GB2092928A - Rolling mill roll - Google Patents

Abstract

The roll is formed by a fixed arbor (12) and a sleeve (13) which is rotatably supported on the arbor by a film of liquid under pressure. The pressure of the liquid is either hydrodynamically generated or liquid under pressure is supplied through passages (20) to hydrostatic pads (22) spaced along the roll barrel. By controlling the pressure supplied to individual pads (22) the camber of the roll may be varied in order to improve the shape of the material being rolled. <IMAGE>

Description

SPECIFICATION Roll This invention relates to rolling mill rolls, and particularly, but not exclusively, to back-up rolls for rolling mills.

Back-up rolls, like other rolls, are usually single castings with integral roll necks by which the rolls are supported in bearing in the roll housings.

Hydrodynamic oil film bearings or rolling element bearings are employed as the roll neck bearings.

In operation, the back-up rolls of a rolling mill, even when of massive construction, tend to bow under the action of the rolling load, with resulting transverse non-uniformity of thickness of the material being rolled. Many expedients have been suggested and tried to alleviate that problem, including cambering the rolls barrels, thermal cambering, supporting the rolls by castors spaced along the barrel, and applying bending moments to the roll ends. All such expedients have however suffered from various objections, either because of the resulting complexity and expense or because of inability to deal properly with changes in the rolling conditions. In particular, none has adequately provided an inexpensive means for varying the camber of the roll along the barrel to improve the profile of the material being rolled.

Each of British published patent applications Nos.

2002494A and 2018949A discloses a roll constituted by a normally stationary arbor and a sleeve which surrounds the arbor with a substantial space and which is supported at each end on the arbor through roller bearings. The arbor further carries a number of hydraulic rams spaced along its length and adapted to be forced against the internal surface of the sleeve. It is claimed that by varying the pressure of the liquid supplied to the rams the crown of the composite roll can be varied as required.

The construction of the rolls described in the above mentioned specifications is extremely complicated and the rolls are unable to stand up to the conditions encountered in the rolling of steel strip and plate. Further, the engagement of the rams with the inner surface of the sleeve is liable to impede the free rotation of the sleeve.

In the present invention, an arbor and rotatable sleeve is again employed, but the sleeve is supported by the arbor solely through a film of liquid under pressure, which may be created hydrostatically, hydrodynamically or partially hydrostatically and partially hydrodynamically.

The present invention thus provides a rolling mill roll comprising an arbor adapted to be supported at its ends, a sleeve or sequence of sleeves which closely surround the arbor over the effective roll barrel length, and means for supplying lubricant under pressure between the arbor and the sleeve or sleeves so that, in use, the sleeve or sequence of sleeves is supported solely on a film of liquid under pressure.

Preferably, means are provided for varying the thickness and/or pressure of the film along the effective barrel length in order to vary the roll camber to counteract bending of the roll in use and/or to compensate for shape irregularities in the material being rolled. Those means may comprise passages in the arbor enabling lubricant to be fed to, or bled from, the oil film at selected locations along the barrel.

The invention will be more readily understood by way of example, from the following description of back-up rolls for a metal rolling mill. In the accompanying drawings, Figures 1, 2 and 3 are respectively an axial section through a roll having a hydrostatically supported roll sleeve, an end view of the roll, and a section on the line Ill-Ill of Figure 1, and Figures 4, Sand 6 are similar views of a roll having a hydrodynamically supported roll sleeve, Figure 6 being a section on the line VI-VI of Figure 4.

The back-up roll illustrated in Figures 1 to 3 consists essentially of a fixed arbor 12 and a rotary sleeve 13 mounted on the central portion of the arbor. The sleeve 13 is carried on the arbor 12 by means of an oil film bearing extending the full barrel length of the sleeve and constituting the sole support of the sleeve.

The arbor 12 has a neck 14 at each end by which the arbor is secured against rotation in the roll housings, each neck having parallel flats 15 for that purpose. Between the necks 14, the arbor has a barrel 16 on which the sleeve 13 is received with a clearance to accommodate the oil film. The sleeve 13 is retained on the barrel 16 by means of thrust collars 17 which are bolted to the sleeve 13 and which carry annular seals 18 engaging against the arbor.

A number of bores 20 extends from the arbor ends, where in use they are connected to valved supply lines leading from a source of oil under pressure. The bores 20 lie on different radii and each is connected to a cross bore 21 leading to a pressure pad 22 on the barrel 16 of the arbor. Figure 2 includes a schematic showing of the upper and lower work rolls 23 and 24 of a mill in which the composite roll 12, 13 is employed as the upper back-up roll. When the roll 12, 13 is so used, the pressure pads 22 are spaced along a line which is parallel to the axis and which is at the lowermost point of the roll adjacent to the line of contact between the sleeve 13 and the upper work roll 23.

