GB1219132A - Improvements in foot-operated control switches - Google Patents

Abstract

1,219,132. Retractive switches. DICTAPHONE INTERNATIONAL A.G. 5 Sept., 1968 [5 Sept., 1967], No. 42359/68. Heading H1N. In a foot-operated switch for a dictating machine a cam 1, Fig. 1, and spring-loaded detent follower 12 provide a changing resistance to motion of the pedal 3 whereby the various switch positions may be sensed by the foot. In the example of Fig. 1, the follower end 12 rests in a detent 16 (at the off position I) whereby a high initial force must be applied through lever 6 from pedal 3 to move the cam 1 to the first " on " position II at which a first set of contacts 14 are closed by a cam face 13. At this position the follower 12 rests on a flat 17 providing no further resistance to movement. Return spring 8 provides a small substantially constant return force which is less than the weight of the operators foot so that the switch remains stable. For switching to the second " on " position III at which contacts 15 are closed the follower 12 rides up a sloping cam face 18 whereby a high and increasing force must be applied and maintained by the foot. In an alternative embodiment the foot switch comprises a hollow spherical foot rest 33, Fig. 3, supported by a pair of T-shaped levers 29, 30 pivoting at 31, 32 and engaging a central cam 49 slidable vertically against the action of a return leaf spring 36. The detent spring 22 is U-shaped and has ends 23, 24 engaging detents on both sides of the cam 19. Pairs of contacts 39, 40 are actuated by movement of the levers 29, 30.