Abstract: A piston operated by a cable stretched out within hand reach along a dangerous zone actuates a tappet whose movements are transmitted to a slider. The slider in turn compresses a spring until in a first phase, before any switch actuation, a pawl engages a groove in the slider. This prevents return of the tappet to its rest position, whereby any attempt to simulate a machine breakdown by fraudulent actuation of the device leaves a trace in the device even before effective switch actuation has occurred. In a second phase the force of the spring exceeds the force necessary to retract locking pins of a striker which is therefore released abruptly to operate the switch. To restore the device to its standby state, a lock plug carrying a cam adapted to release the pawl from the groove in the slider is rotated by means of a key.

Abstract: A cable-controlled electrical safety switch device comprises a piston 15 tensioning a cable 2 under the action of a spring 23 via a rod 10 and a screw thread 12a for adjusting the tension of the spring and of the cable. A piston groove 25 actuates a push member 28 for the switch 40. The piston is angularly adjustable. The flank 32 of the groove remote from the spring is helicoidal. When the cable is long, a higher tension is selected so that the groove flank 31 moves away from the push member 28. This distancing is desirable in order that any length variations due to heat--which are greater with a long cable--may be prevented from triggering the switch. The clearance between the other flank 32 and the push member 28 is then corrected by rotation of the piston.