T 0770/89 16-10-1991

I. European patent No. 0 026 903 comprising three claims was granted to the Respondent on 2 January 1986 on the basis of European patent application No. 80 105 897.5 filed on 29 September 1980 claiming priority of 4 October 1979.

Claim 1 as granted reads as follows:

"1. A rolling mill comprising a pair of work rolls (1,2) brought into contact with a material (3) to be rolled, a pair of intermediate rolls (13, 14) positioned vertically outwardly of the respective work rolls to contact therewith, a pair of backup rolls (28,29) for supporting the respective intermediate rolls, the diameters of the work rolls being smaller than the diameters of the intermediate rolls and the diameters of the intermediate rolls being smaller than the diameters of the backup rolls, wherein the following four features for influencing the shape of the rolled material are realized:

a) the diameters of the work rolls (1,2) are smaller than 25% of the maximum width of the rolled material (3);

b) means (17,26) for axially displacing the intermediate rolls (13,14) to position the end portions of the roll barrel thereof on or near vertical lateral end surfaces of the rolled material (3);

c) means (11,12) for applying a roll bending to the work rolls (1,2); and

d) bending means acting on the intermediate rolls (13,14) are provided."

II. An opposition was filed by the Appellant (Opponent) on 30 September 1986 and by a decision of 16 October 1989, the Opposition Division maintained the patent in an amended form according to a second auxiliary request. The main claim accepted by the Opposition Division corresponds to the granted Claim 1 amended with an additional feature e) which reads as follows:

"e) the two metal chocks (15,15';16) supporting each of the intermediate rolls (13,14) are disposed inside of a block (17,18), which is movable disposed on the roll housing (6) and engaged with the bending means (19 to 22)."

III. The Appellant lodged an appeal on 8 December 1989 and, simultaneously, paid the relevant fee. The written Statement setting out the Grounds of Appeal was filed on 20 February 1990.

The Appellant requested the revocation of the patent in its amended form on the ground of lack of an inventive step of its subject-matter mainly in comparison with the disclosures of the following documents considered in combination:

D1 : BR-A-7 608 285 (corresponding to CA-A-1 101 702)

D2 : US-A-3 818 743

D6 : JP-B-50 12385 and also in view of document DE-A-2 335 809 cited in the search report.

IV. In his Statement of Grounds the Appellant argued mainly the following:

- the addition of feature e) to Claim 1 as granted is not admissible because it has already been claimed in a divisional application;

- the possibility of displacing axially the intermediate rolls during the rolling operation, i.e. under the rolling load, cannot be taken into consideration in favour of the invention because this feature is not disclosed in the application as originally filed;

- D2 already discloses the possibility of displacing the intermediate rolls during the rolling operation;

- at the priority date, it was common knowledge for the skilled man to combine bending of the work rolls with axially displacing the backing rolls of said work rolls in order to compensate deformations;

- feature e) just specifies the means for axially displacing the rolls stated under b); and,

- D6 discloses such means and gives a hint for using them on a rolling mill according to D2.

V. In his reply of 30 August 1990 the Respondent (Patentee) requested the maintenance of the patent as granted and auxiliarily the maintenance of the patent as accepted by the Opposition Division.

He argued that when work rolls of a small diameter are adopted on rolling mills according to either document D2 or D3 (DE-A-2 752 750), a flat shape of the rolled material cannot be realised, composite elongation such as quarter buckle occurs and it is impossible to correct positively the composite control whereas the mill according to Claim 1 as granted enables such a control.

Concerning the rolling mill according to Claim 1 of the auxiliary request, the Respondent contended that it comprises a structure suitable for effecting composite control following the variation in factors during the rolling operation. According to the Respondent, the rolling mill known from D6 would not allow the use of small diameter work rolls and would not permit to effect shape control following the thermal crown.

VI. In a communication sent to the parties for preparing the requested oral proceedings, the Board expressed a provisional negative opinion with regard to the patentability of the main claim of the impugned patent either as granted or as maintained by the Opposition Division, in the light of the teaching of document D2 taken in combination with the disclosure of respectively documents D3 or D6.

