T 0006/80 (Intermediate layer for reflector) of 13.5.1981

Summary of Facts and Submissions

I. European patent application No. 78 100 662.2 (publication No. 0 000 913), received on 14 August 1978, claiming priority from 26 August 1977 and entitled "Reflector for solar collectors", was refused pursuant to Article 97(1) EPC by decision of the Examining Division dated 2 July 1980. This decision was based on a single claim, in the version of 3 March 1980, which has the following wording: "Reflector for solar collectors comprising a sheet of glass mirrored on one surface, said sheet being of less thickness than it would require to be self-supporting and having its mirrored surface adhered to a support, characterised in that a foil is adhesively interposed between the sheet of glass and the support."

II. The stated grounds for the refusal were that the subject-matter of the claim did not involve an inventive step, since patent document DE-A-2 152 642 disclosed a reflector differing from that claimed only in that a flexible intermediate layer rather than a foil was adhesively interposed between the sheet of glass and the support. Such a foil is, however, known from patent document US-A-3 906 927, serving a very similar purpose, so that no inventive step was required to arrive at the teaching of the claim.

III. On 31 July 1980, the applicant lodged an appeal against this decision, paying the fee for appeal and filing the Statement of Grounds in due time. The applicant asserted that the glass fibre sheet in US-A- 3 906 927 was used only to reinforce the support, and thus provided no clue to the solution of the problem addressed in the application, namely how to ensure satisfactory accommodation between large-area mirrored glass sheets and any desired supports on which they are mounted. The applicant requested the grant of a European patent on the basis of the single claim of 3 March 1980 supported by revised documents dated 9 October 1980. Alternatively, the applicant, by letter of 30 September 1980, requested the grant of a European patent on the basis of a new claim in accordance with the documents dated 9 October 1980 and reading as follows: "Reflector for solar collectors comprising a sheet of glass mirrored on one surface, said sheet being of less thickness than it would require to be self-supporting and having its mirrored surface adhered to a support, characterised in that a foil (12) is interposed between the sheet of glass (11) and the support (13), said foil being bonded on one side to the mirrored surface of the glass with a first adhesive and on the other side to the support with a second adhesive."

IV. In his communication to the applicant of 22 December 1980, the rapporteur of the Board of Appeal pointed out that the use in solar collectors of a flexible foil interposed between a thin mirrored sheet of glass and a support for the purpose of accomodation of the glass sheet to the support was also known to a person skilled in the art from patent document CH-A-571 199, which had not been cited in the appealed decision. Moreover the foil in US-A-3 906 927 was used not only to provide additional strength but also to prevent the deformation or fracture of the sheet of glass. In addition the claim did not appear to contain any definite structural distinguishing features which might lead to the reflector claimed functioning in a different or improved manner. Furthermore, the new claim submitted as an alternative could not involve an inventive step, as selection of the most suitable adhesives for the two materials in question was self-evident to a person skilled in the art, as was also evident from US-A-3 906 927. Finally, it was assumed that the application no longer covered the version omitting the foil.

Reasons for the Decision

1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is, therefore, admissible.

2. The present version of the claim meets all formal requirements and is adequately supported by the original documents.

3. According to the applicant, the application addresses the problem of ensuring satisfactory accomodation between the sheet of glass and the support.

4. The applicant acknowledges that the light-directing device disclosed in DE-A-2 152 642 corresponds to the preamble of the claim, and that CH-A-571 199 discloses a solar collector identical in respect of the salient features. On the other hand, the applicant also considers that the known intermediate layers are too thick to provide an adequate fit, and do not protect the sheet of glass against excessive stresses which may damage (fracture) it.

5. DE-A- 2 152 642, which as the most relevant prior art was prominent in the examination proceedings, describes and (in Fig. 3) illustrates an elastic laminate affixed to a high-stability base. This laminate, composed of the flexible, thin, non-self supporting mirrored sheet of glass and a somewhat thicker flexible sheet of acrylic glass adhered to it, is stabilised in the elastically deformed position required for the desired optical contour by bringing the elastically deformed laminate into contact with the mating face of the contoured base and securely bonding the two in this position. With respect to this prior art the use of a foil is novel.

