T 1002/05 22-05-2007

1. Claim 1 of the patent on which the contested decision was based specified a plunging-type constant velocity ('CV') joint for use in a power transmission mechanism of an automobile and the opposition division found that this was not new with respect to a CV joint for use in a railway vehicle (E1). During the appeal procedure the appellant amended claim 1 which now specifies a power transmission mechanism of an automobile, comprising a plunging-type CV joint. By this amendment, which per se leads to no objections, the matter of novelty is resolved and it remains only to consider inventive step. In agreement with both parties the board has exercised its discretion in accordance with Article 111(1), second sentence, EPC and continued prosecution of the case.

Main request

2. Although the subject-matter of the claim is now a power transmission mechanism the matter of inventive step concerns modifications only to the plunging joint. A typical plunging double-offset joint, which conventionally comprises six balls, is known from D1 and it is accepted by the appellant that half shafts as set out in the preamble of claim 1 are known. D1 may be considered as representative of that state of the art.

2.1 Whilst the six-ball joint is conventional and, indeed, is the standard in mass-produced vehicles such as passenger cars, the idea of an eight-ball joint is known from D26 which states that "The number and size of the grooves and the balls therein are basically unrestricted … . Said number may be taken between 3 and 8 for practical purposes. However, 6 is recommended as the best practice for the average construction." D11 considers the factors affecting the capacity of a CV joint to transmit torque, one of which is "the number of balls (n), which is normally four or six, but on larger size joints eight or more balls may have to be employed." It follows that the skilled person wishing to provide a half shaft comprising the joint of D1 would consider increasing the number of balls to eight if the required torque capacity were sufficiently high.

2.2 Claim 1 specifies that the CV joint is comprised in a power transmission mechanism of an "automobile". In the appellant's view this term restricts the subject-matter of the claim to the high volume, cost sensitive category of motor vehicles characterised by passenger cars and light commercial vehicles for which the skilled person would not consider an eight-ball joint because the required torque capacity is not sufficiently high. The term "automobile" has a broad and somewhat vague meaning, as may be judged from the definitions of "self-propelled road vehicle designed to carry passengers" (Collins English Dictionary) and "self-propelled vehicle" (Oxford English Dictionary). The patent specification states that the CV joint described in the embodiment "can be widely utilized as a power transmission element in automobile, industrial machines, etc., and especially the same is preferable as a joint for a power transmission mechanism of automobile, for example, for connection of a drive shaft and a propeller shaft of automobile … ." It follows that neither the general meaning of the term nor the patent specification lends support to the appellant's view.

2.3 According to the appellant and as set out in the patent specification the problem solved by the subject-matter of claim 1 is to reduce the size of the joint whilst maintaining strength, load capacity and durability equivalent to the conventional six-ball joint. In other words, the problem was not to increase the capacity of the joint in accordance with the teachings of D11 and D26 but to provide a smaller joint having the same capacity. The appellant argues that the small joint size is reflected in claim 1 by the ratios r1 and r2.

2.3.1 As regards r1, however, the eight-ball CV joints of E1, E3 and E5 which are for use in railway vehicles all have values of r1 which fall within the claimed range. Indeed, the largest joint of the three, which is shown in E5, has a housing diameter of 315mm and a value of r1 of about 3.3. It follows that the ratio r1 cannot serve to distinguish the joint in claim 1 from one for which the skilled person would have adopted an eight-ball construction for the purpose of increasing capacity.

2.3.2 As regards r2 the description states the following:

"… it is better that the ratio r2 (=DOUTER/PCDSERR) of the outer diameter (DOUTER) of the outer joint member to the pitch circle diameter (PCDSERR) of serrations formed on an inner surface of the inner joint member is established to be 2.5 <= r2 <= 3.5."

