Abstract: The conventional slotted valve plate of an axial piston pump-motor is replaced by an integral or separate barrel extension having a charge-discharge passageway leading to each cylinder. The passageways lead axially from the cylinders and then turn generally radially inward to open at ports in a circular-cylindrical bore in the extension which is coaxial with the barrel and main shaft axis. The end of a fixed pintle shaft extends into the bore. The pintle shaft has fluid supply and return passages that open to charge and discharge areas within the bore which, in turn, communicate through ports in the shaft with the ports in the barrel. The charge and discharge areas are divided by a diametrical wall, and bridges at the edges of the wall and between the pintle shaft ports serve as valves which sequentially close each barrel port and thereby separate the charge and discharge stages of operation of each cylinder.

Abstract: The pintle shaft of a radial piston hydraulic pump-motor is cantilevered from one end frame member by guideways which permit it to be moved laterally for adjustment of the speed, torque output and direction of rotation. A reaction assembly is journaled in a second frame member by means of the input-output shaft. The reaction assembly includes two reaction rings, one on either side of the cylinder block, which rotate on bearing blocks on the pintle shaft, the bearing blocks and shaft having interengaging parallel, flat slide surfaces which permit the shaft to be translated while still being in mutually supported and stabilized relation with the reaction rings. The side loads on the pintle shaft are counteracted by friction forces developed between the slide surfaces on the bearing blocks and pintle shaft so that the pintle shaft remains stable relative to the reaction assembly without direct mechanical support of its blind end against side loads.

Abstract: The efficiency of a radial piston hydraulic pump or motor is improved by making the ports in the block through which the hydraulic fluid flows from and back to the charge and discharge areas, respectively, of the pintle shaft asymmetrical about their centerlines in the axial direction, the area of the part of each port which lies on the side of the axial centerline remote from the supply and return passages in the pintle shaft being substantially greater than the area of the remaining part of the port. Similarly, the ports in the pintle shaft which communicate the charge and discharge areas to the ports in the block have greater areas in the portions thereof on the side of the axial centerline remote from the supply and return passages than in the portions on the side of the axial centerline nearer the supply and return passages.