GB818805A - New or improved current sensitive switches and electric appliances embodying such switches - Google Patents

Abstract

818,805. Thermal switches. MORPHY. RICHARDS Ltd. March 28, 1958 [March 28, 1957], No. 10175/57. Class 38 (5). In a switch similar to that of Specification 727,022, the slow response member is arranged eventually to prevent movement of a part controlled by the fast response member between positions in which that part permits and prevents the slow response member to connect the ancillary circuit to the supply. As shown, the slow response member is a bi-metal 2 secured at its right-hand end to a member 4 carrying a contact 7 and mounted by a leaf spring 5 which biases the left-hand end of the bi-metal against the base 1. The member 2 carries a heater 24 connected to a terminal 25 and to a member 10 carrying by means of a leaf spring 11 a lever 12 to which is fixed one end of a hot wire 14, the other end of which is adjustably mounted at 15. When a low voltage is applied, the bi-metal 2 arches downwardly, thereby engaging contact 7 with a fixed contact 8 to energize the ancillary heater. The bimetal 2 and member 4 carry opposed lugs 20, 22 which when the contacts 7, 8 close are moved sufficiently close together to prevent the lever 12 from passing therebetween. If, however, a high voltage is applied, the hot wire 14 rapidly moves the lever 12 to the right, Fig. 3, before the contacts 7, 8 can engage, thereby preventing the members 2, 4 from moving close enough together to close them. Whether or not contacts 7, 8 close, the bi-metal eventually bends sufficiently to close contacts 26, 27 to short out the hot wire and the heater 24, the heat from the sole plate of an iron with which the switch may be used, being sufficient to maintain the bimetal flexed.