Abstract: A hydrostatic drive system has an internal combustion engine, a main pump driven by the engine and having a control element displaceable to vary the pump displacement, a control pump driven by the engine, an output motor having a control element displaceable to vary the motor displacement and having a rotary output, and conduits interconnecting the main pump and output motor for driving of the motor by the pump. A speed-measuring pump is connected to the motor output and produces a pressure differential corresponding to the speed of the motor output. A pump controller is powered by the control pump and connected to the pump control element for adjusting the pump displacement. A motor controller is connected to the motor control element for adjusting the motor displacement.

Abstract: Disclosed is a control arrangement for a hydrostatic drive of the type having a power-driven adjustable pump, a pressure responsive setting cylinder coupled to the pump, a hydraulic motor connected via pressure conduits to the pump and a measuring motor coupled to the hydraulic motor to rotate with a proportional rotary speed. A supply pump is connected in a control circuit including the measuring motor and a nominal or desired value generator in the form of an adjustable throttle by means of which the desired rotary speed of the hydraulic motor is adjusted. Deviations between the actual and desired speeds produce a differential control flow which is fed to the setting cylinder which adjusts the position of an adjusting member of the pump for so long as until the deviation equals zero.

Abstract: Disclosed is a device for controlling or measuring operational parameters of an axial piston machine. The tilting plate which engages and adjusts the stroke of the piston is provided with two opposite pivot pins supported in fixed bearings. At least one pivot pin is provided with a shearing stress sensor preferably in the form of a magnetoelastic feeler which produces electrical signals the pulsation of which is indicative of rotational speed and the magnitude of the signal is proportional to pressure applied by the pistons and thus to the delivery of the machine. A second sensor is coupled to the tilting plate to indicate the angular displacement of the latter. The output signals from the sensors are separated into the pressure dependent signals, frequency dependent signals and angular displacement signals which upon multiplication are applied to a programmable data processing unit.

Abstract: An electrohydraulic control arrangement for a hydrostatic machine with displacing element having a stroke determined by a control member, which has at least one pressure-actuated regulating piston arranged to adjust the control member, and a valve slider through which a pressure medium acts upon the regulating piston and which is withdrawable to a neutral position in response to adjusting the machine by a feedback signal coming from the control member in correspondence with an electrical input signal, wherein a constant pressure acts upon one side of the valve slider and a variable pressure depending upon a position of the control member acts upon the other side of the valve slider.

Abstract: An arrangement for controlling the lifting mechanism of a tractor or a harvester or a harvester combine comprising a hydraulic actuator (17) connected to the lifting mechanism and controlled by a control valve (19) leaving a hydraulically controlled spool arranged in the bridge diagonal (27-19-27') of a hydraulic bridge circuit (23, 24, 25, 26), in the bridge branches of which two actual force value transducers (41, 42) for generating hydraulic signals proportional to the position of the lifting mechanism and desired force value setting means (32, 52) are respectively located for controlling the hydraulically controlled valve (19). An additional control valve (33) or throttle unit (53a) is provided for selecting one or both of the actual force transducers and if desired for controllably mixing the actual force signals.

Abstract: A pressure regulating valve for controlling a fluid pressure proportionally to an electric nominal value signal has a housing, a valve body in the housing, a proportionally operating magnet, a displacement pickup, a difference amplifier having inputs receiving a nominal value signal and an output signal from said displacement pickup, and an output connected with an input of the magnet, a valve cone associated with the valve body and loaded in a direction opposite to a fluid pressure as well as connected with a movable member of the displacement pickup, and a measuring spring loading the valve cone and fixedly abutting against the housing, wherein the valve member is movable in the housing and adjustable by an armature of the magnet against a force of the measuring spring.

Abstract: The control device for a hydraulically operated load includes a multiway piston valve defining a plurality of working chambers, a plurality of control chambers, a piston having axial and radial bores acting as first choke channels and a control collar cooperating with the control chambers to act as additional choke channels, a piston manometer valve biased by a spring and connected between a pump channel and a return flow channel. A control conduit including at least one choke is connectable via additional choke channels between the pump channel and the return flow channel and has a branch conduit leading to the spring-biased end of the manometer piston. The valve piston is displaceable from its neutral position into an intermediate control position in which in the range of the fine adjustment of the flow the pressure from the load is applied through the control conduit to the manometer piston to provide a load compensated control.

Abstract: A hydraulic control arrangement for at least two hydraulic consumers, comprises two pressure compensated multiple position valves, respectively coordinated with the two consumers, and each including a pressure compensating control member which controls a control conduit coordinated with a reversing or unloading valve, which, depending on its position and those of the multiple position valves control flow of pressure fluid from a pump over the multiple position valves to the respective consumer or to a return conduit. This will assure that even during parallel operation of both consumers, the output of the pump will be adjusted to the consumer load in such a manner that energy losses are substantially avoided and control of the two consumers independent from each other is assured.

Abstract: An arrangement for controlling a hydraulic motor having a movable member with opposite faces to be impinged by pressure fluid, in which first valve means serve to direct pressure fluid against a respective one of the opposite faces to thus control the direction of movement of the movable member, and in which second valve means connected in a hydraulic circuit with the first valve means serve to control the speed of the motor in connection with control means actuated by the movable member for controlling the change of the speed dependent on the position of this member.

Abstract: Each consumer is provided with a load-compensated direction-reversing valve. Each valve performs a throttling function and a pressure-compensation function in order to establish a selected volumetric flow rate, and also a direction-control function. Each valve comprises a first control valve stage and a second control valve stage. One stage performs the throttling function, the other the pressure-compensation function. One of the two control valve stages also performs the direction-control function. The pressure drop across the stage which performs the throttling function at least in part controls the setting of the stage which performs the pressure-compensation function. Each valve is provided with an electromechanical transducer generating electrical signals indicative of the settings of the stage which performs the pressure-compensation function.

Abstract: A hydraulic control system has a three-position valve which in its central position disconnects the high-pressure and low-pressure sides of a pressure source from outlet lines but connects these sides of the source together through a low-pressure valve. Moved to either of its end positions the valve is disconnected from between the sides of the pressure source and the output lines are connected to the high-pressure and low-pressure source sides. A pressure-limiting valve is connected between the sides of the source. In addition, the high-pressure side is connected via pressure-reducing valve and a restriction to a pair of pilot valves which are in turn connected to the low-pressure side. These pilot valves are also connected to opposite chambers of a pilot cylinder that controls the valve body. The pressure-reducing valve between the pilot valves and the high-pressure side maintains a medium-pressure level in the system when the valves move from its central position.

Abstract: A main valve controls the flow to a load in a first or second direction depending upon the signal applied to a pilot valve. A spool of the main valve is biased to a central position blocking flow by springs. A throttle valve having an adjustable restrictor area is connected in one line between the main valve and the load. The restrictor area is adjusted in correspondence to an input signal. The spool is moved to a first or second extreme position by the pilot valve. The pressure difference developed across the throttle valve is applied to the spool in a direction to force the spool towards the central position. The spool is balanced at a predetermined pressure difference across the throttle valve.

Abstract: Hydraulic control valve arrangement for controlling the amount of pressure fluid flowing to a consumer, in which the valve member of a first valve, which selectively controls flow of pressure fluid to at least one consumer or from the latter to a return passage, forms a variable throttle between the pressure fluid inlet passage and a consumer passage connected to the consumer, in which the throttle causes a pressure difference, and in which the pressure difference may be maintained substantially constant by a bypass passage between the inlet passage and the return passage in which a second valve member is arranged which is biased by a spring to a closed position and by the pressure difference produced by the variable throttle to an open position.