T 0006/81 (Electrode slide) of 17.9.1981

Summary of Facts and Submissions

I. European patent application No. 78 100 557.4, received on 31 July 1978 and published on 7 March 1979, was refused by the Examining Division of the European Patent Office by decision of 5 November 1980. The decision was taken on Claims 1 to 3 and 5 to 11 as filed. Claim 1 read as follows: "1. Spot-welding device for electric resistance welding, comprising a carrier for the device, with a delivery (feed) slide guide-mounted on said carrier, and a spring-loaded electrode slide carrying the electrode, said electrode slide moving on ball bearings in said delivery slide, characterised in that (a) the electrode slide (4) is designed to incorporate a welding electrode clamp (5), (b) the spring (21) applying the electrode force is fitted within the electrode slide (4), but the electrode force can be adjusted outside the electrode slide, and (c) the electrode slide (4) is guided along the delivery slide (2) and the latter along the carrier on ball-guide rails (ball-slides) (32 and 33)." As regards the other claims, see the printed application documents (Publication No. 0 000 876).

II. The reason given for refusal was that, with reference to US Patent Specifications 2 912 564, 2 810 062, 2 432 750 and 2 179 326, the subject-matter of Claims 1 to 3 and 5, 7, 9 and 11 did not involve an inventive step; Claims 6, 8 and 10 also had to fail with the unallowable Claim 1, as protection was sought for them only in connection with Claim 1.

III. The applicant lodged an appeal against this decision and paid the appeal fee on 3 December 1980; he filed the statement of grounds and submitted new versions of Claims 1 to 10 on 20 February 1981. He argued that a person skilled in the art could not deduce the subject-matter of the invention from anything in the state of the art; in particular, no welding device having the electrode slide mounted on its own delivery slide was known. The applicant requested that the appealed decision be set aside and a European patent be granted on the basis of the new claims. Alternatively, he requested oral proceedings.

IV. In a communication dated 23 April 1981, the applicant was informed that, on certain grounds stated in the communication, it did not seem possible to set aside the appealed decision with the current Claim 1. It was accordingly decided to hold oral proceedings, as requested in the alternative. At the same time, the applicant was asked to state any sources of which he might be aware for a device having the characteristics given in the preamble of Claim 1 as originally filed.

V. In the oral proceedings held on 2 July 1981, the applicant requested that the appealed decision of the Examining Division be set aside and a European patent be granted on the basis of the Claim 1 thereupon submitted, and Claims 2 to 10 as filed on 20 February 1981. Claim 1 now read as follows: "1. A precision spot-welding device for electrical resistance welding comprising a carrier for the device, having a delivery member, a ball-guided electrode slide and a spring working between the delivery member and the electrode slide to produce a force exerted by the electrode, characterised in that the delivery member is constructed as a slide which is guided so as to be resistant to torsion, in the device carrier (1) by ball-guide rails (33) and which slide, on its part, carries the electrode slide (4) and guides it free of torsion in ball-guide rails (35); that the electrode (6) is clamped in the electrode slide by a clamping member (5) in such a way that it can be exchanged axially and radiallly to one side, and that the spring (21) which serves to apply the electrode force, is housed in the electrode slide (4).". The applicant considered that a precision spot-welding device constructed as described in this claim involved an inventive step in that it was not obvious having regard to the established state of the art. In response to questions from the Board, the applicant explained that a device having the characteristics set out in the preamble to Claim 1 as originally filed was purely in-house state of the art. After deliberation, the Chairman pronounced the opinion of the Board that a European patent could be granted on the application, on the basis of Claim 1 as submitted during the oral proceedings and once the dependent claims had been revised and the description brought into conformity.

VI. By letter dated 14 July 1981, the applicant filed fair copies of Claim 1, as submitted during the oral proceedings, in the preamble to which the reference symbols had been added and the term "a spring" amended to read "an adjustable spring", together with versions of claims 2 to 10, suitably adjusted, and a revised description and drawing. For the wording of Claims 2 to 10, the reader is referred to the file.

Reasons for the Decision

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

2. Examination of the claims received on 14 July 1981 gives rise to the following conclusions:

2.1 One difference between the current version of Claim 1 and the text as originally filed and forming the basis of the decision is that one feature, viz. the delivery slide being guided in the device carrier, originally included together with other features in the preamble, is now contained in the characterising portion. In the view of the Board, this transposition is admissible.

2.2. Under Rule 29(1)(a) of the Implementing Regulations to the EPC, the preamble of a two-part (independent) claim must contain the technical features of the subject-matter of the claim which, in combination, are part of the prior art. In principle, therefore, it may be assumed that the features included by the applicant in the preamble to the claim as filed, in combination with one another, are no longer new. On the other hand, the claim as originally worded must not be regarded as a binding statement as to the novelty of those features, but simply as an attempt to summarise the essential features of the invention. In the view of the Board, the question of which features are known and hence to be included in the preamble in the event of the application being successful must be decided purely in the light of the objective facts of the case.

