PURPOSE: To attain a safety operation by taking over a tripper once held by the second trip release lever before the first trip release lever is dislocated from the tripper, and then releasing the tripper.

CONSTITUTION: During a process of resetting the first trip release lever 100-1 to the old position, the second trip release lever 100-2 also tends to be reset to the oil position, but since a trip pin stop surface of the second trip release lever 100-2 is placed in a trip pin rotational direction a little ahead that of the first trip release lever 100-1, a trip roller 10-a is slightly advanced. Consequently, in the trip pin stop surface of the first trip release lever 100-1, a trip pin 10-a can not be stopped, and the second trip release lever can be reset to the oil original point position by waiting for the trip pin 10-a to pass. However, in this point of time, since nothing is provided for stopping the trip pin 10-a, a clutch can not be reaced, and it is connected. Accordingly, also mechanical safety is made effective.