d) Ambiguous features – role of description and drawings 

In T 23/02 the board said that although the claims as originally filed contained no reference to a method of measurement for the average particle diameter, that did not mean that any method could be used to determine that parameter. If anything, the claims raised doubts as to how the average particle diameter had to be determined, in particular because the skilled person would be aware that the measuring method is decisive in particle size analysis. Therefore the skilled person would use the description and drawings when deciding how the average particle diameter was to be measured. They would then conclude that, when properly interpreted in light of the original description, the claims as originally filed contained restrictions as to the measuring method for the average particle diameter. For the case law on the need to include the measuring method of a parameter in the claim, see however chapter II.C.6.6.9 "Analytical measuring methods".

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 he strives in principle to understand a claim within the wording and terms of the claim itself, he may, where he 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, in order to be able to compare the claimed subject-matter with the disclosure provided by the application as filed, the board first determined the effective subject-matter resulting from the amendments in the original claims. 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 lead, however, to the infringement of Art. 123(2) EPC, since no such feature was disclosed in the application as filed.

In T 195/20 the board held that the issue was not how a linguist would construe the meaning of the sentence in question but how the person skilled in the art would. While a linguistic analysis could be helpful in determining how a skilled person would understand a phrase in a claim, the skilled person would not stop at determining the semantic roles of words in a phrase but would interpret the phrase in the context of the claimed subject-matter and the application as a whole.

On a related issue, see also chapter II.E.1.4.7 "Elimination of inconsistencies and unclear features" below.