T 0269/19 09-02-2022
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Turbine wastegate
BorgWarner Inc.
Bosch Mahle Turbo Systems GmbH & Co. KG
Basis of proceedings
Novelty - main request (no)
Inventive step - auxiliary request (no)
I. The proprietor and the opponent 1 both appeal against the interlocutory decision of the Opposition Division of the European Patent Office concerning maintenance of the European Patent No. 2921671 in amended form.
II. In its written decision the opposition division held that granted claim 1 lacked novelty but that the patent as amended according to the auxiliary request 1 met the requirements of the EPC, having regard in particular to the following documents:
D13a: JP S56-171631 U and its translation D13b
III. Oral proceedings were held on 9 February 2022 in the form of a videoconference.
IV. The appellant proprietor requests that the decision under appeal be set aside and the patent be maintained as granted, or, alternatively, on the basis of the first auxiliary request, filed on 22 March 2019 with the grounds of appeal.
The appellant opponent 1 requests that the decision under appeal be set aside and the patent be revoked.
The opponent 2, party as of right, made requests in support of appellant opponent 1.
V. The wording of claim 1 of the main request and auxiliary request 1 is as follows:
Main request (as granted)
"An assembly (200) comprising:
a turbine housing (210) that comprises a bore (212), a wastegate seat (226)
and a wastegate passage that extends to the wastegate seat (226),
a bushing (242) configured for receipt by the bore (212);
a rotatable wastegate shaft (252) configured for receipt by the bushing (242);
a wastegate arm (254) extending from the wastegate shaft (252); and
a wastegate plug (256) extending from the wastegate arm (254) wherein the
wastegate plug (256) comprises a profile, defined in part by a portion of a cone, for
contacting the wastegate seat (226) to cover the wastegate passage
characterized in that:
the wastegate seat (226) comprises a profile, defined in part by a portion of a torus."
Auxiliary request 1 (addition underlined by the Board)
"An assembly (200) comprising:
a turbine housing (210) that comprises a bore (212), a wastegate seat (226)
and a wastegate passage that extends to the wastegate seat (226),
a bushing (242) configured for receipt by the bore (212);
a rotatable wastegate shaft (252) configured for receipt by the bushing (242);
a wastegate arm (254) extending from the wastegate shaft (252); and
a wastegate plug (256) extending from the wastegate arm (254) wherein the
wastegate plug (256) comprises a profile, defined in part by a portion of a cone, for
contacting the wastegate seat (226) to cover the wastegate passage
characterized in that:
the wastegate seat (226) comprises a profile, defined in part by a portion of a torus; and the portion of the torus comprises a portion of an elliptical torus having a minor axis length that differs from a major axis length."
VI. The appellant-proprietor argued as follows:
- D13 should not be admitted in the proceedings.
- D13 does not directly and unambiguously disclose a seat having a portion of a torus.
- Starting from D13, the technical problem is not just to find an alternative seat configuration. The skilled person would not have obviously modified the shape of a torus to provide an elliptical torus, therefore Claim 1 according to auxiliary request 1 involves an inventive step
VII. The appellant-opponent 1 and respondent opponent 2 argued as follows:
- The opposition division's decision to admit D13 is correct.
- D13 interpreted by the skilled person unambiguously discloses a reversal of the configuration shown in figure 3, thus a wastegate seat that comprises a profile as a portion of a torus.
- Starting from D13 the elliptical torus cannot be seen to provide any effect. It should therefore be seen as an arbitrary selection and thus obvious.
1. The appeals are admissible.
2. Background
2.1 The patent concerns a wastegate valve assembly for a turbocharger, and more specifically aims at improving the wastegate plug. The specific embodiment of wastegate plug having a conical shape bearing against a surface of wastegate seat that comprises a profile, defined by a portion of a torus seeks to address misalignment problems (paragraph 004).
3. D13 admitted by the opposition division is part of the appeal proceedings.
3.1 The appellant-proprietor requests that the decision to admit D13a and its translation D13b into the proceedings be overturned.
3.2 According to established jurisprudence, submissions admitted at first instance are part of the appeal proceedings, cf. CLBA, 9th edition 2019, V.A.3.5.4). D13 though late filed has been admitted in the proceedings in view of its prima facie relevance (Decision point 1.1) and after hearing the parties (Minutes, middle of page 1). Although brief this point makes clear that figures 2 and 3 of D13 were considered relevant for the questions of novelty and inventive step. The division thus appears to have exercised its discretion under Art 114(2) EPC properly and according to the correct criteria.
