GB978321A - Snap switch - Google Patents

Abstract

978,321. Electric switches. TUNG-SOL ELECTRIC Inc. May 25, 1961 [Feb. 6, 1961], No. 18969/61. Heading H2B. A hot-wire-actuated snap switch comprises a resilient rectangular plate 2 having two longitudinal slots 4 defining a waisted central vane 6, the plate being deformed adjacent each vane end 14, 16 to bias it outwardly from the plane of the strips 8 on the outsides of the slots, each strip being shortened relative to the vane by crimps 10. The plate is welded or otherwise affixed, at one end, to a conducting frame 18 in which a contact 32 is insulatedly mounted so as to co-operate with a vane contact 20, whilst an L-shaped anchor member 22 secured on the convex frame mounted vane part is connected by a thermally extensible control-currentcarrying wire or ribbon 28, to an upstanding frame portion 26, the member 28 being mounted in an insulating bead 24, at the vane end, and so tensioned as to bow the vane central portion oppositely to its biased ends, the co-operating contacts being " made " when the control current causes a reduction in tension of the member 28. During operation of the switch the radii of curvature of the vane parts vary, but no alteration of sign occurs. The above snap switch may be combined with a magnetic relay on a common insulated pin mounted base, so as to form a lamp flashing device. Thus, when the wire 21 is cold and hence the contacts 20, 32 are open, a current flows through frame 26, the wire 28, a ballast resistor 30, a relay winding 34, and a lamp 36 intended to be flashed. Due to resistor 30, the current will be insufficient to energize either the relay 34 or lamp 36, but will heat the wire 28, causing it to expand and hence close the contacts 20, 32. Both the wire 28 and the resistor 30 are now shorted so that, the relay 34 will close contact 38 to light a pilot lamp 40, the lamp 36 will light, and the wire 28 will cool, so opening the contacts 20, 32 to repeat the cycle. The ballast resistor 30 may be shielded from the wire 28 by a mica plate. A " stop " for the member 9 in its de-energized position may be utilized as a contact which co-operates with a further vane mounted contact if a thrust over contact configuration is required.