Mannesmann Rexroth Corporation

Mannesmann Rexroth Ag

Rainer Biener

Winfried Rub

Wolfgang Kauss

Richard Rauscher

Hydraulically actuatable directional control valve

A safety circuit for a servo-hydraulic regulating system for the hydraulic control and actuation of load units, such as operating tools on utility vehicles and agricultural machines. The controlling of the load unit is effected via a proportional valve which is actuated in dependence upon a pair of output signals of a measuring bridge in such a way that, in the event of a balanced measuring bridge, it assumes a neutral setting in which the operating line running to the load unit or emanating from the load unit is blocked. In order to prevent the lifting gear from executing a regulating reaction if the measuring bridge is out of tune when the servo-hydraulic regulating system is switched on, a safety valve arrangement is provided in the operating line. Depending on at least one control signal determined by the setting of the proportional valve, when the regulating system is switched on, the operating line is blocked until, via the at least one control signal, the balance of the measuring bridge has been registered.

Safety circuit for a servo-hydraulic regulating system

A circuit for limiting a static and/or dynamic pressure load in a hydraulically actuated use device which is controlled in a closed control circuit by means of a directional control valve and a mechanically or hydraulically releasable blocking device. Aa pressure control valve is arranged between the use device and the pressure relief valve and being adapted to discharge a hydraulic fluid from the use device to a tank when a predetermined hydraulic pressure in the use device is exceeded. The output port of the pressure relief valve is connected to a hydraulic control line is adapted to hydraulically connect the pressure relief valve to a control side of the control valve. Thus, the control valve is turnable by the discharging pressure of the pressure relief valve in a switching position in which a feed line leading to the use device is connected with the tank, and said blocking device is turned in a released state so that the hydraulic fluid in the use device is dischargeable to the tank via the blocking device and the control valve.

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Steinfeld-Hausen, Germany

Rainer Biener