GB2195279A

GB2195279A - Four-high rolling mill

Info

Publication number: GB2195279A
Application number: GB08622969A
Authority: GB
Inventors: Kenneth Thomas Lawson; Thomas Hope
Original assignee: Davy McKee AG
Current assignee: Davy McKee AG
Priority date: 1986-09-24
Filing date: 1986-09-24
Publication date: 1988-04-07
Anticipated expiration: 2006-09-24
Also published as: GB2195279B; GB8622969D0

Abstract

In a four-high rolling mill the upper 3, 5 and lower pairs of rolls are supported in respective pairs of bearing chock assembles 2, 6. The bearing chock assemblies can be moved sideways so that the rolls can be crossed. The actuators 8 for moving the bearing chock assemblies are arranged and controlled to prevent the assemblies from rotating. The bearing chock assemblies may also be displaced vertically by a screwdown mechanism 7. The actuators 8 may be of the hydraulic, screw or wedge type. <IMAGE>

Description

SPECIFICATION Improvements in rolling mills This invention relates to four-high rolling mills in which the upper work roll and the upperback-up roll can be crossed as a pair with respect to the pair consisting of the lower work roll and the lower back-up roll. By crossing the upper rolls as a pair with respect to the lower rolls, the gap between the work rolls provides a profile of crown-shape and, by adjusting the angle of crossing; the amount of crown is adjusted thereby altering the shape of metal strip rolled between the work rolls.

In such rolling mills, there are provided screwdowns or the like for adjusting the gap between the work rolls and, similarly, a hydraulic capsule is often fitted in the bottom of each mill housing with the capsules abutting against the bearing chock assemblies of the lower back-up roll. In order to cross the rolls as a pair, the bearing chock assemblies at each end of the rolls are displaced sideways so that the vertical plane containing the longitudinal axes of the upper pair of rolls is crossed with the vertical plane containing the longitudinal axes of the lower pair of rolls.

When a workpiece in the form of metal strip is passed between the rolls, forces are applied from the bearing chock assemblies of the upper back-up roll to the lower ends of the screwdowns and from the lower back-up rolls to the capsules but these forces are offset with respect to the centres of the bearing chock assemblies. These eccentric forces tend to cause the bearing chock assemblies to rotate with respect to the mill housings and in doing so may cause binding and damage to the screwdowns and capsules.

It is an object of the present invention to provide such a rolling mill in which rotation of the bearing chock assemblies and possible damage to the screwdowns and capsules can be avoided.

The present invention, therefore, resides in a four-high rolling mill in which the corresponding ends of the upper work roll and the upper back-up roll are rotatably supported in respective upper bearing chock assemblies; the corresponding ends of the lower work roll and the lower back-up roll are rotatably supported in respective lower bearing chock assemblies; the upper and lower bearing chock assemblies are displaceable with respect to the mill housings both vertically and horizontally in the direction normal to the longitudinal axes of the mill rolls; means are provided for displacing said bearing chock assemblies si deways.- in said horizontal direction so that the upper rolls can be crossed as a pair with respect to the pair of lower rolls; and the means for displacing the bearing chock assemblies sideways are controlled so as to prevent the chock assemblies from rotating.

Preferably, the means for horizontally displacing the bearing chock assemblies comprise hydraulic rams mounted on or in the mill housings and acting against the bearing chock assemblies or, alternatively, the displacing means may take the form of rotatable screws which are mounted in the mill housings and bear against the bearing chock assemblies.

In a still further arrangement, the displacing means take the form of wedges insertable between the chock assemblies and the mill housings.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawing which shows diagrammatically the upper part of a four-high rolling mill in accordance with the present invention.

A four-high rolling mill has a pair of massive spaced apart housings 1 of which only one is shown in the figure. Each housing defines a window 1A. In each window there is an upper bearing chock assembly 2 which rotatably supports one end of the upper back-up roll 3.

The upper bearing chock assembly also includes a bearing chock 4 for the upper work roll 5. Also in the window 1A there is a similar lower bearing chock assembly 6.

Each bearing chock assembly is displaceable sideways vertically within the window, the upper bearing chock assembly being displaceable in this direction by a screwdown 7, the lower end of which abuts against the top of the bearing chock assembly. The width of the bearing chock assembly is less than the width of the window 1 A so that the assembly can be moved sideways with respect to the window in the horizontal direction which is at right angles to the longitudinal axis of the upper back-up roll.

Each bearing chock assembly is displaceable sideways in this horizontal direction by means of actuators (8) mounted in the mill housings and bearing against the bearing chock asassembly In the arrangement shown in the figure the actuators are hydraulic rams having their cylinders mounted in the mill housings and their pistons bearing against the side walls of the bearing chock assembly.

It is convenient for each bearing- chock assembly to have four actuators associated with it, two acting against each of its side walls.

Wear plates may be fitted between the rams and chock assemblies and cylindrical or spherical seatings may be employed to permit the chock assemblies to turn slightly in the horizontal plane which they necessarily do when the roll axes are crossed.

