Patent GB-458380-A (GB)
Title: Improvements in or relating to controlling systems for electrically driven lifts
IPC: B66B1/12
Filed: 1935-09-18
Abstract: 458,380. Electric braking. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and CHUBB, A. A., c/o General Electric Co., Ltd., Stoke, Coventry. Sept. 18, 1935, No. 25868. [Class 103 (i)] [See also Group XXXVII] An electrically driven lift is decelerated by an eddycurrent brake, the extent of energization of which is determined by a device which moves to a controlling position corresponding to the time taken by the lift to pass between predetermined points when its driving motor is energized to a constant degree. Upon operation of a switch CSU, a switch CS is opened and a self-maintaining relay UD closed to connect the driving motor RO, ST, to the supply. A relay SC, having contacts sc1, sc2, is also energized to shortcircuit sections of rotor resistance. The driving motor starts, a brake BK being released, and a relay VS, energized from the rotor of the motor, operates to energize a relay VA. When the motor has speeded up the relay VS releases, and a relay V is operated to shortcircuit the remaining resistances in the motor circuit, and the motor runs at full speed. When a floor at which it is desired to stop is approached, the switch CSU is opened and CS closes, so that, when an inductor plate in the lift shaft is passed, a relay Z operates momentarily to operate a self-maintaining relay PS which prepares a circuit for a relay C. A series of plates in the lift shaft is then passed and each plate operates the relay C. Upon the first operation of the relay C, a relay EC is operated and the eddy-current brake EB is energized fully, and upon the first release of the relay C, a step-by-step sequence switch A, having contact banks A1, A2, A3, is impulsed one step. The lift begins to decelerate, and, when the relay C is next operated, the switch A operates a further step thereby de-energizing the relay SC which releases relays V, VA. Resistance is thereby reinserted in the rotor circuit of the driving motor and the lift continues to decelerate. When the relay C is again operated, a self-maintaining relay M is energized to energize a step-by-step switch B having contact banks B1, B2, B3. This switch has contacts d b, controlling a relay S which has contacts s<1> controlling the switch B so that the switch is moved step-by-step at a uniform rate until the relay C is again operated by the next inductor plate, whereupon the relay M is de-energized to stop the switch B, which thus positioned in accordance with the time taken by the lift to move between two inductor plates. The amount of resistance inserted in the circuit of the eddycurrent brake by operation of the contact bank B3 thus corresponds to the opposition offered by the load in the lift to the driving motor. The last operation of the relay C referred to steps the switch A to its fifth contact, so that, when the relay C is operated for the last time by the lift reaching a point a few inches from the required floor, a relay NR is energized to release the contactor UD which disconnects the driving motor and effects application of the brake BK. The switches A, B, are then returned to their initial positions.