Patent GB-450469-A (GB)
Title: Improvements in or relating to systems of control for electrically driven lifts
IPC: B66B1/44
Filed: 1935-01-18
Abstract: 450,469. Master control of motors. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and SMART, N. C., and CHUBB, A. A., c/o General Electric Co., Ltd., Stoke, Coventry. Jan. 18, 1935, No. 1679. [Class 38 (iii)] Travelling to predetermined limits. -Means which measure the current supplied to a lift motor after every start from a floor act, after application of a brake and reduction of the driving current during deceleration, to determine at which point in the deceleration curve a current-sensitive device, energized from a winding of the driving motor, operates in response to the slowing down of the lift to effect application of increased current to the motor for the purpose of levelling. A step-by-step switch G is energized when the lift accelerates and varies a resistance G 1 in circuit with a relay E which operates when sufficiently energized from a transformer P having windings energized in accordance with the voltage and current of the motor primary circuit. The operation of the relay E stops the movement of the switch G, the final position of which represents a measure of the current taken by the motor. A second variable resistance G3 adjusted by the switch G is in circuit with a relay M energized from the motor secondary circuit RO. When a switch SU is operated, self-maintaining relays U, B operate, the former connecting the motor to the supply and the latter cutting out resistance from the primary circuit. A relay T is energized from the rotor circuit and closes an energizing circuit for a relay V which inserts resistance in the circuit of the relay T. As the motor speeds up the relay T releases and energizes a relay R which excludes rotor resistances SA, SB, SC. The relay R also energizes the step-by-step switch G which adjusts the resistances G1, G3, as described above. The lift motor now operates at full speed until the switch SU is released some distance from the floor at which it is desired to stop. An inductor relay CB is then operated to release the relay B which inserts resistance in the primary circuit, the brake K being simultaneously applied. As the motor slows down the voltage applied to the relay M from the rotor circuit increases, and the relay operates at a speed adjusted by the resistance G3 in accordance with the current taken by the motor after starting. The operation of the relay M de-energizes the relay R to insert the rotor resistances, and re-energizes the relay B to apply full voltage to the primary circuit, the brake being simultaneously released. When the lift arrives within a few inches of the desired floor, an inductor relay CA operates to energize a relay S which de-energizes relays U and B to disconnect the motor and insert the primary resistance, the brake K being reapplied. The de-energization of the relay U also releases the relays E and M and completes a circuit which causes the switch G to return to its initial position. The system is applicable to single and two phase systems with completely or semiautomatically operated starting and stopping arrangements, and call-storage devices.