text: T 1149/97 (fluid converter) of 7.5.1999
  ECLI: EP: BA: 1999: T114997.19990507
  Converter for liquids
  I. In the absence of an opposition, the adoption of the decision to grant a European patent normally marks a turning point for amendments to the application documents in the European procedure. If an opposition has been filed, a turning point due to the grant of a patent can be seen in the restrictions that apply to further amendments to the patent specification under Rules 57a and 87 and Article 123 (3) EPC.
  II. Although Article 123 (3) EPC only relates to the claims of the European patent, changes to the description and drawings may also extend the scope of protection under Article 69 (1) EPC.
  III. If the application documents have been adapted to amended claims with regard to Articles 84 and 69 EPC before grant and a part of the originally disclosed subject-matter was deleted in order to avoid lack of conformity in the patent specification, the subject-matter deleted for this reason can usually neither can be re-included in the patent specification or in the claims as granted, without there being any breach of Article 123 (3) EPC. This applies analogously to an object that was retained in such an adaptation only for reasons of clarity and with the indication in the patent specification that it does not relate to the claimed invention (see No. 6 of the reasons for the decision).
  Novelty - main request and auxiliary requests 2 and 3 (negative)
  Amendments - Auxiliary requests 4 and 5 (inadmissible): Caesarean effect under Article 123 (3) EPC through the granting of a patent
  I. The appellant (patent proprietor) appealed against the decision of the opposition division revoking European patent No. 0 282 251.
  The respondent (opponent) had filed an opposition against the patent in its entirety on the basis of Article 100 a) EPC because the subject-matter of the patent in suit did not show any novelty and / or inventive step. The opposition was based, inter alia, on the following documents (using the notation used by the opposition division):
  A: DE-C-17 73 815 and
  The opposition division was of the opinion that the grounds for opposition mentioned in Article 100 (a) EPC precluded the maintenance of the contested patent insofar as the subject-matter of claim 1 as granted was not new to the prior art disclosed in document B. Claim 1, as amended in accordance with an auxiliary request, violated Article 123 (2) EPC and was therefore not allowable.
  II. In the communication of February 10, 1999 pursuant to Article 11 (2) of the Rules of Procedure of the Boards of Appeal, the board stated that, in its preliminary view, the subject-matter of Claim 1 as granted was anticipated by the fluid converter disclosed in Document B, since the term "yoke" also includes the screw-in piece according to document B, which also has a "cavity". In addition, the board had serious doubts as to whether the amendments to claim 1 according to the auxiliary requests submitted by the appellant together with the grounds of appeal met the requirements of Article 123 (2) EPC. In particular, an arrangement that has an excitation means in only one of two cavities, the other cavity being empty or containing a sensor element, cannot be derived directly and unambiguously from the application documents originally submitted.
  III. The oral hearing requested by the complainant as an alternative took place on May 7, 1999. During this hearing, the complainant referred to an article in
  The Marconi Review, Vol. XLIII, No. 218, 1980, pages 156-175,
  which the examining division had already cited as document D1 and which had been recognized in the patent in suit. At the end of the oral hearing the decision of the board was issued.
  IV. The appellant requested that the contested decision be set aside and the patent maintained on the basis of the main request (patent as granted) or auxiliary requests 1 to 6 submitted during the oral proceedings.
