A piston arrangement comprising a cylinder, a piston head movable along a piston axis within the cylinder, a con rod, and a track having a path; wherein the con rod has a first end which is coupled to the piston head and a second end which is coupled to the track; wherein the track is adapted to be moved relative to the cylinder and is shaped such that, as the track moves relative to the cylinder, the piston head moves in reciprocating motion along the piston axis in accordance with the path of the track; wherein the path of the track is shaped such that piston head displacement is non simple harmonic with respect to displacement of the track relative to the cylinder. Also an internal combustion engine including the piston arrangement.

A radial piston machine includes at least one piston unit with a piston and at least one rolling element rotatably mounted in a rolling element receptable of the piston. The piston of the piston unit is polished.

A hydrostatic radial piston machine is useable inversely. The hydrostatic radial piston machine has a distributor in which a flushing valve, a pressure-maintaining valve connected downstream of the flushing valve, and two nonreturn valves are arranged.

A piston unit includes a piston which has a rolling element seat configured to rotatably support a rolling element. The rolling element seat has a bearing surface with a surface coating composed of a polymer compound or with a ceramic surface coating.

Disclosed is an offset rotational internal combustion engine in which an outer ring rotates on a one axis and an inner disk rotates on a second offset axis. Pistons are connected to the outer ring, while cylinders and other devices for operating the engine are mounted within an inner disk that rotates on a second axis that is offset from the axis of the outer ring. The inner disk and outer ring rotate together, such that the pistons create conditions of compression and explosive expansion within the cylinders without vibrating reciprocal piston motion. A unique fuel injection system is also disclosed that provides a variable fuel pressure that is created by centrifugal forces on the fuel. Because of the rotating inner disk and outer ring, advantages are taken of centrifugal force and gravity to distribute fuel, air, oil, high-voltage current, and cooling air in the engine.

A rotary cam radial engine formed of two primary components engaged at a mid section to allow for an easy repair to the vehicle. The device features a body having radially oriented apertures; and a plurality of pistons in a respective reciprocating engagement, within each respective said cylinder. The pistons are driven by low pressure fluids and/or a vacuum and the engine being formed of two main components can be taken apart without tools for maintenance and reconfiguration.

The invention relates to a radial piston hydraulic motor. The radial piston hydraulic motor comprises a cam ring provided, with a wave-shaped inner surface and radial cylinders provided in the inner part inside the cam ring and pistons that move therein as well as rollers coupled to the pistons so as to follow the inner surface of the cam ring. By the effect of the working pressure of hydraulic oil conveyed to the cylinders, the rollers that are pressed against the inner surface of the cam ring provide a rotating movement of the cam ring and the inner part relative to each other. The hydraulic motor is provided with disengaging members disengaging the rollers coupled to the pistons from contact to the inner surface of the cam ring when the working pressure stops acting in the cylinders for bringing the hydraulic motor into freewheeling. The hydraulic motor is provided with a control coupling which, when the prevailing pressure of hydraulic oil in the working pressure line that leads to the cylinders drops below a specific level, automatically disengages the cylinders from the working pressure line and couples the hydraulic motor into freewheeling.