It continues:

"The reason why 2.5 <= r2 <= 3.5 is established resides in that the pitch circle diameter (PCDSERR) of the serrations of the inner joint member can not be greatly changed in view of the strength of a shaft connecting thereto. Therefore, the figure of r2 depends mainly on the outer diameter (DOUTER) of the outer joint member. If r2<2.5 is established (mainly in a case where the outer diameter DOUTER is smaller), the thickness of the respective components (outer joint member, inner joint member, etc.) is made too thin, a worry arises in view of the strength. On the other hand, if r2>3.5 is established (mainly in a case where the outer diameter DOUTER is larger), a problem arises in use in view of the dimensional aspect, and the object of making compact can not be achieved. By establishing 2.5 <= r2 <= 3.5, the strength of the outer joint member, etc., and durability of the joints equivalent to or exceeding those of the comparative article (a plunging type constant velocity joint having six balls) can be obtained, and various requirements in use can be satisfied. Especially, by establishing 2.5 <= r2 < 3.1, there is an advantage with which the outer diameter thereof can be made compact with respect to the comparative article (a plunging type constant velocity joint having six balls) having the same nominal type.

Based on the above description, it is better that r2 is set to be 2.5 <= r2 <= 3.5, preferably 2.5 <= r2 < 3.1."

2.3.3 The teaching of the description therefore is that the joint is "compact with respect to the comparative article (a plunging type constant velocity joint having six balls) having the same nominal type" if r2 has a value of less than 3.1. In other words, the eight-ball joint is smaller than the six-ball joint if the ratio r2 is less than 3.1. However, the claimed range of r2 extends to 3.5. Moreover, the ratio r2 for every one of the joints of E1, E3 and E5 falls within the claimed range of 2.5 to 3.5. The appellant argues that the ratio r2 in each of E1, E3 and E5 is based on the size of the associated drive shafts and therefore cannot be compared with the claimed range based on a half shaft for an automobile. However, the size of the shaft is not specified in claim 1 and the term "automobile" fails to limit it to a certain range (see 2.2 above). It follows that also r2 cannot serve to characterise the joint in claim 1 as being smaller than one for which the skilled person would have adopted an eight-ball construction for the purpose of increasing capacity.

2.4 D25 is a publicity brochure issued by companies associated with the respondent and relating to development of a "new generation" of half shafts which are lighter and smaller than their forerunners. A chart indicates that the improved performance permits smaller joints to replace larger, earlier ones and the largest earlier size indicated is 97 mm housing diameter. The appellant argues that the fact that these half shafts still employed six-ball CV joints is evidence that the skilled person attempting to improve half shafts of up to this size would limit himself to developing the standard six-ball joint. However, as already set out above, the subject-matter of present claim 1 is not restricted to half shafts comprising CV joints of the size to which D25 relates. Moreover, D25 indicates that one of the development tasks was cost reduction. It is inevitable that cost will have played a certain role in the establishment of the six-ball joint as the industry standard and it cannot be excluded that it also will have influenced the decision to further develop the six-ball joint for the "new generation" of half shafts announced in D25. D25 therefore cannot serve as an indicator of the actions of the skilled person when unfettered by commercial limitations.

3. On the basis of the foregoing the board finds that the subject-matter of claim 1 does not involve an inventive step (Article 56 EPC) and the present request must be refused.

Auxiliary request

4. Claim 1 according to this request contains the additional features relating to the clearance between the balls and their pockets in the cage and the axial clearance between the inner spherical surface of the cage and the outer spherical surface of the inner joint member. D22 discloses a CV joint which, analogously to D1 in respect of the main request (see point 2 above), may be considered as representative of a half shaft as defined in the preamble of the claim but which, as accepted by the appellant, furthermore comprises the additional features of present claim 1. D22 thereby discloses state of the art which is closer than D1 to the subject-matter of present claim 1 and which forms the closest state of the art for consideration of inventive step.

4.1 Since the additional features according to this request are already known from the closest state of the art D22 the subject-matter of present claim 1 differs therefrom by the same features as for claim 1 of the main request in comparison with its closest state of the art D1. Since the additional features according to this request are already known from the closest state of the art it need not be considered whether or not they combine or are merely juxtaposed with those of the characterising portion of claim 1 according to the main request. It suffices to establish that the additional features do not serve any better than those already considered in respect of the main request to define the subject-matter of the claim as being limited to a particular range of capacity. The matter of inventive step therefore comes down to essentially the same considerations as for the main request, namely whether it would be obvious for the skilled person starting from a power transmission mechanism of an automobile incorporating a CV joint in accordance with D22 to modify it in such a way as to provide eight balls and arrive at the defined ratios r1 and r2. For the same reasons as are set out in respect of the main request this would be an obvious act.

5. The conclusion is therefore the same as for the main request, that the subject-matter of the claim does not involve an inventive step (Article 56 EPC).