  V. The complainant requested that the complaint be rejected.
  VI. Claim 1, according to the requests at the time of this decision, is worded as follows:
  "1. A fluid converter comprising:
  a sensor element (10) which is designed for immersion in a fluid and comprises a pair of prongs (834, 835; or 845, 846) which extend in the axial direction from a common yoke (836 or 842), coupled to one another via the latter are and can be excited to resonance oscillations at the same frequency but in antiphase;
  piezoelectric means (830; or 840, 841) mounted within the sensor element for exciting such resonant anti-phase vibrations of the prongs; and further piezoelectric means (20 or 48) mounted within the sensor element for detecting the frequency of vibration;
  characterized in that the energizing means (830; or 840, 841) is mounted under axial compression in a cavity (831; or 850, 851) in the yoke (836 or 842) in an area thereof close to the point where the inner Side (832 or 833; or 843 or 844) one of the prongs (834 or 835; or 845 or 846) hits the yoke. "
  a sensor element (10) adapted to be immersed in a fluid and comprising a pair of prongs (834, 835; or 845, 846) extending axially from a common yoke (836 or 842) coupled to one another via the latter are and can be excited to resonance oscillations at the same frequency but in antiphase; piezoelectric means (830; or 840, 841) mounted within the sensor element for exciting such resonant anti-phase vibrations of the prongs; and further piezoelectric means (20 or 48) mounted within the sensor element for detecting the frequency of vibration;
  characterized in that the excitation means (830; or 840, 841) is mounted under axial compression in an enclosed cavity (831; or 850, 851) in the yoke (836 or 842) in an area thereof close to the point where the inner side (832 or 833; or 843 or 844) one of the prongs (834 or 835; or 845 or 846) meets the yoke. "
  a sensor element (10) which is designed for immersion in a fluid and comprises a pair of prongs (845, 846) which extend in the axial direction from a common yoke (842), are coupled to one another via this and to resonate vibrations at the same frequency are excitable, but in opposite phase;
  piezoelectric means (840, 841) mounted within the sensor element for exciting such resonant anti-phase vibrations of the prongs; and further piezoelectric means (20 or 48) mounted within the sensor element for detecting the frequency of vibration;
  characterized in that the yoke has two cavities (850, 851) with the energizing means (840, 841) under axial compression in at least one of the cavities (850, 851) in the yoke (842) in an area thereof close to the point is mounted where the inner side (843 or 844) of one of the prongs (845 or 846) meets the yoke. "
  a sensor element (10) which is designed for immersion in a fluid and comprises a pair of prongs (845, 846) which extend in the axial direction from a common yoke (836 or 842), are coupled to one another via this and contribute to resonance vibrations same frequency, but in opposite phase, can be excited;
  characterized in that the yoke has two cavities, the energizing means (840, 841) and the sensing means being mounted under axial compression in the cavities (850, 851) in the yoke (836 or 842) in an area thereof close to the point where the inner side (843 or 844) of one of the prongs (845 or 846) meets the yoke. "
  a sensor element (10) which is designed for immersion in a fluid and comprises a pair of prongs (845, 846) which extend in the axial direction from a common yoke (842), are coupled to one another via this and to resonate vibrations at the same frequency are excitable, but in opposite phase; piezoelectric means (840, 841) mounted within the sensor element for exciting such resonant anti-phase vibrations of the prongs; and further piezoelectric means (20 or 48) mounted within the sensor element for detecting the frequency of vibration;
  characterized in that the yoke has two cavities, the piezoelectric excitation means (840, 841) comprising two piezoelectric elements which are axially compressed in the respective cavities (850, 851) in the yoke (842) in an area thereof close to the Point where the inner side (843 or 844) of one of the prongs (845 or 846) meets the yoke. "
  VII. The complainant submitted the following in support of her applications:
  The more precise information "closed cavity" according to claim 1 of auxiliary request 3 is based on column 10, lines 1 to 4 of the A-script mentioned [of the patent in suit] and is illustrated by Figures 8 and 9 of the patent in suit. It should refer to an arrangement in which the piezoelectric element is enclosed in the cavity. Even if some passages of the original description were not retained in the patent specification, a patent proprietor has the right to include originally disclosed restrictive features in the claims after grant. Since electrical lines would have to be passed through the claimed housing, the person skilled in the art would assume that the cavity is "essentially" closed.
