STRIP GUIDING FOR DOWNCOILERS

Abstract: In an arrangement for coiling metal strip (11) on a downcoiler (8), the strip is directed to the downcoiler by a pair of pinch rolls (4, 6) and one or both of the rolls are used to steer the strip to a desired position on the mandrel so that a coil with tidy vertical sides is formed on the mandrel. One roll of the pair of pinch rolls may be skewed with respect to the other roll or both rolls may be skewed to the direction of travel of the strip material.

Description: This invention relates to the rolling of metal strip and in particular to the guiding of the strip to a downcoiler where it is coiled into a coil of a convenient size. In Figure 1 of the accompanying drawings, a conventional layout at the exit end of a hot strip mill is shown. Strip S leaving the last stand 1 of the hot strip mill passes along a run-out table where it is water cooled and it then pases through a pinch roll unit 3 which deflects the head end of the strip down to the downcoiler 5 where it is gripped and wound into the form of a coil. The plane containing the longitudinal axes of the rolls of the pinch roll unit 3 is set at a slight angle to the vertical so that the rolls turn the head end of the strip down between guiding deflector plates 7 to ensure that the head end is fed correctly to the mandrel of the downcoiler. Usually there are two or more downcoilers and strip can be coiled on either of these downcoilers. An additional pinch roll unit 3′ is associated with a second downcoiler (not shown in Figure 1). In use, both pinch roll units and downcoilers are driven. When the downcoiler 5 is employed, it is first necessary to close the rolls of the pinch unit 3 to their working position so that the gap between the pinch rolls is of the order of, and usually slightly less than, the thickness of the incoming strip. The pinch rolls are rotated at a speed slightly faster than that of the incoming strip so that, when the head end of the strip is gripped by the pinch roll unit, a slight tension is imparted to the strip. Similarly, the downcoiler mandrel is rotated at a speed faster than the incoming strip in order to tension the strip. Once the head end of the strip has been gripped by the mandrel, the mandrel motor is controlled to apply a tension to the strip which is appropriate to the width and thickness of the strip. Just before the tail end of the strip leaves the last stand of the finishing mill, the tension applied by the pinch roll unit is increased until it is roughly equal to the tension being applied by the downcoiler mandrel so that the coiling tension in the strip is maintained. Side guides 9 are fitted on the run-out table, on opposite sides of the strip path, and these guides are normally set slightly wider than the strip width until the head end of the strip has been gripped by the downcoiler but, once tension has been established, the side guides are brought close to the edges of the strip to ensure that the coil on the mandrel is built up with straight sides. When the second downcoiler is in use, the pinch rolls of the unit 3 are opened wide so that the head end of the strip passes unhindered between these rolls to the pinch roll unit 3' associated with the second downcoiler. The side guides 9 suffer from rapid wear by abrasion from the edges of the strip. Wear plates are fitted to the guides and these can be changed rapidly. However, provision of a large number of wear plates is expensive and there is the further disadvantage that the edges of the strip can be damaged. Such an arrangement for coiling hot metal strip is known from US-A-3587274 which forms the base of the preamble of claim 1. It is known from DE-U-8112755 for metal strip leaving the last stand of a cold rolling mill to pass over first and second guide rollers each arranged with its axis of rotation transverse to the direction of movement of the strip and then to be directed to a mandrel of a downcoiler. Both of the rollers engage the same side of the metal strip. The roller nearest to the mandrel can be displaced to move its longitudinal axis in a horizontal plane. It is an object of the present invention to provide an arrangement for steering hot metal strip to a desired position on a mandrel. According to the present invention, an arrangement for coiling hot metal strip moving in the direction of its length comprises a downcoiler having a rotatable mandrel and means for rotating the mandrel; and a pinch roll unit positioned upstream of the downcoiler to direct the strip to the mandrel; said pinch roll unit comprising a pair of horizontal rolls rotatably mounted and engageable with opposite sides of the metal strip and means for rotating the rolls; characterised in that, to steer the strip to a desired position on the mandrel, each roll has provision for skewing the roll about its longitudinal axis and at least one of the rolls is arranged to be skewed in a vertical plane containing its longitudinal axis. According to a second aspect of the invention, an arrangement for coiling hot metal strip moving in the direction of its length comprises a downcoiler having a rotatable mandrel and means for rotating the mandrel and a pinch roll unit positioned upstream of the downcoiler to direct the strip to the mandrel; said pinch roll unit comprising a pair of horizontal rolls rotatably mounted and engageable with