Abstract: A hydraulic drive unit has a tracking regulator valve (19) for controlling a servo drive (18) of a main control valve (16), where the main control valve controls flow to a hydraulic motor (11). The tracking regulator valve is controlled by an actuating element (42), which is controlled by a comparison of a nominal position value, set by an electric motor (36), and an actual position valve, generated by a mechanical feedback (53) connected to the hydraulic motor. The main control valve includes a slide valve piston (87), which forms a housing for the tracking regulator valve, which has two piston slide valve elements (39, 41). The slide valve piston (87) of the main control valve (16) has an axial through-bore (122) through which passes the actuating element.

Abstract: Hydraulic drive mechanism for a machine element with rapid feed movement and under-load feed movement, comprising a double-acting hydrocylinder power drive and a pressure switching valve responding to the pressure at least in a larger operating chamber of the hydrocylinder when the pressure in the operating chamber exceeds a threshold value higher than 1/4 of the operating pressure of the pressure supply source, but lower than half the operating pressure thereof, switches to under-load feed operation and, when the pressure in the drive pressure or operating chamber falls below the threshold value, switches back to rapid feed operation. The pilot valve for the main control valve is equipped with two windings effective in opposite directions.

Abstract: A hydraulic drive system for a machine element performing in one work cycle a sequence of motions comprising a rapid feed motion, a working stroke under load and an oppositely directed rapid-return motion. The drive element includes a hydraulic cylinder having three working surfaces A.sub.1, A.sub.2, A.sub.3. Motion control is effected by an electro-hydraulic follow-up control valve with a pre-setting device controlled by a stepping motor and a mechanical actual-value feed-back device. During rapid feed motion, the relatively small working surface A.sub.1 is subjected to the output pressure of the follow-up control valve only, while during the working stroke the pressure acts additionally on the working surface A.sub.3. The rapid-return movements of the piston of the cylinder are controlled by applying pressure to the working surface A.sub.2, or by relieving pressure from the two other working surfaces A.sub.1 and A.sub.3.

Abstract: A hydraulic driving arrangement for circular indexing tables for the precise positioning of workpieces, with the exact position of the workpieces being determined by an index. A hydraulic motor is provided with an electro-hydraulic follow-up governor using a stepping motor for setting the desired values and a mechanical actual value indication arrangement. A monitoring arrangement positively coupled with the circular indexing table and/or a driving gear of the hydraulic motor indicates whether or not the circular indexing table is in a position suitable for bringing the indexing gear into engagement and, if so, emits a signal triggering the indexing process or, if the circular indexing table is not in the desired position, deactivates the indexing mechanism. The monitoring arrangement comprises a cam disk coupled with the circular indexing table via a gearing so that it performs exactly one rotation by 360.degree. between two desired positions.

Abstract: A hydraulic pivot drive comprising a rotary-piston hydraulic cylinder and control device for maintaining the pressure difference between pressure chambers defined by the rotary vane and at least one radial wall of the cylinder housing required for maintaining a defined relative rotary position between the vane and the housing of the rotary piston hydraulic cylinder. The control a follow-up control valve, wherein the actual condition relative to the pivot angle is fed back via a measuring spindle coupled with the rotating part of the rotary piston hydraulic cylinder and the desired value is pre-set by rotation of a spindle nut engaging the spindle, an actuating member arranged for axial displacement together with the spindle nut and for actuating pairs of seat valves for enabling alternative connection of the at least two pressure chambers of the rotary-piston hydraulic cylinder with a system to obtain the desired rotation.

Abstract: An energy-saving hydraulic driving arrangement includes a motor having two chambers separated by a reciprocable or angularly movable output element which can accelerate or decelerate a mass. One of the chambers receives pressurized fluid from one of a battery of accumulators containing fluid at different pressures (namely, from the accumulator wherein the pressure is slightly higher than the desired pressure in the one chamber) during acceleration of the output element while the other chamber discharges fluid directly into a sump. During deceleration of the output element, the one chamber draws fluid directly from the sump whereas the other chamber discharges pressurized fluid into that accumulator wherein the pressure is slightly less than the pressure of fluid in the other chamber.

Abstract: Feeding device for the cycled feeding of rod or tape-like material into a press, cutter or the like, which includes a metering wheel which rolls off directly or indirectly on the material being fed, serving as a true value indicator. The metering wheel is coupled with a true value input metering spindle which acts upon a hydraulic control valve device. The exactly maintained feeding path is made possible by the mechanical coupling of the true value feeding with the true value input on the control hydraulic valve device.

Abstract: A servomechanism in which the mutual angular position of a threaded spindle relative to a tap is adjustable by a stepper motor wherein the unit of the threaded spindle and tap is connected directly or indirectly with a hydraulic working unit, the servomechanism includes a ball bearing arranged between the spindle and the tap. Consequently, by actuating the stepper motor to which the tap is connected via a coupling, the tap being rotated and moved in axial direction relative to the spindle, thereby actuating a switching mechanism connected to the working unit by which the spindle is caused to rotate. Accordingly, the relative axial movement between the spindle and the tap is compensated and the working unit is in a different position.

Abstract: An electrohydraulic follow-up amplifier comprises a hydraulically operated prime mover constituted by a cylinder and a piston axially movable therein and fixedly connected to a connecting member. The arrangement includes further an electronically controlled motor, for instance a direct current servomotor driving for instance a nut meshing with the threaded spindle carrying a control member cooperating with valves for control flow of pressure fluid into and out from cylinder chambers to opposite sides of said piston of said prime mover. The spindle is connected to the connecting member over a coupling comprising a cylinder fixed to the connecting member and a piston fixed to the spindle.