T 0284/85 24-11-1989

I. European divisional patent application No. 81 200 909.0 (publication No. 0 046 000), which has been divided from earlier European patent application No. 79 300 487.0 and claims a priority as from 27 March 1978 based on an application in the US, was refused by decision of Examining Division 2.2.01.067 dated 27 June 1985.

II. That decision was based on Claim 1 filed with letter dated 6 November 1984, Claims 2-4 filed with letter dated 25 April 1984 and the description (pages 1-7) and drawings (1 sheet) of the divisional application. The ground for refusal was that the subject-matter of Claim 1 was not considered to involve an inventive step with respect to the prior art disclosed in:

DE-U-7 323 419 (D1) and DE-A-2 556 919 (D2).

The decision furthermore cited G. Lenormand & R. Mignée "Construction Mecanique, Éléments de Technologie, Tome 1", Paris 1961, pages 78 and 79.

III. The Appellant (Applicant) lodged a notice of appeal against this decision on 03 August 1985 and paid the relative fee on 8 August 1985. A statement of grounds was filed on 28 October 1985.

VI. On 9 October 1987 the Rapporteur issued a communication in which he cited a new document:

FR-A-2 363 161 (D3), which he considered to be more relevant than the prior art cited previously.

The Appellant replied with letter dated 09 December 1987 in which he compared the teaching of D3 with the subject- matter of the application.

V. Oral Proceedings were held on 24 November 1989. During the oral proceedings the Appellant filed a new set of three claims and amended pages 1, 1a and 7 of the description. He requested that a patent be granted on the basis of these three claims, the description as amended at the oral proceedings and the drawings as originally filed.

VI. The only independent claim reads as follows:

"1. An information disc support assembly comprising: a motor (71) and a spindle (77) for driving a disc (2), said spindle (77) having a central axis, a disc support means (86) positioned about said central axis and having a generally flat annular surface (87) extending perpendicular to said central axis and spaced from said spindle for supporting said disc, a central recess (93) provided in said support means; and a centering member (92) mounted on said spindle and received in said central recess provided in said support means, said centering member (92) having an outer surface generally forming a frustum of a cone which is arranged for engaging a central aperture provided in said disc and centering said disc with respect to the central axis of said spindle, and resilient biassing means (91) for enabling the relative axial position of said centering means and said support means to be adjusted, and further comprising a releasable clamping means (6) arranged to engage the side of a disc (2) opposite from the side en-gaged on said generally flat annular surface (87), characterised in that said disc support means (86) is connected to said spindle (77) to be rotated thereby, in that said generally flat annular surface (87) defines a support plane for said disc which extends at a fixed axial location relative to said central axis, in that said centering member (92) is axially slidable relative to said spindle (77) and to said support means (86), and in that said biassing means (91) are arranged to bias said centering member out of said support means (86) such that, prior to the engagement of a disc on said centering member, said outer surface of said centering member (92) projects beyond said support plane."

Claims 2 and 3 are dependent upon Claim 1.

VII. The Appellant's submissions can be summarised as follows:

The various centring members described in D1 are not provided with conical outer surfaces. If the centring means described in D1 were provided with a conical outer surface then the disc would not be rigidly clamped between the clamping means and the support means connected to the driving motor unless the hole in the disc is larger than the conical portion of the centring member. In this latter case the conical surface would not act to centre a disc. Thus it would not be obvious to provide the centring members of D1 with conical surfaces.

The prior art according to D3, which uses a surface forming a frustrum of a cone (in the following indicated as a frusto-conical surface) for centring a disc, suffers from a number of problems for which no solution is provided in the prior art but which are avoided with the device of the invention. In particular centring a disc by means of the device according to D3 results in distortion or wear of the disc because the disc has to slide on disc support means. In the drive position the disc is not always supported at the same height which creates a problem for focusing the reading beam on the disc. The disc is not clamped securely between the disc support means and clamping means and thus driving the disc relies on the frictional force between the edge of the disc aperture and the frusto-conical surface of the centring member, which can result in distortion or wear of the aperture and disc slippage.