Motors: expansible chamber type – Plural relatively movable or rigidly interconnected working... – Condition responsive means for modifying working member...
Patent
1995-01-13
1996-09-24
Ryznic, John E.
Motors: expansible chamber type
Plural relatively movable or rigidly interconnected working...
Condition responsive means for modifying working member...
91447, 91465, F15B 1105
Patent
active
055580041
DESCRIPTION:
BRIEF SUMMARY
This application is a Rule 371 of PCT/EP93/01680 filed Jun. 30, 1993.
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a control arrangement for at least one hydraulic consumer. Control arrangements are used in particular for mobile machines such as excavators, wheel loaders, or automotive cranes,
From Federal Republic, of Germany 36 34 728 A1 a control arrangement is already known in which the consumer can be controlled in direction and speed via a directional control device and in which two consumer lines lead to the consumer from the directional control valve device, each of which consumer lines can be connected via a directional control valve piston and a metering restrictor to a pump and/or via the directional control valve piston to a tank. The metering restrictor is formed by fine control grooves on an annular collar of the directional control valve piston by means of which grooves the speed of the consumer can be controlled. A throttle valve having a servo-piston is arranged between the metering restrictor and the sections of the directional control valve piston which serve for the directional control. In the position of rest of the directional control valve piston, the consumer lines are blocked off from the tank by the directional control valve piston. The sealing is effected along a slot between the piston and the housing which contains the piston. This sealing is not complete so that leakage losses occur in the consumer lines and may lead to movement of the consumer and thus to a change in the position of the implements of a machine moved with this hydraulic consumer.
From Federal Republic of Germany 34 13 866 A1 a control arrangement for a hydraulic consumer is known in which a throttle valve having a servo-piston is arranged in each consumer line. Structurally, the arrangement is such that the servo-piston of a throttle valve is present in a bore in the directional control valve piston, which can thus be considered a housing of the throttle valve. In a switch position in which the corresponding consumer line is connected to the pump, hydraulic fluid flows from an annular channel in the directional control valve device via bore holes into the inside of the directional control valve piston, and there, via the throttle valve and other bore holes, out of the inside of the directional control valve piston outward into a further annular channel from which the consumer line extends. In the position of rest of the valve piston, the two annular channels as well as a third annular channel which is connected to the tank are sealed off by the narrow slot between the directional control valve piston and the housing of the directional control valve. Thus, also in the control arrangement known from Federal Republic of Germany 34 13 866A1, a consumer line is not blocked off free of leakage so that the consumer can change its position.
SUMMARY OF THE INVENTION
The object of the present invention is so to develop a control arrangement which is provided for at least one hydraulic load, of the above type, and has the features set forth that the blocking-off of the consumer lines to be free of leakage oil is improved so that the consumer reliably retains its position when the directional control valve device is in its position of rest.
This object is achieved in accordance with the invention by a control arrangement of the above type wherein the servo-piston of the throttle valve is initially arranged downstream of the directional control valve piston and of the metering restrictor in the consumer line. Downstream here means that a hydraulic fluid first of all flows through the flow-dividing valve device and the metering restrictor and only then through the throttle valve when the corresponding consumer line is connected with the pressure connection of the pump. Furthermore, the throttle valve is developed as a seating-type valve and has a servo-piston which acts on a valve seat. By means of the throttle valve, the consumer line can thus be sealed off free of leakage. The servo-piston
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patent: 5220862 (1993-06-01), Schexnayder
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Backe, W.: Hydraulische Schaltungstechnik, 2, Edition, 1976, RWTH Aachen, pp. 45-48.
Rose, M,: Weniger Energie--mehr Leistung. In: O+p-olhydraulik und pneumatik, 28/1984,No. 12, pp. 758-759.
Farber Martin A.
Mannesmann Rexroth GmbH
Ryznic John E.
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