Abstract: The invention concerns a hydrostatic drive with a closed hydraulic fluid circuit comprising a hydraulic motor and a variable displacement pump. A feed pump feeds hydraulic fluid under pressure. A control device regulates pressure to a double-sided servo control unit comprising a control piston in a double-sided control cylinder so that the control piston can open a feed line for hydraulic fluid to one side while opening a discharge line on the other. The control device comprises an actuator at the cylinder by means of which force can be exerted onto the piston. A preload element exerts force onto the piston. The pressure generated by the variable displacement pump returns via a return line such that force is exerted in the direction of the piston, if inactive, the piston is maintained by the preload element and the pressure of the variable displacement pump.

Abstract: The invention concerns a hydrostatic drive with a closed hydraulic fluid circuit comprising a hydraulic motor and a variable displacement pump. A feed pump feeds hydraulic fluid under pressure. A control device regulates pressure to a double-sided servo control unit comprising a control piston in a double-sided control cylinder so that the control piston can open a feed line for hydraulic fluid to one side while opening a discharge line on the other. The control device comprises an actuator at the cylinder by means of which force can be exerted onto the piston. A preload element exerts force onto the piston. The pressure generated by the variable displacement pump returns via a return line such that force is exerted in the direction of the piston, if inactive, the piston is maintained by the preload element and the pressure of the variable displacement pump.

Abstract: The invention relates to a drive unit for a mixing drum that is disposed on a motor vehicle, in which an electric motor or a hydraulic drive comprising a displacement pump and a hydraulic motor can be used to drive the mixing drum. The low-power electric motor is used to drive the mixing drum at low rotational speed during the transport journey of the mixed concrete to the building site, while the hydraulic drive drives the mixing drum at high rotational speed during loading, mixing and discharging.

Abstract: The invention relates to a neutral setting device of an adjustable hydraulic machine, in particular the adjustment of the neutral setting of a servo valve. The present invention relates in particular to servo adjustment devices with mechanically adjustable control pistons, wherein the necessary force can be applied mechanically, electromagnetically, pneumatically or hydraulically. The invention relates to a neutral setting device of an adjustable hydraulic machine with a housing in which a mounted input shaft is arranged, at which on one end a torque can be applied for turning the input shaft around an axis. On a second end a cylindrical extension is arranged eccentrically parallel to the axis. An adjustable control piston for opening and closing hydraulic fluid openings for application of pressure of a servo piston adjusts the hydraulic machine with respect to its delivery volume.

Abstract: The invention relates to a method (3) for determining (33) a state characteristic value (28) of a electric device (4) controlled by a temporally variable control signal (17). The at least one state characteristic value (28) is determined using the frequency of the temporally variable control signal (17) and/or the switching characteristics of the temporally variable control signal (17).