Abstract: A variable volume pump for satisfying the requirements of a hydraulic system while absorbing excess fluid volume when the full volume of fluid displacement from the pump is not required by the hydraulic system. The pump includes one or more lines of reciprocable pistons mounted radially around a crankshaft. The rotation of the crankshaft results in centrifugal flow of fluid through crankpin apertures for filling the pistons. Each piston includes a cylindrical tube portion which is slidably movable within a metering sleeve. The metering sleeve is spring biased towards a position for covering metering ports that are located around the periphery of the piston tube portion. When the fluid pressure in the hydraulic system acting on a metering sleeve abutment area exceeds the force of the metering sleeve spring, the metering sleeve moves thereby uncovering the piston metering ports. The movement of the metering sleeve permits the piston to travel an equal distance with its metering ports open.

Abstract: A fixed displacement pump including a variable capacitance flow regulator for absorbing the excess fluid flow from the pump which is not required by a hydraulic system. The variable capacitance flow regulator, in a hydraulic embodiment, includes a pair of pistons slidably movable within a housing for independent movement relative to each other. The fluid pressure in the hydraulic system is communicated to a first of the pistons to bias it to various positions within the housing depending upon the pressure level in the hydraulic system. The second or varibale capacitance piston is acted upon by the fluid pressure in the pump discharge chamber, and when the pressure in the hydraulic system exceeds the spring pre-load against the first piston, the first piston will be displaced away from the second piston.

Abstract: An improved slipper is disclosed for a fluid pressure pump of the radial piston type for operably connecting a piston to a cam lobe on a crankshaft. The slipper includes an inner arcuate side surface for engagement with the cam lobe on the crankshaft and an opening through the slipper body to permit centrifugal flow of fluid for piston filling. The opposite side of the slipper body includes a recess for retaining a hardened annular seat inert. The spherical head of the piston rides on the inner circumference or edge of the insert, and the sharp edge of the insert provides a wiping action on the piston head as relative motion occurs between the piston and slipper. Further, an open area is provided on both sides of the line of contact between the piston and slipper to prevent contaminants from entering between the contacting surfaces which would spoil the seat.