  With regard to the admissibility of the claimed subject-matter according to auxiliary requests 4 and 5, reference is made to decision T 187/91, according to which a specific example was included within a generic disclosure in the application as filed if the skilled reader could use the specific example seriously considered as a possible practice of the invention described. In the present case, the person skilled in the art would seriously consider the excitation of only one of the prongs, because the originally filed claims 1 and 7 disclosed a yoke with one or more cavities and column 2, lines 13 to 17 of the A-script expressly refer to the as possible alternatives Excitation of a single prong and the detection of the vibration frequency of a single prong. It must of course be permissible to use the original disclosure to further restrict the claims. In addition, such single-tine alternatives were part of common knowledge in the technical field concerned. Therefore, the provisional generalizations made under Auxiliary Requests 4 and 5 under Article 123 (2) EPC should be considered admissible.
  Finally, the subject matter of claim 1 of auxiliary request 6 is limited to the exemplary embodiment in Figure 9 of the patent in suit and must be clearly patentable compared to the identified prior art.
  VIII. The Respondent submitted the following:
  In the Respondent's view, under Article 123 (2) EPC, the original disclosure determines the reservoir of amendments that may be made before grant. However, if the subject-matter of the application was restricted by deleting passages from the application documents in the version originally filed, the reservoir of possible amendments under Article 123 (3) EPC would also be restricted. The passages of the A script on which the appellant relied as the basis for the disclosure of the term "closed cavity" could not be used if an attempt was made to change the claims after the grant. The only available source of disclosure would be the text belonging to Figure 9 of the patent in suit, according to which the cavities are closed by stoppers. However, a generalization of this specific embodiment would lead to an expansion of the scope of protection beyond the scope of the patent specification. Since "closed" does not mean "completely closed", the piezoelectric elements in the transducer column 41 of document B could also be regarded as closed by the bridge 44 and the rod-shaped supports in the cavity 14.
  For the same reasons, the claimed subject matter of auxiliary requests 4 and 5 is not admissible. The passages of the A script referred to by the appellant had been replaced or deleted in the patent in suit and could no longer be considered for changes to the claims. The decision T 187/91 referred to a different procedural situation and did not apply to the present case, in which there was room for maneuver only with regard to the content of the patent in suit. In addition, the knowledge of a specialist is completely irrelevant for the admissibility. Otherwise, all direct equivalents would be part of the original disclosure, which, according to the consistent interpretation of Article 123 (2) EPC, is not the case.
  There were no formal objections to claim 1 of auxiliary request 6. However, the description had to be carefully adapted to the wording of the claims, since the patent had been limited to the embodiment of Figure 9. In particular, the other exemplary embodiments would have to be deleted from the patent specification. The matter should therefore be referred back to the first instance if auxiliary request 6 is allowed.
  The appeal complies with Rule 65 EPC and is therefore admissible.
  2.1.5 Consequently, the subject-matter of claim 1 as granted is not new (Art. 54 EPC) and the claim cannot therefore be granted.
  Therefore, in any case, the claimed subject-matter does not involve an inventive step under Article 56 EPC and consequently claim 1 of auxiliary request 1 cannot be considered allowable.
  The subject-matter of claim 1 of auxiliary request 2 is therefore also not new compared to document B (Art. 54 EPC).
  5.1 Admissibility of the changes
  Claim 1 of auxiliary request 3 differs from claim 1 as granted in that "cavity" has been replaced by "closed cavity". It is true that the passage of the A script referred to by the appellant in this connection (column 10, lines 1 to 4) refers to the original figure 10, which was deleted before the grant was granted.
  Nevertheless, the passage mentioned, according to which the piezoelectric element is "enclosed" in the yoke, was retained in the patent specification (see column 9, lines 23 to 26) to describe Figure 8 of the patent in suit (original Figure 11). In the board's view, this adaptation of the original application documents to the wording of the claims intended for grant is justified if one takes into account that the transducer of the original Figure 11 is described in the A-script as being, with the exception of a ring-shaped piezoelectric element, the that is similar to Figure 10 (see column 10, lines 18 to 24 of the A-script).Since the other features of the two types of embodiment are therefore likely to be more or less identical, it is permissible in the present case under Article 123 (2) EPC to replace the rather summary description of the original Figure 11 (now Figure 8 of the patent in suit) with the original Figure 10 to add the corresponding text in a slightly adapted form.
