| 摘要 |
A hydraulic device (10) for controlling a lifting mechanism in tractors is proposed which permits a reliable and quickly operating hydraulic limit position switch-off accompanied by fully hydraulic signal processing in a control circuit. In the control circuit (12) which is constructed as a complete bridge circuit and in whose bridge diagonal (38) the displacement valve (14) with its control terminals (19, 22) is located, the bridge diagonal (38) is connected to a three-way two-position control valve (41), two non-return valves (44, 49) in a first connecting line (43) and in the diagonal (38) prevent an undesired pressure compensation between the centre pressure tap-offs (36, 37) of the complete bridge circuit during the limit position switch-off but permit the desired pressure compensation in the control terminals (19, 22). The control valve (41) which is actuated by the lifting mechanism (24) in its top position controls the displacement valve (14) in such a way that it reliably moves back into its neutral position (18).
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