Abstract: A hollow piston (1) piston engine including a closed annular cavity (9). Said hollow piston constituted of a first piston part (1a) with a base section (3) from which a joint part (4) extends in one axial direction, and from which a peripheral wall (6) that delimits the annular cavity (9) on the outside, and a mandrel (7) that delimits the annular cavity (9) on the inside extend, each as one piece, in the other axial direction. The hollow piston is also constituted of a second piston part (1b) having a cover (8) which is connected to the ends of the peripheral wall (6) and of the mandrel (7), said ends facing away from the base section (3). In order to achieve an economical and simple production while ensuring the provision of a stabile construction, the peripheral wall (6) and the mandrel (7) are formed on the base section (3) without machining.

Abstract: A power- and moment-regulating system for at least two adjustable hydraulic pumps (10, 11). A hydraulic servo control apparatus (22, 23) continuously adjusts delivery as a function of pressure in a delivery pressure line (16, 17) and pressures in control lines (20, 21). Each servo control apparatus (22, 23) is provided with a moment valve (42, 43) having a valve piston (62) which moves in a valve sleeve (61) forming a valve seat and whose closure force is determined by a measuring spring (46, 47) which is connected to pump actuator (37, 38) and is preloaded depending upon the set delivery rate. The pressure in control line (20, 21) or pressure in control lines of the other hydraulic pump(s) (11, 10) act both on the valve piston (62) and on valve screen (61) of moment valve (42, 43) associated with the given hydraulic pump (10, 11).

Abstract: The invention relates to a hydraulic control valve block in standard configuration having a first control valve (2) and a second control valve (3), functionally cooperating with the first control valve and connected therewith via pressure medium channels (28-31, 33), having a valve piston (5) which is controlled on the one hand by a hydraulic control pressure in a pressure chamber (25) and on the other hand is acted upon by a spring pressure part (7). In order to reduce the construction and installation costs of the control valve block, whilst employing a remotely controllable seat valve, and maintaining its functions, it is provided in accordance with the invention that a supplementary pressure medium channel (36) is formed in the control valve block and that the spring pressure part (7) of the second control valve (3) is replaced by an electrically controllable seat valve (60.1; 60.2) having an electromechanical control part (66.1; 66.2) and at least two hydraulic connections (63.1; 64.

Abstract: An axial piston motor of adjustable swept volume for installation in a wheel hub, having a motor housing which is open on one side and is closed by a connection block, an output shaft rotatably mounted in the housing and a connection block, an adjusting device for adjusting the swept volume, a step-down gear unit driven by the output shaft and having a driving toothed wheel for the drive of the wheel hub, and a brake associated with the output shaft on the connection block.

Abstract: A torque control device for an adjustable hydropump is described which is based on an output control device in which the output control is determined as a function of the output pressure of the hydropump and a pressure in a working pressure control line. For this purpose a torque valve is provided whose closure power is determined by a measuring spring or set of springs connected with the pump control member and pretensioned depending on the output setting. The torque valve connects the working pressure control line with the pressureless outlet depending on the pressure in the working pressure control line and the pretension of the measuring spring. The torque valve can be fixed on to the hydropump as a separate unit and the control characteristic can be changed from outside by adjustment of the measuring spring.

Abstract: An adjusting arrangement for a hydraulic pump with a variable flow quantity, having an operating cylinder located in a neutral position through the intermediary of a positively-acting resetting device, the piston of which is adjustable dependent upon the actual discharge pressure and dependent upon a parameter proportional to the actual discharge flow quantity into a position corresponding to the rated discharge flow quantity with consideration being given to the limiting value for maximum power output, maximum discharge pressure, maximum discharge flow quantity and, as required, the flow direction. An electronic control arrangement receives electrical signals corresponding to the rated discharge flow quantity and the actual discharge flow quantity and the actual pressure, which processes these signals under calculation of the actual power output and the actual pressure, and generates corresponding setting signals for the adjustment of the operating cylinder.