Pressure-responsive shut-off valve

A pressure-responsive check valve for use with a pressurized gas cylinder, said check valve comprising:

• a body having a passageway through which gas flows from an inlet to an outlet;
• an annular shoulder surrounding the passageway, said shoulder including a generally chamfered mating surface which depends from the shoulder;
• a plug for sealing against the shoulder, said plug being reciprocally mounted within the passageway and including a relatively soft surface aligned with the chamfered surface and a relatively hard surface aligned with the shoulder;
• first means for moving the plug to engage the soft surface of the plug with the chamfered mating surface of the valve seat when the pressure at the inlet has decreased to a predetermined set point so that the flow of gas through the passageway is shut off when the pressure at the inlet reaches the set point, said first means comprising a spring which at one end engages the plug and at the other end is fixed within the passageway so that said spring applies a constant closing force on the plug;
• and
• second means which is independent of the first means for moving the plug to engage the hard surface of the plug with the shoulder so that the flow of gas through the passgeway can be shut off against pressure at the inlet which exceeds the set point;
• whereby the relatively soft surface assures a seal at low gas pressure and the relatively hard surface assures a seal at high pressure.

A pressure-responsive check valve system for use with a pressurized gas cylinder, said check valve system comprising:

• a check valve which includes:
• a valve body having an inlet and an outlet and a passage therebetween;
• a valve seat which defines a portion of the passageway;
• a valve plug reciprocably mounted within the valve body, said plug having a shoulder and being capable of engaging the valve seat to block the flow of gas through the passageway;
• means for urging the valve plug against the valve seat to shut off the flow of gas in the passageway, said means operating automatically when the pressure at the inlet falls below a predetermined level and capable of being manually operated regardless of the pressure at the inlet;
• and
• a tool for bypassing the flow of gas from the outlet to the inlet for filling the gas cylinder with gas where the pressure at the inlet is below the predetermined level, the tool including:
• a shaft having a passageway therethrough;
• a member at one end of the shaft for engaging the shoulder on the valve plugs, said member being arranged eccentrically with respect to the axis of the shaft;
• means for rotating the shaft about its axis;
• means for securing the shaft to the outlet and for sealing the resulting junction against leakage of gas;
• and
• means for connecting the shaft to a source of gas for refilling the cylinder;
• whereby rotation of the shaft disengages the valve plug from the valve seat.