Patent GB-229754-A (GB)
Title: Improvements in and relating to systems of electric control
IPC: B60L15/20
Filed: 1923-11-28
Abstract: 229,754. English Electric Co., Ltd., and Morris, F. Nov. 28, 1923. Master control systems; controllers, actuating. - A control system comprises a master controller 1 a secondary switch 2 and an electromagnetic reciprocating device 3 under the joint control of the master controller and the switch and adapted to move the latter by ratchet mechanism until it reaches a position corresponding to the master controller. In the system as applied to the remote control of electric motors, the secondary switch serves to position the actual motor controller. Forward movement of controller. 1 causes energization of coil 6, with consequent upward movement of line breaker 5, and energization of coil 7, which sets the device 3 for forward drive of the switch 2, the circuit being completed to earth firstly through contact 8, and after movement of the line breaker 5 through contact 11. The line breaker completes a circuit through the coil of a relay 4, contacts 19 on the device 3, line 14 and switch 2 to earth. The relay 4 causes energization of coil 17 to reciprocate the device 3, with consequent break of circuit at contacts 19 causing de-energization of relay 12 and energization of coil 120 to return device to its initial position. The device 3 continues to reciprocate until the position of switch 2 corresponds to controller 1, with consequential interruption of the circuit from line 14 to earth. Return of the master controller to zero causes de-energization of coil 6 and 7 with consequent drop of the line breaker 5 and setting of the device 3 for backward drive of the notch 2, the circuit of the relay 4 being completed through contacts 19, line 53, and switch 2 to earth until the switch returns to its initial position. The device 3 is shown in detail in Figs. 2 and 3. The alternate energization of coils 17, 120 causes rocking of levers 34, 35 about pivots 36, 37 and through a link 38, oscillation of a sector 39 about a shaft 40. The sector 39 carries pawls 41, 42 tending to engage opposed ratchet wheels 45, 46 on the shaft 40. If the coil 7 is de-energized, a pivoted plate 49 presses on the tail of the pawl 41 rendering it inoperative, so that oscillation of the sector 39 causes backward rotation of the shaft 40 through the medium of pawl 42 and ratchet wheel 46. Energization of the coil 7 rocks the plate 49 against the action of a spring to render the pawl 42 inoperative thereby causing forward rotation of the shaft 40. The contacts 19 are associated with the lever 35. The spring 52 may be replaced by another coil 121, Fig. 1, energized through additional contacts 122 on theswitch 5. In a modification, pawls 64, 65, Fig. 7, are pivoted to separate 'arms 62, 63 so as to be disengaged from their ratchet wheels when they are inoperative. The control circuit is modified so that either of the coils 54, 55 are controlled by the relay 4 according to the position or the line breaker 5, the relay arm only making- contact in its attracted position and the relay coil being in circuit with two pairs of contacts, one associated with each arm 62, 63, instead of the single pair of contacts 19. In a further modification the device 3 has a single coil tending to move both ratchets, one of which is locked in its inoperative position according to the position of the line breaker, and the other not onlydrives its ratchet wheel but also intermittently interrupts the circuit of the operating coif directly instead of through the intervention of a relay. The usual current limit relay in the motor circuit can be adapted to prevent energization of the operating coils of the device 3, and as usual can be rendered ineffective bv manual control. Specifications 152,490 and 175,877 are referred to.