2.3 In the present case, as substantiated below (cf. point 6), the search pursuant to Article 92 EPC did not reveal any patent document or any prior European patent application published on or after the priority date claimed (Articles 54 and 89 EPC) which describes or presents as a feature "a delivery slide guide-mounted on the device carrier" in combination with the other features given in the preamble to Claim 1 as originally filed and the applicant has stated that a device having the features set out in that preamble is purely in-house state of the art. It must therefore be concluded that a device having all the features mentioned in the preamble to Claim 1 as filed does not form part of the state of the art and hence, in accordance with Rule 29(1)(a) EPC, need not be taken into account in the preamble to Claim 1.

2.4 Under these circumstances, the Board felt that the applicant should be given the opportunity of re-wording Claim 1 to tie in with US-Patent Specification 2 912 564 and, in so doing, of transporting the feature not incorporated in the spot-welding device covered by the aforementioned specification, viz. that a delivery slide is guide-mounted on the device carrier, from the preamble to the characterising portion of the claim, with the result that the feature in question also has to be considered when examining whether the subject-matter of Claim 1 involves an inventive step.

2.5 There is likewise no objection to the other amendments to Claim 1, in the preamble to which the device covered by US Patent Specification 2 912 564 is adequately taken into account by the insertion of the "delivery member" and "spring" features. The fact that the device in the application is designed for precision welding is disclosed in page 1, line 10, of the description as filed. The addition to the effect that the delivery member is guided so as to be resistant to torsion in the device carrier simply elucidates a characteristic of ball-slides which is material to the invention and with which a person skilled in the art would be familiar. The instruction that the electrode slide is to be fitted with a clamping member in which the electrode can be clamped in such a way that it can be exchanged axially and radially to one side is supported by page 4, lines 28 to 30, and page 6, lines 14 to 19, of the description as originally filed.

2.6 The additions to dependent Claims 7, 8 and 10 are supported by the information on page 4, lines 33 to 36, also on pages 5, lines 24 to 29 and 6, lines 6 to 11, of the description as originally filed. The amendments to Claims 2, 3, 5 and 6, and to the characterising portion of Claim 4 are merely of an editorial nature. The amendment of the reference to the earlier claims in Claim 4 is likewise above reproach, for it would be quite clear to a person skilled in the art that the teaching of this claim is feasible by the mere fact that each of the two devices required possesses the features mentioned in Claim 1.

2.7. The present claims are thus adequately supported by the documentsas originally filed (Article 84, second sentence, EPC) nor can there be any other formal objection to them.

3. A drawback of the spot-welding device in accordance with US Patent Specification 2 912 564, in the applicant's view, is that, because of the dual guide system, low-friction movement of the electrode slide in the guide-ways is only feasible if there is sufficient clearance, as a result of which the electrode deflects in an undefined manner under the stress of the electrode force. Furthermore, to remove the coaxially mounted electrode, the device has to have a long stroke because the electrode can only be inserted into the slide from below and therefore always has to be moved axially when being replaced. Because of the long stroke, any such replacement is time-consuming.

4. Thus, according to the present description, the problem to be solved by the application lies in the further development of this known spot-welding device so as to make it more suited to precision welding and to ensure easier and faster replacement of the electrode, while retaining a minimal moment in the electrode mount.

5. The Board has no objections to this rephrasing of the problem in the description. The first part of the problem is essentially a summary of the details of the problem given in the second and third paragraphs of the description as originally filed. It has to be read in the context of the preceding paragraph in the present description, concerning the welding device in accordance with US Patent Specification 2 912 564, and it does allow that the suitability for spot-welding of the device in accordance with that specification cannot in principle be denied. Nor can there be any objection to the second part of the problem, which was not included in the original documents. Without it the description would be incomplete, in that it would not make it evident what problem was to be solved by the design of the electrode mount already contained in principle in the original Claim 1, and it would thus not comply with Rule 27(1)(d) EPC. This part of the problem also links up logically to the device in accordance with US Patent Specification 2 912 564, because it derives from the disadvantages of the known coaxial, hence low-moment electrode mount which, as would be quite evident to a person skilled in the art, a clamping mount as in Claim 1 does not have.

