GB484754A - Improvements in and relating to electric control systems for shearing and other machines - Google Patents

Abstract

484,754. Shearing & c. BRITISH THOMSON-HOUSTON CO., Ltd. April 29, 1937, No. 12264. Convention date, April 29, 1936. [Class 83 (iv)] In a machine for shearing or otherwise operating on a moving strip, means is provided for introducing an adjustable time delay, proportional to the speed of the strip, between the instant the bar contacts a flag switch 16 and the initiation of the shearing operation. The shear 12 is operated by a solenoid 13. Rolls 11 of the last mill stand are driven by an electromotor 14. A time-delay device 17 comprises a cam switch with an adjustable stationary contact 17d and a contact 17b biassed by a spring 17c, and rotated in accordance with the speed of the strip by a stator member 18a with a three phrase winding and a rotor 18b with a single phase winding wired to a similar receiving device 19. An electromagnetic clutch 20 connects the device 17 to the receiving device 19. The clutch 20 is energized by a relay 24. A relay 25 energizes the solenoid 13 of the shear mechanism, an interlocking time-delayed relay 26 preventing repeated operation of the shear when the flag-switch is depressed. Operation. When the flag switch 16 is up the interlocking relay is energized and its contacts closed. When the strip strikes the flag switch 16 contacts 16b are closed to energize a relay 24 to complete a locking circuit independent of relay 26 through contacts 24a. At the expiration of the time delay the relay 26 is de-energized. The relay 24 closes contacts 24b in circuit with the clutch 20. Since the device 19 rotates at a speed proportional to the velocity of the strip, the member 17b is similarly rotated from its zero position until the member 17b engages contact 17d to complete a circuit through relay 25 to close contacts 25b of a locking circuit independent of the device 17 and to open the locking circuit of relay 24. The contacts 24b in opening disconnect the clutch 20 and the member 17b is returned to zero position. In the closed position of relay 25 contacts 25c close a circuit through the operating solenoid of the shearing mechanism. After shearing contacts 13a, 13b are opened to open the circuit in relay 25. This opens contacts 25b, 25c to de-energize the solenoid 13 thereby resetting the shearing mechanism. When the relay 25 is de-energized contacts 25a are closed to partially complete the circuit for the relay 24 but no operation of the relay 24 occurs although the contacts 16b are closed because relay 26 is de-energized and its contacts open to prevent relay 24 being energized until the flat switch is restored to its normal position.