T 0167/08 13-10-2009

1. An aircraft engine typically is supported on a pylon beneath a wing and is covered in a nacelle which provides a streamlined outer surface and houses also other components. A nacelle comprises an inlet at the forward end and a series of cowls which may be opened in order to provide access for maintenance. A fan cowl may be adjacent and of similar diameter to the inlet to provide a by-pass flow of air whilst a core cowl towards the rear of the engine is somewhat smaller diameter and may be opened for access to the gas generator. A fan cowl conventionally has two C-section portions each hinged along an upper, horizontal edge for pivoting upwardly into an open position. In the patent specification it is explained that such fan cowls can be large, bulky and heavy, are liable to wind damage whilst open and that their height above the ground may render them difficult to reach whilst power operated mechanisms intended to overcome these problems are heavy. The patent relates to an engine having cowls that are relatively easy to open and close. Only inventive step of the subject-matter of claim 1 is at issue.

2. Claim 1 relates to an engine having a cowl which moves forwards during opening. It does not specify a fan cowl. However, in as far as the problem which is addressed in the patent specification arises in fan cowls they do form the closest state of the art for judging inventive step. Such a cowl is disclosed in D7 and acknowledged in the patent specification paragraph [0003] and is essentially as described under point 1 above.

3. The appellant's first attack on inventive step nevertheless is based on the disclosure of D1 alone. In accordance with the appellant's argumentation the cowl in question would be a core cowl and the only feature distinguishing the subject-matter of claim 1 from the disclosure of D1 would be the direction of longitudinal movement, namely forwards instead of rearwards. D1 relates to an aircraft engine mounted on a pylon beneath a wing. More particularly, it relates to a divided core cowl which in its closed position is partly within the rearmost portion of an outer cowl. Each half of the core cowl is mounted on a parallelogram linkage and is opened in two stages. In a first stage the linkage moves the respective half of the core cowl both radially away from the engine and rearwards beyond the rear end of the outer cowl. In the second stage each respective half of the core cowl pivots upwardly around an upper, horizontal hinge. The essential teaching of D1 therefore is that before each half of the core cowl can be pivoted upwardly it must be moved rearwardly out of the outer cowl. If the rearward movement were to be reversed in the way suggested by the appellant the core cowl would remain within the confines of the outer cowl and so could not be opened by upward pivoting. Under these circumstances it is evident that the skilled person has no choice in respect of the direction of longitudinal movement of the core cowl, it must be rearwards as disclosed in D1.

4. In its first alternative approach the appellant begins from the closest state of the art as set out under point 2 above and argues that combining that with the teaching of D1 would result in the subject-matter of claim 1 in an obvious manner.

4.1 D1 refers in its introduction to earlier state-of-the-art documents. One such document (US-A-4 585 189) relates to a cowl which covers not only the gas generator but extends forwardly to form also a fan cowl, thereby offering access to the whole of the engine. The cowl is in the form of two C-section portions supported on horizontal hinges. D1 comments that that cowl is problematic because it is large and necessitates hydraulic assistance for its opening. It is the similarity between that problem and the one facing the skilled person in the present case which in the appellant's view would draw the skilled person's attention to the teaching of D1. The board disagrees with that view, however. The teaching of D1 relates to core cowls which by their very nature are of a smaller diameter than fan cowls. D1 includes reference to fan cowls only because it explains that the earlier state of the art had proposed a core cowl which became undesirably large as the result of being extended to incorporate a fan cowl. That is not tantamount to a statement regarding the size and bulk of the earlier cowl in its capacity as a fan cowl. The skilled person wishing to solve the problem arising with fan cowls therefore would see no cause to study the detailed teaching of D1.

4.2 Even if the skilled person seeking to solve the problem arising with fan cowls were to further consider D1 he would not find a solution to it. As set out above, that problem arises in fan cowls which pivot about an upper, horizontal hinge. The teaching of D1 does not address that problem and, indeed, during the second stage of opening the core cowl also pivots about an upper, horizontal hinge. Since the pivoting movement is still present in accordance with D1 there is no solution to the problem which arises from that very feature. Moreover, the parallelogram linkage in accordance with D1 is provided only in order to remove the core cowl from within the confines of the outer cowl and thereby to enable the pivoting movement. No such restriction existed in the closest state of the art and the teaching of D1 therefore would offer no benefit to the skilled person charged with solving the set problem.

5. In a further approach the appellant argues that the skilled person would apply his general technical knowledge as particularly exemplified by D2 to the solution of the set problem. D2 relates to an aircraft passenger door which is mounted on a parallelogram linkage such that when it opens it moves both laterally and longitudinally forwards. Whilst the appellant argues with reference to D3 to D6 that parallelogram linkages are well known it considers that D2 is a particularly relevant example of the art because it is in a neighbouring technical field, the door and an engine cowl both belonging to an aircraft and sharing the feature of being panels in a curved surface.

5.1 Neighbouring fields are ones so closely related that the skilled person seeking a solution to a given problem in one would take into account developments in the other, see decision T 176/84 (OJ EPO 1986, 50). This is not applicable to the technical fields of aircraft engine cowls and aircraft passenger doors because they concern components which fulfil widely differing functions under largely different conditions. Moreover, the two components are structurally very different and the only commonality is in closing a curved surface. The skilled person therefore would not be expected to become aware of D2 and its detailed content need not be considered further.

5.2 However, the board does consider that a parallelogram linkage per se does belong to the general technical knowledge of the skilled person. That knowledge would, furthermore, extend to the linkage's particular characteristic, namely permitting parallel relative movement between two elements. However, in moving from the closest state of the art to the subject-matter of claim 1 the skilled person would need to do more than simply replace the existing hinge by the known linkage. He would need to appreciate that the problem could be solved by articulating the cowl in a different manner and in a different direction, an act extending beyond anything to which he would be motivated by his fund of knowledge.

6. In the appellant's final approach D1 is once again regarded as representing the closest state of the art and a combination of that with the disclosure of D2 is argued to render the subject-matter of claim 1 obvious. However, as already set out under point 2 above the disclosure of D1 is such that the skilled person would not consider reversing the direction of longitudinal movement. Moreover, as set out under point 4.1 above the person skilled in the art of engine cowls would not be aware of D2, by virtue of their different technical fields. Even if he were to become aware of D2 and moreover consider it relevant to improving the teaching of D1 there still would be no motivation to remove the upward pivoting of the cowl in D1.

7. On the basis of the foregoing the board finds that the subject-matter of claim 1 cannot be derived in an obvious manner and therefore involves an inventive step (Article 56 EPC 1973). Since claims 2 to 12 contain all features of claim 1 they also define subject-matter which involves an inventive step.