Lift Circuit (Up) - Toro 30821 Service Manual

Lift Circuit (Up)

Raise Cutting Units
The gear pump (P2) is directly coupled to the hydrostat
through gear pump (P1). It supplies hydraulic pressure
(charge pressure) for operating the power steering sys-
tem, raising and lowering the cutting units, operating the
sidewinder unit, and maintaining 100 to 150 PSI (6.9 to
10.0 bar) to the low pressure side of the traction circuit.
The pump takes its suction from the hydraulic reservoir.
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 hydraulic
tank.
Groundsmaster 3500- D
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.
Page 4 - 17 Hydraulic System (Rev. G)