Raise And Lower Cutting Units - Toro Greensmaster 3150 Service Manual

Raise and Lower Cutting Units

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).
During cutting unit hold (not raising or lowering) condi-
tions, flow from the gear pump is by–passed through the
steering control valve and solenoid valve (S2) directly to
the hydrostat and the charge relief valve (R4). Flow then
returns 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 (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
230000801 and up, solenoid valve (S6) is energized
when the cutting units are raised. This forces the return
flow from the reel motors through the .125" orifice, putt-
ing back pressure on the reel circuit, and stopping the
reels from rotating.
Hydraulic System
units with serial numbers
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. Flow into
the flow control valve is slowed by the variable orifice to
allow the rear cutting unit to lower after the front units.
To control pressure while lowering cutting units, the sys-
tem is equipped with adjustable relief valve (R2) in the
hydraulic 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.
Page 4 – 10 Rev. C Greensmaster 3150