Roller with controllable sag

Details Roller with controllable sag Roller with controllable sag

1997-12-16

1999-05-18

Hughes, S. Thomas

Roll or roller

Rotatable relative to supporting shaft

492 46, 492 7, B21B27/00

Patent

active

059046422

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a roller of the type described in the preamble to Patent claim 1.
In rollers of this kind, there are usually 20 to 80 supporting element distributed along the length of the roller in a row, usually on the side of the roller gap; these are in the form of a type of cylinder/piston unit and abut against the inside periphery of the hollow roller, bearing pockets being formed in the contact surface, and these exert hydrostatic pressure against the inside periphery of the hollow roller. Pressurizing fluid flows constantly from these bearing pockets over the edge of the bearing pockets so that a load-bearing film of fluid is maintained, and this prevents metallic contact between the supporting element and the inside periphery of the hollow roller.
During operation, these supporting elements must be supplied with at least one fluid pressurizing medium. In most cases, this is a pressurizing fluid, in particular a hydraulic oil that, under some circumstances, also serves as a thermal transfer medium. Gas-operated, in particular air-operated, supporting elements can also be used.
Rollers of this kind are described, for example, in the following documents: U.S. Pat. No. 3,119,324, DE 22 30 139 B2, U.S. Pat. No. 2,395,915, DE 36 40 902 C2, DE 38 20 974 C2.
In many instances, the supporting elements are combined into a number of groups that are subjected to a common pressure by the fluid pressurizing medium and thus require only a single supply line. The smaller the groups, the greater the number of supply lines there will have to be. If, in an extreme case, each supporting element is to be acted upon separately in order to provide for particularly delicate adjustment of the line force, there will have to be at least as many supply lines as there are supporting elements. Since the supply lines cannot be smaller than a minimum cross section in view of the fact that in order to operate properly, and in particular to maintain the separating film of liquid, each supporting element requires a specific throughput, delivering the pressurizing medium to the individual supporting elements or groups of element is problematic because only a very limited cross-section will be available. The crosshead, which flexes under the line load imposed by the line force in the interior of the hollow roller, may only be weakened by an insignificant amount with respect to its load bearing capacity if the roller is to generate a high level of line pressure.
A first possibility for supplying the supporting element is described in DE 24 07 510 B2; in this, a control valve is provided at the position of each supporting element and this generates an operating pressure that is matched to each supporting element by a reduction process, using fluid that is delivered through a central, main channel. Each valve is remotely controlled, for example, pneumatically. This means that, once again, a correspondingly large number of remote operating lines must be used. The arrangement of a plurality of valves is costly and can also cause considerable weakening of the cross section. However, it is also a disadvantage that the valves are located within the roller, so that in the event of a breakdown not only one valve, but rather the whole roller has to be dismantled.
In other embodiment, the valve system is arranged outside the roller. As described in DE 26 57 061 C2 and DE 25 50 270 C3, one or a plurality of feed lines is configured in that adjustable bulkheads are incorporated in the longitudinal recesses of the cross head, the area between the individual bulkheads being supplied with pressure medium through corresponding bores in the crosshead or by way of concentric tubing systems. This is then apportioned to the group of supporting elements whose feed lines open out in the area between the particular bulkheads in the longitudinal recess. Such arrangements are not, however, suitable for larger numbers of supporting elements or groups of such elements that are to be supplied separately, as is the case, for example, with the roll

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