GB805410A - Improvements in or relating to thermally-actuated electric switches - Google Patents

Abstract

805,410. Thermal switches; cam-operated switches. BRYANT ELECTRIC CO. Dec. 31, 1956 [Jan. 3, 1956], No. 39619/56. Class 38 (5). The switch comprises a bimetal strip fixed at one end and having its other end co-operating with a fixed contact, spring means mechanically connected with the bimetal and manual means movable from an " off " position to move the spring means a variable amount and to close the contacts, the bimetal being heated by the current through the circuit thus completed. In one form, Figs. 2, 3, the bimetal 54 is mounted on a terminal 56 and carries a contact 58 co-operating with a contact 72 on a composite bimetal strip 66 mounted on a terminal 64. The bimetal 54 is connected by a strip 62 to an ambient temperature compensating bimetal 60 mounted on a lever 76 pivoted at 74 and biased clockwise (Fig. 2) by a spring 80. The lever 76 has an adjusting screw 95 co-operating with a manually-adjustable cam 26 having a projection 52 which in the off " position shown, separates spring blades 14, 16, which are carried by a terminal 10, from terminals 4, 6. In the " off position, the lever 76 engages a lateral projection on the strip 62 to hold contacts 58, 72 open. As the cam is rotated, contacts 4, 6, 14, 16 close, and the lever 76 and bimetal 60 move upwards, Fig. 2, to close contacts 58, 72. The bimetal 66 has two parts 68, 70 which bend down and up, respectively, when heated, and which are in series with the load which is connected between terminals 10 and 64. Thus, as bimetal 66 is heated it tends to increase the contact pressure until the bimetal 54 overcomes the pressure imparted to it via bimetal 60 by the cam 26, and opens the contacts. The bimetals then cool down and the contacts reclose, and the switch cycles on and off. The line terminals are 4, 56, and terminal 6 is connected to the neutral via a pilot lamp. In a modification, Fig. 4, the movements of the bimetals 541, 601 and the strip 62<SP>1</SP> are controlled by a snap-acting spring 222, the contact 58<SP>1</SP> on the bimetal co-operating with a fixed contact 72<SP>1</SP>. The springs 14<SP>1</SP>, 16<SP>1</SP> are carried respectively by terminals 4<SP>1</SP>, 6<SP>1</SP> and co-operate with terminal 101, the springs having projections 212, cooperating with the face of cam 26<SP>1</SP> which has recesses 214 in the " off position. The edge of the cam engages an arm 230 secured to a member 228 carrying the bimetal 60<SP>1</SP>. The bimetal 54<SP>1</SP> is heated by the current through it and by a coil 224.