Patent ID: 7766636

Claim:
A pump, comprising: a) a housing having an exterior surface and an enclosed interior chamber with a sidewall, the chamber substantially circular in cross-section; b) an inlet port providing communication between the exterior surface and the interior chamber; c) an outlet port providing communication between the exterior surface and the interior chamber; d) a crankshaft having a longitudinal axis rotatably disposed within said housing wherein the longitudinal axis is substantially coaxially aligned with the center of the circular cross-section of the interior chamber, the crankshaft further comprising an input shaft for receiving input rotational power; e) an offset shaft having an axis disposed on the crankshaft wherein the offset shaft axis is offset and substantially parallel to the longitudinal axis whereby the offset shaft moves in a substantially circular path within the interior chamber when the crankshaft is rotating; f) an annular spacer rotatably disposed about the offset shaft; g) an annular ring disposed about the offset shaft, the annular ring having a sidewall disposed between the spacer and the interior chamber sidewall, the width of the ring sidewall being substantially the same as the minimum distance separating the spacer and the interior chamber sidewall; and h) a valve disposed between the inlet and outlet ports, the valve configured to maintain contact with the ring as the crankshaft is rotating thereby substantially isolating the inlet port from the outlet port.