Patent GB-700941-A (GB)
Title: Improvements in control systems for electric motors
IPC: B21B37/60
Filed: 1951-07-10
Abstract: 700,941. Control of two motors; controllers. AMERICAN BRASS CO. July 10, 1951 [Aug. 5, 1950], No. 16322/51. Class 38(3) The screw-down motors of a rolling mill are operated to re-set the rolls to their original or other predetermined spacing after a bar has been rolled by the mill. The motors 10 and 11 are used to adjust the relative spacing of the rolls and drive a common shaft 20 coupled to a selsyn transmitter 21 which is adapted to be locked in correspondence with a selsyn receiver 22. A cam shaft 23 is driven by the receiver 22 and has cams 32, 33, operating switches 34, 35, which control the automatic operation of motors 10, 11. The cams are shown in the position corresponding to the predetermined spacing of the rolls, wherein the contacts 36, 50 of the switches 34, 35, are open. When there is a bar in the mill a relay 65 is energized through an indicator A, and automatic thickness control apparatus B is rendered effective. When the bar is removed the relay 65 is de-energized thereby supplying current to the re-set control apparatus and disconnecting the apparatus B. A relay 78, has been energized to close contact 80 due to closure of the main switch 31 so that, if the rolls are closer together than the required space setting, the cam 32 will have turned to operate the switch 34 and energize the relay 19. The motor 11 is thus energized to move the rolls apart until the cam 32 is returned to the position shown. If the rolls are further apart than the required spaced setting, the cam 33 operates the switch 35 to energize the relay 15, so causing the motor 10 to move the rolls together. During the course of rolling a bar it may be desired to change the setting of the rolls, and this may be accomplished by means of pushbuttons 14, 18, controlling the motors 10, 11. It is then necessary to re-set the cams 32, 33, so that they indicate the required new setting of the rolls. For this purpose a reversible motor 100 is coupled to the receiver 22 and camshaft 23. When pushbuttons 14 or 18 are actuated during the course of rolling, the shaft 23 is operated by servo devices 21, 22, so causing switch 34 or 35 to be operated, depending upon whether the rolls are to be moved together, or apart, and, when the required new setting is obtained, the switch 31 is opened to unlock the servo transmitter and receiver. The relay 65 is also de-energized to disconnect the automatic thickness control apparatus B and to close contact 67, the relay 78 now being de-energized so that contact 81 is closed. The motor 100 is thus operated in one direction or the other according to which of the switches 34 or 35 has been operated, and rotates the shaft 23 to the position shown whereupon the motor 100 is stopped since current is fed to both of its reversing windings. The master switch may then be closed and rolling proceeded with. To change the spaced setting of the rolls when there is no bar in the mill, the switch 31 is opened to unlock the devices 21, 22, and the motors 10 or 11 operated by pushbuttons 14 or 18 until the required setting is reached. Another form of cam apparatus comprises a base 111 (Fig. 2) mounting the receiver 22 and motor 100 which are adapted in turn to drive a threaded shaft 112 having a carriage 113 supporting the switches 34, 35. The contacts of the switches are actuated by longitudinal cams 118, 119, which are mounted on the base 111. The motors 10, 11, may be replaced by a single reversible motor. Specification 689,217, [Group XXXV], is referred to.