opposite sides of the metal strip and means for rotating the rolls, characterised in that the two rolls are rotatably mounted in a housing structure which is pivotally mounted so as to be displaceable to skew the rolls with respect to the path of travel of the metal strip and means for pivotally displacing the structure. In this way, a coil having flat, parallel, sides can be formed on the mandrel of the downcoiler. In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to Figures 2 - 7 of the accompanying drawings, in which:- Figures 2A and 2B show diagrammatically alternative forms of apparatus to steer hot strip on to the mandrel of a downcoiler; Figures 3 and 4 show diagrammatically alternative forms of pinch roll units which are employed to steer hot strip on to the mandrel of a downcoiler; and Figures 5, 6 and 7 are plan views of alternative pinch roll units. Referring to Figures 2A and 2B, hot metal strip issuing from the last stand of a rolling mill is indicated by reference 11. After the strip has been cooled by means well known, it is wound on to the mandrel 8 of a downcoiler. Close to, and upstream of, the downcoiler there is a pinch roll unit having a pair of rolls 4, 6 of different diameters. The rolls are supported in bearing chock assemblies and the roll 4 is loaded against the roll 6 by a pair of air cylinders 2 which are connected to the bearing chock assemblies of the roll. In the arrangement shown in Figure 2A the bearing chock assemblies 6′ at the ends of the roll 6 are slidable on a base surface 16 and are connected through a pair of substantially horizontal links to a pair of servo actuators 14 which are pivotably secured to a foundation. By energising the servo actuators 14, the roll 6 can be caused to move horizontally relative to the surface 16. By actuating one servo actuator to a greater extent than the other. The longitudinal axis of roll 6 can be skewed with respect to that of the mandrel and also with respect to that of the roll 4. The cylinders 2 allow the gap between the rolls to be opened during threading and after the strip has been threaded between the rolls the rolls 4, 6 are brought into engagement with opposite sides of the strip. The roll 4 is thereafter rotatable about a horizontal axis and the smaller diameter roll 6 is rotatable about an axis which is normally parallel to the axis of rotation of the roll 4 but which can be skewed somewhat in the horizontal plane. When the axes of rolls 4, 6 are parallel, in theory the strip will remain on a particular path between the two rolls. In practice however, because of variations in the gauge and shape of the strip there is a tendency for the strip to move one way or the other in the direction parallel to the longitudinal axis of the rolls. By skewing the axis of the roll 6 relative to that of the roll 4 there is no longer a uniform pressure variation across the width of the strip and the strip is caused to track relative to the longitudinal axis of the rolls so that the strip takes up a different path as it approaches the mandrel. In the arrangement shown in Figure 2B, a pair servo actuators 14 bear against the bearing chock assemblies 6' of the roll 6 and also against a horizontal foundation surface 16. Thus, by operating the actuators 14, the roll 6 is raised and lowered. If both actuators are operated equally, then the longitudinal axis of the roll 6 remains parallel with that of the roll 4 but, if the actuator at one end of roll 6 is operated to a greater extent than that at the other end of the roll, then the longitudinal axis of the roll 6 is skewed in a vertical plane containing its longitudinal axis. When skewing occurs, the pressure applied to the strip by the two rolls will remain substantially uniform along the width of the strip, but the tension distribution between the roll 6 and mandrel 8 will change across the strip and, consequently, the strip moves sideways so that it can be caused to take up a particular path as it approaches the mandrel 8. In both of the embodiments of the invention shown in Figures 2A and 2B, edge detectors 10 are provided upstream of the pinch rolls and are arranged to detect the lateral edges of the strip material as it approaches the pinch rolls and, if it has tended to move away from the desired path between the pinch rolls, the detectors 10 detect the movement away from the desired path and the actuators are controlled accordingly in order to steer the strip on to the correct path betwen the rolls 4, 6, If desired, further edge detectors 12 may be positioned downstream of the pinch rolls and they are used to check the position of the strip relative to the rolls and to provide further adjustment of the servo actuators if this is necessary in order to bring the strip exactly on to the desired path. When the pressure applied to the strip by cylinders 2 is different from one side of the strip to the other, it skews the roll 4 in a vertical plane containing its longitudinal axis and it additionally helps to steer the strip to the desired path. Referring now to Figure 3, a pair of conventional pinch rolls 20 are positioned upstream of the downcoiler (not shown) and a steering pinch roll unit 22 is positioned upstream of the pinch rolls 20. The pinch roll unit 22 consists of a pair of housings supporting a pair of pinch rolls and the housings are mounted on a base 23 which carries a