GB575233A - Improvements in and relating to snap-action devices particularly adapted for electric switches - Google Patents

Abstract

575,233. Snap-action switches. BRITISH THOMSON-HOUSTON CO., Ltd. March 9, 1944, No. 4403. Convention date, March 12, 1943. [Class 38 (v)] In a snap-action switch constructed as set out in Specification 564,681, the relative dispositions of the pivotal points of the compressed members and the contacts or stops are arranged so that the ends of the stressed member move separately and in sequence with a snap. In Fig. 2 the bottom pair of fixed contacts 21, 21 are of different sizes, as also are the top pair 20, 20, so that the tension members 11 of the member carrying the moving contacts 18, 19 when at rest are not perpendicular to the line of movement of the actuating member 30, 31, 32. When that member is depressed against a spring 35, the point of engagement of compression member 16 with the spring 32 on the actuating member first passes the plane in which the tension members 11 lie so that the left hand contact 18 snaps upwards, and this movement or further downward movement of the actuating member causes the end of the other compression member 17 to pass the dead centre point and contact 19 snaps upward. When pressure is removed from the knob 31 it rises under the force of the spring 35 and the contacts 19, 18 snap downwards in sequence. A switch is described in which the sequential movement of the contacts is obtained by a difference in the lengths of the springs 32, 32 of the actuating member, Fig. 3 (not shown). A switch is also described in which only the top pair of contacts aie of unequal size so that contacts 18, 19 move upwards simultaneously and downwards in sequence. Also a diagram is shown of connections in which the switch is used for reversing a motor which has a forward and reverse field windings.