T 1389/08 30-07-2010

European Case Law Identifier

ECLI:EP:BA:2010:T138908.20100730

Date of decision

30 July 2010

Case number

T 1389/08

Petition for review of

Application number

02079517.5

IPC class

B32B 15/01

Language of proceedings

Distribution

NO DISTRIBUTION (D)

Download and more information:

Decision in EN 105.31 KB

Documentation of the appeal procedure can be found in the European Patent Register

Bibliographic information is available in:

Versions

Unpublished

Application title

Brazing sheet

Applicant name

Aleris Aluminum Koblenz GmbH

Opponent name

ALCAN

Board

3.3.09

Headnote

Relevant legal provisions

European Patent Convention Art 54

European Patent Convention Art 56

European Patent Convention Art 123(2)

Rules of procedure of the Boards of Appeal Art 13

European Patent Convention Art 76 1973

Keywords

Admissibility of requests

Main request: novelty (no)

Auxiliary request: amendments (allowable) - novelty (yes) - Inventive step (yes)

Catchword

Cited decisions

T 1170/02

T 0956/07

Citing decisions

T 0113/19

T 2159/11

T 1757/20

T 1526/23

I. Mention of the grant of European patent No 1 291 165 in respect of European patent application No 02079517.5 in the name of Corus Aluminium Walzprodukte GmbH (now Aleris Aluminum Koblenz GmbH), which had been filed as a divisional application of the earlier European patent application 00920702.8, was announced on 27 July 2005 (Bulletin 2005/30). The patent was granted with ten claims, Claim 1 reading as follows:

"1. Brazing sheet having either a two-layer structure having a core sheet made of an aluminium alloy core and on one side thereof a brazing layer of an aluminium alloy containing silicon as main alloying element and said two-layer structure is devoid of a sacrificial anode clad layer, or a three-layer structure having a core sheet made of an aluminium alloy core material and on both sides thereof a brazing layer of an aluminium alloy containing silicon as main alloying element, wherein the aluminium alloy of the core sheet has the composition (in weight %):-

Mn 0.5 to 1.5

Cu 0.5 to 2.0

Si 0.3 to 0.4

Mg < 0.05

Fe < 0.4, preferably < 0.3

Ti < 0.15

Cr < 0.35

Zr and/or V < 0.35 in total

Zn < 0.25

balance aluminium and unavoidable impurities,

and wherein said brazing sheet has a post-braze 0.2% yield strength of at least 50 MPa and having a corrosion life of more than 12 days in a SWAAT test without perforations in accordance with ASTM G-85."

II. A notice of opposition was filed against the patent by Pechiney (now Alcan France S.A.S.) on 10 April 2006. The opponent requested the revocation of the patent in its entirety, relying on Article 100(a) EPC, namely that the claimed subject-matter lacked novelty and inventive step, and on Article 100(b), namely that the European patent did not disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art.

During the opposition proceedings the following documents were cited:

D1: JP 610 82 992 (abstract and original Japanese document);

D1a: English Translation of D1;

D2: WO 94/22633 A1;

D3: US 4 649 087;

D4: R. Benedictus et al "Influence of Alloying Additions on Corrosion Behaviour of Aluminium Brazing Sheet", Aluminum Alloys, vol 3, Proceedings of the 6th ICAA, The Japan Institute of Light Metals, 5-10 July 1998, 1577-1582;

D5: EP 0 718 072 A1;

D6: EP 0 712 681 A2; and

D7: GB 2 321 869.

In the course of the opposition proceedings the patent proprietor filed a main and three auxiliary requests.

III. By a decision announced orally on 8 April 2008 and issued in writing on 28 April 2008 the Opposition Division revoked the patent. It considered that the subject-matter of Claim 1 of all requests (amended Main and Auxiliary Requests 1 to 3) lacked an inventive step.

IV. The Patent Proprietor (Appellant) appealed the decision of the Opposition Division on 24 June 2008 and paid the appeal fee on the same day. The statement setting out the grounds of appeal was submitted on 26 August 2008 together with three new requests, ie a main and two auxiliary requests.

V. In its observations dated 15 December 2008 and 26 October 2009 the Opponent (Respondent) principally defended the decision of the Opposition Division.

VI. With a communication dated 21 July 2010 the Board questioned the admissibility of the amendments to the claims of the new requests and expressed its concerns with regard to the issue of inventive step.

VII. With a fax dated 28 July 2010 the Appellant replaced all previous requests. Its Main Request corresponded to the granted claims. Its Auxiliary Requests 1 and 2 corresponded to two new sets of claims. Auxiliary Request 3 was for a referral of two questions to the Enlarged Board of Appeal.

VIII. Oral proceedings were held before the Board on 30 July 2010. During these proceedings the Appellant declared that it maintained its Main Request. Moreover, it filed a new First Auxiliary Request (hereinafter referred to as "the Auxiliary Request") and a description adapted to it. Lastly, it withdrew the Second and Third Auxiliary Requests.