vertical pivot pin 24. A double acting actuator (not shown) is connected to the base 23 to enable the housing and base to pivot about the vertical pivot pin 24. If the strip approaching the pinch rolls 20 and hence the mandrel moves off of the desired path then a small displacement of the pinch roll unit 22 about the pin 24 will apply forces to the strip which will cause it to move sideways onto the desired path. In use, the gap between the rolls of the steering pinch unit will be set slightly less than the strip thickness so that the roll will grip the strip as soon as the strip enters between them. The rolls are driven by in-built motors (not shown) to spin the rolls up to the strip speed before the strip is received. Alternatively, the rolls may be left open until the strip has entered and become gripped by the pinch roll unit 20 after which the rolls of the steering roll unit 22 may be brought into engagement with opposite faces of the strip. In the Figure 4 arrangement the conventional pinch rolls 20 and the steering pinch roll unit 22 as shown in Figure 3 are combined into a single unit in which the housing and base 23 are supported on an inclined surface and the unit is pivotable about a pin 24 extending normal to the surface. In use, to steer the strip onto a predetermined path to the coiler the unit is pivoted about the pin 24 in order to urge the strip sideways in one direction or another in order take up the desired path. Figures 5, 6 and 7 show alternative forms of steerable pinch roll units. The arrangement shown in Figure 5 is particularly suitable for use in the embodiment of the invention shown in Figure 3 and 4. Referring to Figure 5, the rolls 27 are shown mounted in the housings 22 and are rotated by individual drive motors 29. The base 23 is pivoted about the pin 24 by a piston-cylinder device 25 which is connected to the base and to a foundation. Figure 6 shows an alternative arrangement in which the unit is pivotable about a pin 24 extending through a lug 26 arranged on the base at one end of the rolls. The housing is pivoted by way of a piston-cylinder device 28. Figure 7 shows an arrangement in which the unit 30 is pivotably connected to opposite ends to a pair of links 31, 32 which are fixed at their outer ends. The links permits the unit to be displaced by an actuator 33 such that the unit is moved to a limited extent in the direction of the length of the rolls 27 and can also be made to become skewed in the plane of the strip passing between the rolls. In all these embodiments of the invention the amount of movement made by the actuators will normally be within the range of ± 1/4" (± 63 mm) about the mean position.

Claims: An arrangement for coiling hot metal strip moving in the direction of its length comprising a downcoiler having a rotatable mandrel (8) and means for rotating the mandrel and a pinch roll unit positioned upstream of the downcoiler to direct the strip to the mandrel; said pinch roll unit comprising a pair of horizontal rolls (4, 6) rotatably mounted and engageable with opposite sides of the metal strip and means for rotating the rolls; characterised in that, to steer the strip to a desired position on the mandrel (8), each roll has provision (2, 14) for skewing the roll about its longitudinal axis and at least one (4) of the rolls is arranged to be skewed in a vertical plane containing its longitudinal axis. An arrangement as claimed in claim 1, characterised in that the horizontal roll which is engageable with the upper side of the metal strip is arranged to be skewed in a vertical plane containing its longitudinal axis. An arrangement for coiling hot metal strip moving in the direction of its length comprising a downcoiler having a rotatable mandrel and means for rotating the mandrel and a pinch roll unit positioned upstream of the downcoiler to direct the strip to the mandrel; said pinch roll unit comprising a pair of horizontal rolls (27) rotatably mounted and engageable with opposite sides of the metal strip and means for rotating the rolls characterised in that the two rolls are rotatably mounted in a housing structure (22, 23) which is pivotally mounted so as to be displaceable to skew the rolls with respect to the path of travel of the metal strip and means (25) for pivotally displacing the structure. An arrangement as claimed in claim 3, characterised in that the housing structure includes a base member (23) which is pivotable about a pivot (24) extending normal to the base member. An arrangement as claimed in claim 4, characterised in that the pivot (24) is positioned at one end of the rolls (27). An arrangement as claimed in claim 4, characterised in that the pivot (24) is positioned laterally of the longitudinal axes of the rolls. An arrangement as claimed in claim 4, characterised in that a pair of links (31, 32) are pivotally connected to the base member and to respective pivots extending normal to the base member, said links permitting the rolls to be skewed with respect to the path of travel of the metal strip. An arrangement as claimed in any preceding claim, characterised in that the longitudinal axes of the rolls lie in a plane which is inclined towards the downcoiler.

Inventors: BATHORY, BELA ISTVAN, LAWSON, KENNETH THOMAS
Applicants: DAVY MCKEE (SHEFFIELD) LIMITED
Application year: 1987
Main classification: B21C47
IPC codes: B21C47, B65H23