret the claims, and not only if the person skilled in the art finds a claim to be unclear or ambiguous. The board considered this to be true not only for the question of "patentability of an invention under Articles 52 to 57" but also for the issue of Art. 123(2) EPC (T 873/23, T 2048/22; see also T 727/23). It further stated that G 1/24 otherwise confirmed most of the established case law, including the principle of the primacy of the claims (G 1/24, Order, first sentence: "the claims are the starting point and the basis"; T 1473/19), noting that the primacy of the claims prohibited a feature which was only disclosed in the description or the drawings from being read into a claim (T 1473/19). In the case in hand, the expression incorporated in claim 1 was worded differently from the description. In the board's view, it would be inconsistent with the principle of the primacy of the claims to automatically give the claimed expression the exact same meaning as the expression in the description despite the appellant's different choice of wording in the claim. Following the established practice to interpret a disputed claim more broadly rather than more narrowly (T 1886/22), the board would, for the purposes of assessing Art. 123(2) EPC, have interpreted the feature in question such that the "when" condition was only required for the activation. The board concluded that this would have resulted in added subject-matter.