Oil under pressure is continuously supplied to the bores 20 and thence to the pressure pads 22 and the space between the sleeve 13 and the arbor 12 so that the sleeve is carried on a hydrostatic bearing extending over the entire length of the barrel of the arbor, no other support for the sleeve being provided. Oil escaping laterally between the arbor and sleeve is channelled by grooves 25 in the surface of the arbor 12 at the ends of the barrel and cross-bores to drain lines 26 extending to the ends of necks 14 where they are connected to drain reservoirs.

The pressure of the oil supplied to individual pads 22 can be controlled to vary the pressure between the arbor and sleeve along the barrel length. By so doing, the thickness of the oil film resisting the rolling load can t)e varied to compensate for bending of the composite roll under the rolling load, or to apply a given camber to the roll in order to compensate for bad shape in the strip or plate entering the mill.

The composite roll of Figures 4 to 6 differs from that described above in that the sleeve is supported hydrodynamically rather than hydrostatically. Similar parts in two sets of Figures are given the same reference numerals.

The sleeve 13 in Figures 4 to 6 is retained on the barrel 16 by means of retaining rings 17 which carry annular seals 18 engaging against the adjacent faces of the sleeve 13. The arbor 12 has at each side a flat 30, which extends over a greater part of its otherwise cylindrical barrel. By virtue of the flats 30, segmentshaped spaces 31 are formed between the arbor 12 and the sleeve 13. Those spaces are connected through cross bores 32 with supply and delivery bores 33 and 34, respectively, extending from one end of the arbor 12 parallel to the arbor axis. In the drawings, it is again assumed that an upper back-up roll is illustrated, so that the bottom of the roll engages a work roll and receives the rolling load, and that the sleeve rotates in an anticlockwise direction as viewed in Figure 6.

Oil under pressure is continuously supplied to a union on the left-hand roll neck connected to the bore 33, while a discharge pipe is similarly con nected to the bore 34. Rotation of the sleeve 13 due to its contact with the adjacent driven work roll develops a high pressure liquid film between the arbor and the sleeve, particularly at the bottom of the roll, where it must counteract the rolling load applied to the back-up roll by the work roll.

In order that the camber of the composite roll may be adjusted, a number of auxiliary bores 35 are made in the arbor 12, from the same end, those bores extending parallel to the arbor axis for diffe rent distances as indicated in Figure 4; in the example shown in the drawing there are ten such auxiliary bores, each of which is connected through unions and valves to suction equipment. Each axial bore 35 is connected by two transverse passages 36 which open to the exterior of the arbor 12 at its lowest point, as is clearly visible in Figure 2. The passages 36 are spaced along the barrel of the arbor.

By control of the valve equipment, the thickness of the oil film between the arbor and the sleeve 13 can be varied along the barrel length, thus compensating for bending of the composite roll under the rolling load, orto apply a given camber to the composite roll, in order to compensate for a bad shape in the strip or plate entering the mill.

A shape meter may be provided downstream and/or upstream of the mill, to detect variations in strip shape from the ideal, and the valve equipment controlling the supply of oil to individual pressure pads 22 of the roll of Figures 1 to 3 or the bleed of oil through the passages 26 and the bores 25 of the roll of Figures 4 to 6 may be controlled by the signals from the shape meter or shape meters, in order to provide automatic control of shape.

Claims (5)

1. A rolling mill roll comprising an arbor adapted to be supported at its ends, a sleeve or sequence of sleeves which closely surround the arbor over the effective barrel length, and means for supplying lubricant under pressure between the arbor and sleeve or sleeves so that, in use, the sleeve or sequence of sleeves is supported solely on a film of liquid under pressure.

2. A rolling mill roll according to claim 1, which has means for varying the thickness and/or pressure of the liquid film along the effective barrel length to vary the camber of the roll.

3. A rolling mill roll according to claim 2, in which the sleeve or sequence of sleeves is, in use, supported hydrostatically, and in which the arbor has passages therein for the supply of liquid under pressure to the space between the arbor and the sleeve or each sleeve at a plurality of locations spaced along the effective barrel length.

4. A rolling mill according to claim 2, in which the sleeve or sequence of sleeves is, in use, supported hydrodynamically and in which the arbor has passages therein leading from the arbor sleeve space at locations spaced along the effective barrel length, selectively to bleed liquid from the space and thereby to vary the thickness of the liquid film along the barrel.

5. A rolling mill roll according to any one of the preceding claims, constructed as a back-up roll.