Abstract: An improved pump assembly includes a plurality of pumping elements which rotate with a rotor and engage an inner surface of a cam ring to define pumping chambers which hold liquid and/or air. As the pumping chambers move along an inlet arc, liquid flows through an orifice to the chambers. The orifice restricts the rate of flow of liquid to the pumping chambers to a flow rate which is insufficient to fill the chambers with liquid during high speed rotation of the rotor. As the pumping chambers move along an outlet arc which has a constant slope toward the rotor, the volume of each pumping chamber is decreased. When the fluid pressure in the pumping chamber exceeds a pump discharge pressure, one of a series of a check valves opens and fluid is discharged from the pumping chamber.

Abstract: A pump for pumping low viscosity fuels has a cam defining a pumping chamber bore wall. A plurality of slippers define pumping pockets located within the bore wall. The slippers are rotated through inlet arcs and through outlet arcs. A pair of orifices of predetermined diameter are located in the respective inlet arcs and communicate with each pumping pocket at a location radially inwardly of the slippers. Each orifice is circular in cross-section and has a diameter within the range of 0.067 inches to 0.076 inches. Each orifice diameter is such that pump noise restricted and the pump has a relatively high inlet vacuum.