PURPOSE: To quickly release a bolt by forming a bolt lock with spring clutch so that a claw pivotally fitted to the bolt and for releasing the bolt is turned when a release lever is turned by a spring clutch opening element.

CONSTITUTION: When a handle is turned clockwise, a spring clutch 5 of an opening element 16 is drawn back, and a lever 29 is turned around a support point 30. When the lever 29 rotates a claw 31, the claw 31 pulls a bolt locking element 26 while compressing a spring 27. Continuously, the lever 29 pushes a wing part 26b of the bolt locking element 26 projected from a surface of a tank 23, and moves the element 26 and the bolt 6 to a release position so as to release the bolt 6. In the case where the bolt 6 is released by a key, a reset lever 36 works to the opening element 16 so as to open the spring clutch 5.