  In addition, Figures 8 and 9 of the patent in suit, which are the only remaining embodiments of the claimed invention, clearly show arrangements in which the cavity is "closed off".
  The fact that the "cavity" of claim 1 as granted is designated as "closed" cannot, however, make the claimed subject matter novelty compared to document B.
  As the board informed the parties at the hearing, document B (see in particular Figure 2) already discloses an electronic head 30 with a housing 31, which can also be assumed to "close off the cavity 14 of the screw-in piece 10 in the broadest sense." ".
  Consequently, claim 1 of auxiliary request 3 cannot be granted either (Art. 54 EPC).
  6.1 Admissibility of the changes
  6.1.1. Corresponding to auxiliary requests 4 and 5, claim 1 in the version as granted was amended by the more precise specification that the yoke contains two cavities, the excitation means being attached in at least one of the cavities (claim 1 of auxiliary request 4) or the excitation means and the Detection means are attached in the cavities (claim 1 of auxiliary request 5).
  In the appellant's view, these amendments are based on the original claims 1 and 7, which disclose a yoke with at least one cavity, i. H. with one or more cavities, and on column 2, lines 13 to 17 of the A document, which discloses the excitation of a single prong and / or the detection of the vibration frequency of a single prong.
  6.1.2 However, the original claims 1 and 7 have been replaced in the patent specification by claim 1 as granted, and the aforementioned passage in the A-script was deleted when the description was adapted to the amended claims prior to grant.
  There is another passage in the patent (see column 5, line 56 to column 6, line 20) which could be understood to refer to the excitation of a single prong and / or the detection of the vibration frequency of a single prong ( see in particular column 6, lines 17 to 20 of the patent in suit). Apart from the fact that the board is of the opinion that the wording of the passage is ambiguous and z. B. could also relate to the design options for one of two prongs, the other prong would be the same, it can be seen from the patent specification that the passage mentioned does not refer to the claimed invention, but to an object that is expressly stated in the patent for reasons of clarity of the claimed subject matter in the granted version was retained (see column 2, line 31 to column 3, line 1 and column 9, lines 13 to 18 of the patent in suit: In the first passage, on the one hand, between "for understanding the Invention useful examples "and" embodiments of the invention "and on the other hand between devices" of the kind to which the invention relates "and" devices according to the invention "are differentiated, while the last passage refers to the" inventive "changes to the converters described so far ).
  Furthermore, the only embodiment of the patent in suit which has two cavities, i. H. The embodiment of Figure 9, which corresponds to Figure 12 of the application as filed, has a piezoelectric excitation element in each cavity, the sensing means being positioned at any suitable point on the prongs or yoke where it is deflected back and forth by the vibration of the prongs (see column 9, lines 40 to 56 of the patent in suit).
  6.1.3 In view of the changes made under Auxiliary Requests 4 and 5 and taking into account the arguments of the parties, the question of admissibility under Article 123 EPC therefore focuses on two aspects:
  - Firstly, it must be clarified whether the full text of the original disclosure can be used as the basis of disclosure for the amendment of the claims after grant, even if the cited passages were deleted before the grant or are presented in the patent specification as not belonging to the claimed invention, and
  - secondly, whether the embodiment of Figure 9 of the patent in suit can serve as such a basis.
  6.1.4 According to Article 123 EPC, the right of a patentee to make changes after grant depends on two conditions:
  - A European patent may not be amended in such a way that its subject matter goes beyond the content of the application as originally filed (Art. 123 (2) EPC).
  - In opposition proceedings, the claims of the European patent may not be amended in such a way that the scope of protection is extended (Art. 123 (3) EPC).
