T 0389/86 (Time limit for appeal) of 31.3.1987

Summary of Facts and Submissions

I. European patent application No. 83 111 212.3 filed on 10 November 1983 and published on 11 July 1984 under No. 0 113 003 was refused by the Examining Division in its decision dated 10 December 1985, of which the applicants had been advised verbally at oral proceedings held on 16 October 1985. The minutes of the proceedings were sent to the applicants in a communication dated 24 October 1985. The decision was based on Claims 1 to 13, filed in a letter dated 25 April 1985, together with the amendments to Claim 1 made during oral proceedings before the Examining Division.

II. In its decision the Examining Division concluded that, although the subject-matter of Claim 1 was new, the invention lacked inventive step in view of the prior art described in DE-A-2 125 671, the July 1976 issue of "Plastics Engineering" (pp. 33-35) and GB-A-1 445 598. Furthermore, Claim 12 was not allowable as the process it described had also been anticipated in "Plastics Engineering".

III. On 28 November 1985 the appellants appealed against the decision and submitted a statement of grounds, paying the appeal fee at the same time. In their statement of grounds they argued that the subject-matter of Claim 1 under the main request as submitted with the notice of appeal was not obvious from the background art. The appellants also submitted for alternative consideration a Claim 1 delimited vis-à-vis an earlier European application.

IV. In a communication attached to the invitation to attend oral proceedings the rapporteur pointed out that in the Board's preliminary view the subject-matter of Claim 1 under neither the main nor the auxiliary request involved an inventive step.

V. In their letter dated 13 March 1987 the appellants commented on the Board's communication and submitted new claims and a revised description.

VI. At oral proceedings held on 31 March 1987 the appellants requested that a patent be granted on the basis of the documents furnished on that occasion, namely Claims 1 to 10, pages 1 to 12 of the description and Figures 1 to 9. The earlier Claims 12 and 13 were abandoned.

VII. Claim 1 as now worded reads as follows: "1. Heat exchanger (1) comprising a heat exchanger block (4), consisting of a large number of tubes (2) and fins (3) disposed transversely to them, and at least one tube plate (5) and one water tank (6), both made of a plastic material, the water tank (6) being secured in a watertight manner to the tube plate (5) and the tube plate (5) having on one side conical thickened portions (9), in which are apertures (7) to receive the ends (8) of the tubes, the tube plate (5) having in its marginal zone a continuous flat surface (14) to which is connected the likewise continuously flat edge (12) of the water tank (6), characterised in that the ends (8) of the tubes are fixed to the tube plate (5) by an expansion in a radial direction of that portion of them which is located within the tube plate (5), or by the tubes being pressed into tube plate (5) in an axial direction, the tube plate (5) is connected to the water tank (6) by vibration welding along the flat surfaces (13, 14) and along one or more of these surfaces (13, 14) on one side at least are grooves (15, 16) serving as flash traps, the tube plate (5) having on its long sides a shoulder (17) to guide the water tank (6) along the tube plate (5) during vibration welding".

Reasons for the Decision

1. The Board must first consider whether an appeal against a decision of the Examining Division is allowable if filed before that decision together with written reasons have been notified.

1.1 The answer is in the affirmative since it is not a prerequisite for an appeal that the contested decision should be accompanied by reasons. An appeal may therefore be filed as soon as a decision has been formulated. This happened in the present case, the decision having been announced on 10 October 1985 during oral proceedings.

1.2 An appeal filed before commencement of the two-month time limit stipulated in Article 108, first sentence, EPC complies with that time limit. In the Board's opinion, Article 108 EPC by no means precludes the filing of an appeal before the decision has been notified but merely requires that it be filed no later than two months from the date of notification.

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

2. Essentially, Claim 1 as now worded brings together the features of the original Claims 1, 5 and 6 with the added characteristic that that portion of the tube ends located within the tube plate has been expanded. This feature can be implied from page 3, lines 9 to 11, and page 8, last paragraph, of the description. Accordingly, Claim 1 does not extend beyond the original disclosure.

3. The subject-matter of Claim 1 is new vis-à-vis the background art. For one thing, none of the documents on hand during the proceedings discloses a heat exchanger in which the tube plate and water tank are joined by vibration welding. Nor do they refer to tube ends joined to a plastic tube plate by expanding that portion of the ends located within the tube plate or by pressing them in axially. Finally, the background art alludes nowhere to the provision of a shoulder on the long sides of the tube plate for the purpose of guiding the water tank. Since the Examining Division did not dispute the novelty of the invention, however, that aspect requires no further discussion.

4. It is now necessary to consider whether the subject-matter of Claim 1 also involves an inventive step.

4.1 Assuming a heat exchanger in accordance with the pre- characterising portion of Claim 1 as known from Figure 10 in conjunction with page 3, lines 111 to 126, of DE-C-956 820 (DE-A-2 125 671 being further removed: the tube plate has no pre-formed apertures or conical thickened portions and the connecting edge of the water tank is not initially flat, but has at least one projecting fin), the problem solved by the subject-matter of Claim 1 still consists in joining the water tank to the tube plate and the tube plate to the tubes both as simply as possible and in such a way that a fluid-tight join and the requisite mechanical strength are ensured.

4.2 The invention is thus concerned with the two-part problem of joining the water tank to the tube plate and the tube plate to the tubes. Accordingly, the characterising portion of Claim 1 contains two sets of features relating to the solutions to these parts of the problem. As the Examining Division correctly stated in its decision, there is no interaction between these two sets of features that brings about a technical solution in excess of the sum of their individual effects, the said features being merely juxtaposed. Although the appellants are correct in arguing that the two parts of the problem referred to above have a common basis in so far as they both derive from the applicants' decision to use a plastic tube plate, the fact still remains that the two claimed sets of features are not functionally interdependent for the purpose of solving the two parts of the problem.

