Toro 41188, Service Manual

Page: 61 / 353

Multi Pro 1750 Hydraulic System Page 4 − 13
Spray Boom Lift/Lower Circuit
A single section gear pump supplies hydraulic flow to the
steering control valve, steering cylinder and spray boom
lift cylinders. The gear pump is directly coupled to the
engine and takes its suction from the transaxle. When
the ignition is switched to the ON position, the hydraulics
enable valve is energized, allowing hydraulic fluid flow
from the gear pump to the remainder of the hydraulic
system. When the ignition is switched to the OFF posi-
tion, the hydraulics enable valve closes and decreases
the time required for the engine and gear pump to stop
turning.
Hydraulic circuit pressure is limited to 1000 PSI (69 bar)
by a relief valve located in the gear pump. Hydraulic flow
and pressure supplied by the gear pump can be moni-
tored at the outlet of the pump. Spray boom lift/lower cir-
cuit pressure can be measured at a diagnostic fitting in
port G on the boom lift control manifold.
The boom lift control manifold includes three (3) electri-
cally operated valves. Solenoid valve (S1) is used to di-
rect oil flow toward the boom lift cylinders when
energized. Solenoid valve (S2) controls hydraulic flow to
raise or lower the left side boom lift cylinder. Solenoid
valve (S3) controls hydraulic flow to raise or lower the
right side boom lift cylinder.
While operating the machine during conditions of not
raising or lowering a spray boom (boom lift switches in
the neutral (center) position), all of the boom lift control
manifold valves (S1, S2 and S3) are de−energized
(Fig. 10). The de−energized valve (S1) allows hydraulic
flow to return to tank through the boom lift control man-
ifold.
Raising the Spray Boom (Fig. 9)
When a boom lift switch is depressed to the raise posi-
tion, manifold solenoid valves (S1) and the top coil for
either (S2− LH cylinder) or (S3− RH cylinder) are ener-
gized. The energized (S1) directs oil flow toward the
boom lift cylinders. The other energized valve (S2 or S3)
shifts to allow pump flow to be directed toward the rod
end of the lift cylinder through a manifold check valve
and orifice that controls lift speed. The lift cylinder re-
tracts to raise the boom section.
Displaced oil from the barrel end of the lift cylinder re-
turns to the manifold, bypasses an orifice, is routed
through the shifted valve (S2 or S3), exits the control
manifold through port T, is routed to the oil filter and then
returns to the hydraulic reservoir/transaxle.
When the lift switch is returned to the neutral (center)
position, the manifold solenoid valves are de−ener-
gized. The de−energized valve (S1) allows hydraulic
flow to return to tank through the manifold. The boom lift
cylinder is held in the raised position by check valve
(PC1 − LH cylinder) or (PC2 − RH cylinder).
Lowering the Spray Boom (Fig. 9)
When a boom lift switch is depressed to the lower posi-
tion, manifold solenoid valves (S1) and the lower coil for
either (S2 − LH cylinder) or (S3 − RH cylinder) are ener-
gized. The energized (S1) directs oil flow toward the
boom lift cylinders. The other energized valve (S2 or S3)
shifts to allow pump flow to be directed toward the barrel
end of the lift cylinder through an orifice that controls
lowering speed.
As circuit pressure increases, a manifold sensing line
shifts the check valve (PC1 for the LH cylinder or PC2
for the RH cylinder) to allow a return path for oil from the
rod end of the lift cylinder. Displaced oil from the rod end
of the lift cylinder returns to the manifold, bypasses an
orifice, flows through the shifted check valve, is routed
through the shifted valve (S2 or S3), exits the control
manifold through port T, is routed to the oil filter and then
returns to the hydraulic reservoir/transaxle.
When the lift switch is returned to the neutral (center)
position, the manifold solenoid valves are de−ener-
gized. The de−energized valve (S1) allows hydraulic
flow to return to tank through the manifold. The boom lift
cylinder is held in the raised position by check valve
(PC1 − LH cylinder) or (PC2 − RH cylinder).
Figure 10
STATIONARY
BOOM CYLINDERS
(SOLENOIDS S1, S2 AND S3 ALL DE−ENERGIZED)
OR1
.036” OR2
.036” OR4
.036” OR3
.036”
T
P
C2 C1 C3 C4
RETRACT TO
RAISE
BOOM LIFT
MANIFOLD
RH CYLINDER LH CYLINDER
S1
PC1 PC2
S3 S2
TOP
COIL
TOP
COIL BOTTOM
COIL
BOTTOM
COIL
Hydraulic
System