T 1208/21 09-04-2024

1. The respondent's main request and its auxiliary requests 1 and 2 were filed with its grounds of appeal and are broader than auxiliary request 3 corresponding to the auxiliary request found allowable by the opposition division. While the main request and auxiliary requests 1 and 2 have not been explicitly withdrawn, the Board understands the respondent's withdrawal of its appeal as an implicit withdrawal of these requests. Without an appeal by the respondent, any request broader than that found allowable by the opposition division would otherwise be inadmissible as constituting a violation of the principle of reformatio in peius.

Auxiliary request 3 - interpretation of claim 1

2. A claim which is clear by itself should be interpreted as broadly as technically reasonable in the relevant technical field. This represents the commonly accepted approach on claim interpretation by the Boards of Appeal when assessing inter alia the patentability requirements of Articles 54 and 56 EPC, as was also confirmed in recent decisions, for example T 1628/21, reasons 1.1.2 and 1.1.7, or T 447/22 reasons 13.1 (see also the case law cited in these decisions). The opposition division too correctly relied on this approach in the impugned decision.

3. It is undisputed that claim 1 of auxiliary request 3, in particular the expression "gas turbine blade", is clear for a skilled person in the field of axial turbo-machinery. Knowledge in this field encompasses knowledge on inter alia gas turbine engines, their general structure, components and operating conditions. The skilled person will be aware that a gas turbine engine is generally composed of (seen in axial direction of incoming air flow) a compressor section for compressing the incoming air, a burner or combustor for combusting fuel in the presence of the compressed air and a downstream turbine section in which the exhaust gases resulting from the combustion drive the turbine (for example to generate electrical power). The skilled person will also be aware that the compressor and turbine sections are each composed of one or more stages of alternating rows of respective stationary blades (frequently also called vanes or nozzles) and rotating blades.

4. It is undisputed that the expression "gas turbine" can be understood by the skilled person to refer either to the entire gas turbine engine or to only the turbine section of such engine. Both interpretations are technically reasonable, and no argument or evidence has been submitted to the contrary. Similarly, the term "blade" used in this context will be understood by the skilled person to designate either a rotating or a stationary blade, without any of these understandings being technically unreasonable or illogical.

It has not been argued, and the Board cannot see, that any of the further features defined in claim 1 would narrow the meaning of the expression "gas turbine blade" with regard to the interpretation above. To the contrary, and as also pointed out by the appellant, dependent claim 11 makes reference to an "actively-cooled rotating turbine blade", thus implying that the subject-matter of claim 1 would not be understood as necessarily being limited to rotating blades of a turbine section of a gas turbine engine.

5. The Board therefore agrees with the interpretation of this expression adopted by the opposition division as designating a rotating or stationary blade of a gas turbine engine in general, which could be either a rotating or stationary blade of either a turbine section or of the compressor section of such engine. Although the opposition division considered there to be another "indistinctive" interpretation of the expression, the second meaning, i.e. "a blade of the turbine section of a gas turbine engine", is in fact covered by the above interpretation.

6. The opposition division was therefore correct to reject the respondent's approach of a limited interpretation of the claim in the light of the description, on which the respondent in essence also relied in the present appeal proceedings. The respondent's arguments submitted with its statement of grounds of appeal are found unconvincing for the following reasons.

6.1 The Board considers that the principles summarised by the respondent on the basis of certain passages taken from decisions T 454/89, T 860/93 and T 1127/03 (see above item XII.) do not lead to the conclusion that a claim which has a clear meaning for the skilled person shall be given a limited interpretation in the light of the description. In particular, the Board cannot find any consideration in the passages from these decisions referred to by the respondent, nor from the broader context from which the citations have been taken, which would support the respondent's conclusion that, if the wording of a claim is clear within the meaning of Article 84 EPC, the broadest technically reasonable interpretation (see item 2. above) would be excluded.

As to the extent to which the description and the figures of the patent have to be taken into account for interpreting the wording of a claim, reference is made to the principles set out in decisions T 1628/21, reasons 1.1.11 to 1.1.16, and T 1473/19, reasons 3.16, 3.16.1, with which the present Board agrees.

6.2 Moreover, the description of the patent in suit does not lead to a different conclusion either. The description of the patent as granted states in the final sentence of paragraph 1: "Generally, the gas turbine blade according to the present invention is not restricted to a gas turbine: rotor blades or guide vanes of a turbo-machinery fall legally under the present invention". Correspondingly, granted claim 13 is directed to a blade suitable for use as a rotor blade or guide vane for turbo-machinery.

This confirms that the patent itself considers the term "blade" in claim 1 to cover rotating and stationary blades (vanes) as well as their use in turbo-machinery in general, thus not limited to the turbine section of a gas turbine. Although the description and the claims have been amended in auxiliary request 3 by deleting these statements of the granted patent, such an amendment of the description does not constitute a limitation of the claimed subject-matter.

