PURPOSE: To obtain a product prevented from the generation of malfunction and stabilized in operation by providing a guide path engaged with an engaging pin fitted to an operation rod and extended in the pushing direction of the operation rod and an inclined path for disengaging the engaging pin.

CONSTITUTION: The engaging pin 25 is protruded upwards into the operation rod 11 side of an opposing part. The recessed groove-like guide path 26 engaged with the engaging pin 25 and extended in the pushing direction of the operation rod from its leading end position (a), the inclined part 28 for disengaging the engaging pin 25 continuously from the guide path 26 and a projected receiving chip 29 for receiving the engaging pin 25 disengaged by the inclined part 28 in the exciting direction of a spring 8 are formed on the inside of the rotary lever 9 side of the said opposing part. Such a constitution makes it possible to prevent the generation of malfunction and obtain a product with stable operation.