T 0612/07 30-10-2008

Reasons for the Decision

1. Admissibility

The appeal is admissible.

2. Document D7a

2.1 This document was filed after the opposition period had expired. Thus it has to be considered as being late filed and its admittance into the proceedings is a matter of discretion under Article 114(2) EPC 1973.

In contrast to document D8 which was filed in due time, document D7a shows the combination of a cylinder head and a cylinder block in figure 7 which is also described in the description. This disclosure is particularly relevant for the additional features of introducing coolant into the head and venting the air through the second passage in claim 1 of auxiliary request 5. Moreover it shows that the interconnecting passages can be drilled through the outer surface of the head. Hence, document D7a is more relevant for the decision to be taken than document D8.

Therefore, the Board does not see any reason to suspect that the Opposition Division has wrongly exercised its discretion to admit document D7a into the proceedings under Article 114(2) EPC 1973.

3. Auxiliary request 1 - inventive step

3.1 Closest prior art

3.1.1 Document D7a is considered to represent the closest prior art and discloses a method for making a liquid cooled cylinder head for a multi-valve internal combustion engine. The head 4 has an outer surface and includes a first cooling cavity 12 and a second cooling cavity. This method comprises:

- machining a first opening through the outer surface of the head to form a first passage 13 intersecting the first and second cooling cavities 12 and 14, 18 to provide for liquid coolant communication between the first and second cooling cavities within the head, wherein said machining includes drilling a bore into the head to form the first opening 13 (see in particular page 9, lines 2 - 4 and figures 2 and 6); and

- closing the first opening 13 formed by said machining in the outer surface of the head with plug 22 (see page 9, lines 4 and 5).

Thus, the Board concludes that the features b) and c) of claim 1 are disclosed in this document.

3.1.2 According to the well-established case law of the Boards of Appeal, any prior art disclosure anticipates a claimed feature if it can be inferred directly and unequivocally from that disclosure, including information which for the skilled person is implicit in what is explicitly disclosed (see e.g. T 511/92 of 27 May 1993, point 2.2, not published in the Official Journal of the EPO). In this respect, the Board concurs with the findings in T 823/96 (mentioned in "Case Law of the Boards of Appeal of the European Patent Office", 5. English edition 2006, page 261) that implicit matter must be a clear and unambiguous consequence of what is explicitly mentioned for the skilled person.

(a) Document D7a also discloses the step of:

- machining a second opening as a second passage interconnecting the first and second cooling cavities 12 and 18. This second passage is the inclined passage that can be seen in figure 2 and will be referred to in the following as the "inclined passage".

The inclined passage is described on page 3 in lines 17 to 21 as "Verbindungsbohrungen", i.e. connecting bores. Already this term implies that it is made by drilling, i.e. by machining. Such understanding is confirmed by the statement on page 9, lines 2 - 4. Although superfluous for the cooling bores 13, it is observed that also the inlet 10 and the cooling channels 19 can, at least partially, be drilled. Moreover, the skilled person, on the basis of the disclosure of this document, would drill the inclined bore, because it is a "metering" bore (see page 3, line 19: "dosierten Kühlstrom") which requires minimised variations in dimensional accuracy.

It is not explicitly described how the inclined passage is drilled. However, only two alternatives exist, either from the left side or from the top (see figure 7). Since the first alternative does not require a long drill as the second alternative, the Board is convinced that the skilled person would drill the hole from the left side of the cylinder head. Thus, on the basis of the disclosure of document D7a, the skilled person would machine the second opening through the outer surface of the head to provide a second passage in the form of the inclined bore mentioned above as required by feature d) in claim 1. In figure 7 it can be seen that the outer surface through which the bore is drilled is closed by a plug. On the other hand, this cannot be seen in figure 2. However this must not mean that it is not drilled from the outer surface. It only means that the inclined passage shown in figure 2 has an axis not ending in the outer surface of the head that can be seen in figure 2.

Thus, the Board concludes that also features d) and e) of claim 1 are at least implicitly disclosed in document D7a.

(b) Moreover, it discloses that the first cooling cavity 12 defines a lower cooling chamber and the second cooling cavity 14, 18 defines an upper cooling chamber as can be seen for example in figures 2 and 4. The inclined passage is positioned generally above the first passage 13 and thus vents air when coolant is introduced. It can be seen in figures 2 and 7 that the diameter of the inclined passage is smaller than the diameter of the first passage 13. Since the throat area increases with the square of the bore diameter, it can be stated that the inclined passage has a second throat area smaller than the first throat area of the first passage.

Thus, the Board concludes that also the last features of claim 1 are known from document D7a.

(c) Finally, document D7a discloses the step of:

- casting the head, see page 2, line 32 "beim Gießen des Zylinderkopfs".

However, the disclosure of this document leaves doubts whether the inclined bore is made only by drilling, thus not casted at all, or casted and then finished by drilling.

Therefore, the Board concludes that feature a) is not directly and unequivocally disclosed in this document.

3.2 Derivation of the technical problem

3.2.1 It is established case law of the Boards of Appeal that an objective definition of the technical problem to be solved should normally start from the technical problem that is described in the patent in suit. Only if it turns out that an incorrect state of the art was used to define the technical problem or that the technical problem disclosed has in fact not been solved, can an inquiry be made as to which other technical problem objectively existed (see e.g. T 644/97 of 22 April 1999, point 2.3, not published in OJ EPO).

The technical problem to be solved is specified in paragraph [0004] of the patent specification and is based on a different document than the one mentioned above which is considered to represent the closest prior art. In the method disclosed therein, the first and second passages are at least finally machined, so that casting fins are not present in these passages. Thus, the problem specified in the patent was already solved, at least partially.

