ROLLING MILLS

Abstract: A rolling mill has a transducer for measuring the separation of a movable part of the mill from the fixed part of the mill. The transducer comprises a magnetostrictive ele­ ment secured to one end of the parts, a transmitter for transmitting magnetostrictive signals into the element, a receiver for receiving signals reflected back along the element and magnetic means secured to the other part which produces a magnetic field which serves to reflect the signals along the element. Time measuring means measure the time interval between transmitting the energy and receiving the echo and this is representative of the distance between the two parts of the rolling mill.

Description: ROLLING MILLS This invention relates to rolling mills having an electrical transducer arranged to indicate the position of a movable part of the rolling mill with respect to a fixed part thereof. Rolling mills consist essentially of at least one pair of rotatable rolls mounted at their ends in bearing chock assemblies which are supported in a fixed mill housing. Means are provided for moving at least one of the rolls and its bearing chock assemblies with respect to the mill housing in the direction to thereby adjust the gap between the rolls. This movement of the roll and its bearing chock assemblies may be brought about by means of screws threaded in nuts positioned in the fixed housing and bearing on the chock assemblies of the roll or alternatively each bearing chock assembly may have a hydraulic ram disposed between it and the fixed part of the mill housing. By expanding or contracting the rams, the roll and its bearing chock assemblies are moved relative to the mill housing in the direction to adjust the gap between the rolls. To determine the position of the roll and its bearing chock assemblies relative to the fixed housing, it is usual to include some form of measuring device which measures the movement of the roll. When the roll and its bearing chock assemblies are moved by screws, the rotation of each screw may be transmitted by a Selsyn train to a measuring device. This arrangement suffers from the disadvantage of the need for couplings, and back-lash in the couplings, and a Selsyn train brings about a reduction in the overall accuracy of the arrangement. When hydraulic rams are employed, it is usual to connect an electric linear transducer between the movable and fixed parts of each ram to determine relative positions of the parts. Difficulties can occur in obtaining transducers of sufficiently long stroke which are sufficiently accurate along the entire length of their stroke. According to the present invention a rolling mill has a fixed part, a part movable linearly with respect to the fixed part and an electrical transducer for indicating the position of the movable part with respect to the first part, said transducer comprising an elongate magnetostrictive element secured to one of the parts, an electronic transmitter for transmitting magnetostrictive signals into said element, an electronic receiver for receiving magnetostrictive signals reflected back along said element, magnetic means secured to said other part and associated with said element to produce a magnetic field which serves to reflect said signals transmitted along said element back to said receiver and timing means for measuring the time interval between the transmission and the reception of said signals, said time interval being representative of the separation of said parts. A prime advantage of the invention is that there is no contact between the fixed and movable parts when the measurement is made. 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 drawings, in which: Figure 1 is a diagrammatic side elevation of part of a rolling mill in accordance with one embodiment of the invention,. Figure 2 is a diagrammatic side elevation of part of a rolling mill in accordance with another embodiment of the invention, Figure 3 is a diagrammatic side elevation of part of a rolling mill in accordance with a further embodiment of the invention, and Figure 4 is a circuit block diagram showing the operation of the transducer. Referring to Figure 1, a rolling mill has a fixed housing 1 defining a window 3. Contained within the window there are bearing chock assemblies for upper and lower roll assemblies. The upper roll assembly consists of a work roll 5 and a back-up roll 7 and the ends of these rolls are supported in bearing chock assemblies 9 and 11 respectively. The lower roll assembly similarly consists of a work roll and a backup roll supported at their ends in bearing chock assemblies but only the work roll 13 is shown in the figure. The upper work roll assembly is connected to the lower ends of a pair of screws, one of which 15 is shown in the figure. Each screw is threaded in a nut 17 fixed in the housing 1 and the screws are rotated in the nuts by worm and wheel apparatus 19 to raise and lower the screws and hence the roll assembly relative to the fixed mill housing. To determine the angular position of the screws and hence the position of the roll assembly relative to the housing, each screw has a transducer associated with it. Each transducer comprises an elongate magnetostrictive element 21 projecting from a casing 23 which is mounted on the top of the housing. The element projects into a central bore 25 in the screw 15. The length of the element is such that its end is always spaced from the closed end of the bore 25. In the upper end of the screw there is an enlarged central opening containing a plastics casing 27 which supports an annular permanent magnet 29 in surrounding relation with the element 21. The casing 23 encloses a transmitter and a receiver of magnetostrictive signals. In use, the transmitter is energised causing it to transmit waves of magnetostrictive energy into the element 21. The waves pass along the element until they encounter the magnetic field'set up by the magnet 29 and they are reflected by the magnetic field back along the element to the receiver. A timer is employed to measure the time interval between the transmission and the reception of the waves and this value is representative of the distance between the transmitter/receiver and the magnet. When the screw is rotated, magnet 29 is displaced lengthwise of the element, thereby changing the position of the magnet with respect to the casing 23. The time interval for the passage and return of the waves along the element is representative of the distance between the magnet 29 and the upper end of the fixed housing and this is representative of the distance between the upper roll assembly and the upper end of the housing. In the arrangement shown in Figure 2, there is no necessity for the screw 15' to have a central bore. A tube 31 is mounted on the upper end of the screw with the bore of the tube in line with the axis of the screw. The tube projects through an opening in the upper end of the housing and an annular magnet 33 is mounted on the upper end of the tube. The elongate element 21 extends through the magnet 33 into the tube 31. The casing 23 at the upper end of the element is moumted on a bracket 25 on the upper end of the housing. In the alternative arrangement shown in Figure 3, the invention is applied to a hydraulic rolling mill. The lower end of the mill housing is shown in this figure and, at the bottom of the window 3 beneath the bearing chock assembly 37 of the lower roll assembly, there is a piston-cylinder device 39. This device comprises a fixed piston 41 in a cylinder 43 beneath the work roll assembly. By introducing fluid under pressure into the cylinder, the lower roll assembly is raised and lowered relative to the fixed housing. The transducer associated with the pistoncylinder device 39 comprises a magnetostrictive element 45 projecting upwards from a casing 47 mounted on a bracket 49 attached to the piston 41. The element projects through an annular permanent magnet 51 secured to a bracket 53 extending from the cylinder 43. As the cylinder 43 moves vertically with respect to the piston 41, the magnet 51 is displaced along the length of the element 45. A circuit diagram of the transducer which is applicable to all the embodiments of the invention is shown in Figure 4. The magnetostrictive element 21 is shown surrounded by the permanent magnet (29, 33, 51). A transmitter of magnetostrictive energy 55 and a receiver of the reflected energy 57 are shown positioned at the upper end of the element. A timer 59 is set by a control 61 when the energy is transmitted and is stopped when the reflected energy is received, thus giving a measure of the time taken for the energy to be transmitted along the element to the magnet and then returned to the receiver. A display device 63 displays this measure and, by calibrating the device, the display device can be used to display a direct reading of the distance between the fixed and movable parts of the rolling mill. The magnetostrictive waves transmitted along the element conveniently have a frequency of the order of 8 Kc/s. The magnetostrictive element and the associated electronic equipment may be purchased from TEMPO SONICS of Long Island, New York, U.S.A.

