US 4,307,559 AGranted

Turf maintenance machines

AssigneeRahsomes Sims & Jefferies Limited

InventorsRobert A. Jupp, deceased, Edward J. Aldred

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Abstract

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.

Claims7

Dependent claims

A turf maintenance machine having at least one working unit and hydraulically actuated means for effecting lowering into, provision of at least partial counterbalance in, and lifting from, a working position of said unit, comprising:

a selector valve having a valve body formed with first and second inlet ports, first, second, third and fourth outlet ports and a movable member within said body, said member having a "neutral" position, a "lift" position for lifting said unit, a "lower" position for lowering said unit and a "counterbalance" position for providing counterbalance in the working position of said unit;
a pump connected to said first and second inlet ports in parallel;
an hydraulic fluid reservoir connected with said first and second outlet ports;
a working unit lifting ram connected with the third outlet port;
an hydraulic accumulator connected with the fourth outlet port;
and
respective pressure relief valves connecting the pump and the accumulator with the reservoir;
wherein said selector member is movable from the "neutral" position in which the pump is connected to the reservoir by way of the first inlet and the first outlet ports selectively to the "lift" position in which the pump is connected by way of the second inlet port with the lifting ram, to the "lower" position in which the lifting ram is connected by way of the second outlet port to the reservoir and the pump is connected by way of the second inlet port to the accumulator, or to the "counterbalance" position in which the lifting ram is connected to the accumulator and the pump is connected to the reservoir by way of the first inlet and first outlet ports.

5 more elements

Dependencies are inferred from the claim text.