6. The spot-welding device in Claim 1 is, as already stated, new vis-à-vis the patent documents discovered in the search. Of these patent documents, only US Patent Specifications 2 810 062 and 2 912 564 concern welding devices having a ball-guided electrode slide. In the device according to US Patent Specification 2 810 062, the slide is activated by a feed member in the form of a piston-cylinder drive. The device in Claim 1 thus differs from the latter device by the very fact that its delivery (feed) member is in the form of a slide. Contrary to what is stated in lines 11 to 15 on page 2 of the contested decision, the spot-welding device in accordance with US Patent Specification 2 912 564 likewise does not have a feed slide. In fact its feed member consists of a piston-cylinder drive mechanism in which the piston rod is connected to the electrode slide. The other known welding devices are further removed from the subject-matter of Claim 1 than the above-mentioned devices. They are equipped neither with a feed slide nor with an electrode slide for mounting the electrode: in the case of the welding devices described and set out in French Patent Specifications 1 245 047 and 1 329 747, and US Patent Specifications 2 286 104, 2 432 750 and 2 839 665, the electrode mount is fitted to a piston travelling in a cylinder, while in the welding device according to US Patent Specification 2 179 326 the mount is non-slidably attached.

7. The device in Claim 1 is not obvious from the state of the art.

7.1 According to the teaching of US Patent Specification 2 912 564, the spot-welding device's electrode is to be inserted in the electrode slide coaxially from below, the feed member is to be designed as a piston-cylinder drive and the electrode slide activated by the piston is to be provided with a bearing on the piston rod in the form of a ball bushing. Since, because of this bearing arrangement, the slide could rotate about the electrode axis, it must in addition be keyed within the cross-sectionally rectangular device carrier. There is no way in which this known device could be developed into the subject-matter of Claim 1.

7.2. The question of whether, in the case of a device as known from US Patent Specification 2 912 564, the possibility of replacing the ball bushing by ball-slides to prevent slide rotation - a locating system for electrode slides of welding devices which is not new per se (cf. US Patent Specification 2 810 062) - would be obvious to a person skilled in the art does not have to be decided, since claim 1 does not seek protection for this point alone. Neither US Patent Specification 2 810 062 nor any of the other documents contain anything from which the other features could be deduced that are mentioned in the characterising portion as providing a solution to the stated problem.

7.3 To design the electrode mount in such a way that the electrode could be inserted into the mount from either above or below, i.e. axially, was, it is true, known from US Patent Specification 2 810 062. However, for the latter's mount this possibility is realised at the expense of an increase in the mass to be moved and a not inconsiderable moment on the electrode, since the electrode is held in the projecting end of an arm fixed to the electrode slide. On these grounds alone, therefore, that solution cannot be considered as being a model for the method of incorporating the electrode clamp in the electrode slide in the manner set out in Claim 1, and at the same time designing it in such a way that the electrode can also be exchanged in one radial direction and is barely subject to moments, together with offering the facility, by combined use of a number of the devices as claimed, for a minimal-gap array of multiple spot welds. Even less could the above patent specification suggest to a skilled person that he design the feed member in the form of a slide, so as to reduce the mass to be moved, since its teaching in this respect, as already outlined, indicates the use of a piston-cylinder drive as feed member. The same applies to housing the electrode bias spring within the electrode slide, thus minimising the torsional moment between action and reaction force; because the spring in the device according to US Patent Specification 2 810 062 is after all fitted on the piston rod, external to the slide.

7.4 The other patent documents are no nearer the subject-matter of Claim 1 than the two documents discussed above. As mentioned earlier, the welding device constructions they disclose likewise do not use a feed member in the form of a slide. Moreover, their design of the electrode mounting is such that electrode removal can be effected only by withdrawing the electrode towards the weld. Thus, those documents, too, either individually or combined, could not suggest the combination of features given in the characterising portion of Claim 1.

7.5 The precision spot-welding device in Claim 1 thus involves an inventive step (Article 56 EPC). Claim 1 is thus allowable in accordance with Article 52(1) EPC.

8. Dependent Claims 2 to 10 relate to special embodiments of the invention in Claim 1 and are thus also allowable.

9. The amendments to points in the description other than the statement of the problem are also allowable. The addition of a passage to the description, dealing with the device according to US Patent Specification 2 912 564 (page 1, line 31, to page 2, line 19, of the description) is useful for understanding the invention (Rule 27(1) (c) and (d) EPC), since that device represents the state of the art which the invention in Claim 1 takes as a starting point, and aims to advance. The new second paragraph on page 3 of the description forms the basis for the statement in Claim 1 that ball-guide rails are known. There can likewise be no objection to the amendments and transpositions in the part of the description dealing with a number of embodiments of the invention given in the dependent claims. These take due account of the amendments to the dependent claims and the inter-relationships between those claims as well as obviating discrepancies between the description and the claims. The other minor changes are of an editorial nature.

10. The additions and corrections to certain reference symbols in the drawing are also allowable. It is immediately evident (Rule 88 EPC) from the description of the figures in the original documents what the correct position of reference symbol 3 should be, what the correct reference symbols should be or to which part of the drawing they refer.

ORDER

For these reasons, it is decided that:

The decision of the Examining Division of the European Patent Office of 5 November 1980 is set aside. The case is remitted to the first instance with the order to grant a European patent containing the 10 claims received on 14 July 1981 together with the description and drawing filed on the same date.