Moreover, claim 1 as granted was subsequently held to lack novelty with respect to D13, and the reasons for this finding expressed in point 1.2 of the decision form part of the decision under appeal upon which appeal proceedings is based pursuant Art 12(1)a) RPBA. The Board does not see any legal basis for retroactively unadmitting a document into the proceedings which forms the basis of the decision appealed against.
3.3 Thus the Board does not see any reason for reversing the opposition division decision to admit D13 and its translations, which forms part of the impugned decision.
4. Main request - Novelty
4.1 It is undisputed that D13b discloses a turbocharger arrangement with a turbine housing 10 that comprises a bore receiving a bushing supporting a rotatable wastegate shaft; a wastegate arm 25 extending from the wastegate shaft; and a wastegate plug 24 (see D13b page 3, lines 19 to 39; D13a figures 2 and 3). The wastegate valve translated as bypass valve 15 is described in detail starting from page 4, line 4 of D13b. A main embodiment of the bypass valve arrangement as depicted in figure 3 of D13a is described in the translation D13b as comprising a valve body 24 beveled to a convex spherical shape (page 4, lines 17-21) so as to form part of a spherical surface with center on the axis of the air bleed hole (sentence bridging pages 4,5). A valve seat 23 is formed by beveling the outlet air bleed hole 22 to form a circular conical surface (page 4, lines 29-33) i.e. part of a circular conical surface having the vertex on the axis of the air bleed hole (page 4, lines 31-33).
As explained in lines 23 to 26 of page 4 when the valve is closed this configuration results in linear contact of valve and seat around the whole circumference.
Such a linear contact produces a high surface pressure during valve seating that crushes and repels carbon that might otherwise result in inadequate sealing and the valve sticking during operation, page 5, lines 4 to 11. Furthermore, it maintains a stable relative contact surface between seat and valve body, even if the valve body is inclined with respect to the seat, as explained further down in lines 24 to 27.
In the Board's understanding of the underlying geometry this single line of contact between two opposing surfaces - here the conical surface of the seat and the convex outer surface of the valve body- is only possible if they contact each other tangentially about the circumference of valve body.
4.2 D13b further indicates that the same effect can be obtained if at least either one of the contact surfaces is formed as any curved surface, page 5, 17-19. Indeed, further below on page 5, lines 31 to 35, this is briefly discussed in an alternative configuration in which the plug and seat shapes are effectively inverted, "in a manner opposite" to the exemplary embodiment of figure 3. In this alternative embodiment the valve seat 23 should be formed with a "spherical" surface and a valve body with circular conical surface seating thereon. Both main and inverted configurations with either one of the valve seat or seating surface of the valve body as "spherical" surface are repeated on page 6, lines 15 to 22 as ensuring linear contact to prevent inadequate sealing caused due to adherence of carbon resulting in the valve sticking.
4.3 Though the main arrangement is shown in figure 3 and explained in detail, the reverse configuration is not shown and only cursorily described in the two passages mentioned. There what is meant by a seat formed with "spherical" surface is, upon consideration, not immediately clear. If it is taken at face value and read literally, as does the appellant proprietor, it would appear to imply that the seat surface lies on or forms part of the inner surface of a sphere (or forms part of a "negative" sphere as the appellant proprietor calls it). The seat surface would then be concave with the valve body positioned on the top edge of the seat, see figure 3, page 8, of the appellant proprietor's grounds, represented below.
FORMULA/TABLE/GRAPHIC
A further similar reading by the appellant proprietor has a seat shaped as a bowl with its sides formed by parts of the outside surface of a torus and the valve body seated by its edges within the bowl shape, as in the following figure copied from page 9 of the appellant proprietor's grounds:
FORMULA/TABLE/GRAPHIC
However, neither reading would result in a linear contact of the seat and valve body contact surfaces as in the figure 3 embodiment. In either case contact would be achieved between an edge and an opposing surface, and not by tangential contact between the two opposing surfaces as in the figure 3 embodiment that must produce the required single line of contact.
