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Greensmaster 3320/3420 Hydraulic SystemPage 5 -- 15
Lower Cutting Units
The gear pumpis directlycoupledto thepiston (traction)
pump. The gear pump supplies hydraulic flow for the
steering circuit (priority flow), for raising and lowering
the cutting units and for the traction charge circuit. The
gear pump takes itssuction fromthe hydraulicreservoir.
Maximum circuit pressure of1160 PSI (80 bar) is limited
by the relief valve located in the power steering valve.
The lift control manifold includes four (4) electrically op-
eratedsolenoidvalves. Solenoidvalve S1causescircuit
flow to by--pass the lift cylinders when de--energized
and directs f low to the cylinders when energized. Direc-
tional solenoid valve S2 is used to direct oil flow to raise
the cutting units when de--energized and lower them
when energized. When energized,solenoid valve S3al-
lows hydraulic flow to and from the front cutting unit lift
cylinders (#2 and #3) and prevents oil passage to and
from the lift cylinders when de--energized. When ener-
gized, solenoid valve S4 a llows hydraulic flow to and
fromthe center cutting unit lift cylinder( #1) andprevents
oil p assage to and from the lift cylinder when de--ener-
gized.
Theconsolearmjoystickisusedtoraiseandlowerthe
cutting units. The joystick acts as an input to the TEC
controller to send electrical outputs to appropriate lift
control manifold solenoid coils in order to raise or lower
the cutting units.
While operating the machine during conditions of not
raising or lowering the cutting units (joystick in the neu-
tral (center) position), all of the lift manifold solenoid
valves (S1,S2, S3and S4)arede--energized. Flowfrom
the gear pump is directed through the power steering
valve, de--energized solenoid valve S1 in the lift control
manifold, oil filter and to the traction charge circuit. Flow
inexcess of chargecircuit needsthen returnsto thegear
pump input.
Lower Cutting Units
When the joystick is moved to the lower position, the
Toro Electronic Controller (TEC) energizes all of the lift
controlmanifold solenoidvalves for approximatelythree
(3) seconds. This time f rame ensures that the cutting
unitswill befullylowered toallowthem tofloat duringop-
eration. The controller also provides a short delay in en-
ergizing solenoid valve S4 which delays the lowering of
the center cutting unit (#1).
Energizedlift manifold solenoids S1 andS2direct circuit
flow toward the lift cylinders in the correct direction to
lower the cutting units. The front lift cylinders extend to
lower the cutting units while the center lift cylinder re-
tracts to lower the cutting unit. Hydraulic pressure
against the lift cylinder pistons moves their shafts caus-
ingthecuttingunitstolower.Atthesame time,thelift cyl-
inder pistonspush the hydraulicfluid out ofthe cylinders
to energized solenoid valves S3 (front lift cylinders) and
S4 (center lift cylinder). Return flow continues through
energized solenoid valve S2, to the oil filter and then to
thetractionchargecircuit.
Lowering speed for each of the front cutting units (#2
and #3) is controlled by a 0.028 orifice ( OR2 a nd OR3)
in the liftcontrol manifold. A 0.037 orifice (OR1) controls
lowering speed for the center cutting unit (#1).
If the lift cylinders should reach the end of their stroke
whilethelift manifoldsolenoids arestill energized,lift cir-
cuit pressure will increase. The lift circuit lower relief
valve(RV)intheliftcontrolmanifold allows lift circuit
pressure to be limited to 400 PSI (27.6 bar) while lower-
ing the cutting units.
NOTE: Adjustment of the lift control manifold lift circuit
lower relief valve (RV) is not r ecommended.
When the lift control manifold solenoid valves are de--
energized by the TEC controller, spring action returns
the valves to their original position 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. Hydraulic flow by--passes the lift cylinders
andisroutedtotheoilfilterandchargecircuit.
Hydraulic
System