In use, in order to centralise each bearing chock assembly in the window so that the assemblies are symmetrical with respect to the screwdowns, the rams are energised essentially equally. On the other hand, if a bearing chock assembly is to be moved to the left, to the position shown in the figure, then the rams on the right-hand side of the housing are actuated to a greater extent than those on the left-hand side of the housing, thus displac ing the assembly towards to left-hand side of the window. By displacing the bearing chock assembly at one end of the upper rolls in one direction and the bearing chock assembly at the other end of the rolls in the opposite di rection, the upper rolls as a pair are inclined with respect to the lower rolls.Furthermore, the lower rolls can also be displaced sideways with respect to the mill housings so that the vertical plane containing the longitudinal axes of the upper pair of rolls is crossed with the vertical plane containing the longitudinal axes of the lower pair of rolls.

When the mill rolls are not crossed, the roll bearings are normally in line with the mill screwdowns and capsules. When the rolls need to be crossed, the roll chock assemblies are moved sideways by the hydraulic rams.

Linear transducers would be mounted so as to measure the movement of the chock assem blies relative to the mill housing and a control system would be employed to ensure that the top and bottom rams move equal amounts so that the assemblies are kept vertical at all times.

When material is passed between the work rolls during rolling, the rolling load on the bearing chock assemblies acts through the centre line of the bearing but, when the rolls are crossed, the bearing is eccentric to the screwdowns and the capsules. The forces act ing between the bearings and the screwdowns than apply a bending couple which tends to make the chock assembly rotate with respect to the mill housings. However, rotation of the chock assembly is prevented by the hydraulic rams which hold it securely in position. In one form of the invention the valves, which allow fluid to pass into or out of the rams, are closed when the assembly has been moved to the required position and before rolling com mences. Closing the valves prevents further movement of the rams and, hence, the chock assemblies are maintained in their preset posi tion.

When the assemblies are in the desired an gular position, the rams may bear lightly against the assemblies or they may be pres surised to exert a preset force against the assembly or, alternatively, they may be backed-off slightly to provide a clearance of, say, 0.5-1 mm with the assembly. Valves controiling the supply of hydraulic fluid to the rams are then closed before rolling com mences. (In the case of screwdowns, brakes would be applied to the drive motors).

Although in the arrangement shown the rams are shown to act horizontally, it could be arranged so that one or more rams act in a vertical direction and one or more rams act horizontally so that between them they can rotate the assembly in both clockwise and anticlockwise directions.

During movement of the bearing chock assemblies into the required positions for roll crossing, small frictional forces are set up between the screwdowns and the upper bearing chock assemblies and between the lower bearing chock assemblies and the capsules at the bottom of the housings and these can cause damage to the lower ends of the screwdowns and the capsules. To reduce the possibility of damage being caused, separate wear plates can be introduced between each bearing chock assembly and the corresponding screwdown or capsule. The wear plates extend for the width of the housing windows and sideways forces from the moving bearing chock assemblies are transmitted by the wear plates directly to the housings without causing damage to the screwdowns and the capsules.

Claims

1. A four-high rolling mill in which the corresponding ends of the upper work roll and the upper back-up roll are rotatably supported in respective upper bearing chock assemblies; the corresponding ends of the lower work roll and the lower back-up roll are rotatably supported in respective lower bearing chock assemblies; the upper and lower bearing chock assemblies are displaceable with respect to the mill housings both horizontally in the direction normal to the longitudinal axes of the mill rolls and vertically; and actuator means are provided for displacing said bearing chock assemblies in said horizon- tal direction so that the upper rolls can be crossed as a pair with respect to the pair of lower rolls, said actuator means being posi -tioned relative to the chock assemblies and controlled so as to prevent the chock assemblies from rotating.

2. A four-high rolling mill as claimed in claim 1, in which each bearing chock assembly has four horizontally acting actuator means associated with it, said actuator means being arranged in pairs on opposite sides of the bearing chock assembly with one actuator of each pair being at a higher level than the other.

8. A four-high rolling mill as claimed in claim 1 or 2, in which each bearing chock assembly has position transducers associated with it and the actuator means are controlled in re sponse to the transducers to prevent the bearing chock assembly from rotating with re spect to the housing.

4. A four-high rolling mill as claimed in any preceding claim in which each actuator means is a hydraulic ram acting between the bearing chock assembly and the mill housing.

5. A four-high rolling mill as claimed in claim 1, 2 or 8, in which each actuator means is a rotatable screw acting between the bearing chock assembly and the mill housing.

6. A four-high rolling mill as claimed in claim 1, 2 or 8, in which each actuator means is a wedge insertable between the chock assembly and the mill housing.

7. A four-high rolling mill as claimed in claim 4, 5 or 6, in which each actuator means can be locked in a predetermined position.

8. A four-high rolling mill substantially as hereinbefore described with reference to the accompanying drawing.