Automatic shut-off valve

An automatic shut-off valve having a lower closing pressure than an opening pressure, comprising:

• a housing having an inlet, an outlet, and a partition formed with a valve opening connecting the inlet to the outlet;
• a valve member movable in the outlet side of the partition to an open or closed position with respect to said valve opening;
• a piston movable in the outlet side of said partition independently of said valve member and defining a chamber with said partition;
• said piston being formed with a passageway therethrough establishing communication between the housing outlet and said chamber;
• and a spring urging said piston towards the valve member and the valve member to its closed position against the force of the inlet pressure;
• said piston having a larger cross-sectional area than said valve member, such that the valve member opens the valve opening at a predetermined inlet pressure and closes the valve opening at a lower inlet pressure, said valve member being formed with a stem passing through said valve opening in the partition to the inlet side of the housing, said valve opening in the partition comprising a first bore therethrough for accommodating the valve stem and a second bore therethrough having a seat engageable by said valve member, said first bore being of smaller diameter than said second bore.