Patent drawings - not necessarily what they appear to be

In its decision T 1488/10, the Technical Board of Appeal of the European Patent Office (EPO) considered whether measurements taken from a prior art drawing can be used to invalidate a patent. In this case the drawing in question had some measurements indicated for the device shown, but not the particular ones that were needed to invalidate the claim under attack.

When an invention is defined using particular measurements there may be considerable difficulty in finding a piece of prior art that expressly discloses the same dimensional constraints.

In earlier case T 204/83 (OJ EPO 1985, 310) the EPO stated that: “Features shown solely in a drawing form part of the state of the art when a person skilled in that art is able, in the absence of any other description, to derive a technical teaching from them. Dimensions obtained merely by measuring a diagrammatic representation in a document do not form part of the disclosure.”

In T1488/10, the examining division had decided that the prior art drawing (“Figure 4”, reproduced below) did disclose a device in which the “segment of the connection which is free of connection constitutes between 50% and 75% of an overall length of the connector” (85 in the Figure) as required by Claim 1, particularly because the ratio between L1 and L2 was provided and these dimensions are along the same axial dimension. However, the Board of Appeal disagreed.

After discussing the meaning of L1 and L2 (and also of the other indicated dimension, t) and the fact that these parameters were important to the performance of the apparatus being described, the Board turned to the components whose length was neither indicated in the drawings nor discussed in the description of the prior art document [Reasons for the Decision, 3.5]:

“However, the dimensions of the other parts of the ultrasonic transducer shown in Figure 4 have to be distinguished from L1, L2, and t. First of all, they are not referred to by any reference signs in the Figure. Furthermore, they are not described as having any specific significance for the claimed invention. For example, no advantages are mentioned in the description concerning particular choices of the dimensions of these other parts.

“Regarding the representation of the dimensions of these other parts of the device, factors like the clear visibility in the Figure of these parts may well have induced the draughtsman to represent their dimensions in a manner that does not correspond to their actual dimensions. Therefore, in relation to these other parts of the ultrasonic transducer, the board is of the opinion that dimensions obtained merely by measuring the schematic drawing in Figure 4 does not form part of the disclosure of document D3 (see T 204/83, point 7 of the Reasons).

“Accordingly, the relative dimensions of the length of the stud 85 and the length of the connection-free part thereof, as obtained by carrying out measurements on Figure 4 does not constitute part of the disclosure of document D3. Hence, feature (ii) of claim 1 of the main request has not been disclosed in document D3.”

Thus, the claims were found to be novel over the device shown in Figure 4. They were, however, found to lack an inventive step over a further document, but this case illustrates that an opponent seeking to invalidate a European patent may not be able to rely on dimensions or ratios derived from measurements made on the drawings in prior art documents. That said, the Board’s reasoning in T1488/10 may have been influenced by the fact that Figure 4 was described as “schematic”.

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