T 0028/97 22-08-2000

1. The appeal is admissible.

2. Amendments

All the amendments to claim 1 are supported by the original disclosure and they have the effect of narrowing the scope of the claim and meet the requirements of Article 123(2) and (3) EPC, accordingly.

The expression "the support shoe means and the guide shoe means being structurally independent of each other" was inserted in order to make a distinction from the apparatus of Document D5, where the support shoe means and the guide shoe means are both mounted on a single arm and are, therefore, constrained to always move together in the vertical direction. The above expression is the correct way of expressing this difference and is clear. Moreover, although this feature is not explicitly supported by the description it is deducible from the drawing and the description of the construction and manner of operation of the apparatus. Furthermore, it merely reinforces the feature already in claim 1 as granted, that the guide shoe means bear directly on the roll shaft, are in slidable engagement therewith, and are operably movable independently of the support shoe means. This feature is, therefore, adequately supported by the original disclosure.

3. Novelty

None of the cited document discloses the combination of features of claim 1, so that the claimed apparatus is novel. This was not disputed by the Respondent at the oral proceedings before the Board.

4. Inventive step

4.1. The closest prior art

The opposed patent is concerned with a controlled deflection roll for use in the press and calender sections of a papermaking machine, wherein the roll shell is rotatably and positionably supported by vertically movable and hydraulically actuated support shoes on a stationary shaft, and by lateral guide shoes to stabilise the roll shell. The support shoes slide on parallel planar surfaces of a stationary roll shaft, and the support shoes and guide shoes are structurally independent of each other and have respective hydraulic means, whereby the supporting engagement of the support shoe means and the stabilizing forces of the guide shoe means are controlled independently of each other.

Document D1 discloses such a deflection roll and is the closest prior art, which was agreed by all parties.

4.2. The technical problem

This is set out in column 2, lines 6 to 28 of the opposed patent, and may be summarised as follows: The prior self-loading type of controlled deflection rolls cannot accommodate dimensional variations between the roll shell and stationary shaft due to manufacturing tolerances and temperature changes which affect different components in different degrees depending on the coefficient of thermal expansion of their materials. In some prior designs of self-loading rolls, the pressurized hydraulic fluid could escape more quickly from one stabilizing shoe, or at the interface of a stabilizing shoe and the supporting roll shaft at one location than at another. This could cause variations in the stabilizing pressures provided between the shaft and inner surface of the roll shell and thus permit the roll shell to shift its radial position laterally of the plane of the nip, or even to oscillate relative to the shaft.

4.3. The solution

The above technical problem is solved by the features of the characterising part of claim 1, which defines details of compensating means. This comprises a two-part guide shoe means including a guide shoe with a stabilising surface contacting the roll shell, and a compensating piston having a support surface slidably engaging the corresponding planar guide surface of the stationary roll shaft. A chamber between the guide shoe and compensating piston is in fluid communication with the guide shoe hydraulic means to apply hydraulic pressure to the guide shoe. This arrangement permits relative reciprocal movement between the support surface and the stabilizing surface of the guide shoe means to compensate for the dimensional variations between the roll shell and stationary shaft due to manufacturing tolerances and temperature changes.

4.4. However, the same solution is used in the apparatus of Document D5 for solving the same technical problem.

This Document is concerned with the problem of counteracting different forces acting on a roll shell. The passage commencing in column 2, at line 3 discusses the origin of these forces and refers to tangential forces (for example, column 2, lines 3 to 8), transverse forces (for example, column 2, lines 20 to 22), and tilting forces (for example column 2, lines 48 to 51). The description goes on to describe the effects of these forces, which is to deform the median portion of the roll shell if it has end bearings, and to shift the roll shell laterally if it has no end bearings. These forces may cause a bearing element within the roll shell to shift laterally or to tilt, see also column 8, lines 9 to 62. Starting at the bottom of column 2 prior art efforts to counteract the various forces are described and their drawbacks mentioned.

