| 摘要 |
The subject-matter of the application is a valve arrangement for shutting off hydraulically actuated devices, such as couplings, when the hydraulic pressure medium is at a negative pressure. The arrangement comprises a housing and a piston which is axially displaceable in the housing and is acted upon on the one side by the pressure medium and on the rear side by at least one coaxially acting compression spring and via which a return passage for the pressure medium is opened as a result of displacement by the spring during negative pressure. Such a valve arrangement is now to be arranged in a bypass for the relevant working cylinder in order to connect its pressure connection to the return to the tank of the hydraulic system during negative pressure, leakages being avoided at the operating pressure applied to the valve arrangement. To this end, a seat valve is arranged with a valve body in a surrounding pressure-medium space coaxially to the piston in the housing, and the return passage leads into this pressure-medium space, the valve body, in its closed position, closing off the return passage from the pressure-medium space, and at least one mechanical transmission member being arranged between the valve body and the piston, which transmission member, with the displacement of the piston during negative pressure, drives the valve body from its closed position into the open position.
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