To shorten the length of a swing handle by constituting a releasable stopper as one arm lever, providing a button radially protruded from the rotating handle, and pushing the stopper radially from a locking projection into the cavity of a stopper ring by this button.

This device comprises a releasable stopper 5 constituted as one arm lever, and a button 6 radially protruded from a swing handle 3. The stopper 5 is constituted as a deflection spring, and its end section 53 having the spring elasticity is fixed to a horizontal member 4. In order to push the releasable stopper 5 from a locking position to the annular cavity 22 of a stopper ring 22, the button 6 is held within the snap hole 41 of the horizontal member 4 through a lever arm 51 and a pin 610 in such a manner as to be radially rotatable. Accordingly, the releasable stopper can be constituted relatively short.