| 摘要 |
<p>In turf maintenance machines, lifting and lowering of e.g. cutter units and partial counterbalancing of such units in their working positions may be provided by hydraulically actuated means comprising at least one selector valve, the or each valve having ports connected with at least one unit lifting ram, a pump, a reservoir and an accumulator. An operator can be certain that, when a unit is lowered to the ground, the required degree of partial counterbalance can be provided. The selector valve is a four position spool valve which in the "lower" position thereof permits discharge of fluid from a ram to the reservoir thereby lowering an associated unit, while connecting the pump to charge the accumulator. When the unit reaches the ground the operator moves the valve to the counterbalance position, thereby counterbalancing the unit to the required extent by connecting the ram to the accumulator. The valve has six ports and preferably is connected in series-parallel relationship with other valves to permit independent lifting and lowering of units associated with respective valves.</p> |
