T 0170/87 (Hot-gas cooler) of 5.7.1988

European Case Law Identifier: ECLI:EP:BA:1988:T017087.19880705
Date of decision: 05 July 1988
Case number: T 0170/87
Application number: 81105938.5
IPC class: C10J 3/86
Language of proceedings: DE
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Documentation of the appeal procedure can be found in the Register
Bibliographic information is available in: DE | EN | FR
Versions: OJ
Title of application: -
Applicant name: Sulzer
Opponent name: -
Board: 3.3.01
Headnote: 1. A figure which serves only to give a schematic explanation of the principle of the subject-matter of the patent and not to represent it in every detail does not allow the sure conclusion that the disclosed teaching purposively excludes a feature not represented. Such a "negative" feature (here: "with no internal fittings") may not subsequently be incorporated into the claim.
2. A disclaimer can be used to make an inventive teaching which overlaps with the state of the art novel but it cannot make an obvious teaching inventive.
Relevant legal provisions:
European Patent Convention 1973 Art 56
European Patent Convention 1973 Art 123(2)
Keywords: Inventive step (no) -
Further solution to a problem already solved without overcoming a prejudice or achieving an unexpected result
Original disclosure (no)
Lack of a feature in schematic drawing/only ground for its exclusion
"Negative" feature
Disclaimer only for substantiation of inventive step


Cited decisions:
Citing decisions:
G 0001/03
G 0002/03
G 0002/10
G 0001/16
T 0278/88
T 0650/88
T 0511/89
T 0839/90
T 0156/91
T 0393/91
T 0410/91
T 0857/91
T 0885/91
T 0597/92
T 0606/92
T 0653/92
T 0710/92
T 0039/93
T 0084/93
T 0448/93
T 0521/93
T 0885/93
T 0121/94
T 0681/94
T 0917/94
T 0159/95
T 0399/95
T 0645/95
T 0448/96
T 0571/96
T 0863/96
T 0963/96
T 0013/97
T 0308/97
T 0323/97
T 0739/97
T 1154/97
T 1217/97
T 0740/98
T 0264/99
T 0451/99
T 0507/99
T 0525/99
T 0974/99
T 0118/00
T 0162/00
T 0500/00
T 0548/00
T 0827/00
T 0002/01
T 0853/02
T 1028/02
T 1120/05
T 0564/08
T 0380/09
T 2136/10
T 0474/15
T 0621/15
T 0462/19

Summary of Facts and Submissions

I. On 27 December 1984 European patent No. 48 325 was granted in respect of European patent application No. 81 105 938.5, which had been filed on 28 July 1981 with Swiss priority from 19 September 1980, on the basis of five claims, the first two of which are worded as follows: "1. A hot gas cooler comprising a vertical pressure vessel and, disposed therein, a vertical cooling insert forming the interior through which hot gas flows, said insert shielding the pressure vessel wall from impermissible heat and consisting of tubes welded together so as to be sealing-tight and having a heat- transfer medium flowing therethrough, the hot gas inlet side of the cooling insert being connected to a hot gas source via an inlet duct which extends through the pressure vessel wall, while the gas outlet side has an outlet duct which also extends through the pressure vessel wall, the inlet and outlet ducts being of smaller cross-section than the interior, a pressure equalization connection to a cooling zone extending from the hot gas inlet area to the intermediate space between the cooling insert and the pressure vessel wall, characterised in that the inlet duct (8; 71) for the hot gas is disposed at the top end of the interior (7) and the pressure equalization connection (30; 82, 84) extends from the topmost part of the interior." ....

II. On 21 September 1985 the present respondents filed notice of opposition to the granted patent, claiming lack of inventive step. In support of their claim they cited the following documents: (1) DE-A-2 726 716 and (2) DE-A-2 705 558.

III. By decision of 5 March 1987 the Opposition Division revoked the disputed patent, saying essentially that the problem whereby, in the event of a leak forming, the pressure vessel wall would have only cooled gas passing over it was already known from (1). This problem was solved there by fitting a cooled pressure equalisation connection at the inlet end of the hot-gas cooler, which in that case involved the bottom end of the cooler. From document (2), which did not in fact mention a pressure equalisation connection, it was nevertheless already known to be advantageous to locate the inlet duct for the hot gas at the top end of the cooler. It was therefore obvious - irrespective of any new effect claimed - to modify the device described in (1) accordingly, at the same time keeping the arrangement of the pressure equalisation connection at the inlet end, now the top end. It could therefore be left open as to whether the new effect claimed did not already occur in accordance with (1). ....

IV. On 5 May 1987 the proprietors of the revoked patent entered appeal against the Opposition Division's decision, at the same time paying the prescribed fee ...

