Patent GB-423804-A (GB)
Title: Improvements in or relating to lift controlling systems
IPC: H02P7/34
Filed: 1933-08-16
Abstract: 423,804. Master control of D.C. motors. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and SMART, N. C., c/o General Electric Co., Stoke, Coventry. Aug. 16, 1933, No. 22853. [Class 38 (iii)] A control system for an electrically driven lift includes an electromagnetic step - by - step switch of the type used in telephone systems, positioned according to the load in the lift, whereby the accelertion and deceleration are rendered independent of the load. Upon operation of a press - button switch U, Fig. 2, electromagnetic switches E, UR, H, are closed so that the field of a Ward-Leonard generator is connected to a supply K, Fig. 1, in an appropriate direction through a potentiometer PT, and a step-by-step switch LC is energized through a vibrator VR. The lift is thus started, and when an inductor plate is removed from coils LA2, LB2, a relay R is operated to energize an electromagnetic switch M which opens the circuit of LC and transfers the circuit through the vibrator VR to a step-by-step switch S. Thus the contact bank LC1 of the switch LC is adjusted to an extent depending upon the time taken by the lift to move a certain distance, and therefore, the resistance SR in the potentiometer circuit PT is adjusted in accordance with the lift load, and this initial adjustment is effective for the subsequent acceleration and deceleration of the lift. The switch S in its movement accelerates the lift to its maximum speed by means of the contact bank S1. Relays responsive to the voltage of the generator, and having contacts v1, w1, hold up the switch S if the generator voltage has not built up in time so that overloading is prevented. A bank of contacts S6 of the switch S control relays F, G, which control the coils LA1-LA4 and LB1-LB3. When the switch S is moved to its full speed position the circuit of its stepping coil is opened and it stops. Upon release of the button U at a point greater than one floor in advance of the desired stopping floor, the relay H is de-energized, and, when a first inductor plate passes the coils LA1, LB1, the relay R is released, a relay P is operated, and a step-bystep switch C is moved one contact. The relay P transfers the generator field circuit to contact banks of a step-by-step switch A. When the plate leaves the coils LA1, LB1, the relay R again operates the step switch C to its third contact, so that the switch A is energized through the first bank of contacts on A2 and the third on S3. The switch A is therefore, stepped round to reduce the generator field by means of a contact bank A1, until the switch circuit is broken when the second group of contacts on A2 is reached. The switch waits in this position until the next inductor plate passes the coils LA2, LB1, the change over from coil LA1 to LA2 being made by a bank of contacts C6 on the switch C which opens the relay G. The relay R thus steps the switch C two contacts as before, and the circuit of the switch A is again made, but through the second bank of contacts on A2, so that the generator field is still further reduced. The switch A is, in similar fashion, moved to its final position, the five inductor plates being counted on the switch C, and the speed of the lift checked at the several contact banks. If the lift does not decelerate quickly enough the stepping circuit of the switch A is completed through a contact bank C2 and its own interrupter a, and the speed of the switch is increased. When the fifth inductor plate is encountered the relay R steps the switch C to its tenth contact, and a relay Q is operated to deenergize UR and E, the generator field being opened and returning circuits for the switches A, C, S and LC being completed. If the lift reaches only an intermediate speed when the button U is released, the switch S stands on its second contact group, relay G is not operated and only four inductor plates are effective. The circuit for the switch A is also made through the contact bank A6 and the second contact bank on S3. Similarly the contact bank A5 with fewer contacts is employed for reducing the generator field so that the lift is brought to rest quickly. If the lift moves only from one floor to the next it 'is at its lowest speed when U is released, and the switch S is stopped on its first bank of contacts. The relays F and G are not operated, and only three inductor plates are effective. The circuit of switch A in this case is made through contact bank A8, and the bank A7 with fewer contacts effects the reduction of generator field. The step-by-step electromagnetic switches LC, A, S, and C, may be as shown in Specification 349,180. The potentiometer PT may be replaced by a series resistance suitably tapped, while the inductor plates may operate on relays fixed to the lift, interrupt or deflect a light beam, or conduct a magnetic or electrostatic field between the coils. The potentiometer may be supplied with alternating-current with a rectifier inserted in circuit.