Abstract: In a summation power output regulating system for first and second hydrostatic machines (3, 4), having a common drive and comprising at least two hydrostatic transmissions (1, 2), each of the machines (3, 4) having a hydraulic control device (7, 8), wherein the second machine (4) is provided with a hydraulic power output regulator (24) which regulates the pressure acting on the control device (8) in dependence on the power output of the second machine at that time and a control pressure, dependant on the working pressure of the first machine, is transmitted by means of a hydraulic actuator to the power output regulator (24), substantially 100% utilization of the power available is attained with a simple construction and function by providing the first machine (3) with a power output measuring valve (34; 63, 64) which determines the power output at the time and regulates the control pressure (P.sub.3) in dependence on the power output of the first machine.

Abstract: A control apparatus for several drive assemblies, which consist of hydrostatic drive units, is described. The hydraulic pumps of the hydrostatic drives are driven by means of a common prime mover and are controlled in terms of output. The output control device consists of an adjusting piston, which is connected with the control element of the hydraulic pumps and upon both sides of which pressure acts, and of a spool valve which controls the pressure action on both pressure chambers at the front surfaces of the adjusting piston and upon which, on one side, the working pressure of the pumps acts and upon which, on the other side, an adjustable spring acts.

Abstract: A power regulation device for a hydraulic pump includes a slidable piston having a first end face with a first diameter and a second, opposite end face with a smaller diameter, the second end face being biased by operating fluid pressure from the hydraulic pump and the first end face being biased by an adjustable fluid pressure for controlling the operation of the hydraulic pump; a compression spring which biases the piston in a direction against that of the adjustable fluid pressure; a measuring spring, one end of which biases the piston in the same direction as the compression spring; a power valve having a control slider member which is biased in one direction by the other end of the measuring spring and by the operating fluid pressure from the pump and in the opposite direction by a compression spring, the control slider member including a transverse channel for supplying the adjustable fluid pressure to the first end face of the piston during idling and normal operations and for connecting the adjustable