Abstract: A radial type of fluid-pressure apparatus, such as a pump or motor, wherein a crankshaft is supported for rotation about its axis and has a crankpin radially spaced from its axis and connected with the inner end region of a piston which extends outwardly away from the crankshaft axis and which has an outer end region extending into a chamber of an outer housing structure which surrounds the crankshaft axis. This chamber communicates with a fluid passage. An inner circular housing structure is surrounded by the outer housing structure and surrounds the crankshaft while being formed with an opening through which the piston extends, this inner housing structure having a seat at its opening which surrounds the piston. The latter seat forms part of a sphere. The piston extends slidably through a sleeve which has an outer surface also forming part of the latter sphere and seated on this seat.

Abstract: A rotor is rotatably mounted in a housing and formed with angularly spaced radially oriented cylinder bores in each of which a piston is radially reciprocable. The radially outer end of each piston is formed with an inwardly extending recess having a length greater than the length of the piston stroke. A control ring which is eccentric relative to the rotor surrounds the latter, and its inner circumferential surface is slidingly contacted by respective piston shoes each of which is associated with one of the pistons and each of which has a shaft that is freely received in the recess of the associated piston and whose length is also greater than the length of the piston stroke.

Abstract: The bearing surface of each piston is provided with hydrostatic pressure medium during operation to maintain the axis of the piston perpendicular to the guide surface. The pressure medium is supplied through throttle passages which terminate in feed openings at the corners or at uniformly distributed points remote from the piston axis. Cooperating guide ledges are also provided on each foot and on the guide member to prevent the piston bearing surfaces from falling away from their respective guide surfaces of the guide member.