Abstract: A positioning drive having a hydraulic motor with a cam disc which is rotatable with a motor shaft and has a cam, a control valve which, with the hydraulic motor forms a unit with a housing and has a valve piston which is displaceable between several positions, a control element via which the valve piston can be supported on the cam disc, and an adjustment element which is operatively disposed between the control element and the valve piston and coaxial to the latter. The relative position between the valve piston and control element is variable by relative adjustment of the adjustment element with respect to the valve piston. The position of the adjustment element relative to the valve piston is securable by a releasable locking element. The outer of the two parts, valve piston and adjustment element, is guided outwards through the housing, and the locking element is accessible externally of the housing.

Abstract: Closed loop control circuit for a variable hydraulic pump the output flow of the pump being variable by control means and the pump including at least two closed loop controllers actuating the control means, wherein at least one hydraulic switching element is provided which automatically connects to the control means the closed loop controller providing the highest or the lowest pressure.

Abstract: A vane pump or a vane motor is here specified, having a variable displacement volume. The vane pump has a vane rotor and an annular stator that surrounds the rotor eccentrically and that is stabilized by means of a piston arrangement for adjusting the eccentricity that determines the displacement volume. The piston arrangement includes at least one pendulum piston that is acted upon by a pressure medium, the pendulum piston being guided in a sealed manner in a housing bore by a piston head that delimits a control space. To simplify the assembly and to decrease manufacturing costs while simultaneously improving the sealing action and increasing the peripheral life of the guide surfaces, plastic rings, which are composed of wear resistant, sliding material, or are prestressed radially, to guide the piston in the piston bore and to seal the control space are embedded, inserted or emplaced in the piston head.

Abstract: A hydraulic circuit comprising a control pump having first and second adjustment means for changing the output volume of fluid pump, and a regulating valve adapted to suppy user means with a pressurized liquid.

Abstract: The invention relates to a radial piston machine comprising height adjustment means, control means and adjustment means all having abutment means designed such that the cam ring of the machine will carry out during its adjustment a substantially rolling movement.