T 0052/04 31-03-2006

Summary of Facts and Submissions

I. The grant of European patent No. 0 808 912 on the basis of European patent application No. 97108226.8 was mentioned on 30 August 2000.

II. The granted patent was opposed by the present respondents (opponents OI and OII) on the grounds that its subject matter lacked novelty and did not involve an inventive step (Article 100(a) EPC).

III. With its decision posted on 13 November 2003, the Opposition Division held that the claimed subject matter of the independent claims 1 and 4 as granted lacked novelty and revoked the patent.

As the only citation of interest, document

D1: US-A-3 480 410

was relied upon. This document was held to disclose explicitly all the processing steps of claim 4, except for the heating rate that was claimed in the patent in suit to be between 3 and 100 ºC/min. In the Opposition Division's view, however, the heating of the powder blend referred to in document D1 was automatically performed at a rate falling within the claimed range and thus could not make a patentable difference. The process steps and the starting material in D1 being the same as claimed in the patent, the tungsten carbide (WC) powder obtained through the known process was rated to exhibit the claimed polycrystalline structure satisfying the inequality Y > 0.61 - 0.33log(x) cited in claim 1. Consequently, the Opposition Division concluded that the process stipulated in claim 4 and the composite carbide powder set out in claim 1 and produced by this process were not new over the disclosure of document D1.

IV. An appeal against this decision was filed by the patentee (the appellant) on 12 January 2004 and the fee for appeal was paid on the same date. A written statement setting out the grounds of appeal was filed on 15 March 2004 within the time limit given in Article 108 EPC.

V. In order to meet the requests of all parties, oral proceedings before the Board were held on 31 March 2006.

In the letters dated 28 February 2006 and 21 February 2006, respectively, the respondents OI and OII informed the Board that they would not attend the oral proceedings. Pursuant to Rule 71(2) EPC, the appeal proceedings were continued without them.

VI. The following requests were made:

- The appellant (patentee) requested that the decision under appeal be set aside and the patent be maintained as granted (main request) or, in the alternative, on the basis of a first or second auxiliary request.

- The respondents requested that the appeal be dismissed.

Independent claims 1 and 4 as granted read as follows:

"1. A composite carbide powder comprising, as a main component, tungsten carbide powder, which consists essentially of fine primary crystal particles of tungsten carbide, and a chromium containing powder, wherein said tungsten carbide powder satisfies an inequality given by:

Y > 0.61 - 0.33 log(x)

where Y denotes a half-value width of (211) crystal planes in the tungsten carbide (JCPDS-card 25-1047, d = 0.9020) measured by X-ray diffraction method where x denotes a grain size measured by a FSSS method, said grain size x being between 1.0 and 7.0 µm."

"4. A method of producing a composite carbide powder having tungsten carbide as a main element, according to one of claims 1 to 3, the method comprising the steps of:

preparing tungsten powder, which has a mean grain size between 1 and 7 µm;

mixing the tungsten powder with carbon powder and chromium containing powder into mixture; and

heating the mixture in an atmosphere selected from one of a hydrogen atmosphere, a vacuum atmosphere, and an inert gas atmosphere at a heating rate between 3 and 100ºC/min to a temperature between 1200 and 1700ºC, where it is held for 10 to 300 minutes, to form fine primary crystal particle carbide as the composite carbide powder,

said chromium containing powder being added in the form of a selected one of metal chromium, organic chromium compound and inorganic chromium compound, such as chromium oxide and chromium carbide."

VII. The appellant essentially argued as follows:

In the claimed process fine tungsten carbide (WC) primary crystal particles were created by diffusing Cr into coarse W particles before the WC particles were formed. The chromium diffusion process was strongly influenced (i) by the mean grain size of the tungsten powder and (ii) by the heating rate when the mixture was heated up to a temperature between 1200 and 1700ºC. It was evident from the comparative examples 1 to 4 given at the end of Table 1 of the Japanese priority document JP 8-125537 of 21 May 1996 that heating rates outside the claimed range could also be applied. Specifically, heating rates of 1ºC/min (example 3) or 150ºC/min (example 1) were tried but failed to promote the Cr-diffusion and thus did not produce the fine grained composite tungsten carbide powder satisfying the inequality stipulated in claim 1. Given that document D1 was totally silent on the heating rate, the subject matter of claim 4 was novel vis-à-vis the disclosure of this document and so was the composite carbide powder defined in claim 1.

VIII. In their written submissions in reply to the grounds of appeal, the respondents relied upon document D1 and concurred with the reasoning given by the Opposition Division in the impugned decision. It was admitted that document D1 failed to disclose a heating rate at all. Notwithstanding that the respondents argued that heating rates within the claimed range were "typical" for the conventionally used batch furnaces or continuous tunnel furnaces, the more since rates below 3ºC/min were uneconomical and those higher than 100ºC/min were difficult to achieve. The specific heating rate claimed in the opposed patent therefore did not make a technical difference to the process known from document D1. The subject matter of process claim 4 and product claim 1 therefore lacked novelty.