Patent GB-727732-A (GB)
Title: Improvements in or relating to hydraulically operated rolling or drawing mills
Inventor: SPENCER ARTHUR
IPC: B21B35/08
Filed: 1952-02-21
Abstract: 727,732. Fluid-pressure servomotor-control systems. VICKERS-ARMSTRONGS, Ltd. May 20, 1953 [Feb. 21, 1952], No. 4610/52. Class 135. [Also in Group XXII] In a strip rolling mill or wire drawing machine in which both the coiler-off and coiler - on are driven by coupled, variable stroke pumps and motors, the pump stroke is variable to set the speed of the mill and the motor stroke is variable in response to a first pressure signal representative of the pressure in the pump-motor system (and, hence, of the actual tension in the strip) and to an opposing, second, independently - generated pressure signal which includes components corresponding to the strip tension desired and to the compensation required when the direction of rolling is reversed so that a constant tension is maintained in the strip. In the embodiment shown, material is being drawn off a roll 1, Fig. 1, reduced between rollers 9, and coiled on to a roll 2. The sets of apparatus associated with the two operations, i.e. coiling-off and coiling-on, are substantially identical to allow for reversal of the direction of rolling, but they are, in general, actuated in opposite senses. The reducing rollers 9 are driven through gearing 10 from a hydraulic motor 17 with a fixed swash-plate, and the motive fluid energizing this motor is supplied by a pump 18 driven by an electric motor 18A. Pump 18 has a variable tilt swash-plate which is adjusted from a remote station through a rod 23 and a servo device 20. The remote station is described in Specification 727,731, [Group XXII]. Roll 2 is driven through gearing 6 by a motor 12 which is supplied with hydraulic fluid by a pump 27A, the latter being driven by an electric motor 31. The speed at which the roll runs is set by adjustment of the swash-plate which is effected from the remote station through a rod 37 and servo device 55. A piston and cylinder 53 is interposed between the rod 37 and servo device 55, and, when the mill is stationary, a valve 41, actuated electrically from the remote station, diverts pressure fluid to actuate the piston and cylinder 53 so that the swash-plate of pump 27A will be set to maintain a " stalling " tension on the strip. The swash-plate adjusting lever 13 of motor 12 is controlled by an apparatus II in which the various pressure signals act on compound rams 101, 102, Fig. 2, situated on opposite sides of a lever 107, the latter being centred by springs 112, 113 and acting on a floating lever 117 connected to a valve 124. The latter controls a jack piston 131 which, through a hydraulic servo device 140, adjusts lever 13. Movement of piston 131 is fed back to valve 124 to recentre the latter through a hydraulic link 139 and a piston rod connected to the floating lever 117, and this feed-back movement is regulated by an adjustable leak 135 from the hydraulic link and a leaf spring 119 which loads the rod. Dither is applied to the system by means of a ram 136 which is connected to a dither mechanism 138. The pressures in the flow and return conduits of the pump-motor system-representing the tension in the strip-are applied to the rams 101, 102 through pipe 86 and through pipe 85, a reversible distributing valve 95, and line 97 or line 98. A second signal pressure is applied through a pipe 83, valve 95, and line 97 or line 98, this second pressure being the output pressure of a variable tilt swash-plate pump controlled by an apparatus III; and a third signal pressure representative of the so-called " churning loss " of motor 12 is applied through a pipe 91. In apparatus III, the adjusting linkage 190, 192 for pump 49 is actuated by a ram 197, Fig. 3, subject to the output pressure of the pump applied through a pipe 198 and to a spring loading 199 which is set by a servo-device 202 controlled by a floating lever 205. The position of the latter lever is determined by a number of factors of which the tension required in the strip being rolled is set by an electric motor 228 which acts through a worm and worm-wheel 226, a rod 224 threaded through the worm-wheel, a floating lever 208, and a link 207. Motor 228 also drives both a Selsyn transmitter 237 sending signals to the remote station and stops 232, 233 which actuate limit switches 235, 236. A ram 210 is connected to lever 208 and, under the control of a reversing valve 214 actuated electrically from the remote station, it imparts to lever 208 a correction for the direction of rolling. The upper position of ram 210 is limited by an abutment 241 connected to, and adjusted by, rod 224. The position of lever 205 is also adjusted by a floating link 242 which moves between fixed stops and is acted upon by compound differential rams 246, 256. These rams are controlled by reversing valves which are electrically actuated from the remote station, and they impart to lever 205 a component to compensate for acceleration or deceleration of the strip. The speed and capacity of motor 12 represents the " churning loss " thereof, and the pressure corresponding to these variables is obtained by applying to pipe 91 the output pressure of an auxiliary pump 155 driven from the motor. A factor corresponding to the capacity of the motor is obtained by connecting a choke IV as a by-pass across pump 155. The choke consists of two annular restrictions provided between plungers 164, 165, Fig. 4, and their containing cylinders, and the restrictions are connected in series hydraulically between lines 158, 159 leading to the input and output sides of the pump. The mid-point of the choke is connected by a line 160 to the circulation system connected to the input of the pump. Plungers 164, 165 are adjusted in position to vary the amount of fluid by-passed across pump 155 by means of their connection through a pivoted plate 175, bell-crank 179, 181, and a link 182, with the lever 13 which adjusts the swash-plate of motor 12. Specification 727,733, [Group XXII], also is referred to.