Toro Greensmaster 3250-D 04383 Service Manual page 55

Raise and Lower Cutting Units (Serial Number Under 260999999)
The gear pump (P2) is directly coupled to the hydrostat
through gear pump (P1). It supplies hydraulic pressure
for raising and lowering the cutting units, for the steering
circuit, and for maintaining 100 to 150 PSI (6.9 to 10.3
bar) to the low pressure side of the traction circuit
(charge pressure). The gear pump (P2) takes its suction
from the hydraulic reservoir. Maximum circuit pressure
is limited by relief valve (R5).
During conditions of not lifting or lowering cutting units,
flow from the gear pump is by--passed through the steer-
ing control valve and solenoid valve (S2) directly to the
hydrostat and the charge relief valve (R4). Flow then re-
turns to the hydraulic reservoir.
Raise Cutting Units
When the cutting units are to be raised, solenoid valve
(S2) is energized and blocks flow directly to the hydros-
tat. Flow is directed to energized solenoid valve (S3),
which directs flow to de--energized solenoid valve (S4)
and the lift cylinders. Hydraulic pressure against the cyl-
inder pistons moves their shafts causing the cutting
units to raise. At the same time, the pistons push the hy-
draulic fluid out of the lift cylinders and back through so-
lenoid valves (S4 and S3) to the hydrostat.
When the solenoid valves de--energize, spring action
returns the valves to their original position and by--
passes flow back to the hydrostat stopping lift cylinder
movement. The lift cylinder position is locked in place
since there is no complete circuit of flow to and from the
lift cylinders.
Note: On traction units with serial numbers from
230000601 to 260999999, solenoid valve (S6) is ener-
gized when the cutting units are raised. This forces the
return flow from the reel motors through the .125" orifice,
putting back pressure on the reel circuit, and stopping
the reels from rotating.
Greensmaster 3250--D
Lower Cutting Units
Circuit operation for lowering the lift cylinders is similar
to raising them. However, the solenoid valve (S3) re-
mains de--energized and in the down position and sole-
noid valve (S4) is energized and shifts down. Flow is
reversed to and from the lift cylinders, thus moving the
cutting units down.
When the cutting units are to be lowered, solenoid valve
(S2) is energized and blocks flow directly to the hydros-
tat. Flow is directed to de--energized solenoid valve
(S3), which directs flow to energized solenoid valve (S4)
and the lift cylinders. Hydraulic pressure against the cyl-
inder pistons moves their shafts causing the cutting
units to lower. At the same time, the pistons push the hy-
draulic fluid out of the lift cylinders and back through so-
lenoid valves (S4 and S3) to the hydrostat. Flow into the
flow control valve is slowed by the variable orifice to al-
low the rear cutting unit to lower after the front units.
To control pressure while lowering cutting units, system
is equipped with adjustable relief valve (R2) in the hy-
draulic manifold.
When the solenoid valves de--energize, spring action
returns the valves to their original position and by--
passes flow back to the hydrostat stopping lift cylinder
movement.
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Hydraulic System (Rev. I)