<p>In order to perform maintenance of a working robot, a worker pulls a handle of a slider (12) and moves the slider (12) backward to thereby withdraw a slider fitting portion (37) from a fitting hole portion (15) and withdraw an actuator from an operating portion of a door switch. In this case, a key (18) inserted into a key hole of a lock is rotated through 90° to vertically orient an interference protruding portion to thereby prevent fitting of the slider fitting portion (37) into the fitting hole portion (15).
Only in this state, the key can be withdrawn from the key hole of the lock.</p>
