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.

The crankless sinusoidal engine has at least one cylinder, one standard piston and head with combustion chamber and inlet and exhaust valves. A main shaft with one flywheel with incorporated sinusoidal track, Connection between the piston and the sinusoidal track consists of four items; to wit, one connecting rod, one bearing trolley and two segmented rollers, said rollers being in constant contact with said sinusoidal track, one bearing on each side thereof. The bearing trolley sliding on guide pins anchored in opposite ends of cast (alternatively fabricated) housing, said guide pins positioned parallel to the main shaft.

Pressure from the piston forces the segmented rollers against the sinusoidal track, causing rotation.

A variable-displacement hydrostatic axial piston motor of bent-axis construction includes a drive shaft, a cylinder drum that pivots in a pivoting plane, and a one-piece port plate nearly symmetrical with a central plane and with two working ports. The motor further includes an adjusting device with an adjusting piston arranged in the port plate, a control valve arranged on the port plate and with a control valve piston, a feedback spring arranged in the port plate and clamped between the adjusting piston and the control valve piston, a counterbalance valve with a counterbalance spool, and two secondary pressure-limiting valves inserted as cartridge-type inserts into the port plate. The counterbalance spool is accommodated in a valve bore in the port plate. The two working ports are situated on the port plate opposite to the first side. The two secondary pressure-limiting valves are arranged on the same side as the port surfaces.

An axial piston machine may include a shaft and a housing surrounding at least a portion of the shaft. A cylinder arrangement may be disposed within the housing in a circular manner. The cylinder arrangement may include a plurality of cylinders and a plurality of pistons each extending within each of the plurality of cylinders and may be constructed and arranged to drive the shaft. The plurality of cylinders may each include an expansion volume with an inlet and at least one outlet opening for a working medium. A cylinder head may be provided on the housing and may be constructed and arranged to close the plurality of cylinders of the cylinder arrangement. A cavity may be defined around the shaft in a central region of the cylinder arrangement and may be in operative communication with a plurality of auxiliary outlet openings of the expansion volume of each of the plurality of cylinders via a temporary connection. A cylindrical roller slider may rotate within the cavity in the central region of the cylinder arrangement and may be constructed and arranged to drive the shaft. A temporary connection between the cavity and the expansion volume of each of the plurality of cylinders may be formed by at least one of a channel through the cylindrical roller slider and a recess on an outside surface of the cylindrical roller slider. The recess may extend laterally from a casing of the cylindrical roller slider at a height of the plurality of auxiliary outlet openings in each of the plurality of cylinders and at a distance to the cavity in the central region of the cylinder arrangement.

An axial piston machine may include a rotor having a shaft rotatably mounted in a housing. A plurality of cylinders may be arranged annularly around the rotor. A plurality of pistons may each be disposed within each of the plurality of cylinders and may be constructed and arranged to selectively translate within each of the plurality of cylinders. Each of the plurality of cylinders may be disposed within a cylinder head and may be in operative communication with an inlet opening defined in the cylinder head and at least one outlet opening defined in the housing. An auxiliary outlet rotary slide valve may be operatively connected to the shaft in a rotationally fixed manner. The auxiliary outlet rotary slide valve may comprises an auxiliary outlet rotary opening constructed and arranged to connect to a vent duct of one of the plurality of cylinders based on an angle of rotation, and may vent the one of the plurality of cylinders. At least a portion of the auxiliary outlet rotary slide valve may comprise a material constructed and arranged to reduce a sliding friction resistance, and wherein the material comprises one of a carbon containing material or a polymer containing material.

A bent axis plunger-type variable hydraulic motor pump, including a cylinder body, a plunger, a ball connecting rod, a plunger spherical hinge, a multistage ball track spherical hinge shaft, a multistage ball track bearing ring, a retainer plate, an oil distributing plate, an oil distributing plate pin shaft, a suspension circle, a bushing bearing ring, a box bushing shaft, a box, a large variable ball connecting rod assembly, and a small variable ball connecting rod assembly. The large and small variable ball connecting rod assemblies are mounted on the box. The multistage ball track spherical hinge shaft is supported on the multistage ball track bearing ring, and a multistage rolling element holder in which a rolling element is provided is mounted in the multistage ball track spherical hinge shaft. Two ends of the ball connecting rod are hingedly connected to the multistage ball track spherical hinge shaft and the plunger.