Claim 1 of the Auxiliary Request reads as follows:

Mn 0.7 to 1.4

Cu 0.8 to 1.5

Si 0.3 to 0.4

Mg < 0.03

Fe < 0.3

Ti < 0.15

Cr 0.05 to 0.25

Zr 0.05 to 0.25

Zn < 0.25

balance aluminium and unavoidable impurities,

with the proviso (Cu+Mn) > 2.0,

and wherein said brazing sheet has a post-braze 0.2% yield strength of at least 50 MPa and having a corrosion life of more than 20 days in a SWAAT test without perforations in accordance with ASTM G-85."

IX. The Appellant (Patent Proprietor) requested that the decision under appeal be set aside and the patent be maintained as granted, alternatively on the basis of the Auxiliary Request filed during the oral proceedings.

The Respondent (Opponent) requested that the appeal be dismissed.

X. The arguments put forward by the Appellant in its written submissions and at the oral proceedings can be summarized as follows:

- The subject-matter of the Main Request (granted claims) was novel. Claim 1 differed from the disclosure of D1/D1a (Alloy 20b) regarding the features of post-braze 0.2% yield strength and of corrosion life. Furthermore, the Respondent was wrong when it combined D2 and D4 with D1 in order to demonstrate that these properties were inherent in the brazing sheet of D1/D1a. For the assessment of novelty it was not appropriate to combine D1 with D2 and D4.

- The claims of the Auxiliary Request fulfilled the requirements of Articles 76 and 123 EPC. In particular Claim 1 was based on the combination of originally filed claims of the earlier application, with preferred embodiments taken from the originally filed description of the earlier application (Article 76 EPC) and on the same combination from the originally filed divisional application (Article 123(2) EPC). This was common practice.

- In particular, the Si-content of 0.3 to 0.4 wt% was derived from the combination of the lower value of the broader range of 0.3 to 1.5 wt% with the preferred lower value of 0.4 wt%. This combination was admissible according to the established case law. Apart from this, the skilled person would seriously contemplate working within the claimed Si-content range: on the one hand in view of the general teaching concerning the Si-content in the originally filed earlier application (page 6-lines 20-25) and on the other hand in view of the fact that the majority of the examples had a Si-content which was very close to 0.4 wt%.

- For reasons which will become clear later, it is not necessary to recite the parties' arguments on inventive step as regards Claim 1 of the Main Request.

- As regards the subject-matter of Claim 1 of the Auxiliary Request, this was not obvious in view of the cited state of the art. D5 should be considered to represent the closest state of the art.

- The technical problem to be solved was the provision of a brazing sheet which met the requirements of excellent brazeability during flux brazing and had improved post-braze strength and good corrosion resistance. This problem was not addressed by D5, which was silent about brazeability during flux brazing.

- The effective solution of this problem was illustrated by the inventive Alloy 5 (Table 1). Though the Si-content of this alloy fell outside the now-claimed narrower range of Si-content, it fell within the originally-claimed broader range of 0.3-1.5 wt% and the preferred range of 0.3-0.8 wt% (Claim 1 and page 6, lines 20-25) of the originally filed earlier application. Thus the skilled person would consider it plausible on the balance of probabilities that the exemplified excellent combination of properties shown for a Si-content falling within the range of 0.3-1.5 wt%, preferably 0.3-0.8 wt%, would also apply to the claimed range of 0.3-0.4 wt%. In support of this argument, the appellant compared the inventive alloys of Examples 5 and 7 (Table 1) with a Si-content of 0.47 and 0.75 wt%, respectively, and concluded that the linear extrapolation to a Si-content within the claimed range of 0.3-0.4 wt% would make it plausible that the claimed lower Si-content would provide a brazing sheet with equally good post-braze properties.

- The skilled person starting from D5 and seeking a brazing sheet which met the requirements of excellent brazeability during flux brazing while having improved post-braze strength and simultaneously having a good corrosion resistance, would, on the basis of his technical knowledge, eventually consider the reduction of the Mg-content. However he would not go against the teaching of D5 and reduce this content to values lower than the disclosed minimum content of 0.1 wt% (Claim 1), in particular when the best results for the post-braze properties were obtained by Alloy C8 with a Mg-content of 0.5 wt% (Table 1).

- Furthermore, the reduction of the Mg-content would unavoidably lead to the reduction of the post-braze yield strength, which meant that the skilled person would have to compensate for that reduction. Compensation by combining a specific amount of Cu - under the specific proviso regarding (Cu+Mn) - with a specific amount of Cr and Zr was not disclosed by D5 or any other document forming the state of the art. The reasoning of the Respondent in this respect was based on hindsight.

XI. The arguments put forward by the Respondent in its written submissions and at the oral proceedings can be summarized as follows:

- The brazing sheet of Claim 1 of the Main Request lacked novelty over Alloy 20b of D1/D1a. The values for post-braze 0.2% yield strength and the corrosion life, which were not explicitly disclosed, were inherent to Alloy 20b of D1/D1a. The values of these properties in the claimed subject-matter were banal and systematically obtained in a great number of alloys such as those of D1/D1a. This was supported by D2 and D4 which disclosed alloys similar to that of D1/D1a having the claimed post-braze properties. Additionally, the opposed patent did not disclose any specificity of the process used to manufacture the claimed brazing sheet, which could be the cause of any technical differences.

