GB805683A - Improvements in snap-action electric switches - Google Patents

Abstract

805,683. Retractive switches; actuation of switches; switch cases. DOWTY EQUIPMENT Ltd. Feb. 28, 1957 [March 1, 1956], No. 6489/56. Class 38 (5). A snapping blade 1 has a cut-out 2 and lugs 6 ... 8 resting on the bottom of recesses 10, 13, 14 on the switch base 9, the contactcarrying end 4 being crimped or set so that the blade is normally curved longitudinally and transversely to the configuration shown in Figs. 4, 5 in which a fixed contact 16 is engaged. To reverse the switch, a dimple 26 on a spring blade 25 engages the blade midway between lugs 6, 7, whereby increased downward pressure is imparted to the contact 4 to compensate for the diminishing curvature of the blade until it snaps over. As the pressure produced by the blade 25 is withdrawn, the blade 1 snaps back to its original position, the contact-pressure being compensated as before. To produce the movement of blade 25, the cover 11 contains a push-button 31 having a conical part 36 which acts on a ball 37 in a recess 38, the ball bearing on the blade 25 through the intermediary of a metal plate 39 and rubber sheet 29. The casing parts 9, 11 have flanges 27, 28 respectively, and sheet 29 is enclosed within flange 28 and engaged by flange 27 to produce a water-tight joint. Current is led from pin 23 to the contact 4 by way of a spring sheet 22 having three limbs which fit into recesses 10, 13, 14 under the lugs 6 ... 8. In a modification (not shown), the blade 1 is continued beyond the lugs 6, 7 to provide a second curved blade, so producing a double-break switch. Also, the curvature may be produced by transversely lengthening the fixed end of the blade. The Provisional Specification states also that the blade may be stiffened by laminating for greater current-carrying capacity, or made of bimetal for temperature sensitiveness.