To easily open/close a valve by simplifying the operation of a crank lever for opening/closing the valve.

A spring 11 for energizing in the retreat direction a slide adapter 14 having a valve 15 which is closed when it is moved forward and is opened when it is move backward and which is always energized in the forward direction by a spring 21 is interposed between a socket body 3 and the slide adapter 14 and a sleeve 25 which connected to the slide adapter 14 by a connecting pin 27 through a hole 26 made in the socket body 3 is slidably fitted on the outer peripheral surface of the socket body 3 and an eccentric cam 30 which is abutted on the end of the sleeve 25 and which is rotated by operating the crank lever 28 to move the sleeve 25 forward is provided on a crank lever 28 mounted on the outside of the socket body 3. The maximum radius position of the eccentric at the maximum forward position of the sleeve 25 is set at a position slanting against the moving direction D of the sleeve 25 which passes the pivot C of the eccentric cam 30.