  The appellant alleged that both requirements were met by the amendments in accordance with auxiliary requests 4 and 5 insofar as further restrictive features were included in claim 1 as granted and these features were clearly disclosed in the application documents as originally filed be. Therefore, the scope of protection was not extended and no subject matter was added that went beyond the content of the application as originally filed.
  With regard to this formal argument, the appellant disregards the fact that in the present case the new restrictive features are based on subject-matter which was deleted from the description before grant or which the description states in the description to no longer belong to that before grant claimed invention belongs; it therefore denies that such deletions or information made before granting have a substantive effect on the admissibility of changes after granting.
  Against the appellant's view, the respondent asserts that such deletions or information generally have a substantive character insofar as they reduce the original disclosure to the subject matter retained in the patent specification, i.e. H. the granting of a patent represents a turning point because it prevents a resumption of the subject matter "dropped" prior to grant.
  6.1.5 The board is not aware of any decision that expressly deals with the issue at hand, although this is unlikely to be a rare exception. In their opinion, it should therefore be examined more closely in the present case whether the granting of a patent has a turning point.
  6.1.6 There are only a few decisions about the waiver of an object with substantive effect (see examples in "Case Law of the Boards of Appeal of the European Patent Office", third edition, European Patent Office 1999, Chapter VI, I-3.1.1). In these decisions it is apparently undisputed that a waiver usually has substantive effect if a certain subject matter has been expressly given up and the original claim and its basis have been completely deleted from the patent specification (see e.g. T 61/85, No. 11 of the reasons for the decision and T 64/85, nos. 2.1 to 2.3 of the reasons for the decision; both decisions not published in the OJ EPO). In this case, it is no longer possible to resume the abandoned item.
  Since, in the case of a caesura allegedly caused by the granting of a patent, such express declarations of waiver of objects were not necessarily made prior to the granting, in the opinion of the board a caesura would not arise directly from a "waiver" in the narrower sense, i. H. in that it was expressly declared, but only indirectly on the basis of the files.
  6.1.7 Decision T 420/86 (not published in the OJ EPO; see No. 4 of the reasons for the decision) briefly deals with the patent proprietor's request in the inter partes proceedings, the deletion of a feature from the original main claim to undo; this deletion had been made with the approval of the examining division prior to grant. The board found that such a deletion could not be reversed after the patent had been granted because it was equivalent to a waiver. A resumption of the deleted feature at this stage is therefore prohibited. The application must therefore fail for purely formal reasons.
  It can be concluded from this decision that the granting of a patent generally results in a waiver prior to grant.
  However, decision T 420/86 did not give any legal grounds for finding that the deletion was tantamount to a waiver, and since this decision was taken before decision G 7/93 of the Enlarged Board of Appeal (OJ EPO 1994, 775), it is not clear whether the determination at that time was based on the assumption that the applicant's consent to the notified version under Rule 51 (4) EPC has binding effect. In its subsequent decision, the Enlarged Board of Appeal rejected such an assumption, stating: "Neither the applicant's agreement with the notified text nor the issuing of a communication from the EPO under Rule 51 (6) EPC 'binds' the applicant or the EPO as such In the sense of the word, ie in such a way that any subsequent amendment of the application would be excluded from the outset. Contrary to the legal opinion advocated by the President in his opinion before the Enlarged Board of Appeal, amendments are made at the discretion of the examining division before a decision to grant is issued Application by the applicant or on his own initiative "(see No. 2.1 of the reasons for the decision, emphasis placed by the board).
  6.1.8 Although the normal procedural declarations of an applicant under Rule 51 EPC cannot be ascribed a general turning point before grant, the above passage from G 7/93 indicates that there is a procedural turning point that is the last due to the adoption of a decision to grant Step of the European procedure comes about.