VII. With his reply dated 30 September 1991, the Respondent filed three new auxiliary requests respectively based on the three following amended claims:

A. Claim 1 according to auxiliary request III:

It corresponds to Claim 1 as granted amended to read additionally after feature c):

"d) bending means (19 to 22) acting on the intermediate rolls (13,14) are provided for applying an increased bending or a decreased bending to the intermediate rolls (13,14); e) the two metal chocks (15,15';16) supporting each of the intermediate rolls (13,14) are disposed inside of a block (17,18), which is engaged with the bending means (19 to 22) and movable disposed on the roll housing (6) under the action of an hydraulic cylinder (26); and

f) mechanisms (23,24) are provided for connecting and disconnecting the metal chocks (15,15';16) of the intermediate rolls (13,14) with the movable blocks (17,18)."

B. Claim 1 according to auxiliary request IV:

It corresponds to Claim 1 according to request III with features c) and d) amended as follows:

"c) means (11,12) for applying a roll bending to the work rolls (1,2) for controlling the shape of the lateral end portions of the rolled material (3); d) bending means (19 to 22) acting on the intermediate rolls (13,14) are provided for applying an increased bending or a decreased bending to the intermediate rolls (13,14) and are controlled in interlocking relation to the control of the work roll bending and in conformity with the rolling load."

C. Claim 1 according to auxiliary request V:

It corresponds to Claim 1 according to request IV amended so as to incorporate as feature g) the content of Claim 2 as granted i.e.:

"g) the work rolls (1,2) are supported by metal chocks (4,5) including bearings (50) for mainly supporting radial loads and mechanisms (54 to 60) for directly supporting the work rolls (1,2) to support thrust loads acting on the work rolls."

Moreover, the Respondent also filed three technical articles (Enclosures I to III) to illustrate the state of the art at the priority date and the use of the invention and he contended mainly that:

- it was not obvious to combine the teachings of D2 and D3;

- it appears from Claim 8 of the European patent application as originally filed that the axial movements of the intermediate rolls can be performed during the rolling operation;

- there is no hint in D6 that the described device for moving axially the rolls can be employed in a mill according to D2, and, even if it would, the idea of bending the displaceable intermediate rolls would not be present; and,

- even more, the feature of using thin and thus flexible work rolls in combination with the other three control parameters would also not be envisaged.

VIII. The day before the oral proceedings, the Respondent filed a new Claim 1 to be considered as the basis for auxiliary request number 1; this new auxiliary main claim corresponds to Claim 1 as granted amended to read additionally after feature b):

"c) means (11,12) for applying a roll bending to the work rolls (1,2) for controlling the shape of the lateral end portions of the rolled material (3); d) bending means (19 to 22) acting on the intermediate rolls (13,14) are provided for applying an increased bending or a decreased bending to the intermediate rolls (13,14) and are controlled in interlocking relation to the control of the work roll bending and in conformity with the rolling load; so that the shape or crown of the rolled material can be controlled by controlling the axial movement of the intermediate rolls, work roll bending action and intermediate roll bending action in combination in such a manner that control of the shape or crown of the rolled material across the width thereof is mainly effected by the intermediate roll bending and control of the edge portions of the rolled material is mainly effected by work roll bending."

IX. The oral proceedings were held on 16 October 1991 and the discussion took place in German by common consent of the parties.

A. The Appellant requested first that the last petition of the Respondent filed the day before as first auxiliary request be rejected since:

- it was filed much too late;

- the protection conferred by the corresponding Claim 1 is extended in comparison with the one of the claim accepted by the Opposition Division because feature e) has been omitted;

- the new paragraph added at the end of the claim does not bring anything more and results already from the combination of the features described in Claim 1 as granted.

The Appellant also requested that the decision under appeal be set aside and that the impugned patent, whether as granted or in its various auxiliary amended forms be revoked on the ground of lack of an inventive step of its subject-matter. To support his request, the Appellant contended essentially the following with regard to Claim 1 according to:

A1. The main request (as granted):

- At the priority date, the skilled technician knew exactly all of the limited number of possibilities he had at his disposal to control the shape of the rolled material, i.e. rigidity and profile of the rolls, roll bending, axial moving, cooling etc. ... (cf. D3, Figure 5 and pages 17, 18 and 20), and according to the needs, he would have combined these different parameters at will.

