Abstract: The hydraulic internal gear machine includes a positive displacement unit for the working fluid, the unit being formed of a rotary outer gear which is rigidly connected to a rotary control plate provided with control openings arranged between respective teeth of the outer gear. An inner gear surrounds the outer gear and meshes at one point with the latter to define a plurality of increasing fluid displacement chambers. The inner gear is supported in the machine housing for performing a circular wobbling movement about the center axis of the outer gear. A stationary control plate adjoins the rotary control plate and is provided with second control openings cooperating with the first control openings in the rotary plate. An axially movable plunger is spring-biased against the stationary control plate and forms with the housing cover two annular spaces connected respectively to the intake port and to the discharge port of the working fluid.

Abstract: A radial piston pump has a housing, a shaft mounted for rotation in the housing and including an eccentric provided with a cam track, inlet and outlet ports in the housing, valve means installed in the ports, a plurality of radially reciprocable pistons spaced about the eccentric and each having a radially inner surface in sliding engagement with the cam track, and a layer of synthetic plastic material having a low coefficient of friction on each of the surfaces, so as to reduce friction between the same and the cam track.