  This conclusion is in line with the finding of the Enlarged Board of Appeal in its earlier decision G 1/84 (OJ EPO 1985, 299; see No. 1 of the reasons for the decision) and is well documented in the specialist literature (see M. van Empel: "The Granting of European Patents ", AW Sijthoff, Leyden 1975, No. 542; R. Schulte:" Patentgesetz ", 5th edition, Carl Heymanns Verlag KG, Cologne 1994, § 49, No. 16; F. Blumer:" Formulation and Change of patent claims in European patent law ", Carl Heymanns Verlag KG, Cologne 1998, No. 17.1.1, last paragraph). It is based on the formal aspect that the granting of a patent is an official act which marks the end of an administrative procedure. This official act is binding for the authority and the applicant, who thereby accepts the consequences, "i.e. he waives further claims from this official act" (see M. van Empel, loc. Cit.).
  As soon as a decision to grant has been issued, the European examination procedure is therefore concluded and its results are binding on the applicant and the EPO insofar as no further amendments (apart from corrections under R. 89 EPC) are permitted. If no opposition is filed, the European patent normally enters the national phase in this version.
  6.1.9 However, if an opposition is filed with the EPO, further changes can be made to the patent in suit. Although such changes are not within the general discretion of the patent proprietor because the opposition proceedings are not a continuation of the examination procedure (see G 1/84, loc. Cit .; No. 9 of the Reasons for the decision), the patent proprietor can, under Rule 57a EPC, respond to the opponent's objections respond with amendments to the description, claims and drawings, provided that the amendments are caused by the grounds for opposition referred to in Article 100 EPC, even if the opponent has not invoked the ground concerned. In addition, Rule 87 EPC allows changes caused by earlier national laws.
  In the board's view, these provisions of the EPC reflect at most the formal aspects of a procedural turning point that is associated with the grant of a patent in the opposition phase. The granting of a patent does not constitute a general turning point insofar as the patent must be defended in its unchanged form. However, changes are only permitted in response to actual or possible grounds for opposition or to conflicting earlier national rights. Before considering a possible substantive break in opposition proceedings for amendments after grant, one must therefore ensure that the restrictions imposed by Rules 57a and 87 EPC have been observed.
  6.1.10 In the board's view, such a turning point in substantive law could only be based on Article 123 (3) EPC.
  Article 123 (3) EPC expressly refers only to the claims of a European patent and this choice of words could possibly be understood to mean that changes to the description and drawings after the grant of a European patent are not restricted in any way.
  However, there seems to be consensus in the literature that this provision should be interpreted broadly in view of its purpose and the connection with Articles 69 and 138 EPC (see, for example, BG Paterson: "The European Patent System", Sweet and Maxwell, London 1992, Paragraph 5-40; R. Schulte: "Patentgesetz", 5th edition, Carl Heymanns Verlag KG, Cologne 1994, § 22, Nos. 4 to 9; R. Singer et al .: "The European Patent Convention", Revised English (1995) edition, Sweet & Maxwell, London 1995, Article 123.10D; F. Blumer: "Formulation and amendment of patent claims in European patent law", Carl Heymanns Verlag KG, Cologne 1998, No. 17.1.5.1).
  In line with the general intention of Article 123 (3) EPC, there should be legal certainty for third parties who trust that the protection afforded by a patent can only be limited and not extended. Since, under Article 69 (1) EPC, the scope of protection is determined by the content of the claims, taking into account the description and the drawings, care must be taken that changes to the description and the drawings do not expand the scope of protection. These principles have been confirmed by the case law of the Enlarged Board of Appeal (see G 2/88, OJ EPO 1990, 93, No. 4 of the Reasons and G 1/93, OJ EPO 1994, 541, No. 11 of the Reasons). In addition, under Article 138 (1) (d) EPC, an extension of the scope of protection of a European patent under national law can constitute a ground for invalidity.
  The principle contained in Article 123 (3) EPC can therefore be summarized as follows: "When a European patent has been granted, the act of a third party which would not infringe the patent as granted, as a result of an amendment after grant, must not can become an act of infringement "(see G. Paterson, loc. cit.).
