Abstract: A hydraulic piston machine is proposed, with a cylinder body (1), which comprises at least one cylinder (2) with a piston (3) movable therein, and a control counter-plate (7) which engages the cylinder body (1) by way of a contact surface (6) and, on relative movement between the cylinder body and the control counter-plate parallel to the contact surface, connects the cylinder in dependence upon its position with inlet and outlet channels (11, 12) respectively, the control counter-plate (7) and/or the cylinder body (1) being provided, at least in the region of the contact surface (6, 9), with a friction-reducing layer (13). A machine of that kind should be inexpensive to manufacture yet should operate reliably even when the hydraulic fluid has no or only slight lubricating properties. For that purpose the friction-reducing layer (13) is in the form of an injection-moulded part.

Abstract: A hydraulic machine with a piston and slider shoe unit (1) is disclosed, in which the piston (2) and the slider shoe (3) are joined to one another by way of a ball-and-socket joint (4) forming a first contact surface, and the slider shoe (3) lies via the intermediary of a second contact surface on a control surface (9), a friction-reducing layer being arranged on one contact surface. It is desirable for a hydraulic machine of the that kind to be capable of reliable operation even when using hydraulic fluids having only a operation even when using hydraulic fluids having only a poor or no lubricating effect at all, yet to be inexpensive to manufacture. For that purpose, the friction-reducing layer (11) is extended to at least one further contact surface.

Abstract: A hydraulic piston machine is disclosed, having a cylinder drum and a control plate, which control plate has at least one high-pressure "kidney" and at least one low-pressure "kidney" and also a contact surface against which the cylinder drum bears in operation, at least the contact surface being provided with a friction-reducing layer. It is desirable for such a machine to have better operational behavior and a longer service life. For that purpose, the contact surface in the region of the low-pressure kidney has a recessed region forming a gap between the cylinder drum and the control plate.

Abstract: A hydraulic pumping device for use in a hydraulic machine having a piston and slider shoe unit made of a combination of plastic and metal material to operate with virtually lubricant free fluid.