In T 416/87 (OJ 1990, 415) the board was confronted with the situation where a feature was not included in the claims which the description on its proper interpretation specified to be an overriding requirement of the invention. The board held that, following Art. 69(1) EPC 1973 and its Protocol, the claims might be interpreted as requiring this as an essential feature, even though the wording of the claims when read in isolation did not specifically require such feature (confirmed in an obiter dictum in T 717/98).
In T 121/89, on the other hand, the board used the description to interpret an ambiguous term ("loose ignition charge"), but at the same time stressed that only features recited in or deducible from the claims could be set forth to distinguish the invention from the state of the art. The examples cited in the description did not limit the scope of the claims unless they were explicitly mentioned in them (see also T 544/89).
In T 1208/97 certain known molecules were encompassed by the terms of the product claim. Appellant 1 had argued that a novelty objection could not apply because the patent specification stated the clear intention not to cover these molecules. The board did not agree with this view. For the purposes of judging novelty, Art. 69 EPC 1973 offered no basis for reading into a claim features which could be found in the description. As this article and the Protocol concerned the extent of protection, they were primarily for use by the judicial organs which dealt with infringement issues. According to the board, it had to be established whether or not the wording of claim 1, independently of any alleged intention derivable from the description, allowed a clear distinction between the claimed molecules and the known molecules.
In T 932/99 claim 1 was directed to a product per se. The claim defined only the structure of a membrane as such, independently from its installation in an apparatus for gas separation. The board pointed out that, for this reason, the indication in the claim "capable of separating oxygen from oxygencontaining gaseous mixture" merely served the purpose of defining a capability of the claimed membrane, without imparting any limitations on any actual use of the structure claimed. The respondents had argued that, if claim 1 was interpreted in the light of the description, those limitations would be apparent. However, the board held that a distinction had to be drawn between, on the one hand, the fact that it might be necessary to take into account any explicit definition as given in the description for interpreting a claim's term and, on the other hand, the attempt to use Art. 69 EPC 1973 as a basis for reading limitations derived from the description into claims in order to avoid objections based on lack of novelty or inventive step. The latter approach to interpretation, whereby features mentioned only in the description were read into claim 1 as necessary limitations, was incompatible with the Convention (T 1208/97; see also T 945/99, T 2049/07).
In T 1018/02 the board emphasised that, although a claim must not be interpreted in a way which was illogical or did not make sense, the description could not be used to give a different meaning to a claim feature which in itself imparted a clear, credible technical teaching to the skilled reader. This also applied if the feature had not been initially disclosed in the form appearing in the claim (see also T 373/01 and T 396/01).
In case T 223/05 claim 18, which was directed to a certain compound, was silent on the value of X, when Y was not present. The opposition division had held that the skilled reader would have referred to the content of the description and would have deduced that all the claimed compounds had a Michael acceptor side-chain. Hence, the skilled reader would have corrected the lack of information in claim 18 by referring to the content of the description and would have concluded that, in the absence of Y, X had to be a Michael acceptor side chain. For this reason the subject-matter of said claim was novel over document (3).
The board, however, emphasised that Art. 69 EPC 1973 and its Protocol did not provide a basis for excluding what was literally covered by the terms of the claims. Applying this to the case at issue, the board considered it inconsistent with proper claim interpretation to read into claim 18 a particular meaning for X which only appeared in the description, and then to rely on this feature to provide a distinction over the prior art (see T 881/01). In T 681/01 too it was stressed that Art. 69 EPC 1973 and its Protocol could not be relied on to read into the claim an implicit restrictive feature not suggested by the explicit wording of the claim. On this issue see also T 1105/04 and T 299/09.