Hydromatik Gmbh

Wilhelm Appel

Mathias Maul

A control circuit for a reversible hydrostatic transmission including a reversible pump having first and second working lines, and a control member having forward and reverse positions to normally direct a working fluid through the first and second working lines respectively. A servo-motor has forward and reverse positions to hold the pump control member in either its forward or reverse positions, and a first subcircuit is provided to conduct a control fluid to the servo motor to hold that motor in either its first or second positions. This first subcircuit includes a pair of piston and cylinder units, with each of these units having a control pressure chamber and a working pressure chamber. A second subcircuit is provided to conduct the working fluid from the working lines to the working pressure chamber of either the first or second piston cylinder unit, and this second subcircuit includes a change over valve to insure that the working pressure is maintained in the appropriate working pressure chamber even if there is a sudden reversal in the load on the pump.

Control device for a hydrostatic gear

A drive system having two hydrostatic gears (1, 2) driven by a common driving motor or by a plurality of driving motors having a fixed speed ratio, each having a pump (5, 6) and a hydraulic motor (7, 8) and in which the delivery or intake volume setting of the pumps (5, 6) and/or the hydraulic motors (7, 8) is performed by hydraulic servomechanisms (13, 14) of which the control pressures in the control pressure lines (23, 24) can be varied as desired either independently or together by means of pressure indicating valves (26) connected to each of the gears (1, 2) and supplied by an auxiliary source of pressure (9, 10) is arranged so that, at least on starting, the outputs of the gears (1, 2) are as nearly as possible equal. This is done by means of an adjustable differential pressure valve (41) connected to the control pressure lines (23, 24, 25) which is set to compensate for differences in output values of the gears (1, 2) arising from departures from the intended values by a corresponding pressure change in at least one of the control pressure lines.

Drive system with two hydrostatic gears

The invention relates to a speed regulating device for a hydrostatic drive unit comprising a pump of variable feed volume and a motor in a hydraulic circuit, wherein the pump is driven by a drive motor of variable speed, and there is provided a regulating valve which controls the loading of a hydraulic adjustment device on the pump in dependence on the pressure differential in front of and behind an adjustable throttle arranged in the hydraulic circuit, in such a way that the feed volume is changed in inverse proportion to a speed change in the drive motor. It is the aim of the invention to produce a simple construction for the speed regulating device which can also be easily controlled in reverse operation and can be easily operated. This is achieved by the fact that the hydraulic circuit is a closed circuit, the pump and the hydraulic motor are set-up for operation in both feed directions, the throttle can be adjusted out of a central zero position or a position of minimum feed volume in two opposite directions at maximum feed volume, and the adjustment movement of the throttle is mechanically coupled to the adjustment movement of a directional control valve which produces the hydraulic connection of the relevant working space of the adjustment device with a pressure line.

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Ulm-Donaustetten, Germany

Wilhelm Appel