Claims: Claims: 1. A rolling mill having a fixed part, a part movable linearly with respect to the fixed part and an electrical transducer for indicating the position of the movable part with respect to the first part, characterised in that said transducer comprises an elongate magnetostrictive element (21) secured to one of the parts (1), an electronic transmitter (55) for transmitting magnetostrictive signals into said element, an electronic receiver (57) for receiving magnetostrictive signals reflected back along said element, magnetic means (29) secured to said other part (15) and associated with said element to produce a magnetic field which serves to reflect said signals transmitted along said element back to said receiver and timing means (59) for measuring the time interval between the transmission and the reception of said signals, said time interval being representative of the separation of said parts. 2. A rolling mill as claimed in claim 1, characterised in that the transmitter (55) and the receiver (57) are contained within a casing (23) at one end of the element. 3. A rolling mill as claimed in claim 1 or 2, characterised in that the element is stationary and extends into an opening (25) in a screw (15) for raising and lowering a movable part (5) of the rolling mill, and the magnetic means (29) is secured to the screw. 4. A rolling mill as claimed in claim 1 or 2, characterised in that the element (21) is stationary and projects into a tube (31) mounted on the upper end of a screw (15) for raising and lowering a movable part of the rolling mill and the magnetic means (33) is secured to the tube. 5. A rolling mill as claimed in claim 3 or 4, characterised in that the magnetic means is an annular permanent magnet (33). 6. A rolling mill as claimed in claim 1 or 2, characterised in that the movable (43) and fixed (41) parts are respective parts of a hydraulic ram (39) forming part of the rolling mill. 7. A rolling mill as claimed in claim 6, characterised in that the ram is positioned between the underside of the bearing chock assembly (37) of the lower roll assembly and the upperside of part of the fixed housing (1) of the mill, with the element (45) extending vertically from the fixed part (41) of the ram and the magnetic means (51) movable with the movable part of the ram.

Inventors: FOSS, ALAN
Applicants: DAVY MCKEE (SHEFFIELD) LIMITED
Application year: 1981
Main classification: B21B37
IPC codes: B21B31, B21C51, G01B7, B21B38