| 摘要 |
A hydraulic control device (10) with control spool (34), hydraulically pilot-controlled stop block (15) and choke valve (13) is proposed which in the lowering position enables control pressure to be produced largely free of leakage flow for actuating the push-open piston (17) in the stop block (15). The choke valve (13), working as a pressure balance in the lifting position, works during lowering as a pressure reducer whose regulated outlet pressure in the outlet space (23) is fed by the control spool (34) to a pressure space (57) at the push-open piston (17), while the spring space (24) at the choke spool (18) is relieved to the tank (48). To this end, the control spool (34) has two oblique passages (78, 79), passing through several piston sections (58, 65, 67), and control notches (76, 77) lying offset on the same piston section (65). Instead of a continuous leakage flow, only small control-oil quantities are required for regulating movements of the push-open piston (17) so that the control device (10) works in an energy-saving manner irrespective of the respective pressure of the variable displacement pump (81). <IMAGE>
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