| 摘要 |
Hydraulic valve circuitry adapted for automatic weight-responsive control of load-clamping members of a load-lifting system having a free lift mast. The load-lifting system generally includes one or more fluid power actuator (101, 103) for applying a gripping force to a load, at least one elongate, longitudinally-extensible fluid power lifting device (154, 156) having a free lift range of motion and at least one main lift range of motion, and manually operated load-clamping and load-lifting selector valves (134, 146). The hydraulic valve circuitry provides, independently, weight-responsive control of the load- clamping members when lifting a load, full-time automatic weight-responsive force control of the load-clamping members without concurrent manual actuation of load-clamping or load-lifting selector valves, and equalization of sensed load weight so that the sensed load weight is substantially independent of the longitudinally-extensible position of the lifting device. |
