GB648355A - Improvements in instantaneous snap-action devices and in the uses of such devices - Google Patents

Abstract

648,355. Snap-action switches. LIEUBRAY, L. L. Feb. 23, 1948, No. 5285. Convention date, Feb. 22, 1947. [Class 38(v)] [Also in Groups XXIX and XXXII] In a snap-action switch a substantially square spring plate has a slot extending from the edge of the plate along a diagonal to a point adjacent the centre of the plate, the end of the slot being forced apart by a fixing member so as to cause the plate to buckle. In Figs. 1 and 4, the slot 2 extends to point just short of the centre of the plate 9 and its end is forced apart by a screw 4, which secures the plate to a support 5 fixed to the switch base 6. The corner of the plate opposite to the slot co-operates with fixed contacts 11, 17. Abutments 10a, 10b engage the underside of the buckled plate 9 and the operating member. 25 engages the plate on the other side at a point 28 adjacent the end of the slot. When the member 25 is depressed, the plate takes or tends to take a position in which its curvature is reversed, the movement occurring with a snap-action. In a modification, Figs. 5 to 7, (not shown), the slot extends beyond the centre of the plate and the operating member engages the plate adjacent the 'side of the slot. The switch, if hand-operated, may be retractive and operated by a push-button as shown, or non-retractive and operated by a push-pull member, a screw, a cam or other suitable member. It may be operated electromagnetically, in which case the armature is attached to the spring plate. Figs. 8 and 9 (not-shown), illustrate thermal switch arrangements utilizing bellows though a bimetallic strip may be used. For fluid pressure actuation of the switch, one or more pressure-sensitive bellows may be used, Figs. 10 and 12, (not shown), and the switch may also be operated by a float, Fig. 11, (not shown). The plate 9 may be of spring steel, phosphorbronze or beryllium-bronze.