GB233767A - Improvements in and relating to means for energizing an electric winding, relay or the like, after a definite time lag - Google Patents

Abstract

233,767. British Thomson-Houston Co., Ltd., and Fitzgerald, A. S. Feb. 12, 1924. Thermal switches in which the time taken to heat up and cool down again is considerable are employed to give a time-delay action so that the energization of a winding takes place some time after a hand-controlled switch is closed. As shown in Fig. 1, in which the hand closure of the switch 11 is arranged to energize the winding 23 after a certain time, the closure of switch 11 energizes the primary 13 of a transformer through the normally-closed contacts 19 of an electromagnetic switch. The secondary of the transformer supplies current to a thermal strip 15 which rapidly heats up, leaves the contact 16 and engages the contact 17, thereby short-circuiting a resistance 22 through which the electromagnet has been feebly energized on the closure of switch 11. The electromagnet switch opens at 19 and prepares the circuit of the winding 23 at 24. It remains in this position, under the weak energization through the resistance 22, while the thermal strip cools down and finally completes the circuit of winding 23 by engaging the contact 16. The winding 23 may be weakly energized through an additional resistance when the contacts 24 are closed and effectively energized when the thermal element cools down, the weak energization being adequate to hold a core when once it has been attracted.