- Since D2 already describes a mill provided with small diameter work rolls (15/18% of the length of the rolling surface), benders for these rolls and also means for axially shifting the intermediate rolls, no inventive step should be acknowledged in the simple fact of providing additional bending means to said intermediate rolls to obtain a foreseeable effect on the rolled material.

- Displacing the rolls during the rolling operation, i.e. under load, is disclosed neither in Claim 1 of the impugned patent nor in its description.

A2. Auxiliary request II (as accepted by the Opposition Division):

The Appellant referred to his written Statement of Grounds (cf. paragraph IV above).

A3. Auxiliary request III:

To increase or decrease the bending of intermediate rolls according to feature d) is known per se from D3. As far as amended feature e) and new feature f) are concerned, D1 discloses in Figure 5 hydraulic cylinders and mechanisms provided for the same purpose as according to the invention.

A4. Auxiliary request IV:

To bend the work rolls according to feature c) for controlling the edges of the strip to be rolled is common use as disclosed in D2 and D3. The measure according to amended feature d) is also known per se from D3 and to control the forces in combination stands to reason for the skilled man.

A5. Auxiliary request V:

During rolling, the rolls are submitted to a "screw effect"; consequently radial and axial supports cannot be avoided, as represented in Figure 2 of D2.

B. In reply, the Respondent requested that the appeal be dismissed and the patent be maintained as granted or in an amended form according to one of the auxiliary requests.

B1. With regard to the main request:

He maintained that since D2 and D3 teach completely different solutions (displaceable rolls or rolls of different lengths) to solve the same problem of edge waves on a rolled strip, the skilled technician would never envisage to combine the opposite teachings of these documents, more especially as no hint can be found in any of the anticipations so to do.

The Respondent argued further that neither D2 nor D3 would recommend the use of flexible work rolls on six-high rolling mills and that D2 teaches that the work rolls must have a high rigidity in order to influence the shape of the central portion of the rolled strip and to avoid the "quarter buckles".

In his opinion, the essential teaching of D3 should be the use of non-displaceable intermediate rolls having a working surface longer than that of the backup-rolls but shorter than the work rolls as shown in Figure 4. Consequently, among the six embodiments described in D3, the skilled man would have no reason to consider the one represented in Figure 5 rather than the one shown in Figure 4. Moreover, D3 shows at the end of page 7 that the heating effect on the rolls was not correctly understood, unlike in the present invention which has been immediately taken up in industry.

B2. With regard to auxiliary request II:

The Respondent contended that in the German translation of D6, the passage of page 2 relating to the six-high mill does not make sense and he supplied the Board with a new translation in English.

According to the Respondent the Japanese document concerns only a four-high mill and no indication is given of the use of small diameter work rolls.

Even the percentages cited in D2 (15-18%) could not lead the skilled person to the use of rolls having diameters as small as according to the invention since D2 refers to percentages of the length of the rolling surface of the rolls that is generally larger than the maximum width of the rolled material.

According to the Patentee, there is no incentive for combining D6 with D2 and using flexible work rolls; and new feature e) added to Claim 1 as granted specifies the means for allowing the intermediate rolls to move under load which appears from Claim 8 of the application as originally filed and such a feature cannot be found in any anticipation.

B3. With regard to auxiliary requests III, IV and V:

The Respondent argued that nowhere could be found a mechanism that would be strong enough to move axially the rolls and D1 and D6 were concerned with something else. Also, there was no disclosure in the state of the art of such a reciprocal effect between the bending of the rolls and the rolling load, as in accordance with the invention.

As far as the thrust supporting mechanisms referred to in feature g) of auxiliary request V are concerned, it should be considered that the invention relates to a special case where very high thrust loads are involved, such a case being not considered on a six-high mill of the state of the art.

At the end of the oral proceedings both parties maintained their requests unamended.