Gm Global Technolgoy Operations, Inc.

Liping L Wang

Paul Richard Meernik

Francis Hap-Kwong Chen

A crescent pump including a housing having an inlet port and a discharge port, a driving gear, and a driven gear meshing with driving gear in a gap between the inlet and the discharge ports. External and internal troughs on the driving and the driven gears define pump chambers. A stationary crescent-body has a pair of arc-shaped walls which cooperate with the tips of the external and the internal gear teeth thereon in defining fluid seals. The edges of an inlet ramp at an upstream end of the crescent body and the edges of a discharge ramp at a downstream end of the crescent body define inner and outer upstream and downstream metering orifices which close and open in complementary fashion to maintain constant the rate of fluid leakage from the discharge port toward the inlet port. A pair of shaped metering grooves in the pump housing cooperate in defining a flow path between the discharge port and the inlet port through a succession of trapped volumes between the driving and the driven gears. The flow path has a pair of variable orifices therein calibrated to reduce the fluid pressure in the succession of trapped volumes at a controlled rate.

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Clinton Township, MI, United States of America

Liping L Wang