In analogy to, for example, the situation underlying decision T 454/89 referred to by the respondent, in which it was held that a lack of clarity in a claim could not be cured by relying "on Article 69 EPC as a replacement for the Article 84 requirements, i.e. as a substitute for an amendment which would be necessary to remedy a lack of clarity", (ibid., reasons 4.1.(viii)), also in the context of the requirements of Article 54 and 56 EPC, a technically reasonable and not illogical understanding of the claim wording cannot be restricted by reference or an amendment to the description. In such a situation, it would, rather, be the claim wording that would require amendment (see for example T 1628/21, reasons 1.1.18).

6.3 The references of the respondent to a number of prior-art documents in which the term "vane" is used exclusively to designate the stationary component, in contrast to the term "blade" used in these documents to refer to the rotating component, does not lead to a different conclusion. These documents, which represent a small selection of prior art, cannot be considered to constitute proof that the skilled person would have understood the term "blade" to exclusively designate a rotating component. In fact, the respondent acknowledged that the term "blade" is also used to designate a stationary component, as evidenced by the patent and inter alia D3.

Auxiliary request 3 - Article 56 EPC

7. With this interpretation in mind, and contrary to the finding of the opposition division, the Board comes to the conclusion that claim 1 of auxiliary request 3 underlying the impugned decision does not involve an inventive step starting from the gas turbine blade disclosed in D3 as the closest prior art and in combination with common general knowledge. Under these circumstances, the appellant's objection to the admittance of auxiliary request 3 into the proceedings does not require further consideration.

8. The Board can agree with the opposition division, as stated in item 15 and 15.2 of the impugned decision, that features 1.1.a, 1.1.b, 1.1.c and 1.2 to 1.7, where features 1.1.a and 1.1.b are understood by the skilled person as set out in item 5. above, are disclosed in D3 by the embodiment of Figure 4 together with the content of paragraphs 2, 43 and 59.

8.1 It is noted that the disclosure of features 1.1.c and 1.2 to 1.6 by the (fixed) blade described in relation to Figure 4 of D3 has not been contested by the respondent. The respondent, however, did contest the disclosure of the combination of features 1.1.a, 1.1.b and 1.7.

8.2 In regard to feature 1.1.b, reference is made to paragraph 51, relating to the embodiment of Figure 4, which accordingly shows an airfoil blade which "can be incorporated into a fixed blade assembly", thus disclosing a blade and confirming the meaning of the term "blade" as also designating stationary components, as covered by claim 1.

8.3 It is common ground between the parties that the embodiment of a (stationary) blade in Figure 4 relates to a steam turbine (see also paragraph 45). It was contentious, however, whether the further indications in D3 directed to using the blade in a gas turbine as well constituted a direct and unambiguous disclosure for feature 1.1.a, i.e. a "gas turbine" blade.

The opposition division correctly also considered feature 1.1.a of claim 1 to be anticipated by the embodiment disclosed in Figure 4, taking into account the content of the three paragraphs 2, 43 and 59, instead of only paragraph 59 as argued by the respondent according to a first line of argument in its statement of grounds of appeal.

The Board considers that, contrary to the respondent's understanding, paragraph 59 is not directed to a generic disclosure of the patent. The paragraph reads "While the disclosure has been described in relation to the use of short height HP/IP fixed blades in a steam turbine of the low reaction disc and diaphragm type, it can also be applicable to other types of axial flow turbine and compressor, and to moving airfoil blades as well as fixed airfoil blades". The paragraph therefore makes reference to the specific embodiment described before, i.e. to the use of the previously described (stationary) blade in a "short height HP/IP fixed blades in a steam turbine of the low reaction disc and diaphragm type".

This specific use is set out in paragraph 45, at the beginning of the description of the specific embodiment of which the blade in Figure 4 is a part. Therefore the skilled person would have understood directly and unambiguously from the final statement in paragraph 59 that this previously-described blade for use in that specific, exemplary embodiment could be used in other types of axial flow turbines and compressors. In view of previous statements in paragraphs 2 and 43, which explicitly disclose that the axial flow turbomachine employing the turbine blade can be a steam or gas turbine, the skilled person would have understood the expression "other types" mentioned in paragraph 59 unambiguously to mean gas turbines.

The respondent's further arguments, based on an assumed inaptitude of the specific fixed blade geometry shown in Figure 4 for application as a rotating component in a turbine section of a gas turbine, are found unconvincing. As set out above, claim 1 is not limited to an application as a rotating component, as argued by the respondent. In addition, D3 explicitly envisages the application of the blade as a rotating component and also in different sections of a gas turbine.

The Board concludes and thereby confirms the view of the opposition division that feature 1.1.a is also disclosed in D3.

