In T 500/89 it could only be seen from the disclosure considered in its entirety that the prior art document did not deprive the claimed invention of novelty, because the method constituting the closest prior art differed from the claimed method in one functional characteristic. The disputed patent related to a method for the production of photographic material by the simultaneous application of several layers of fluid photographic coating materials. Although the document cited in support of the opposition listed the numerical ranges for layer thickness, viscosity, coating speed, etc. used in the method claimed, the latter was nevertheless held to be new because the cited document described the choice of these numerical ranges as leading to intermixing between two particular layers. The contested patent was to be assessed according to a different criterion because it described the application of the layers as being "substantially free from intermixing". The "intermixing" described as an objective in the citation was not merely a stated purpose not constituting one of the technical features of the method described, but a functional feature – a criterion, in effect – forming an essential element of the teaching set out in this publication.
According to the established case law, where a claim concerns an apparatus differing from a known apparatus only as regards to the use indicated, then the use is not an apparatus feature, meaning that two apparatuses (differing only in the intended use) are identical in terms of structure. If the known apparatus is suitable for the claimed use, the claimed invention lacks novelty. If, however, the claim is for a process, the situation is not comparable. In such a case, the use feature is a functional process feature comparable in category with the other features (steps) of the process (T 848/93 cited by T 1931/14). The opponent in T 1931/14 also referred to decision T 304/08, but the board stated that the situation in T 304/08 was quite different. The board in T 1931/14 concluded that T 848/93 and T 304/08 demonstrated that in the context of a method it was important to differentiate between different types of stated purpose, namely those that define the application or use of a method, and those that define an effect arising from the steps of the method and implicit therein. Where the stated purpose defines the specific application of the method, in fact it requires certain additional steps which are not implied by or inherent in the other remaining steps defined in the claim, and without which the claimed process would not achieve the stated purpose. In this manner the stated application represents a genuine technical limitation of the method and the claimed method must be applied in that manner. On the other hand, where the purpose merely states a technical effect which inevitably arises when carrying out the other remaining steps of the claimed method and is thus inherent in those steps, such a technical effect has no limiting effect because it is not suitable for distinguishing the claimed method from a known one.
In T 872/09 the board stated that the claimed sensor was defined by reference to characteristics of its response when used in a measurement set-up. Since none of the determining aspects of the measurement set-up was defined in claim 1, the technical features of the claimed sensor which were responsible for providing the measurement referred to in the claim remained obscure. Legal certainty required that a claimed subject-matter cannot be regarded as novel over the prior art on the basis of an ambiguous feature (see T 1049/99). Hence, defining a functional feature of the claimed electrochemical sensor under undefined operating conditions was not appropriate to provide any distinction of the claimed subject-matter over the prior-art electrochemical sensors.
T 2170/13 dealt with the re-drafting of claim 1 as a method claim (auxiliary request). The board endorsed the approach in T 1822/12 that G 2/88 (in relation to functional technical features) related only to a use claim, namely to a claim for the new use of a known compound, that the case law had constantly interpreted G 2/88 in a very restrictive manner and that there was no possibility to expand the ruling in G 2/88 and G 6/88 to a claim worded otherwise. Hence the undisclosed purpose could not be considered to be a distinguishing functional technical feature of the claim. Following long technical arguments, the board also concluded (on the main request) that the final claimed feature was implicitly disclosed in prior art D1.
The term "means" is frequently used in the plural in the wording of patent applications, especially for functional definitions, but this does not actually rule out that there is only a single structural element (T 1794/12).