6. In the above patent document the glass sbeet in its curved form is kept under bending stress indirectly, thus indicating to a person skilled in the art that the known sheet of acrylic glass is already capable of meeting the requirement of accommodation. A person skilled in the art can also see from CH-A- 571 199, which in the applicant's own opinion corresponds to DE-A-2 152 642, that a layer of flexible material between the large thin mirrored sheet of glass and the base makes it possible for the mirror glass to be deformed into the desired parabolic shape without fracturing. The flexible intermediate layer thus effectively protects the mirror glass against excessive stress, as it does in the subject-matter of the application.

7. It may thus be noted that the flexible intermediate layer known in the art is capable of functioning in the same way as the foil mentioned in the characterising part of the claim. More specific information regarding the dimensions and physical properties of this foil would be required to show that the foil as claimed is capable of performing this function more effectively. However, the application merely mentions briefly that the foil is made of metal and/or glass fibre and that the mirror, comprising the sheet of glass, the layer of reflective material and the coating of varnish, is thin. This does not permit adequate conclusions to be drawn as to the nature of the foil. It is also mentioned that an optimal relationship of tensile to compressive stress can be established through selection of the appropriate thickness of foil, which makes it clear that a person skilled in the art is in a position to select the appropriate properties of the intermediate layer, which means in turn that no inventive step is required.

8. It is not necessary to go into the question of whether the lack of distinction between the foil and the known intermediate layer is not in itself prejudicial to the novelty of the claim, because the use of a foil in place of an elastic intermediate layer of some other kind can no longer constitute an inventive step in view of the US-A- 3 906 927. To the person skilled in the art this patent document contains the proposal that a glass fibre layer be adhered between the mirror glass and the support. The applicant himself mentions an intermediate layer of glass fibre as being a suitable foil (cf. description of 9 October 1980, bottom of page 3).

9. US-A-3 906 927 discloses a compact, high-stiffness support of honeycomb structure. This support must retain some flexibility not only to meet the fine-tuning requirement but also for the purpose of adjusting and fixing the curvature of the mirror without risking fracture; in addition, it must also prevent fracture of the reflective material as a result of curvature deformation caused by external forces. No person skilled in the art is thus in any doubt that the purpose of the foil is not only to reinforce the support but also to protect the reflective material. Moreover, the overall thickness of the intermediate glass fibre matting can, for purposes of achieving an optimal relationship under bending stress, be adjusted by one or several layers of glass fibre, so that in this design, too, appropriate choice of the foil thickness yields an optimal stress relationship.

10. Furthermore, a comparison of the features of US-A-3 906 927 with those of the current claim shows that the sole difference is that in the latter a single sheet of glass is used, instead of separate parallel strips of mirrored glass. As under stress the strips of glass may also be deformed longitudinally it is apparent to a person skilled in the art that in this case, too, the intermediate layer of glass fibre has the effect of preventing excessive stress. In view of the teaching contained in US-A-3 906 927, no inventive step (Article 56) is required for a person skilled in the art to make the intermediate layer, known from DE-A-2 152 642 or CH-A-571 199, in the form of a foil; consequently, under the terms of Article 52, paragraph 1, EPC, the application cannot lead to the grant of a patent.

11. The applicant has agreed to the removal of parts of the description relating to an embodiment no longer covered by the claim. Comments by the applicant in support of the inventive step of such embodiments cannot therefore be taken into consideration when assessing the inventive step of those still covered by the claim.

12. The new claim of 9 October 1980 submitted as an alternative contains only those features contained in the original description and does not extend the scope of the original disclosure.

13. This claim relates to different adhesives used between the foil and its mating components. However, it is obvious to a person skilled in the art to select the adhesive yielding the optimum desired bonding properties with the two materials in question, as is evident from US-A-3 906 927. There, too, the strips of glass are bonded to their base with an adhesive different from the one used between the glass fibre matting and the support. The selection of suitable adhesives for bonding the foil cannot therefore be considered to constitute the inventive step required pursuant to Article 56 EPC, and as a result the claim cannot be allowed.

ORDER

For these reasons, it is decided that:

The appeal is dismissed and the appealed decision of the Examining Division is upheld.