Safety switch

摘要

A safety switch is improved by the feature of staying in an open position in the event of breakage of a working rod or breakage or dropout of an operation portion and having a simple structure facilitating size reduction. Even if a rotary shaft is released from a supported state in an operation portion because an operating force of an operation or the number of operations of extracting an actuator from the operation portion exceeds a breakage tolerance, a working rod is permitted to move in an urging direction of a coil spring and is assuredly moved to the operation portion. Therefore, a switch can be assuredly set to an open position and, hence, the safety switch can achieve the safety improvement.

主权项

1. A safety switch comprising:
an operation portion provided with a driving cam as an operable member which operates as rotating in either direction in response to an external operation of inserting or extracting an actuator; a switch portion provided with a first switch including a movable contact and a stationary contact; urging means for urging the movable contact in a direction away from the stationary contact; and a working rod interlocked with the rotation of the driving cam, the working rod moving against an urging force of the urging means to move the movable contact into contact with the stationary contact when the driving cam is rotated by the insertion operation, or the working rod moving under the urging force of the urging means to move the movable contact in the opposite direction of the movement during the insertion operation and separating the movable contact from the stationary contact when the driving cam is rotated by the extraction operation, the safety switch further comprising a permission structure which, when broken, permits at least the movement of the working rod in an urging direction of the urging means, wherein the permission structure is formed in a support portion for supporting a rotary shaft of the driving cam, and wherein a breaking strength of the support portion is set by the permission structure in a manner that a breakage of the support portion is induced when an operation force of the extraction operation or the number of extraction operations exceeds allowable values below which no damage occurs on the safety switch, while, at the breakage of the support portion, the permission structure permits at least the movement of the working rod in the urging direction of the urging means by releasing the support of the rotary shaft by the support portion, thus separating the movable contact from the stationary contact.