  6.1.11 The adaptation of the description and the drawings to the version of the amended claims to be granted is therefore absolutely necessary under Articles 84 and 69 EPC in order to establish correspondence between the claimed invention and its description with regard to support and the scope of protection (see e.g. decision T 977/94, not published in OJ EPO; point 6.1 of the reasons for the decision).
  In the procedure prior to grant, deletions are usually made because the deleted passages of the original disclosure relate to subjects that no longer correspond to the version of the claims to be granted, i.e. H. because these passages would, among other things, collide with the protection sought in the claims. Likewise, protection is not sought for deviating items that are clearly identified in the patent specification as not belonging to the invention. A corresponding adaptation of the description is an alternative to deletions if the intelligibility of the other subjects would suffer from such deletions.
  6.1.12 The reintroduction of features which, in order to avoid lack of conformity in the patent specification before grant, were either deleted from the documents or provided with the clear indication that they no longer relate to the claimed invention, consequently affects the scope of protection as a rule of the patent, regardless of whether these features are added to the claims or reintroduced in the specification.According to the above principle, this consequence is inevitable because a third party who relies on the deviating subject matter not falling under the scope of protection of the granted patent is confronted with an expansion of the scope of protection as a result of the resumption of this subject matter and thus opens up the possibility of a patent infringement that has been excluded up to that point would.
  Therefore, such re-inclusion of subject-matter which, with a view to Articles 84 and 69 EPC, in order to avoid lack of conformity in the patent specification prior to grant has been deleted or indicated that it no longer relates to the invention is usually after Article 123 (3) EPC not admissible after grant. As a result, the board comes to the conclusion that such deletions and references must be assumed to have a turning point before grant insofar as Article 123 (3) EPC gives them substantive effect after grant.
  6.1.13 In the present case, the application was limited to an excitation means arranged in a cavity in the yoke, and all contradicting passages relating to the originally disclosed alternative, according to which the excitation means are arranged in cavities in the prongs, were rightly drawn from the for the granting of certain documents is deleted or - if the deletion was not appropriate for reasons of clarity - provided in the patent specification with the note that they no longer relate to the claimed invention. This finding applies in particular to the passages on which the amendments according to auxiliary requests 4 and 5 should be based, in the opinion of the complainant.
  Therefore, the board considers that the subject-matter of claim 1 as granted, when interpreted on the basis of the specification and drawings (see Figures 8 and 9, which are the only embodiments retained in the granted patent), pending grant the symmetrical excitation of both prongs has been restricted by the excitation means attached in the yoke. A person skilled in the art would therefore not expect that single prong excitation, which was mentioned in the original application documents as a general possibility in connection with piezoelectric elements arranged in the prongs, would continue to be protected by the patent in suit.
  6.1.14 Although the subject-matter of claim 1 has been formally restricted in accordance with auxiliary requests 4 and 5 for reasons of patentability under Article 100 (a) EPC by the inclusion of features relating to two cavities in the yoke, the fact that the reopen the possibility of exciting a single prong, at the same time the scope of protection of the contested patent, since the granted patent no longer permitted such a possibility as a whole.
  The present case is therefore different from T 673/89 (not published in the OJ EPO; see point 3.1.2 of the Reasons for the decision), where there was no indication in the file that the intention was to have one in the patent specification to exclude any further execution options still contained from the protection area.
  As a result, taking into account the legal effects of the grant of a European patent under Article 123 (3) EPC, the board takes the view that the original subject-matter, which in the present case was in the original application documents either by deletion or by an express declaration before grant "has been dropped "does not provide a basis for admissible changes after grant.
  6.1.15 With regard to Article 123 (2) EPC, contrary to the appellant's view, such a basis could not be derived from the application documents originally filed. The only embodiment that reveals two cavities in the yoke is that shown in Figure 12 of the A font, which corresponds to Figure 9 of the patent in suit. A piezoelectric excitation element 840, 841 is provided in each of the cavities. In the board's view, the original disclosure did not contain any clear indication that in this particular embodiment a cavity could be empty or contain a piezoelectric sensor element, and the claimed generalizations could not be derived from the above figure and the associated description.
