T 0198/01 11-03-2003

Reasons for the Decision

Main request

1. Novelty

1.1. The subject-matter of claim 1 is a screw having a lobate-socket head in which each lobe comprises two faces directed inwardly with respect to the axis of the screw. According to the claim these faces are "substantially parallel".

1.1.1. As set out in Article 84, first sentence in conjunction with Rule 29(1) EPC the purpose of patent claims is to define the matter for which protection is sought. In order to avoid an excessively restrictive interpretation of a claimed property when determining matter to be protected it is common practice when drafting the claims to qualify absolute properties by terms such as "substantially" such as not to exclude variations due to manufacturing tolerances. This does not change the basic teaching as regards the desired value of the property as disclosed in the description. In the present case the text in the description of the patent specification relating to the orientation of the two inwardly directed faces of the lobes defines the faces as "parallel" and this is consistent with further statements indicating that the faces are not radially orientated (column 5, lines 14 to 21). There is nothing in the patent specification which would lend support for the idea that the wording "substantially parallel" was ever intended to mean that the faces are intentionally not parallel. The Board therefore accepts the view of the appellant that the wording in question has the meaning of parallel within manufacturing tolerance.

1.1.2. Both D1 and D2 relate to cross-point screw heads having a lobate socket. According to D1 each lobe comprises side faces 18 which converge in both the outward (plan view Figure 2) and downward (elevational view Figure 9) directions at angles of 2° to 4°and 8° to 10° respectively. Although it is stated in page 4, lines 100, 101 that the latter angle may be varied according to requirements there is no teaching to remove the convergence. Similarly, whilst D2 contains no quantitative indication of the angular orientation of the faces 14 it is clearly stated in page 3, line 14 and shown in Figure 4 that they are mutually inclined.

1.1.3. According to the respondents the designation "substantially parallel" is unclear and so cannot be used to distinguish the subject-matter of the claim from the prior art. They refer in this respect to the Guidelines for examination at the EPO in which at C-III, 4.5a it is stated that "particular attention is required whenever the word "about" or similar terms such as "approximately" are used ... the word can only be permitted if its presence does not prevent the invention from being unambiguously distinguished from the prior art with respect to novelty and inventive step." However, as set out above, the Board considers that the meaning in the present case of "substantially parallel" is clear and leads to no ambiguity when comparing the subject-matter of claim 1 with that of the prior art.

1.2. The Board therefore concludes that the feature of present claim 1 that the inwardly directed faces of the lobes are "substantially parallel" renders the subject-matter of the claim novel with respect to the disclosures of both D1 and D2. The same conclusion applies to claims 2 to 5. Since neither of D1 and D2 is relevant for assessment of inventive step it is not necessary to consider whether any further features of claim 1 are novel in comparison with these documents.

1.3. Claim 6 concerns a lobate wrench which has a form corresponding to that of the socket according to claim 1. D1 and D2 both disclose screwdrivers which conform to the respective screw heads and which comprise side faces which are angled in a manner corresponding to the sockets. The subject-matter of claim 6 and therefore also claims 7 and 8 thus is novel with respect to the disclosures of D1 and D2.

2. Inventive step

2.1. The Board agrees with all parties that the closest prior art is that which is acknowledged with reference to Figure 2 in the patent specification. Lobate sockets were developed in order to increase the efficiency of applying torque from the wrench to the screw by virtue of the arrangement of the inwardly directed side faces of the lobes close to the radial direction whereby the applied force is closely aligned to the tangential direction. The prior art shown in Figure 2 is such a hexalobate socket having also intermediate faces between the lobes arranged as a regular hexagon. According to the description of the patent specification this prior art socket can if required be operated by a hexagonal wrench in engagement with the intermediate faces. However, two disadvantages arise in such a case. Firstly, the applied force is directed at an angle well removed from the tangential direction and so higher forces are required than with a hexalobate wrench in order to achieve a given torque. Secondly, the necessary clearance between the wrench and the intermediate faces permits a certain rotation of the wrench relative to the socket, leading to high stress and consequent deformation of the corner between a side face of a lobe and the adjacent intermediate face. This deformation may result in the movement of material of the socket wall into the lobe space and thereby prevent the subsequent insertion of a lobate wrench.

2.2. The subject-matter of present claim 1 differs from that of the prior art by the following features:

- each portion of the reaction surface included between two adjacent lobes comprises a pair of intersecting faces inclined to each other to form an angle concave towards the outside of the screw so that in the lobate-socket head one face of each intersecting pair thereof forms part of the side of a first regular polygon and the other face of each intersecting pair thereof forms part of the side of a second similar, regular polygon, said polygons being angularly rotated with respect to each other about the axis of the screw and being operative to constitute two different sets of reaction surfaces for a wrench of the same polygonal profile.

