Abstract: A device for limiting a working stroke of a hydraulic cylinder has a working cylinder and a working piston comprising a hollow piston rod connected to its top portion. A pressure reservoir is connected to a first working chamber for constantly supplying a pressure medium thereto, and a pressure source is connected via an inlet line to a second working chamber for supplying a pressure medium thereto. A shut-off valve comprises a push piston and a return spring for holding the push piston in its closed position. A drag link is slidably connected inside the push piston and extends through the working piston into the interior of the hollow piston rod. One end of the drag link has a first abutment that comes into contact with the working piston before the working piston reaches its end position.

Abstract: An electrohydraulic control arrangement for controlling a hydraulic cylinder having a double-acting working piston. At least one control valve having a control slide unit that is spring-loaded at one end and can be shifted by a servomotor against the spring force is provided. A valve housing having at least one section is provided with at least one control valve for alliance with each of the pressure chambers of the hydraulic cylinder, with the control slide units of the control valves being spaced from one another and being coaxially disposed in a mirror symmetrical manner relative to one another. A common control element of the servomotor is disposed between the inner ends of the control slide units for moving the same in the same direction.

Abstract: A hydraulic control mechanism to control operating elements, such as a hydraulic motor, or hydraulic cylinder, employing presetting of a set point, for example via a stepping motor, and mechanical feedback of an actual value. Functional elements are provided in the form of rotary pistons that fit inside one another, rotating relative to one another, and serving for the sensitive regulation of the direction and quantity of a pressure medium stream that is supplied from a pressure medium source to the operting element and flows back therefrom to the tank. One rotary piston is positively connected with the presetting of the set point, and the other rotary piston is positively connected with the operating element for the mechanical actual value feedback. In this way, in contrast to known control mechanisms where a slide or seat valve is actuated by a longitudinal movement, the rotational movement of the set point and actual value are directly compared with one another.

Abstract: An electrohydraulic control system for a hydraulic working cylinder, for example of a press, the piston of which has a main working surface and a smaller working surface on the rod side. A low-pressure circuit is provided for the feed or retraction movement of the piston, and a high-pressure circuit is provided for the loading movement at increased feed force and reduced speed. The connection or disconnection of these two circuits, when required, is produced with two 3/2 way valves that are coupled together. To control these control valves, there is provided an electrical reference motor that drives a cam disk which brings about the deflection of the coupled control slide valves of the control valves against a spring. A mechanical feedback is provided via the power piston, so that altogether a closed hydromechanical position control circuit is formed.