Abstract: A hydraulic switching mechanism for the mobile hydraulics of, for example, hydraulic excavators, with a valve block, with electrohydraulically activatable valve units for controlling the movement of a working cylinder whose cylinder chambers can be selectively connected to a pump connection for hydraulic fluid, to a tank connection or to one another, and with pre-control valves for activating the valve units, wherein the hydraulic switching mechanism, by means of separate tank valve units and pump valve units, and also a suitable pre-control system, makes it possible to achieve a directional control valve function and a directly controlled and superimposed pre-controlled lowering braking function, a maximum pressure safeguarding of the cylinders and a proportional throttle valve function for the controlled displacement under negative load forces in the direction of movement and braking in an emergency; and mobile hydraulic machines having such a hydraulic switching mechanism and also to valve units therefor.

Abstract: A hydraulic switching mechanism for the mobile hydraulics of, for example, hydraulic excavators, with a valve block, with electrohydraulically activatable valve units for controlling the movement of a working cylinder whose cylinder chambers can be selectively connected to a pump connection for hydraulic fluid, to a tank connection or to one another, and with pre-control valves for activating the valve units, wherein the hydraulic switching mechanism, by means of separate tank valve units and pump valve units, and also a suitable pre-control system, makes it possible to achieve a directional control valve function and a directly controlled and superimposed pre-controlled lowering braking function, a maximum pressure safeguarding of the cylinders and a proportional throttle valve function for the controlled displacement under negative load forces in the direction of movement and braking in an emergency; and mobile hydraulic machines having such a hydraulic switching mechanism and also to valve units therefor.

Abstract: The invention relates to hydraulic control in a hydraulic system for the operation of a machine tool such as a press for processing material of a certain type, especially for the operation of the scrap cutters. Said control allows for impact attenuation and combined rapid motion switching with load compensation and transfer of a hydraulic medium of a hydraulic cylinder for the movement of the other. According to the invention, said control comprises hydraulic media of a hydraulic cylinder for pre-control of a first main valve element (2.4.0), a second main valve element (2.7.0) and a third main valve element (3.7.0) which are functionally combined and a fourth valve (2.5).

Abstract: The invention relates to hydraulic control in a hydraulic system for the operation of a machine tool such as a press for processing material of a certain type, especially for the operation of the scrap cutters. Said control allows for impact attenuation and combined rapid motion switching with load compensation and transfer of a hydraulic medium of a hydraulic cylinder for the movement of the other. According to the invention, said control comprises hydraulic media of a hydraulic cylinder for pre-control of a first main valve element (2.4.0), a second main valve element (2.7.0) and a third main valve element (3.7.0) which are functionally combined and a fourth valve (2.5).

Abstract: A two port cartridge valve comprises a valve sleeve with a two-step guide hole, a valve piston, which forms a closing element for a valve seat, and a piston shoulder, which divides the second step of the guide hole axially into an end-side first control chamber and an annular second control chamber. An auxiliary piston is fitted in an inner guide hole of the piston shoulder. The cross-section A.sub.s of the inner guide hole is the same size as or larger than the cross-section A.sub.c of the first step sealed by the valve piston. The piston shoulder forms an annular pressure area A.sub.X in the first control chamber. A connecting hole connects the inner guide hole to an orifice in the end face of the valve piston. The valve is used to achieve by means of the pressure to be shut off a hermetic shut-off function. It can be hydraulically locked and unlocked by a pilot valve.

Abstract: A pilot controlled servo-valve has four main flow connections, an axially sliding main control piston with four control edges and a front restoring spring that defines a spring-centered middle position of the main control piston. A control sleeve has ring shaped openings for the first, second and third main flow connections and a front opening for the fourth main flow connection. A first front face of the main control piston is axially opposed to the front opening. A pressure compensation surface is formed by the second front face of the main control piston in a spring chamber. The main control piston applies the pressure in the fourth main flow connection on said pressure compensating surface through a pressure relief channel. A traverse bore connects said pressure relief channel to an auxiliary connection chamber connected to the third main flow connection by the forth control edge.

Abstract: A two-port cartridge type seat valve has a valve sleeve with a stepped guide bore for a poppet. The poppet includes a piston flange that divides the second step of the guide bore axially into an end-face first pilot chamber and an annular second pilot chamber. A first connection channel through the valve sleeve connects the annular second pilot chamber with an annular chamber into which a lateral main flow port opens. The free cross-section of a valve seat and of an axial main flow bore correspond approximately to the cross-section of the first step of the guide bore.

Abstract: A pilot stage for pressure control valves includes an axially displaceable valve piston which bounds a valve chamber axially on one side and includes a valve seat for a closure cone therein. Valve piston has an actuating surface in a pressure chamber that is substantially larger than the free cross section of the valve seat. By pressurization of this pressure chamber, a large hydrostatic force is exerted on the valve piston which opposes the closing force of the pressure-setting spring. A housing stop fixes a first axial end position of the valve piston in the direction of this hydrostatic force. The pilot control stage has improved properties for both manually adjustable pressure control valves and proportional pressure control valves.

Abstract: A hydraulic throttle valve is disclosed which includes a choke piston slideably mounted in a bore for movement between an open position and a closed position. A differential piston is coaxially mounted with respect to the choke piston, and a control valve is mounted for slideable movement in a second bore which is laterally spaced from and parallel to the first bore. The control valve is operated by an electromagnet to selectively direct a control fluid to either side of the differential piston, and thereby open or close the choke piston. A feedback spring arm interconnects the choke piston and the control valve, with the spring arm resisting the opening of the choke valve and with the resisting force being a function of the force applied to the control valve by the electromagnet. A balance of forces acting on the choke piston is thereby achieved, with the choke piston being opened to an extend functionally related to the magnitude of the input current to the electromagnet.