Toro Greensmaster 3250-D 04383 Service Manual page 57

Raise and Lower Cutting Units (Serial Number Above 270000000)
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 10.0
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) which is located in the
steering control valve.
During cutting unit hold (not raising or lowering) condi-
tions, flow from the gear pump (P2) is by--passed
through the steering control valve and de--energized so-
lenoid valve (S2) directly to the hydrostat and the charge
relief valve (R4). Flow then returns to the hydraulic res-
ervoir.
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 en-
ergized solenoid valve (S3) to the hydrostat. Raise
speed for the front cutting units is controlled by a .055
orifice. A .055 orifice in the return line for the center cut-
ting unit allows a slight delay in raising that cutting unit.
When solenoid valves (S2) and (S3) 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.
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 solenoid valve (S4) is ener-
gized. Flow is reversed to and from the lift cylinders,
lowering the cutting units.
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 the lift cylinders. Hydraulic
pressure against the cylinder pistons moves their shafts
causing the cutting units to lower. At the same time, the
pistons push the hydraulic fluid out of the lift cylinders to
energized solenoid valve (S4). Flow continues back
through solenoid valves (S3) to the hydrostat. Lower
speed for the front cutting units is controlled by the .055
orifice. A .055 orifice and adjustable flow control valve
for the center cutting unit allows a slight delay in lowering
that cutting unit.
To control pressure while lowering the cutting units, the
system is equipped with adjustable relief valve (R2) in
the hydraulic manifold.
When solenoid valves (S2) and (S4) 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)