| 摘要 |
<p>A hydraulic load lifting system having a vented load check valve disposed in the main control line connected between the load supporting end of a hydraulic motor and a spool-type control valve to normally isolate the load generated pressures from the control valve is provided with venting apparatus which is operative to selectively prepressurize the main control line between the control valve and the load check valve prior to the venting of the load check valve and the shifting of the control valve to effect the lowering of a load being supported by the hydraulic motor so as to substantially balance the pressures on the opposite sides of the load check valve to prevent momentary load drop and hydraulic hammering.</p> |
