| 摘要 |
A weight-balancing system for a farm implement, such as a disk harrow with foldable wings operated by wingfold cylinders, includes a selective control valve for controlling fluid communication to the head and rod ends of the wingfold cylinders. A pair of pressure-reducing/relieving valves permit individual adjustment of the pressures in both the head and rod ends to achieve the desired balance. In a preferred embodiment, a pilot-operated, two-position valve is connected between the rod ends and one of the pressure-responsive valves. The two-position valve is operated by pressure signals generated by a flow-responsive switching valve connected between the two-position valve and the selective control valve. The switching valve and the two-position valve cooperate to block the pressure-controlled outlet of the one pressure-responsive valve and the rod ends and to bypass return fluid flow from the rod ends to sump when the cylinders are being extended. Then, when cylinder motion stops and this return flow ends, the switching valve and the two-position valve are connected to the control pressure outlet of the one pressure-responsive valve to the rod ends to achieve the desired balance. |