These features have the effect that the portion of the reaction surface engaged by the wrench is more closely aligned with the respective surface of the wrench whereby the surface stress is reduced, resulting in a lower risk of damage to the socket. Furthermore, the force transmitted from the wrench to the hexagonal faces of the socket is applied at an angle closer to the tangential direction, thereby achieving higher efficiency. The corresponding problem to be solved was to reduce the risk of damage to the lobate form whilst improving efficiency when using a polygonal wrench.

2.3. D7 relates to hexagonal bolt heads and correspondingly shaped socket wrenches. According to D7 there exists the problem that the use of a socket mounted on an impact wrench can lead to rusting of the bolt head as the result of damage to its corners caused by rotation of the head within the socket due to the clearance between them (see D7 Figure 4). D7 relates to a technical field close to that of lobate headed fasteners and the skilled person faced with the problem set out in 2.2 above would be aware of it. However, in the Board's view he would not consider D7 as offering a solution to his problem. The solution to the problem posed in D7 is to form the sides of the hexagon on the bolt head or in the wrench socket as two inclined portions. In the case where the modification is made to the wrench, the two inclined portions are arranged to subtend an obtuse angle directed away from the bolt axis (Figure 3). However, this modification serves to protect the external corners of the bolt head. If this teaching were notionally transposed to the closest prior art in the present case the corresponding external corners would be on the wrench. These corners are, however, not subject to damage, firstly because they are located within the space defined by the lobes and secondly because they would be of a material which would be less prone to damage than that of the screw head. It follows that D7 sets out to solve a problem different from that to be solved in the present case. Moreover, D7 relates only to a conventional hexagonal bolt head which in comparison with a lobate socket head is relatively inefficient at applying torque and does not concern itself with this aspect of the problem in the present case. The respondents argue that the problem to which present claim 1 relates merely concerns the interaction of two hexagonal shapes and that D7 teaches a solution to it. However, in the Board's view this oversimplifies the situation. The prior art socket of Figure 2 of the patent specification includes by virtue of its lobate form a particular design of hexagon which comprises inwardly directed corners on the walls of the socket which are prone to damage but which do not exist either in D7 or in a hexagonal socket in general and which, moreover, are employed on a screw head for use in high torque applications. Furthermore, contrary to the respondents' assertion, the teaching of D7 is restricted to the avoidance of damage to the external corners of a hexagonal bolt head. In the Board's view the skilled person would need to exercise inventive imagination to apply the specific teaching of D7 in respect of a conventional hexagonal bolt head to solve the problem posed in respect of the prior art in the present case which concerns a particular design of socket for use in high torque applications. Any other conclusion relies on an ex-post analysis.

2.4. The respondents essentially argue that only one of various possible combinations of dimensional tolerances of the socket defined in present claim 1 and a wrench for use therewith will result in the working surfaces becoming parallel, thereby reducing the stress level sufficiently to avoid damage. They conclude that the features of present claim 1 which are novel with respect to the closest prior art fail to solve the problem set and so, following T 72/95, are to be disregarded for assessment of inventive step. The Board cannot accept these arguments. Firstly, in comparison with the prior art arrangement, the modifications of the socket according to present claim 1 reduce misalignment between the respective faces of a hexagonal wrench and the socket and so lead to a reduction in stress on the corner of the lobe irrespective of the tolerance combination. Secondly, deformation of the corners between the respective pairs of inclined faces which, according to the respondents, would occur at the tolerance extreme when the wrench is the largest dimension which can enter the socket, would not be detrimental to the subsequent insertion of a lobate wrench because the damage would increase the space available for insertion of the lobate wrench. Finally, T 72/95 concerns itself not with failure to solve the problem set but technically non-functional or disadvantageous modifications (reasons 5.4) and so fails to support the respondents' case.

2.5. The Board therefore concludes that the subject-matter of present claim 1 is not rendered obvious by the cited prior art.

2.6. Claim 6 concerns a lobate wrench which has a form corresponding to that of the socket according to claim 1. The subject-matter of this claim is not rendered obvious by the cited prior art for the same reasons as for claim 1.

2.7. It follows that both claims 1 and 6 involve an inventive step (Article 56 EPC). The same conclusion applies to claims 2 to 5, 7 and 8.