Patent ID: 6997209

Claim:
A locking device of an air-operated normally-closed valve for a gas cylinder, said gas cylinder being provided with a valve port and a valve body which opens and closes said valve port, said locking device comprising: a housing which can be detachably attached to said valve port of said gas cylinder; a piston assembly provided in said housing, said piston assembly being biased by a spring force to move said valve body in a direction to close said valve port when said housing is attached to said valve port; a tapered axial member positioned coaxially with an axis of said piston assembly on an opposite side of said valve port, said tapered axial member having an annular outer tapered surface which gradually reduces in diameter thereof in a direction away from said valve port; a lock nut which is screw-engaged with said housing to be coaxial with said tapered axial member; an annular inner tapered surface formed on an inner peripheral surface of said lock nut to correspond to said annular outer tapered surface; an intermediate cylinder member which is integral with said housing and positioned between said annular outer tapered surface and said annular inner tapered surface, said intermediate cylinder member having at least one radial through hole; and at least one lock piece which is inserted into said radial through hole to be freely movable therein, and contacts with said annular outer tapered surface and said annular inner tapered surface, wherein said lock nut can press said lock piece against said annular outer tapered surface via said annular inner tapered surface to lock said piston assembly by changing an amount of screw engagement of said lock nut with said housing.