Abstract: A pressure-limiting valve coaxial with the drive shaft is installed in a multi-piston pump. The valve is biased by a compression spring to closed condition to prevent output flow from the pump into a pressure-collecting dome of the housing. The spring is supported for reaction against a gasket having a throttle bore leading directly for flow toward a return chamber wherein the end of the pump shaft is a radial wall. When pressure in the pressure-collecting dome reaches a certain value, it will open the pressure-limiting valve against spring bias to relieve pressure through the throttle bore back into the suction channels of the pump. However, the relief flow through the throttle bore causes heating of the oil, an effect which is an important purpose of the invention on pump start-up. Thus, by making the return flow of reduced viscosity due to heating, such oil impinging against the shaft of the pump does not cause a sudden shift of the shaft against the pump housing.

Abstract: A pump and a centrifugal impeller are arranged so that the pump has a suction line in which the centrifugal impeller is installed effecting a countercurrent opposite to the suction feed flow direction to the pump. The effect is to regulate the pump flow responsive to the speed of the centrifugal impeller so that the pump output flow decreases with rising pump speed.

Abstract: A plural piston pump is provided wherein the pistons are carried in bores in a body or hub on a radial plane surrounding an actuating cam and wherein a common pulsator chamber is provided comprised of axial recesses in the hub intermediate the pistons communicates with an annular channel in the hub. The arrangement provides a compact form of pump consisting essentially of a hub member externally sealed in a cylindrical housing open at its ends. The hub is provided with inlet and outlet ports, thus eliminating the need for housing ports and housing end pieces or closures and a relatively large pressure or pulsator chamber volume is formed for smoothing out pump pulsations.

Abstract: An annular elastic valve element is deformed under fluid pressure to control flow of fluid from a piston chamber to a pressure chamber of a piston pump by separation from the peripheral wall surface of a valve seat at a location through which a passage bore extends. The valve seat overlies the outer end of the piston and its peripheral wall has reduced diameter portions spaced from the bore to accommodate elastic deformation of the valve element.