4.4 The only interpretation that does give rise to a similar tangential contact between the opposing surfaces is where the seating surface is convex and the valve body surface conical. Considered in cross-section this simply transposes or inverts the cross-sectional shape of the opposing surfaces vis-a-vis the figure 3 embodiment. Where in the figure 3 embodiment the cross section of the spherical valve body contact surface is convex and lies on a circle (with center on the axis of the air bleed hole, see above), in the transposed or opposite configuration the seat surface likewise is convex and lies on a circle. The entire seat surface is then seen to be formed by the revolution of that circle about the air bleed hole axis, thus forming part of a torus. It becomes clear that the term "spherical" is a misnomer in the context of the opposite configuration, as the skilled reader will easily recognize from their understanding of the mechanics of the seating arrangement.
4.5 The appellant proprietor has argued that even if this were the only technically sensible interpretation then the resultant valve seat would not necessarily be toroidal for a skilled person, because they understand that term to denote only a doughnut shape. The Board disagrees as in geometry the term "torus" is not exclusive to shapes in which the circle as generatrix does not touch the axis of revolution about which it is revolved (producing a doughnut torus). It includes also "horn" torus, where the circle is tangent to the axis, and "spindle" torus where the axis passes through the circle.
4.6 Thus, the only technically sensible reading of the "opposite" embodiment is that where the seat shape is formed as part of a torus (and is convex), corresponding to that arrangement claimed. The Board thus confirms the decision's finding that the subject-matter of claim 1 as granted lacks novelty in view of D13.
5. First auxiliary request - inventive step
5.1 Claim 1 of this request (as upheld) further adds the definition (from granted claim 2) that the portion of the torus comprises a portion of an elliptical torus having a minor axis length that differs from a major axis length. Here the seat shape thus forms part of a torus generated by rotation of an ellipse, as illustrated in the bottom three examples shown of figure 11 of the patent. This further specification that the portion of the torus comprises a portion of an elliptical torus constitutes the sole difference between the subject-matter of claim 1 and the disclosure of D13 in its alternative embodiment. As explained above the only technically sensible reading of the "opposite" embodiment of D13a has a seat surface lying on a torus generated by a circle.
5.2 The technical effect related to this particular elliptical generatrix for the torus instead of the conventional circular ("spherical") generatrix as well as the formulation of the associated objective technical problem is however disputed.
The appellant proprietor agrees that D13a/D13b already addresses the problem of misalignment, page 5, lines 21 to 29, producing a similar effect and that the problem requires reformulation in a less ambitious manner according to constant case law (CLBA, 9th edition 2019, I.D.4.4.1). They however submit that the different shapes of exhausts allow an optimization of flow, and therefore that the problem should be reformulated correspondingly rather than as relating to the mere provision of an alternative.
5.3 It may be plausible that a variation in the outwardly flared shape of the outlet influences the flow behaviour as argued by the appellant proprietor. However, there is no indication in the patent that links the specific choice of an ellipse as generatrix to improved flow behaviour. Indeed, as argued by the appellant opponent, any such improvement must depend on a number of parameters that are not specified in the claim or even mentioned anywhere in the patent. These include in particular the orientation of the ellipse and the relative length of the axes.
Paragraph 030, which the appellant proprietor has cited in this context, describes the different seat profiles of the wastegate seat 1110,1120,1130 and 1140 shown in figure 11, but does not mention any associated effect or advantage either on its own for any of these profiles or with respect to a conventional toroidal shape of seat 1110, let alone that it identifies the parameters that might be critical for an effect.
5.4 Absent any particular technical effect the sole distinguishing feature cannot be seen to solve any technical problem. In particular it does not contribute to the problem of improving flow, as that depends on the values of the critical parameters mentioned above, which are not mentioned in the claim. In the Board's view such a feature that does not contribute to the problem alleged is thus arbitrary and need not be considered when assessing inventive step, see CLBA, 9th edition, 2019, I.D.9.5, in particular T1009/12 cited therein. As it is the only difference, the claimed invention lacks inventive step.
5.5 The Boards adds that if it were to be assumed the sole difference is meant to offer an alternative way of addressing sealing misalignment, then using an ellipse rather than a circle, which is a limiting example of an ellipse, to generate the toroidal seat surface is considered obvious for anyone, including the skilled person, with a good knowledge of toroidal geometry.
5.6 In view of the above the Board concludes that the subject-matter of claim 1 of the auxiliary request, contrary to the decision's positive assessment, does not involve an inventive step in the light of the prior art cited as required by Articles 52(1) and 56 EPC.
6. As no allowable request remains, the Board must revoke the patent pursuant to Article 101(2) and (3)(b) EPC.
For these reasons it is decided that:
1. The decision under appeal is set aside.
2. The patent is revoked.