| 摘要 |
What is proposed is a control unit (10) for a hydraulic power lift (11) in a mechanical/hydraulic lifting-mechanism control in tractors, which, during operation with preceding additional directional valves (45, 46), during their change-over from the working position to neutral, prevents pressure surges in the neutral circulation channel (49) of the following control unit (10) and therefore undesirable lifting pulses on the power lift (11). A mechanically activated pilot-control slide (14), in which the spring-loaded main control slide (19) with assigned pressure space (21) is arranged, passes through a control chamber (17) which is connected to a pump channel (38) and which is separated from the circulation chamber (15) connected to the neutral circulation channel (49). In the absence of a neutral circulation flow and therefore if the pressure in the circulation chamber (15) has collapsed as a result of a switched additional directional valve (45), the inflow pressure conveyed from the switched pump channel (38) into the pressure space (21) prevents the pilot-controlled main control slide (19) from closing. <IMAGE>
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