A rotatable piston assembly for a reciprocating piston type hydraulic machine includes a rotatable piston configured for a controlled rotation and configured to reciprocate within a cylinder bore of the reciprocating piston type hydraulic machine.

A variable displacement axial piston pump including a cylinder block defining a plurality of cylinder bores, each receiving a piston. A swash plate having a piston-supporting surface is pivotally supported relative to the cylinder block. A port block defines first and second pumping ports arranged in fluid communication with the plurality of cylinder bores such that, during operation of the pump, one of the first and second pumping ports is configured to supply fluid to the cylinder bores for pumping, and the other of the first and second pumping ports is configured to receive fluid pumped from the plurality of cylinder bores. The swash plate partially defines at least one variable volume control chamber, and the swash plate is operable to tilt with respect to the port block in response to a fluid pressure change in the at least one control chamber.

In accordance with at least one aspect of this disclosure, a system includes, a cylinder barrel configured to rotate within a pump housing of a pump operatively connected to a driving member of the pump via a first shaft. A piston is seated within a bore defined in the cylinder barrel. The piston is operatively connected to the driving member of the pump via a second shaft. The first shaft and the second shaft each include a ball end configured to seat within the driving member. In embodiments, the ball end of at least the second shaft is of silicon nitride.

In accordance with at least one aspect of this disclosure, a system includes, a cylinder barrel configured to rotate within a pump housing of a pump operatively connected to a driving member of the pump via a first shaft. A piston is seated within a bore defined in the cylinder barrel. The piston is operatively connected to the driving member of the pump via a second shaft. The first shaft and the second shaft each include a ball end configured to seat within the driving member. In embodiments, the ball end of at least the second shaft is of silicon nitride.

A piston pump/motor includes a cylinder block rotated with a shaft; a piston slidably inserted into a cylinder that is formed on the cylinder block; a shoe rotatably connected to a tip end portion of the piston, the shoe being in sliding contact with the tip end portion; and a swash plate with which the shoe is in sliding contact. The shoe has a piston slide portion in sliding contact with the piston and a swash-plate slide portion in sliding contact with the swash plate; a shoe body portion on which the piston slide portion and the swash-plate slide portion are mounted; and a first lock portion and a second lock portion provided across the shoe body portion, and the piston slide portion and the swash-plate slide portion, respectively, the first lock portion and the second lock portion regulating relative rotation between the shoe body portion, and the piston slide portion and the swash-plate slide portion.

A hydrostatic positive-displacement machine, in particular a hydrostatic axial piston machine, having a cylinder drum with at least one cylinder, in which a longitudinally displaceable piston is received, which is supported directly or indirectly by a support portion on an inclined plane of the positive-displacement machine. An outer circumferential surface portion of the piston is in bearing contact with an inner circumferential surface portion of the cylinder.

A piston pump configured to suction and discharge a working fluid includes a plurality of pistons, a cylinder block accommodating the pistons, a shaft combined with the cylinder block, swash plate configured to reciprocate the pistons in accordance with rotation of the cylinder block, a casing accommodating the cylinder block, and a valve plate placed between the cylinder block and the casing. The valve plate has a suction port providing communication between capacity chambers and a suction passage, and the suction port is a cutout part formed by cutting out an outer edge of the valve plate.

A sliding shoe for supporting a piston of a hydrostatic axial piston machine against a swash plate includes a sliding face that defines a central concentric pressure pocket that is flat in order to stabilize the sliding shoe. The pressure pocket has radial supply grooves in order to ensure an optimal supply of pressure medium to the pressure pocket from a central mouth opening. The radial supply grooves extend through the pressure pocket and as far as a circumferential groove which surrounds the pressure pocket.

In accordance with at least one aspect of this disclosure, a system includes, a cylinder barrel configured to rotate within a pump housing of a pump operatively connected to a driving member of the pump via a first shaft. A piston is seated within a bore defined in the cylinder barrel. The piston is operatively connected to the driving member of the pump via a second shaft. The first shaft and the second shaft each include a ball end configured to seat within the driving member. In embodiments, the ball end of at least the second shaft is of silicon nitride.

In accordance with at least one aspect of this disclosure, a system includes, a cylinder barrel configured to rotate within a pump housing of a pump operatively connected to a driving member of the pump via a first shaft. A piston is seated within a bore defined in the cylinder barrel. The piston is operatively connected to the driving member of the pump via a second shaft. The first shaft and the second shaft each include a ball end configured to seat within the driving member. In embodiments, the ball end of at least the second shaft is of silicon nitride.