8.4 The Board also considers feature 1.7 to be disclosed in combination with features 1.1.a, 1.1.b (and the remaining features 1.1.c, 1.2 to 1.6) in D3. In fact, the respondent did not dispute that D3 disclosed feature 1.7 as such in relation to the embodiment of Figure 4, as is apparent from item 15.1 of the impugned decision. The respondent, rather, disputed that the specific geometric blade configuration defined by feature 1.7 for a gas turbine blade according to features 1.1.a and 1.1.b was disclosed on the basis of the general disclosure in paragraph 34 together with paragraphs 2, 43 and 59, on which the opposition division had also relied, because the options disclosed in the cited paragraphs amounted to far too many possibilities, contrary to specific disclosure. The Board does not find this line of argument convincing since

(i) the reference by the opposition division to paragraph 34 of D3 was only an additional argument which did not contradict the previous finding in point 15.2, on the upper half of page 11 of the impugned decision, relating to the disclosure of the combination of features 1.1.a, 1.1.b, 1.1.c, 1.2 to 1.7 by paragraphs 2, 43 and 59 together with Figure 4, and moreover

(ii) claim 1 covers both rotating and stationary blades, so anyway no selection from a number of possible options would be required in this respect on the basis of the embodiment of Figure 4, which indisputably describes a blade with feature 1.7 (see also paragraph 52 of D3), and

(iii) claim 1 also not being limited in regard to the location of the rotating or stationary blade in any particular section (compressor or turbine) of such gas turbine engine, the teaching of paragraph 59 of D3 to apply the specific steam turbine (fixed) blade described to other turbo-machinery would have led the skilled person directly and unambiguously to apply it to a gas turbine, specifically mentioned in paragraphs 2 and 43 as an alternative axial flow turbomachine to a steam turbine, so

(iv) as a consequence the facts underlying decision T 12/81 are not comparable with those of the present case.

9. The only distinguishing feature of claim 1 compared with the blade disclosed in D3 is thus the claimed aspect ratio range ("the blade provides an aspect ratio span/axial chord length at 5% ± 5% span ranging from 1,6 to 2,1 [sic]"), as also argued by the appellant.

10. As noted in the Board's communication pursuant to Article 15(1) RPBA, the technical effect attributed to this single distinguishing feature by the opposition division - albeit with respect to some other piece of prior art, resulting, however, in the same single distinguishing feature - seemingly had no basis in the patent, as argued by the appellant in sections 2.1.4 and 2.1.5 of its statement of grounds of appeal. Indeed, paragraph 20 of the patent in suit, which is the only mention of this claimed aspect ratio range, is silent as to any effect achieved by this feature. The assumed effect of improved vibrational behaviour is rather speculative, in particular since a number of other blade parameters (blade structure, hollow or massive, wall thickness, etc.) may influence the natural frequencies.

Therefore the Board also agrees with the appellant that, in the absence of any technical effect achieved by the single distinguishing feature, the objective technical problem can be formulated as to further geometrically specify the blade disclosed in D3.

11. It was not disputed that the aspect ratio as defined in the characterising portion of claim 1 is well known to the skilled person in the technical field of axial flow turbomachine blades. The particular range selected constitutes an arbitrary selection and therefore does not involve an inventive step.

12. The respondent, apart from maintaining its unsubstantiated view that the distinguishing feature in the characterising portion of the claim (together with a further allegedly distinguishing feature 1.7) influenced the natural vibration frequencies of the blade without worsening the aerodynamic behaviour, did not indicate any passage in the patent supporting its allegation of the technical effect, in particular not in relation to the claimed aspect ratio range.

The respondent did not submit any argument either in reply to the Board's communication in which the Board had endorsed the appellant's view in regard to the arbitrariness of the claimed aspect ratio range. Consequently, the Board had no reason to change its provisional opinion.

13. Since claim 1 of auxiliary request 3 does not involve an inventive step (Article 56 EPC), the patent cannot be maintained in this form.

Auxiliary requests 4 and 5 as filed during the opposition procedure

14. The respondent has only provided comments as regards the appellant's objections against patentability of auxiliary requests 4 and 5 filed in the opposition proceedings, without however specifying, formulating or filing corresponding explicit requests in this regard. Even after the Board pointed out this deficiency in the communication under Article 15(1) RPBA and the corresponding lack of substantiation under Article 12(3) RPBA (see above item V.), the respondent did not provide further submissions in this respect.

Thus the Board's assessment is to be based on the submissions on file. Even if the respondent's comments were to be interpreted as an implicit reference to the auxiliary requests 4 and 5 filed at the department of first instance, the provisions of Article 12(3) RPBA are not complied with, as it is required inter alia to specify expressly all requests relied on.

The Board has therefore exercised its discretion under Article 12(5) RPBA not to admit the submissions directed to auxiliary requests 4 and 5 filed only before the opposition division into the appeal proceedings.

15. In the absence of any set of claims which meets the requirements of the EPC, the Board can only accede to the appellant's request that the patent be revoked.