Toro Groundsmaster 3500 30807, Service Manual

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Groundsmaster 3500 Hydraulic System Page 5 - 23
Lift Circuit (Up)
Raise Cutting Units
The gear pump (P2) is directly coupled to the hydrostat
through gear pump (P1) and driven by the engine. It sup-
plies hydraulic pressure for operating the power steer-
ing system, raising and lowering the cutting units,
operating the sidewinder unit, and replenishing the
closed loop traction circuit (charge pressure). The pump
takes its suction directly from the hydraulic tank.
During conditions of not lifting or lowering cutting units,
flow from the gear pump (P2) is by- passed through the
power steering valve, 2- spool lift/sidewinder valve, and
hydraulic manifold directly to the hydrostat and the
charge relief valve. Flow then returns to the gear pump
inlet and hydraulic tank.
When the cutting units are to be raised, the 2- spool
valve is positioned by moving the cutting unit shift lever
to RAISE. Flow is directed to cap ends of the lift cylin-
ders. Hydraulic pressure against the cylinder pistons
moves their shafts causing the cutting units to raise. At
the same time, the pistons push the hydraulic fluid out
of the lift cylinders and back through the hydraulic man-
ifold to the hydrostat.
When the cutting unit shift lever is released, spring ac-
tion returns the valve to its original position and by-
passes flow back to the hydrostat stopping lift cylinder
movement. The cylinder position is locked in place by
the load holding checks in the lift control valve.
Hydra
ulic
System