According to T 517/98, if the disclosure of a patent in suit was limited to products which, when prepared by the method according to the invention, were characterised by distinctive parameters, then a claim which did not stipulate these parameters a priori encompasses embodiments which were not obtainable by the method disclosed. Such disclosure of a single way of performing the invention would only be considered sufficient if it enabled a person skilled in the art to carry out the invention within the whole ambit of the claim. In T 172/99, the board found that in the case of claimed subject-matter relying on a newly formulated and hence unfamiliar parameter to define the solution of a technical problem by which a relevant effect is achieved, the patentee is under a particular obligation to disclose all the information necessary reliably to define the new parameter not only (i) in a formally correct and complete manner such that its values can be obtained by a person skilled in the art without undue burden, but also (ii) in a manner which reliably retains the validity of the parameter for the solution of the technical problem for the application or patent in suit as a whole in the sense that the values routinely obtained will not be such that the claimed subject matter covers variants incapable of providing the relevant effect or, therefore, of solving the associated technical problem (followed in numerous decisions; see, for example, T 914/01, T 179/05 and T 75/09).

In T 815/07 the board pointed out that the purpose of a parameter contained in a claim is to define an essential technical feature of the invention. Its significance is that the presence of this technical feature contributes to the solution of the technical problem underlying the invention. The method specified for determining the parameter should therefore be such as to produce consistent values, so that the skilled person will know when he carries out the invention whether what he produces will solve the problem or not. This decision was cited in T 120/08 and T 593/09. According to the latter decision, what is decisive is whether the parameter is so ill-defined that the skilled person is not able, on the basis of the disclosure as a whole and using his common general knowledge, to identify (without undue burden) the technical measures (e.g. selection of suitable compounds) necessary to solve the problem underlying the patent at issue (see also in this chapter II.C.7.2 " Article 83 EPC and clarity of claims").

The fact that no direct independent method of specifically determining the parameter has been described is not in itself prejudicial to the sufficiency of the description where the claims do not relate to a method of determining the parameter (T 256/87, case concerning Art. 84 and 83 EPC, compliance of amended claim 1). In T 83/01 the board held that where the skilled person had no reason to doubt the definition of the parameter given, but there was no indication in the patent how to measure this parameter, the patent failed to fulfil the requirements of Art. 83 EPC 1973. In T 808/09 (cartridge for use in a beverage preparation machine / liquid chocolate ingredient), the board considered that the patent failed to enable the measurement of the essential parameter of the invention, i.e. the viscosity of the liquid chocolate ingredient. Even if this viscosity feature had been shifted into a preamble of method claim 1 and supposing this preamble had been directed to the prior art, this shifting of the feature would still not have solved the problem of insufficiency. For a reference to prior art in the preamble to adequately serve this purpose the patent in suit still needs to contain all the necessary information in sufficient detail in order to enable the person skilled in the art to perform the invention. In the case before the board this would require information as to the viscosity measurement device to be used and the parameters to be observed. All this information was missing. The board's decision, taken in line with the long-standing jurisprudence, cited T 805/93 (dealing with viscosity measurement at "room temperature"), T 83/01 and T 1250/01 (both concerning the measurement of an essential parameter).

The board in T 602/10 found that the proprietor had deliberately decided to use a method for determining rugosity which was different from the one commonly used in the state of the art. It was therefore its duty to provide full information with regard to the means and the procedures for implementing said method. In general terms, when the issue of sufficiency concerned the description of a method for determining a parameter, the less common the method the more accurate the information provided in the description should be. In the case at issue, in the absence of any known prior-art work applying the same method used in the patent for measuring the rugosity, the skilled person had to rely primarily on the teaching of the patent to put the method into practice.

Where the calibration of (undisclosed) test conditions may be achieved although the methods of determination of the parameter are incompletely described, the invention may be sufficiently disclosed. See for example T 1062/98. In both T 485/00 and T 225/93, three methods were known in the art for the determination of the specific surface area of a CaCO3 particle. In neither case did the description or common general knowledge indicate a preference for one of them. In T 485/00, the board held that reproducing an example and measuring the surface area of the resulting product by two or three well-known methods did not represent an undue burden for the skilled person. In T 225/93, however, the board found that, as there were three different measuring methods which did not always lead to the same result, this amounted to an undue burden. In T 641/07 the board held, citing T 485/00, that when a skilled person was enabled to reproduce the invention, and it was sufficient for him to reproduce one of the examples in order to identify the method employed to measure the value of a parameter, there was no insufficiency in the description since the identification procedure in question could not be regarded as involving an undue burden. In T 1712/09, the board held that the opponent had failed to prove that the method of measuring the parameters was unworkable. The tests referred to in its experimental reports had been carried out using measuring apparatus different from that described in the patent, and so not as instructed there. The board found that no attempt had been made to reproduce the invention (no attempt at calibration), which was the first condition for an objection under Art. 100(b) and 83 EPC. It cited T 815/07 (need for consistent values) and T 1062/98 and T 485/00 (possibility of calibrating methods of determining the relevant parameters).

In T 45/09 too, the opponent's test conditions were called into question since the tests had been carried out using a commercially available product. Observing that two products of the same brand but available on the market at different times would not necessarily have the same properties, the board found that it had not been established that the properties had been the same in this specific case. The board also considered the issue of calibrating the method of measuring the parameter. The board concluded that the opponent had failed to show that the method of measuring the parameter could not be reproduced and thus to prove insufficient disclosure. It was, indeed, for the opponent to do so, and it could have discharged its burden of proof by attempting to reproduce the method using at least one of the claimed silica.

Where it is obvious that a skilled person would select a particular analytical measuring method, (none being disclosed in the patent), balancing its simplicity and convenience against the required accuracy, the requirements of Art. 83 EPC are met (see e.g. T 492/92). This differed substantially from the case considered in decision T 466/05. In T 492/92 it was considered that the fact that two methods suggested by the appellant did not necessarily lead to identical results when measuring a specific parameter was not sufficient evidence that a skilled person could not determine this parameter of the claimed compositions with the required accuracy. In T 466/05, the skilled person did not even know which parameter should be determined and the invention was insufficiently disclosed.

The board in T 2403/11 acknowledged that an ambiguity of a parameter in the claim was not enough in itself to deny sufficiency of disclosure. Whether such an ambiguity led to insufficiency of disclosure was to be decided on a case-by-case basis (see T 593/09). The case at issue was different from T 882/03, which also concerned viscosity and where the variations resulting from the ambiguity were only minor, and from T 492/92, where the skilled person knew which method to choose. In T 2403/11 the method and the measurement parameters to be chosen were not known to the skilled person. T 482/09 also concerned a method of measuring viscosity (see also T 808/09 and T 805/93 supra). In T 1697/12 the claims covered, through open-ended ranges, embodiments that could not be obtained with the process disclosed in the patent, but which might be obtainable with different methods still to be invented in the future (insufficiently disclosed invention).

Where inventions are defined by claims containing unclear features, e.g. ambiguous parameters, which cannot be clarified in the light of the description, the effect sought may be the only means of understanding such inventions. This effect must then be taken into consideration and assessed under Art. 83 EPC with a view to establishing whether the invention can be reproduced (see T 862/11, headnote).

See also in this chapter II.C.7.2.

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