VII. The appellants request that the contested decision be set aside and the opposition rejected; that in accordance with a first subsidiary request made shortly before the end of the oral proceedings the words "with no internal fittings" be added after the word "interior" in the final line of Claim 1; and that in accordance with a second subsidiary request ...

Reasons for the Decision

1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is, therefore, admissible. Re the main request

2. The nearest state of the art, which the preamble to Claim 1 rightly takes as its point of departure, is indisputably document (1). In its broadest wording (cf. Claim 1) that document already describes a hot-gas cooler with an interior lying at a pressure above atmospheric, at one end of which the gas to be cooled is led in and at the other end of which it is led away (whether the inlet or outlet is at the top or the bottom end is not specified) and in which the tubular walls used for cooling and forming a sealed-off intermediate space are surrounded by a pressure casing and the intermediate space is connected via a cooled adjacent circuit which produces pressure equalisation. The most important result presented so far as a solution to the problem is concerned is "that in the event of a leak in one of the tubular walls no current of hot gas arises in the intermediate space which could cause the temperature of the gas in the intermediate space to rise and cause damage to the ... pressure casing" (page 3, paragraph 3). This is in substance the same as what is presented as the problem to be solved by the disputed patent in column 1, lines 20 to 26 of the patent specification. Where in the place cited in (1) it goes on to say that "in the event of a leak ... the ... gas gets into the intermediate space after being cooled in the adjacent circuit", this can only be understood - as the appellants confirmed in the oral proceedings - to mean a "suction effect" as a result of gas flowing out of the intermediate space into the interior at the point of the leak, and this can only happen if at the point concerned the pressure in the interior is lower than in the intermediate space. This is quite convincing in view of the facts described under point VI. above and also, because of the steam pipes (w), as regards the embodiment sketched in Figure 1 of (1). The problem described in column 1, lines 20 to 26, has therefore already been solved by (1).

3. Since on the other hand the appellants have not demonstrated any unexpected, e.g. superior effect of the hot-gas cooler claimed, from an objective point of view the task of the disputed patent can be seen only as to suggest a further solution to the above problem. This problem is in the Board's opinion convincingly solved by the claimed arrangement of the inlet duct at the top end of the interior and, in association with this, the pressure equalisation connection starting from the top part of the interior, an opinion not disputed by the respondents either.

4. The proposed solution claimed, with all its features, cannot actually be inferred from the state of the art demonstrated, and is therefore novel. Since this too is indisputable it is unnecessary to make any more detailed statements in this connection.

5. It thus remains to look into whether the subject-matter of the disputed patent is based on inventive step or was obvious to the skilled person in view of the existing technical problem.

5.1 In view of, on the one hand, the broad disclosure of document (1), according to which the gas to be cooled should be led into the cooler at one end and out again at the other, and on the other hand the embodiment specifically described there in accordance with Fig. 1 (in at the bottom, out at the top), in looking merely for a further solution it would not only be obvious but from the outset positively the most obvious idea to reverse the proposal in Fig. 1 and have the gas go in at the top and out at the bottom, while keeping the pressure equalisation connection located at the inlet end, now at the top.

5.4 All in all, the subject-matter of Claim 1 of the disputed patent in accordance with the main request involves a modification of the embodiment shown in Fig. 1 of (1) which would lie within the capability of a person skilled in the art and against which there was clearly no prejudice and with which no unexpected result is obtained. This subject-matter therefore lacks inventive step. ..... Re the first subsidiary request

6. This subsidiary request is directed at inserting a single word*) in Claim 1 as per the main request and was made just before the end of the oral proceedings. The Board therefore initially asked itself whether the request could be considered at all or whether it should be left out of consideration as having been brought up too late. In reaching a decision the Board took into account the following: By inserting the word "einbautenfreien" (in the English version the words: "with no internal fittings") the intention is obviously to contrast the subject-matter of the disputed patent more sharply against the embodiment described in Fig. 1 of (1) according to which fittings in the shape of steam pipes (w) are provided in the interior. In the aforementioned embodiment of the state of the art (gas flow from bottom to top) the fittings are a prerequisite for pressure conditions which enable the desired result to be achieved. This technical fact only became clear in the course of the oral proceedings on 5 July 1988, however (cf. above under point VI.). Under these particular circumstances the argument advanced by the appellants in this connection is not to be considered late. The first subsidiary request can therefore be taken into account.

