Seal in high pressure pneumatic booster valve

A booster valve for providing pressurized air to a pneumatic conveyor, comprising:

• a) a generally cylindrical housing having an air inlet opening and an air outlet opening;
• b) a hollow chamber within said housing;
• c) a cuplike member located coaxially within said chamber with an air-flow space between said cuplike member and said housing, said cuplike member open at an end toward said air inlet opening and closed at the other end;
• d) an air inlet passageway providing air communication between said air inlet opening and said open end of said cuplike member into the interior of said cuplike member;
• e) an air outlet passageway providing air communication between said air outlet opening and said air-flow space;
• f) an air passageway from the open end of said cuplike member to said air-flow space;
• and
• g) a generally cylindrical resilient seal around the exterior of said cuplike member in said air-flow space, said seal biased to close off air flow in said air-flow space, said seal resiliently flexed radially outward to permit air flow from the open end of said cuplike member through said air-flow space when the air pressure at said chamber is greater than the air pressure at said air outlet passageway.