- The subject-matter of Claim 1 of the Auxiliary Request was not disclosed in the originally filed earlier application. The reason was that in a first step the Appellant defined the Si-content as being 0.3 to 0.4 wt% by combining the lower limit disclosed for its broader definition, namely 0.3-1.5 wt%, with the preferred lower limit of 0.4 wt%. This Si-content was then in a second step combined with a proviso that (Cu+Mn) > 2.0 wt%, coupled with specific values for the other elements of the core alloy. The combination of these values was not disclosed in the originally filed earlier application.

- In the present case it was not acceptable to amend each metal content independently as if there was no interaction among these metals. In fact, D2 disclosed that at least Al, Mn and Si interacted with each other.

- The subject-matter of Claim 1 of the Auxiliary Request lacked an inventive step. In particular the brazing sheet of D5 resulting from the combination of Claims 1, 4 and 14, should be considered to represent the closest state of the art. The claimed brazing sheet differed from that disclosed by D5 at least as regards the Mg-content.

- The technical problem mentioned in the opposed patent [0005] was to provide a brazing sheet which met the requirements of excellent brazeability during flux brazing, while having improved post-braze strength and simultaneously having a good corrosion resistance. The opposed patent, however, did not contain any technical evidence, such as examples with the claimed Si-content of 0.3-0.4 wt%, in order to substantiate that the technical problem was indeed solved. The Appellant's argument in this context was based on a linear extrapolation from examples with a higher Si-content. This argument was, however, not correct because Si interacted with other elements and its behaviour in lower contents was not predictable.

- Notwithstanding this deficiency, the solution of the technical problem using the features of the claimed brazing sheet was obvious. Thus the skilled person departing from D5 and aiming at providing a brazing sheet which met the requirements of excellent brazeability during flux brazing, while having improved post-braze strength and simultaneously having a good corrosion resistance would know from his ordinary technical knowledge that the reduction of the Mg-content would improve flux brazeability. He would therefore reduce the Mg-content in the core alloy to values within the claimed range without exercising any inventive skill. A hint in that direction was contained in D5 itself. Indeed the comparison of Alloys C6 and C8 showed that the reduction of the Mg-content did not jeopardize the excellent brazing sheet properties. A linear extrapolation of these properties from the exemplified Alloys C6/C8 to alloys with a lower Mg-content, in particular to those with a Mg-content within that claimed, would be expected to provide still acceptable values. Such an expectation was confirmed by D4, which disclosed advantageous brazing sheet properties for an alloy similar to that of D5 except that it did not contain any Mg at all.

- Contrary to the argument of the Appellant, D5 would not prevent the skilled person from reducing the Mg-content to values lower than the disclosed lower limit of 0.1 wt%. What D5 disclosed as a determining factor was the sum of Cu+Mg, the one amount compensating that of the other. D5 would not dissuade the skilled person from increasing the Cu-content given in the examples (0.3-0.75 wt%). This increase would not have a negative effect on yield strength since the examples at lower Cu-content had satisfactory values (Table 3). Furthermore the Cu-content claimed was very close to that exemplified in D5 (0.8 instead of 0.75 wt%).

- With regard to the alleged effect on the brazing sheet properties of the claimed sum (Cu+Mn) > 2.0, this was not substantiated. The combined effect was the mere juxtaposition of the hardening effects of Cu and Mn.

- Finally with regard to Cr- and Zr-content, D5 disclosed the claimed ranges and the fact that these elements improved post-braze mechanical strength. Thus the skilled person would be motivated to make use of them in order to counterbalance the loss of mechanical strength resulting from the reduction of the Mg-content without involving any inventive skill.

1. The appeal is admissible.

2. Admissibility of the requests

2.1 The Main Request of the Appellant corresponds to the claims as granted. It was reinstated with the fax of 28 July 2010. The Respondent did not contest its admissibility and the board sees no reasons to do so.

2.2 The Auxiliary Request, filed as First Auxiliary Request during the oral proceedings held before the Board, was a reaction to the communication of the Board. The Respondent did not raise any objection concerning its admissibility. The Board also saw no reason to raise an objection on its own because the brazing sheet of Claim 1 of the Auxiliary Request was based on the brazing sheet as granted, which was further limited by features relating to preferred embodiments. Further, the claimed subject-matter was not complicated and did not require any measures to be taken at that state of the proceedings which would have had a detrimental effect on procedural economy. Thus the Board, exercising its discretion under Article 13 RPBA, admitted the Auxiliary Request into the proceedings.

The Main Request

3. Novelty

3.1 The Respondent contested the novelty of the subject-matter of Claim 1 of the Main Request in view of the disclosure of D1/D1a.

3.2 Document D1/D1a relates to a brazing sheet with a two- or three-layer structure. Its core sheet is made of an aluminium alloy which has a brazing layer on one or both of its sides. The two-layer structure is devoid of a sacrificial anode clad layer. The brazing layer consists of an aluminium alloy containing silicon as main alloying element (see D1a: page 2, Tables 1 and 2 and first paragraph). D1a discloses in Table 3 Alloy 20b, a specific core alloy, having the following composition in wt%: