GB721435A - Improvements in or relating to electrical relays - Google Patents

Abstract

721,435. Switching systems for consumption apparatus. WILCOX & CO., Ltd., E., and WILCOX, E. R. May 20, 1952. [Feb. 20, 1951], No. 4062/51. Class 38 (4). [Also in Group XXXVII] The current of a system is limited during periods when the system voltage falls below a certain value by a relay comprising an undervoltage release switch whose contacts, when closed, short circuit the actuating element of a re-settable overload release switch. The undervoltage switch comprises a bimetal strip i which has a heater j permanently connected to supply terminals b, f and insulatingly carries a contact bar k, having contacts m, n cooperating with contacts o, d. The latter is carried by a rigid, fixed bar a connected at one end to the terminal b and supporting a spindle r which is urged to rotate by a spring s and carries a cradle t supporting a bimetal strip x. Strip x carries a contact y which co-operates with the contact o which is mounted on a spring p. When the voltage is normal, the contacts are closed as shown, so that strip x is shorted out, but if the voltage falls, strip i bends down and removes the short from strip x which, if an excessive current occurs, arches upwards until it clears a pin e, whereupon it is rotated counter-clockwise about pin r by spring 8 to separate contacts o, y. The operating current is determined by the pressure of a spring v and the size of strip x. The latter is restored, after cooling, by a push-button indicated at z. It is stated that the relay may alternatively be operated electromagnetically, or by a combination of the two methods.