  Even the complainant had not claimed this, who had spoken in this connection of alternative constructions that would be obvious to a specialist based on his general specialist knowledge. According to the established practice of the boards of appeal, the obviousness of a feature is not a substitute for the original disclosure.
  Finally, decision T 187/91 (OJ EPO 1994, 572) referred to by the appellant does not apply to the situation here, as it deals with the admissibility of a specific example falling under the more general term disclosed, while in the present case it This is about the admissibility of a generalization of the special term disclosed in Figures 12 and 9.
  6.1.16 Therefore, auxiliary requests 4 and 5 cannot be allowed (Art. 123 EPC).
  7.1 Admissibility and clarity of the changes
  The subject matter of claim 1 according to auxiliary request 6 has been further restricted in relation to the subject matter of claim 1 as granted in that the yoke has two cavities and the piezoelectric excitation means has two piezoelectric elements mounted in the respective cavities.
  As stated above (see No. 6.1.2), a liquid converter of this type is disclosed in Figure 9 and column 9, lines 40 to 51 of the patent in suit, and Figure 12 and column 10, lines 32 to 43 of the application documents as originally filed correspond.
  Therefore, the board has no objection to claim 1 of auxiliary request 6 under Articles 123 and 84 EPC; The Respondent did not raise any such objections either.
  7.2.1 The subject matter of claim 1 of auxiliary request 6 differs from the most relevant document, i. H. the document B, through the newly introduced features: In the closest prior art there is only one "cavity" 14 in the "yoke" 10 (see document B, Figure 3), in which the piezoelectric excitation means 65 is attached (see document B, Figure 6). Although the excitation means may consist of two piezoelectric elements 59, 61, these are electrically connected in parallel and mechanically in series in order to increase the mechanical deformation of the free part of the diaphragm 21, which is arranged between the end faces of the prongs 22 and 23.
  The other, less relevant documents of the prior art also do not disclose the features mentioned above. The claimed subject-matter therefore meets the novelty requirement (Art. 54 EPC).
  7.2.2 As can be seen from Figure 9 of the patent in suit and as the appellant has pointed out, the presence of two cavities in the yoke close to the prongs enables a completely different construction of the vibration system: each prong is excited separately, and it can act on a flexible one Diaphragm can be dispensed with, which tends to react to fluctuations in external pressure. It can therefore be assumed that the technical problem solved by the claimed subject matter in relation to the closest prior art consists in eliminating the effect of the external pressure on the measuring accuracy of the transducer (see in this context also column 7, lines 21 to 30 of the patent in suit).
  7.2.3 Since the available state of the art does not say anything about this problem and gives no indication of its solution, the board is convinced that the claimed subject-matter involves an inventive step within the meaning of Article 56 EPC.
  7.2.4 Therefore, claim 1, as amended in accordance with auxiliary request 6, must be regarded as allowable.
  The dependent claims 2 to 8, which have been adapted to the wording of claim 1 and relate to the preferred embodiments of the claimed subject matter, are also allowable.
  Although the appellant also submitted changes to the description at the hearing, the board, exercising its discretion under Article 111 (1) EPC, considers it appropriate to refer the case back to the first instance for further decision. In view of the findings under point 6, the adaptation of the description and the drawings to the now claimed, more restricted subject matter must be carefully examined in order to ensure full compliance with the amended claim 1.
  In this context, the first instance should deal in particular with the question of whether the embodiment of Figure 8 of the contested patent, which no longer falls under amended claim 1, should be deleted from the patent specification or retained in an amended form as not belonging to the invention .
  2. The matter is referred back to the first instance with the order to maintain the patent with the following claims and to adapt the description and the drawings: