T 1269/13 21-01-2019

1. Main Request

1.1 Document D1 can be considered the closest prior art document. That is not disputed.

1.2 Figure 1 and the corresponding description of document D1 disclose an electric motor 1 comprising the features of the preamble of claim 1. In particular, they disclose:

- a wound rotor 20 having a shaft 21, a rotor core 22, a commutator 24 and windings 23 wound about the rotor core and connected to the commutator;

- a stator 10 confronting the rotor;

- brush gear (see paragraph [0014]) connecting the commutator to motor terminals;

- first and second bearings 31, 30 for rotatably supporting the rotor 20; and

- a splash ring (i.e. an oil stopper) 27 fitted to the shaft 21 between the commutator 24 and the first bearing 31 for preventing oil migrating along the shaft 21 from the first bearing 31 reaching the commutator 24, the oil stopper being of metal (see paragraph [0020]) and having a boss (i.e. body portion) 28 for fixedly mounting to the shaft 21 and a flange (i.e. oil collecting portion) 29.

1.3 Considering the characterising features of claim 1, the oil stopper 27 of document D1 is fixed fast to the shaft 21 by an oil tight press fit (see paragraphs [0021] and [0024]). Furthermore, given that the application does not give any indication as to what might be considered to be a "high temperature" metal, the metal of the oil stopper can be considered to be a "high temperature metal" at least in so far as this feature can be interpreted.

1.4 The Board considers that document D1 does not disclose the features of claim 1 according to which the body portion of the oil stopper (splash ring):

(a) is adapted to function as a spacer;

(b) is arranged to make contact with an axial end face of the first bearing 31 as a thrust bearing; and

(c) thereby limits movement of the shaft 21 through the first bearing 31.

In this respect the Board does not share the examining division's view that it is unambiguously derivable from document D1 that if an extremely high axial load were to be applied to the shaft 21, the splash ring 27 would come into contact with the axial end face of the bearing 31 (cf. communication of 7 November 2012, pages 3 to 5). Document D1 does not describe what would happen in the event of the shaft moving axially. Figure 1 of D1 shows an end plate 43 that has a central projection aligned with the axial end face of the shaft 21 and it is at least plausible that if the shaft 21 were to move to the left as viewed in figure 1 the end of the shaft would contact the projection of the end plate before the splash ring 27 made contact with the axial end face of the bearing 31 (see figure 3). As to what might happen if an extremely high axial load were to be applied to the shaft, the Board sees this as a matter of speculation about an abnormal situation that D1 does not foresee. Hence, it is not directly and unambiguously derivable that when the shaft moves axially to the left there will be contact between the splash ring and the bearing, and thus it is not derivable that the splash ring functions as a spacer, acts as a thrust bearing and limits axial movement of the shaft.

1.5 As to the technical problem solved by the features (a), (b) and (c) identified above, several possibilities have been put forward, namely:

- to find an alternative to the thrust bearing in the end plate of D1 (cf. contested decision);

- to reduce the size of the motor (cf. paragraph [0005] of the application as published); and

- to improve the axial positioning of the rotor (cf. paragraph [0006] of the application as published).

The Board has reservations as to the appropriateness of the first of these possibilities; D1 does not state that the end plate acts as a thrust bearing and does not show the shaft bearing onto the end plate, so it is questionable whether seeking an alternative thrust bearing is an appropriate problem to be solved. As to the second possibility, again the Board has doubts as to its appropriateness, as it has not been demonstrated that the features (a) to (c) would necessarily lead to a smaller motor. Considering the third possibility, however, it is evident from feature (c) that the technical effect of the features (a) and (b) is to limit axial movement, i.e. improve axial positioning, of the shaft. For these reasons the Board considers that the problem of improving the axial positioning of the rotor is the most appropriate choice when considering inventive step. This was discussed in the oral proceedings before the Board and the appellant did not challenge this choice.

1.6 Faced with the problem of improving axial positioning of the D1 rotor the Board considers that it would be obvious for the skilled person to consult document D2 for the following reasons. Document D2 concerns electric motors of the same basic type as D1, i.e. motors with a pair of bushings supporting a rotating shaft on which a wound armature, a commutator and an oil throw washer are mounted. In the prior art acknowledged in the background of the invention of D2 the oil throw washer, a separate wear washer and a separate isolation washer are mounted between the armature and the second bushing. The oil throw washer is disposed in engagement with the commutator. The isolation washer is then interposed between the oil throw washer and the wear washer, the latter acting as a wear surface in contact with the second bearing (see column 1, lines 35 to 47). As an improvement over this arrangement D2 proposes to replace the three separate washers with a single-piece oil slinger that provides the same functions (cf. column 2, lines 39 to 50). In both the background arrangement and the inventive arrangement of D2 the contact between the wear surface and the bushing creates a thrust bearing that would position the shaft in the axial direction while allowing it to rotate. That would be evident to the skilled person with a basic knowledge of mechanical engineering. Thus the skilled person would take from document D2 the teaching that the rotor of a motor can be axially positioned using an oil slinger that is positioned between the commutator and the bushing and that forms a thrust bearing with motor bushing either directly or via the intermediary of a washer (cf. paragraph [0022], first sentence of the application as published).

1.7 Applying this knowledge to the motor of document D1 the Board considers that it would be an obvious matter for the skilled person to arrange any of the splash rings 27 disclosed in D1 such that they make contact with the axial face of the bushing 31 to form a thrust bearing (feature b). With such an arrangement the splash ring 27, which is fixed fast to the shaft, would function as a spacer (feature a) and limit movement of the shaft 21 through the bushing 31 (feature c). The Board considers that the skilled person would thus arrive at the subject-matter of claim 1 of the main request without involving an inventive step, Article 56 EPC.

1.8 The Board is not convinced by the appellant's argument that the skilled person would discard any thoughts of using the splash ring 27 of D1 as a thrust bearing due to a risk of the tip portion 28a of the boss 28 being pushed too far into the resinous portion of the commutator and causing damage to it.

Document D1 discloses in paragraph [0021] (see translation of D1 filed during the oral proceedings before the Board) that:

"The boss portion 28 has an insertion hole 28 b for inserting the rotation shaft 21 and the inner diameter dimension of the insertion hole 28 b is set slightly smaller than the outer diameter dimension of the rotation shaft 21".

Furthermore, in paragraph [0023] D1 discloses that:

"... the splash ring 27 is disposed such that a part of the boss portion 28 bites into the mold portion 25 of the commutator 24 when the splash ring 27 is fixed to the rotation shaft 21 by press fitting".

The Board considers that such a press-fitting operation would be able to fix the splash ring to the shaft sufficiently securely to withstand the axial force of a thrust bearing in at least some applications. Hence, at least in such applications there is no reason for the skilled person to consider that the splash ring might slip on the shaft and cause damage to the commutator.

1.9 For these reasons the Board could not accede to the appellant's main request.

2. First to Fifth Auxiliary Requests

2.1 The amendments made according to the first to fifth auxiliary requests are not apt to establish an inventive step for the reasons that follow.

2.2 In the line of reasoning set out above for the main request the axial movement of the shaft that would be limited by arranging the splash ring 27 of D1 so that it contacts the bushing is end play movement. Hence, the introduction of this feature in claim 1 of the first and fourth auxiliary requests is not apt to establish an inventive step.

2.3 In document D1 the bearings are sintered oil impregnated bearings, i.e. bushings (see paragraph [0016]). Hence, this feature of claim 1 of the second and fifth auxiliary requests is also not apt to establish an inventive step.

2.4 In the line of reasoning set out above for the main request the contact that would be established between the splash ring 27 of D1 and the bushing would be direct contact. Hence, the limitation to "direct" contact according to claim 1 of the third, fourth and fifth auxiliary requests is not apt to establish an inventive step.

2.5 The other amendments made according to the second and fifth auxiliary requests concern the deletion of "as a thrust bearing" and the amendments to read "adapted to make contact" and "to limit". None of these amendments restrict the claimed subject-matter.

2.6 For these reasons the Board could not accede to any of the appellant's first to fifth auxiliary requests.

3. Sixth Auxiliary Request

3.1 According to the appellant, the newly-introduced feature according to which the electric motor is "applied to an engine compartment of a vehicle" is to be understood in the sense that the motor is installed in the engine compartment of a vehicle, but that the claimed subject-matter does not include the engine compartment or the vehicle.

3.2 The Board considers that with this formulation the matter for which protection is sought is not clearly defined. The claim is formulated as a device claim (i.e. a motor comprising various technical features) but the feature that the motor is "applied to" another device (i.e. the engine compartment of a vehicle) can be interpreted either in the sense that the combination of two devices is claimed, or in the sense that it is the use of the motor in a particular environment that is claimed. With this ambiguity the category of claim is unclear and the requirements of Article 84 EPC are not met. Furthermore, it is not clear in what way the characteristics of the device would be limited by use in this particular application.

3.3 For these reasons the Board could not accede to the appellant's sixth auxiliary request.

4. Seventh Auxiliary Request

4.1 According to claim 1 of the seventh auxiliary request the metal of the oil stopper is brass. The appellant argued that this choice of metal is particularly advantageous as its coefficient of expansion is similar to that of steel, which would be the material of the shaft. This would be good for ensuring an oil-tight seal and would not be obvious.

4.2 The Board does not find these arguments convincing in terms of establishing an inventive step. Firstly, due to its low-friction properties, brass is one of the most commonly-used metals for sliding-contact bearings. With the splash ring of document D1 positioned to form a thrust bearing with the bushing, brass would for this reason be an obvious choice of metal for the splash ring. Secondly, there is no indication in the application that brass would be beneficial for the reason given and the coefficient of thermal expansion of brass (about 19 x 10**(-6) K**(-1)) is not particularly close to that of steel (about 13 x 10**(-6) K**(-1)). Hence, the Board is not convinced that this choice of metal would lead to any surprising effect.

4.3 Hence, the choice of brass does not involve an inventive step. For this reason the Board could not accede to the appellant's seventh auxiliary request.

5. Conclusion

In the absence of an allowable request the appeal had to be dismissed. In view of this finding the documents and observations submitted by the third party did not need to be considered.