| 摘要 |
The system comprises normally closed pilot-operated holding valves 52, 52A which are physically located on or near the lift cylinders and are operable in response to pilot fluid controlled by a pilot control valve 48. A pressure equalization conduit 100 is connected between the pair of lift cylinders to prevent overloading of one cylinder. Fluid flow orifices 101, 101A are located in the pressure equalization conduit to prevent rapid fluid loss from the lift cylinders and uncontrolled load dropping in the event of fluid loss caused by equalization line breakage. In one embodiment, the pilot control valve for the lift cylinders is actuable in response to a directional control valve 47 for the lift cylinders, and pilot fluid is supplied to the holding valves from the raise side of the cylinders as the pilot control valve opens. In another embodiment, a manually operable pilot control valve supplies pilot fluid from an auxiliary pump to operate the directional control valve and the holding valves. In this latter embodiment, in the event of auxiliary pump failure, pilot fluid is supplied from the raise side of the lift cylinders. <IMAGE> |
