Mannesmann Rexroth Ag

Mannesmann Rexroth Corporation

Brueninghaus Hydromatik Gmbh

Dieter Roth

Georg Rausch

Jochen Beck

Bernd Obertrifter

Mikko Erkkila

Disclosed is a hydraulic steering system () for a vehicle, especially a mobile working machine, comprising at least two steering cylinders () within which two cylinder pistons () can be displaced, and a first hydraulic pump () that can be adjusted regarding the swept volume. The position or the direction of displacement of the cylinder pistons () in the steering cylinders () defines the steering angle or the steering direction of the steerable vehicle wheels relative to a body () of the vehicle. The displaceable cylinder pistons () divide the associated steering cylinder () into two respective pressure chambers (andand). The first connection () of the adjustable hydraulic pump () is joined to one of the pressure chambers (oror) of the two steering cylinders () according to the steering direction while the second connection () thereof is joined to the other respective pressure chamber (oror) of the two steering cylinders () in a closed circuit.

Hydraulic system

A hydraulic steering system, which is used, in particular, for a mobile working machine, and has a steering unit that can be actuated by a first steering member, which is constructed as a steering wheel, that has a first fluid connection, which is connected to a pressure chamber of a steering motor, the pressure chamber being subjected to pressure for a steering movement to the left, and that has a second fluid connection, which is connected to a pressure chamber of the steering motor, the pressure chamber being subjected to pressure for a steering movement to the right, and which has a control valve that can be actuated by a second steering member, which is constructed in the manner of a joystick, and likewise has fluid connections that are connected to the pressure chambers of the steering motor. There is provided priority for steering with the first steering member over steering with the second steering member, wherein the control valve can be activated only when the steering unit is in the neutral position.

Hydraulic steering system for a vehicle, especially for a mobile working machine

A hydraulic control arrangement for a mobile working machine has at least one hydraulic cylinder with the aid of which a working tool is moved, a directional control valve for controlling pressure-fluid channels between chambers of the hydraulic cylinder, a pressure-fluid source and a tank, a hydraulic accumulator connected to the pressure-fluid source via a filling line, and a control valve to open and to close a connection between the hydraulic accumulator and a pressure chamber of the hydraulic cylinder. To achieve a damping of pitching movement of the machine, a pilot-operated shutoff valve is connected upstream of the pressure chamber of the hydraulic cylinder, and opens when the directional control valve is actuated to allow pressure fluid to flow off from the pressure chamber to the tank.

Hydraulic control device for a mobile machine, especially for a wheel loader

An hydraulic control arrangement which is chiefly used for a mobile working machine, especially for a wheel loader, and has at least one hydraulic cylinder with the aid of which a working tool can be moved, a directional control valve for controlling the pressure-fluid channels between the hydraulic cylinder, a pressure-fluid source and a tank, a hydraulic accumulator which can be connected to the pressure-fluid source via a filling line, and a control valve with the aid of which a connection between the hydraulic accumulator and the hydraulic cylinder can be controlled to open and close. The aim of such a hydraulic control arrangement is to avoid undesired movements of the hydraulic cylinder. This is achieved wherein the fact that the hydraulic accumulator can be filled up only when the directional control valve is actuated.

Hydraulic control system for a mobile work machine, especially a wheel loader

The present invention provides for a control apparatus for independently operating at least two users. The users can be the tilt cylinders and the lift cylinders of a loader. The control apparatus provides for the adjustment of the control valves and for the adjustment of the pressure control apparatus of the variable displacement pump means in dependency of each other. In accordance with the invention, the control position of the control spool of the control valve controlling the user with the largest load provides for a measure (or for the adjustment) of the pressure control device of the variable displacement pump. In this manner an extremely effective and economic operation of the hydraulic system comprising the control apparatus and the users is obtained.

Hydraulic control apparatus for a plurality of users

A hydraulic control circuit for building machinery includes a hydraulic cylinder to operate a tool. To stabilize vibrations of the tool around the pitch axis, a hydraulic accumulator is provided to be connected to a pressure source via a fill line. A shut-off valve is disposed in the fill line, which valve is subjected to the pressure in the accumulator such that in operating the cylinder the accumulator is loaded to a pressure corresponding to the load pressure. The system is very simple in structure and fluid losses are eliminated.

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Schlüchtern, Germany

Dieter Roth