T 1389/08 – Boundaries

The present decision will not at all surprise those who are familiar with the case law concerning ranges of values, but I have to say that I never really got used to it.

The appeal was filed against the decision of the Opposition Division to revoke the opposed patent. 

Having found the main request before it to lack novelty, the Board then considers the auxiliary request, claim 1 of which read:

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 0.7 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.

The opponent pointed out that the subject-matter of this claim was not disclosed in the parent application as filed. The reason was that in a first step the patent application 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 following paragraphs the Board examines whether or not the subject-matter complies with A 76(1) EPC 1973:

[5.1] Claim 1 of the Auxiliary Request corresponds to Claim 1 of the parent application combined with preferred embodiments stemming, on the one hand, from dependent claims of the parent application as filed:

• Claim 8 (the two-layer structure is devoid of a sacrificial anode clad layer),
• Claim 2 (Mg < 0.03 wt%), 
• Claim 4 (Mn: 0.4 to 1.4 wt%), 
• Claim 5 (Cu: 0.8 to 1.5 wt%), 
• Claim 7 (corrosion life of more than 20 days), 

and, on the other, from preferred embodiments disclosed in the parent application as filed:

• page 7, lines 14-15 (most preferred Fe-content), 
• page 6, lines 22-24 (Si-content), 
• page 7, lines 20-21 (more preferred Cr-content), 
• page 7, lines 25-26 (more preferred Zr-content), and 
• page 7, lines 1-2 (most preferred proviso (Cu+Mn) > 2.0).

[5.2] In particular with regard to the Si-content of 0.3 to 0.4 wt% required in Claim 1, this range is based on a combination of the lower limit of the general range for Si, namely 0.3 to 1.5 wt% (Claim 1, page 4, line 27), with the more suitable minimum level for Si of 0.40 wt% (page 6, line 24). Thus the claimed Si-content derives from the limitation of the originally filed Si-content of 0.3 to 1.5 wt% by splitting it into two ranges:

• one being a “suitable” range of 0.4 to 1.50 wt%, which corresponds to the preferred range of the parent application (page 6, line 24; page 10),
• the other being the implicitly considered “less suitable” range of 0.3 to 0.4 wt%, which is claimed in present opposed patent (“divisional”).

The fact that the Si-content range of 0.3 to 0.4 wt% is considered less preferred would not prevent the skilled reader from applying “the invention” in this range. On the contrary, in the Board’s opinion the skilled reader would seriously contemplate exploiting the whole Si-range disclosed, i.e. including core alloys having a Si-content of 0.3-0.4 wt%. There is also nothing in the parent application as filed or the common general knowledge which would cause the skilled reader to exclude the possibility of working in that range.

This finding is, as pointed out by the Appellant, supported by T 1170/02 and T 956/07. Finally, the Respondent did not provide any evidence that the invention would not work in this Si-content range.

[5.3] With regard to the combination of a Si-content range of 0.3 to 0.4 wt% with preferred features stemming from dependent claims and the description, the Board considers that this combination is directly and unambiguously derivable from the originally filed parent application. The skilled reader would seriously contemplate combining the most preferred embodiments with the whole originally disclosed Si-content range, i.e. also with the range of 0.3 to 0.4 wt%. Furthermore, the majority of the examples in the patent in suit had a Si-content very close to 0.4 wt%. Thus, the combinations leading to Claim 1 do not generate “new” subject-matter.

[5.4] Claims 2 to 5 of the Auxiliary Request correspond to Claims 9 to 13 of the parent application as filed.

[5.5] In view of the above considerations the subject-matter of the Auxiliary Request is considered to fulfil the requirements of A 76 EPC 1973.

Although I am more relaxed on this topic than some of the A 123 hardliners I have come across, I have never been comfortable with the case law allowing to claim disclosed preferred lower limits as new upper limits or vice versa. According to me, this goes beyond the teaching of the application as filed. But then, let us face it : this is very ancient (T 2/81!) and clearly established case law, … and it may come in handy from time to time.

To read the whole decision, click here. The file wrapper can be found here.