Therefore, it is necessary to reformulate the technical problem based on the method known from document D7a.

3.2.2 Distinguishing features

(a) In view of the foregoing, the subject-matter of claim 1 is distinguished from the known method by feature a) i.e. that the inclined passage is completely made by drilling and is not cast at all.

(b) This ensures that an intricate inner core for forming the inclined passage can be avoided so that the casting procedure is simplified but also the producability is improved (see patent specification, paragraphs [0003] and [0004].

3.2.3 Formulation of the problem

Thus, the technical problem to be solved may be seen in providing a method for making a liquid cooled cylinder head for a multi-valve internal combustion engine with improved producibility.

3.3 Obviousness of the solution

3.3.1 The inclined passage could be fabricated either by drilling it completely, or by casting it first and then finishing it by drilling.

3.3.2 In the judgement of the Board, to select either one of these ways does not involve inventive considerations:

(a) The skilled person is considered to be a graduate engineer with experience in the field of the construction and casting of combustion engines. He knows the advantages and disadvantages of these techniques. Casting is the technique of choice for the production of complex forms in an efficient and economical way. However, problems with the dimensional accuracy and intricate inner cores may be encountered. In contrast, with the machining of bores, a good dimensional accuracy can be achieved so that they may be used, for example, as metering bores. However, the expenditure of manufacture is higher.

(b) In view of this and since drilling the second passage is a necessary step of the method of document D7a, it is an obvious choice for the skilled person not to cast the inclined passage at all but to completely drill it for avoiding an intricate inner core for forming the inclined passage.

The casting of the cylinder head without any integral liquid cooling passages connecting the first and second cooling cavities within the head according to feature a) of claim 1 is thus obvious for the skilled person.

3.3.3 Appellant 1 argued that it was usual practice to cast interconnecting passages, and then to remove casting fins or artefacts by post-cast drilling. For that purpose two affidavits were filed to confirm the advances made by the claimed invention over the state of the art at the time.

It is not denied that the claimed method makes advances over the state of the art as stated in the two affidavits. However, this argument does not demonstrate the necessity of inventive considerations. When considering the state of the art it is necessary to consider all known practices, not only the most common practices or the practices carried out by Appellant 1. Therefore these two affidavits are not relevant for the assessment of inventive step.

Documents D2 to D7 demonstrate that the casting of interconnecting passages and successive removal of casting fins by post-cast drilling was not the only usual practice. In fact, documents D2 - D5 demonstrate that the bores are drilled.

3.3.4 In view of the foregoing, the Board concludes that the subject-matter of claim 1 of auxiliary request 1 does not involve an inventive step as required by Articles 52(1) and 56 EPC 1973. Consequently, auxiliary request 1 is not allowable.

4. Inventive step - auxiliary requests 2 - 4

4.1 Auxiliary request 2

4.1.1 It is the established case law of the Boards of Appeal that drawings are part of the disclosure of a patent document and that proportions can be taken from drawings, see for example T 748/91 (not published).

In the present case, it can be seen in the drawings that the diameter of the inclined passage is less than the diameter of the bores 13 and 19. Therefore (see above 3.1.2(b)), the inclined passage has a second throat area smaller than the first throat area of the first passage.

It is questionable, though, whether the skilled person discerns from the drawings that the throat area of the first passage has to be at least twice the throat area of the second passage as required by claim 1 although it is appreciated that the respective feature in claim 1 is rather general, only defining a minimum requirement.

4.1.2 With the throat area of the inclined passage, the coolant exchange is controlled (see page 3, line 19). Since no surprising effects are achieved by this feature, the Board concludes that it is for the skilled person a simple matter of workshop practice to dimension the relative sizes of the passages to achieve the required flow. Hence, the skilled person selects the throat areas according to the intended coolant exchange.

4.1.3 Thus, also the subject-matter of claim 1 of this request does not involve an inventive step as required by Articles 52(1) and 56 EPC 1973.

4.2 Auxiliary requests 3

4.2.1 The feature added in its claim 1 in comparison with auxiliary request 2, is known from document D7a. Figure 2 shows a generally horizontal first passage 13.

4.2.2 Thus, the subject-matter of claim 1 of this request does not involve an inventive step for the same reasons as set out above for claim 1 of auxiliary request 2.

4.3 Auxiliary request 4

4.3.1 With auxiliary request 2 it is claimed that the minimum throat area of the first passage is greater or equal ("at least") twice the minimum throat area of the second passage. With auxiliary request 4 it is claimed that the second throat area is smaller than half the first throat area, i.e. that the first throat area is greater than (but not equal) twice the minimum throat area of the second passage. Hence, the throat area ratio claimed with auxiliary request 4 is already covered by auxiliary request 2.

4.3.2 Thus, the subject-matter of claim 1 of this request does not involve an inventive step for the same reasons as set out above for claim 1 of auxiliary request 2.

4.4 Consequently, none of auxiliary requests 2-4 was allowable.

5. Auxiliary request 5 - Article 123(2)

Claim 1 requires that the first opening is closed before the second opening is machined and coolant is introduced into the head and vented through the second passage before the second opening is closed. However, original claim 8 discloses that the first and second openings are closed after the machining of the second opening has taken place. Since no other basis for the amendment in claim 1 of this request can be found or was indicated, it is concluded that claim 1 contravenes the requirements of Article 123(2) EPC 1973. Consequently, also auxiliary request 5 was not allowable.