Abstract: A hydrostatic piston machine has a housing, a rotor, a plurality of pistons rotatable with the rotor, and a displacing element operative for effecting reciprocation of the pistons and having a surface which is in sliding contact with the latter. Means is provided for reducing friction between the surface of the displacing element and the pistons during the sliding contact. This means includes a recess formed in the surface of the displacing element and communicating with a space which is under pressure so that a cushion of pressure fluid develops between the surface and the piston. The space under pressure may be constituted by a low pressure zone of the machine or by the low pressure and a high pressure zone of the machine.

Abstract: A sliding piston joint of a hydrostatic piston machine has a piston having a recess or cavity and a sliding shoe having a head portion receivable into the recess or cavity of the piston so as to support the latter. The sliding shoe has a base portion having a surface which faces away from the piston and faces toward a hydrostatic pressure zone generated during operation of the machine. The head portion of the sliding shoe and the piston have surfaces which are in sliding contact with one another. A throughgoing passage extends through the sliding shoe so that a portion of working fluid flows from the hydrodynamic pressure zone to the contacting surfaces of the sliding shoe and the piston to thereby relieve the latter.

Abstract: A control arrangement for preventing overloading of a prime mover which drives a pump comprises a pair of hydraulically operating adjusting units operative for adjusting the volume of fluid discharged by the pump. The arrangement further comprises a negative-feedback stabilizing circuit connected to the adjusting units and to a multi-setting regulating valve. The stabilizing circuit is operative for causing the valve to regulate the operation of the pump by controlling the operation of the adjusting units in dependence upon the output pressure of the pump. In order to protect the prime mover when the loading thereof has reached a predetermined value, an overload signal is generated which actuates an over-ride device. The override device is operative in response to the overload signal to cause the valve to assume a setting such that the adjusting units decrease the quantity of fluid discharged by the pump so as to unload the prime mover.

Abstract: A hydrostatic drive system for connecting a prime mover and a hydraulically operable load such as a hydraulic motor connected to the vehicular wheel has a constant-displacement pump and a variable-displacement pump both connected to the prime mover. The variable-displacement pump is completely reversible and is of maximum displacement substantially greater than the constant displacement pump. This variable-displacement pump is permanently connected across the hydraulic motor of the load. A clutch connects the constant-displacement pump to the same shaft as the variable-displacement pump. The outputs of the constant-displacement pump may be connected by a valve either in parallel to the outputs of the variable-displacement pump, or may simply connect them together for operation of the load only by the variable-displacement pump.

Abstract: In a piston machine of the type having a housing, a reciprocable piston in the housing and provided with an axial end portion and a piston-reciprocating element having a glide surface located opposite and movable with reference to the end portion for effecting the reciprocation of the piston, the invention provides for a glide shoe which is articulately connected to the end portion of the piston and which has a glide face in gliding contact with the glide surface of the piston-reciprocating element. The glide face has a recess which communicates via a passage with a source of pressure fluid, a sealing rim of substantially constant width surrounding the recess, and a plurality of face portions which are located outwardly of the sealing rim and configurated so that hydrodynamic pressure fields develop between the face portions and the respectively juxtaposed surface portions of the glide surface.

Abstract: A first pump and a second pump have respective mechanical inputs and are operative when the mechanical inputs are driven at constant speed for pumping fluid at an adjustable volumetric flow rate and at a constant non-adjustable volumetric flow rate, respectively, the maximum volumetric flow rate of the first pump being at least as great as that of the second pump. Connecting conduits connect the first pump in hydraulic circuit with an hydraulic consumer. An adjusting mechanism is provided for adjusting the volumetric flow rate of the first pump. A control arrangement is provided for bringing the second pump into and out of hydraulic circuit with the consumer in dependence upon the operation of the adjusting mechanism.

Abstract: A pressure regulator for an adjustable pump has an adjustable member for regulating the amount of fluid delivered by the pump. The position of the adjustable member is adjusted by two pistons of different diameters acting from opposite sides of the adjustable member and in which pressure of the fluid delivered by the pump is directed through a passage controlled by a control valve to one of the cylinder bores in which one of the pistons is closely guided. The control valve is movable by the fluid pressure between a neutral position in which fluid from the pump is prevented from flowing into the cylinder bore of the one piston, and two working positions, in one of which fluid from the pump will flow to the cylinder bore of the one piston while part of the fluid will flow over a throttle to a space at atmospheric pressure, and in the other of which fluid will flow unthrottled from the cylinder bore of the one piston to the aforementioned space.

Abstract: In a piston machine of the type having a housing, a reciprocable piston in the housing and provided with an axial end portion and a piston-reciprocating element having a glide surface located opposite and movable with reference to the end portion for effecting the reciprocation of the piston, the invention provides for a glide shoe which is articulately connected to the end portion of the piston and which has a glide face in gliding contact with the glide surface of the piston-reciprocating element. The glide face has a recess which communicates via a passage with a source of pressure fluid, a sealing rim of substantially constant width surrounding the recess, and a plurality of face portions which are located outwardly of the sealing rim and configurated so that hydrodynamic pressure fields develop between the face portions and the respectively juxtaposed surface portions of the glide surface.