The case law according to T 169/83 (OJ 1985, 193) which has been frequently cited, even in recent decisions T 523/88 and T 818/93 showed that the EPC did not prohibit the amendment of claims to include features from drawings, provided the structure and the function of such features were clearly, unmistakably and fully derivable from the drawings by the skilled person and not at odds with the other parts of the disclosure. Nor could any element be dropped.
Indeed, in T 169/83 (OJ 1985, 193), T 465/88 and T 308/90 it was pointed out that where drawings existed they were to be regarded as an integral part of the documents disclosing the invention. Drawings were to be treated on an equal footing with the other parts of the application (see also II.E.1.1 "General issues"). Further, the fact that features were disclosed solely in the drawings did not preclude these features from becoming essential in the course of the proceedings (T 818/93). The features for which a skilled person could clearly derive the structure and function from the drawings could be used to define more precisely the subject-matter for which protection was sought (T 372/90).
In T 398/92, the board made particular reference to the case law on this subject. In the case at issue the patent claims as amended contained features that had not been mentioned expressis verbis in the written part of the original application but had been derived from the figures for the application as filed. In this case the drawings in question illustrated the curves in a system of Cartesian co-ordinates with a precise, defined scale. The curves therefore could not be compared to the schematised representation of an invention given by a graph. The board recognised that the points of these curves were not purely intellectual graphic constructions but, on the contrary, corresponded to real experimental values, representing the percentages of a particular drug released in solution. Although these percentages were not mentioned expressis verbis in the original document, the board was of the opinion that for a skilled person they would have been clearly and unambiguously derivable from the scale given on the Y-axis, since the figures were sufficiently precise for the ordinate values to be read exactly and thus for the same numerical features as introduced in the claims to be derived from them. The incorporation into the text of the claims of the numerical features derived from the curves therefore did not contravene Art. 123(2) EPC 1973 (as far as a graph representing a mathematical equation is concerned, see T 145/87). This case related to a process for regulating the print quality of printers which could only be carried out using statistical calculations. On the basis of a formula given expressis verbis, its representation as a graph according to the Cartesian co-ordinate system and a basic knowledge of statistics, the possible values of two parameters in the formula, though not expressly disclosed, could be deduced.
In T 191/93 amendments were based exclusively on the original drawings and introduced only some of the features disclosed in the drawings. The board held that the subject-matter of the patent had been extended compared to the application as filed because it was not derivable from the drawings that the two newly introduced features could be isolated from the other features shown in the drawings. The subject-matter defined in the claims thus amended was ambiguous. In this case, however, the ambiguity could be removed by also introducing into the claim a third feature, disclosed in the drawings as filed, together with the other two features.
In T 676/90 the applicant wished to delete the rolling-device features of a carrying aid for a pair of skis. The board found, however, that the original documents had disclosed only a carrying aid consisting of a rolling device and a carrying strap or only of a rolling device, but not an option without a rolling device. Nor was the board swayed in its view by the applicant's argument that the carrying strap was shown separately in a drawing. It held firstly that, according to the description, this drawing was an expanded view of the carrying strap shown in Figure 1 (which, moreover, showed a ski with the carrying strap in conjunction with the rolling device). Secondly, a drawing could never be interpreted in isolation from the overall content of the application but only in that general context. The content of an application was defined not only by features mentioned or shown therein but also by their relationship to each other.
In T 497/97 the board noted that, since drawings were often approximate and therefore unreliable, they could only be used in interpreting amended claims if the description did not contain a more precise indication of what was meant. Moreover, in the case at issue, the drawings showed only a preferred embodiment of the invention, which did not rule out the possibility of other embodiments covered by the claimed subject-matter. The board concluded that the contested wording, inserted in the characterising portion of claim 1, had been validly based on the description according to the application, i.e. that the wording had been inferable from its context without extending its meaning.
In T 748/91 the board reached the conclusion that size ratios could be inferred even from a schematic drawing as long as the delineation provided the relevant skilled person with discernible and reproducible technical teaching. In the board's view, schematic drawings depicted all the essential features.
