Mannesmann Rexroth Corporation

Mannesmann Rexroth Ag

Thyssen Industrie Ag

Georg Rausch

Dieter Roth

Gotz-Dieter Machat

Karl Cords

Manfred Hartwig

Karlheinz Hunschede

Hubert Feser

Heinrich Wilkens

Klaus Biermann

G&uuml;nter Fertig

Georg Zoller

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

A hydraulic control arrangement for a mobile working machine which serves for damping pitching vibrations and has a hydraulic accumulator which can be connected to a hydraulic fluid source via a filling valve and which can be connected to a pressure chamber of a hydraulic cylinder, and a shut off valve which, with a first condition fulfilled, can be moved into a through position in which hydraulic fluid can flow through it in the direction from the hydraulic accumulator to the pressure chamber of the hydraulic cylinder and vice versa. The shut off valve may, at the same time, also be the filling valve. A first condition may be that a certain traveling speed is exceeded. Limiting the accumulator pressure to a limit pressure is intended to keep the wear on the hydraulic accumulator low and to increase the safety. These two aims are achieved to better effect, wherein the shut off valve can also be moved, with the first condition fulfilled, into its shut off position when the load pressure in the pressure chamber of the hydraulic cylinder or the accumulator pressure reaches a maximum pressure.

Hydraulic control mechanism for a mobile machine tool, especially a wheel loader, for damping longitudinal oscillations

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

Directional control valve

Two-way insert valve

Hydraulic control for a dividing machine tool

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.

Vibration suppression apparatus for hydraulic system with improved

A pilot controlled sequence valve having a pilot valve and a main valve is provided. This sequence valve is preferably used for switching on and switching off a charging operation of a hydraulic accumulator. The displacement volume of the main spool of the main valve is directed via an orifice to the tank when the switching into the pressureless circulation occurs.

Pressure sequence valve

For the relief of a highly pressurized hydraulic liquid in a working chamber of pilot controlled 2/2 poppet valve is used. The working chamber is further connected to a pressure relief valve, the output of which is connected to a control conduit extending between a control chamber of the 2/2 poppet valve and the pilot valve. The apparatus of the invention requires a shorter period of time for the pressure relief without the danger of relief noise.

Apparatus for providing relief to a working chamber

To reduce the noise on response of a pressure-limiting valve, downstream of the valve seat an annular space, an annular gap and a further annular space are provided. This flow-off system gives a reduction of the noise level. Moreover, in pressureless circulation the flow resistance of the valve is low because the annular gap is freed by the piston.

Pressure-limiting valve

A hydraulically operated two-way seat type valve includes a housing a forming valve seat, and a locking body displaceable in the housing and cooperating with the valve seat. A cover is mounted on the housing. An actuating piston for actuating the locking body of the valve is guided in the cover. The piston has two opposing piston-shaped extensions one of which is secured to the locking body whereby a non self-closing valve can be switching into the self-closing valve.

Hydraulically operated self-closing two-way seat-type valve

In a balanced pressure valve with a switching valve for switching over to pressureless circulation, restrictors are provided in the line carrying the system pressure in such a way that the opening motion of the main piston of the balanced pressure valve is heavily damped, and the throttle losses in the bypass line leading from the line carrying the system pressure via the switching valve to the tank are very low when the main piston is open, and with this also the resistance of the main flow via the main piston is correspondingly low.

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Lohr/Main, Germany

Georg Rausch