7. In the case of changes made during opposition proceedings, including opposition proceedings on appeal, according to established Board of Appeal case law Article 84 EPC must be observed, although this does not in itself constitute grounds for opposition. In particular, care should be taken here to ensure that such changes do not affect the lucidity (clarity) of the claims. In the present case the Board has considerable doubts as to whether the feature of an interior "with no internal fittings" is consistent with the embodiment in Fig. 2 of the disputed patent specification, or whether the parts serving to divert the gas flow (e.g. the shell 42) should not likewise rather be considered as "fittings". In view of the statements that follow, however, it is not necessary to reach a final decision on this.

8. The Board is in fact of the opinion that the first subsidiary request must in any case fail because of the requirement of original disclosure in Article 123(2) EPC.

8.1 It is indisputable that the feature in question is not mentioned at all in the description or the claims of the first documents; the appellants nevertheless consider it justifiable to introduce it in the claim because in the drawing (in Fig. 1 at any rate) no fittings are shown in the interior.

8.2 The "content of the application as filed" beyond which, according to Article 123(2) EPC the subject-matter of a European patent may not extend as a result of amendments also includes what the specialist reader can unequivocally infer from the drawing originally filed. The Board would therefore in a hypothetical case, for example, have no misgivings from the point of view of Article 123(2) EPC about the claim being restricted by a feature according to which the pressure equalisation connection (30) was located near the top end of the conical surface (6), although in the description (column 2, lines 21 to 22) it says only "in the area of the conical surface"; this hypothetical feature would in fact be unequivocally inferable from Fig. 1.

8.3 In the present case, however, it is a matter of the, as it were, "negative" feature "with no internal fittings" (einbautenfrei) which is apparently only justified by the fact that Fig. 1 does not show any fittings in the interior. By its very nature, Fig. 1 serves only to give a schematic explanation of the principle of the subject-matter of the disputed patent and not to represent it in every detail. Therefore the mere absence of a feature in the representation given by Fig. 1 does not make it unequivocally inferable that such a feature is to be excluded. Thus even from the first documents as a whole the person skilled in the art is not able to infer the teaching of purposively not having any fittings in the interior. The feature in question may well be covered by the disclosure of the original documents but it cannot be inferred in an individualised form either from the original version of the description or claims or - unequivocally - from the drawing, so it is not specifically disclosed originally and may not therefore be incorporated in the claim.

8.4 Nor is a more favourable result for the appellants obtained if the aforementioned feature is interpreted as a disclaimer intended to exclude from protection hot-gas coolers which do have internal fittings.

8.4.1 According to established Board of Appeal case law, in cases where what is claimed in general overlaps with the state of the art it is permissible to exclude a special state of the art from the claimed invention by means of a disclaimer, even if the original documents give no (specific) basis for such an exclusion (cf. Decision T 04/80, "Polyether polyols/BAYER", OJ EPO 1982, 149; also, for example, T 433/86 dated 11 December 1987, unpublished, especially point 2).

8.4.2 In Decision T 313/86 dated 12 January 1988 (unpublished) the Board also stated that the same principles apply when a smaller partial area of the generally defined subject-matter of the invention is to be excluded not in view of the state of the art but because it does not solve the existing technical problem (sub-section 3.5, pages 8 to 9, of the aforementioned decision).

8.4.3 The practice referred to in the two preceding sub-sections is justified on the basis of the following considerations: The inventive teaching originally specifically disclosed in the application is not changed as a whole merely by delimiting it with respect to the state of the art or with respect to what has proved not to be functional; rather through the disclaimer (or through a "positive" wording leading to the same result), only the part of the teaching which the applicant cannot claim owing to lack of novelty or reproducibility is "excised" in the sense of a partial disclaimer. A considerable practical need for this exists. All that is necessary is to define appropriately what under the given circumstances is left of the inventive teaching originally disclosed that is still capable of being protected.

8.4.4 The present case differs fundamentally from this in that the insertion of a new feature is intended to remove the objection of lack of inventive step. The intention is therefore not to excise something from an inventive teaching originally disclosed but - as shown in section 5 above - to bestow inventive quality on a thoroughly obvious teaching by subsequently adding a feature which was not originally specifically disclosed. This would mean that the technical teaching contained in the original documents would be substantially modified. Because of the correlative between disclosure and protection of an invention, however, this can be no more permissible by way of a disclaimer than it would be in any other way. Expressed in simple terms, whereas a disclaimer can be used to make an inventive teaching which overlaps with the state of the art novel, it cannot make an obvious teaching inventive.

8.5 To sum up, the result is that the first subsidiary request has to fail, being inadmissible on formal grounds. Re the second subsidiary request ....


For these reasons, it is decided that:

1. The contested decision is set aside.

2. The appellants' main and first subsidiary requests are dismissed.

3. The case is remitted to the Opposition Division for continuation of the opposition proceedings on the basis of the second subsidiary request.

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