4.3 In these circumstances, the combined effect of the two sets of features cannot be said to involve an inventive step. What has to be established instead is whether each of them separately is obvious in the light of the prior art. Moreover the subject-matter of Claim 1 can be regarded as involving an inventive step if only one of the sets is found to be inventive.

4.4 The two alternatives claimed for joining the tubes to the tube plate - radial expansion of the tube ends within the tube plate and axial pressing-in - cannot be described as known processes in the current state of the art for plastic tube plates. Nor is there any prior art in which such techniques are shown to be suitable for joining a tube or bar-shaped component to a flat and relatively thin piece of plastic.

4.5 Figure 10 in DE-C-956 820 discloses the radial expansion of the tube ends in order to attach them to a plastic tube plate; in this case, however, the expansion is not within the thickness of the tube plate itself but on the projecting tube end, the main purpose being to provide a secure base for a circular welding seam. Such a weld is also present on the side of the tube plate facing the heat exchanger block. However - as Figure 1 in that document shows - the flaring of the tubes within the tube plate is not intended as a means of attachment by radial expansion but is meant to embed the previously shaped ends in the tube plate. The claimed method of joining the tubes is thus not obvious from either of the designs cited above.

4.6 In GB-A-1 445 598, moreover, the tubes of a heat exchanger are joined to a metallic tube plate by expanding the tube ends, the metal plate having on one side a collar to ensure a tight join without the need for any additional sealing device. However, a person skilled in the art would not apply this teaching direct to a plastic tube plate in view of the considerably lower strength of the material. The Board doubts whether a skilled person confronted by these problems with the materials involved would be prompted by this document to expand the tube ends radially in order to join them to a tube plate. And even if he were, he would not necessarily think of expanding the tube ends only within the tube plate - conically thickened at those points - instead of beyond it as suggested by Figure 10 in DE-C-956 280, and dispensing with any additional securing means (welds).

4.7 Although the second means of joining the tubes to the tube plate according to Claim 1, namely by axial pressing-in, is cited in FR-A-2 371 662 and FR-A-1 089 816, the context differs from that claimed. Those documents propose that the tubes be pressed into apertures in the tube plate after interposing a flexible sealing bush with an inward projection (FR-A-2 371 662), or that the tube plate itself be made of an elastic, rubber- like material ensuring that the tubes are adequately sealed and securely seated when pressed in radially (FR-A-1 089 816). The Board accepts the appellants' argument that this citation does not obviously suggest pressing the tubes axially and direct, i.e. without interposing a seal, into a tube plate made of plastic - a relatively rigid material - in order to obtain a sufficiently tight and secure mounting for the tubes.

4.8 The second set of features in the characterising portion of Claim 1 comprises the tube plate joined to the water tank by vibration welding, a groove serving as a flash trap on at least one side of the connecting surfaces and a shoulder on each of the long sides of the tube plate to guide the water tank during welding.

4.9 Given the technical teaching contained in the July 1976 issue of "Plastics Engineering", pp. 33-35, whereby vibration welding is recommended in particular for fluid- tight joining of large-format plastic components (cf. page 33, left-hand column, last paragraph and page 35, last paragraph) with one or more grooves provided as flash traps along the surfaces to be welded (cf. page 34, right-hand column, penultimate paragraph and Figure 5), a person skilled in the art of welding would have considered it obvious to adopt these measures in the present case. Consequently, neither of the above features can be said to constitute an inventive step.

4.10 On the other hand, the documents comprising the background art considered in these proceedings contain no suggestion whatever of the third feature, namely the provision of a guide shoulder along each of the long sides of the tube plate. As the appellants succeeded in convincing the Board during oral proceedings, this is of particular relevance to solving the problem when heat exchangers of substantial length are to be manufactured. The long sides of the water tank then tend to cave inwards through shrinkage, so that the distance between the long edges is reduced in the middle section while kept constant at the ends by the cross-walls of the water tank. The appellants maintained that, in practice, the insufficient overlap of the welding surfaces could produce a weld having inadequate strength and tightness and thus result in wastage. The claimed feature provided a simple remedy involving no modification to the tool.

4.11 Since the prior art documents make no mention of the above problem and no tube plate with a guide shoulder has ever been disclosed, this feature cannot be regarded as obvious in the light of the background art. Nor does the Board feel that it forms part of the relevant general technical knowledge. While a skilled person certainly knows that vibration welding requires the two parts moving relative to each other to have some system of guidance, this does not mean that he would necessarily arrive at the particular solution claimed. In fact he would have tended to go for other options concerned first and foremost with the tool, such as guide projections arranged on the hood which encloses the water tank and interacting with the water tank's outer flash grooves, or the use of spacers between the long sides of the water tank.

4.12 Thus, both sets of features contain aspects not obviously derivable from the available state of the art. The subject- matter of Claim 1 therefore involves an inventive step within the meaning of Articles 52(1) and 56 EPC.

5. Claim 1 is thus allowable.

6. Claims 2 to 10 contain further embodiments of the subject- matter of Claim 1, on which they depend (Rule 29(3) EPC). They are thus likewise allowable.

7. Nor are there any objections to the description as now worded, which satisfies the requirements of Rule 27(1)(c) and (d) EPC.

ORDER

For these reasons, it is decided that:

1. The contested decision is set aside.

2. The matter is remitted to the department of first instance, which is instructed to grant a European patent on the basis of the following: Claims 1 to 10 Description, pages 1 to 12 Figures 1 to 9 submitted at the oral proceedings held on 31 March 1987.