One of the objects of the invention is to resist these forces, see particularly the objects in column 3, lines 64 to 68 and column 4, lines 1 to 4 and 47 to 55, and the latter also mentions forces which "tend to shift portions of or the entire shell in a direction transversely of the direction of forces which urge the roll against the cooperating complementary roll". Thus one object is to counteract forces that tend to move the bearing element laterally and/or to tilt it.

Although the Document D5 does not mention that manufacturing tolerances and temperature changes may cause problems, these latter causes have, in fact, the same effect as the lateral forces in the apparatus of Document D5, viz. they may cause a lateral bending or displacement of the roll shell. The person skilled in the art, upon use of the apparatus of Document D1, would notice any such lateral bending or displacement of the roll shell, and would turn to Document D5 for a solution since this also treats the same lateral bending or displacement effect.

The problems of counteracting forces that deform the shell or tilt it are separate problems in Document D5, and one is not subordinate to the other. In particular, these problems are defined as separate objects in column 4, lines 1 to 4 and lines 25 to 28, respectively and are given equal importance in this document, and they may be solved independently of each other. The Appellant's argument that this document deals exclusively with problems caused by tangential forces is not valid, accordingly.

4.5. Document D5 discloses a deflection roll for use in engaging an opposing support, the roll including a stationary roll shaft 100 (Figure 9), support shoe means 101a mounted on the shaft, and guide shoe means 108, 109 for sliding movement on the corresponding guide surfaces of the roll shaft. The apparatus includes means for counteracting tilting forces acting on the roll shell, including the devices 108 and 109 mounted on arms 105 and 106, respectively, and convex portions 120, 121 on the roll shaft 100 that enable the arms to tilt.

Further compensating means for counteracting lateral forces acting on the roll shell permit relative reciprocal movement between the support surface of the roll shaft 100 and a stabilizing surface 117. These means are provided in the devices 108 and 109 and include a guide shoe 115 having the stabilizing surface 117 and a compensating piston 106 having the support surface slidably engaging the corresponding guide surface on the shaft 100 to permit the guide shoe means to move parallel to the nip plane. An interface gap between the guide shoe 115 and compensating piston 106 permits relative movement therebetween, and a chamber 111 between the guide shoe 115 and compensating piston 106 is in fluid communication with the guide shoe hydraulic means 124 to apply hydraulic pressure to the guide shoe 115.

This further compensating means is effectively the same solution as used in the patent in suit for counteracting the lateral forces.

4.6. In the apparatus of Document D5, however, the support shoe means and the guide shoe means are not structurally independent of each other since they are both mounted on a single arm. The reason for this is that this prior art apparatus is built to counteract both tilting forces as well as lateral forces tending to shift the shell, as stated in column 15, lines 44 to 52.

However, were the person skilled in the art only interested in the latter problem, as in the patent in suit, then he would build an apparatus that included only those features relevant to this problem. In the apparatus of Document D5 the features relevant to counteracting the tilting forces are the concave surfaces 120 and 121 and the mounting of the support shoe means 102 and the guide shoe means 108 and 109 on a single arm, which arrangement allows the whole structure to tilt and to counteract the applied tilting force. If only the roll shifting forces are important the features relevant to tilting could be dispensed with. The support shoe means and the guide shoe means would then not be mounted on a single arm so as to tilt, i.e they would become structurally independent of each other and the sliding surfaces would be truly parallel and in contact with each other, as in the Document D1.

This situation would follow automatically upon discarding the unwanted features relating to tilting forces, without any other modification of the apparatus, and is not the consequence of inventive activity.

4.7. The person skilled in the art, faced with the problem of counteracting only the lateral forces on a roll shell would, therefore, apply the solution given in Document D5 to the apparatus of Document D1, modified to ignore tilting forces, and would arrive at the claimed apparatus as an obvious development. Therefore, the deflection roll of claim 1 does not involve an inventive step.