US Patent 7633029 Safety switch

A safety switch capable of detecting withdrawal of an actuator from a switch main unit in a sure and reliable manner even when the safely switch, including a lock mechanism, is in a locked condition and an attempt is made to forcibly withdraw the actuator from the switch main unit. Even when a drive cam becomes capable of rotation since not less than one of a notch cut-out section and a lock member is broken by forcibly extracting an actuator with rotation of the drive cam locked, a cam curve section of the drive cam and an operating rod are in a normal condition and free of breakage. Accordingly, if the drive cam rotates in a counter-clockwise direction, normally-closed contacts of a contact section adopt an open condition normally, and even in situations where the actuator is withdrawn from the switch main unit with a force equal to or greater than the fracture strength of the safety switch, withdrawal of the actuator from the switch main unit can be detected in a sure and reliable manner.