Lift Circuit (Raise) - Toro Groundsmaster 3505-D Service Manual

Lift Circuit (Raise)

A two section gear pump is directly coupled to the the hy-
drostat which is driven by the engine. Gear pump sec-
tion (P2) supplies hydraulic flow for raising and lowering
the cutting units, operating the steering system and
maintaining 100 to 150 PSI (6.9 to 10.3 bar) to the low
pressure side of the traction circuit (charge). The pump
section (P2) takes its suction from the hydraulic reser-
voir.
During conditions of not lifting or lowering cutting units,
flow from the gear pump (P2) is by--passed through the
steering control valve, lift control valve and hydraulic
manifold directly to the hydrostat and the charge relief
valve. Flow then returns to the hydraulic tank.
Groundsmaster 3505--D
When the cutting units are to be raised, the lift control
valve is positioned by moving the lift control lever to
RAISE. Flow is directed to the 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 block to the hydrostat (charge).
When the lift control lever is released from RAISE,
spring action returns the valve to its original position and
by--passes flow back to the hydrostat (charge), stopping
lift cylinder movement. The cylinder position is locked in
place by the load holding checks in the lift control valve.
Page 4 - - 13 Hydraulic System