However, a figure which served only to give a schematic explanation of the principle of the subject-matter of the patent and not to represent it in every detail did not allow the sure conclusion to be drawn that the disclosed teaching purposively excluded a feature not represented. A "negative" feature of this sort (in this case, "with no internal fittings") could not subsequently be incorporated into the claim (T 170/87, OJ 1989, 441). Regarding the absence of a feature in a figure which served only to give a schematic explanation of the principle of the invention, see also T 264/99, in which the board found the circumstances to be different from those in T 170/87.
Likewise, in T 906/97 the board held that the parent application as filed failed to disclose unambiguously the position of a door. The only indication of this position could be found in some figures, and in the board's view there was no suggestion whatsoever in the description itself that this detail of the schematic representation was actually meant to correspond to a technical feature of the apparatus shown in the figures, rather than being merely an expression of the draughtsman's artistic freedom.
In T 1120/05 the invention concerned an "arrangement for and a method of managing a herd of freely walking animals" and the amendment introduced a negative feature namely "but not to the milking station (2)". This negative feature was not expressly disclosed in the description and in the claims of the patent application as filed. Features could be taken from the drawings if their structure and function were clearly, unmistakably and fully derivable from the drawings. It was not possible to derive a negative or missing feature on its own, i.e. without the context of the other, existing features of the claim. It remained to be decided if a combination of features including the negative feature could be derived or not. This approach accepted, arguendo, that the skilled person was actually capable of finding - and indeed willing to search for - negative features in a drawing, albeit in combination with some other features.
Furthermore the board accepted in case T 1120/05 - for the sake of argument only - that the skilled person would look closely at the features relating to the animal passage. The question arose whether the skilled person would clearly, unmistakably and fully derive from the drawings that this animal passage had a further feature besides those explicitly stated in the application, i.e. whether the skilled person would positively realise that this animal passage did have some negative features as well. Were the board to accept that this were the case, then, as a matter of logic, the board would have to establish that the skilled person would, inevitably, realise the presence of further negative features, and potentially a large number thereof. Choosing arbitrarily one of these was not permitted, because the skilled person not only had to realise the possible negative features, but because they were derived from the drawings, he also had to establish which one of the features was essential to the invention and which ones were not. The board found that in the absence of a teaching from the description, the skilled person would be unable to establish the essential nature of a single negative feature, seen against a background of a multitude of potentially essential features, even if this selected single negative feature in the drawings could be recognised by the skilled person in the drawings. It was mentioned that the case law also confirms that negative features cannot be deduced from a schematic drawing only. More generally, in the context of Art. 123(2) EPC the original drawings cannot be considered as a reservoir of features on which the applicant or a patent proprietor can draw when amending the claims. Decision T 169/83 required that "the structure and function" of the negative feature should be clearly, unmistakably and fully derivable for the skilled person from the drawings. This was not the case here. Furthermore the drawings related to a specific embodiment. The disputed negative feature "the entrance device forms a passage leading from the receiving station to the separation device but not to the milking station" was not directly and unambiguously derivable from this specific embodiment. Therefore, this specific embodiment shown in the drawings could not serve as a basis for the desired amendment. A further passage referred to by the respondent/patent proprietor defined the result to be achieved without disclosing either explicitly or implicitly this negative feature. This negative feature therefore added subject-matter extending beyond the content of the application as filed. Moreover, the board did not consider this undisclosed negative feature as being an allowable disclaimer within the meaning of decision G 1/03, because the anticipation necessitating the amendment could not be considered as accidental (T 1120/05 is cited in T 777/07).
If drawings are originally filed in colour at the date of filing of an application, then the technical content of these original colour drawings should be determined taking into account the available evidence when establishing the content of the application as filed, for the purpose of examining compliance of amendments with Art. 123(2) EPC (T 1544/08, points 4.4 and 4.5 of the Reasons).