Toro Greensmaster 3120 - Lift Circuit

LiftCircuit
Atandemgearpumpisdirectlycoupledtothepiston(traction)pump.Therear
gearpumpsection(P3)supplieshydraulicowforthesteeringcircuit(priority
ow),forraisingandloweringthecuttingunitsandforthetractionsystemcharge
circuit.Thegearpumptakesitssuctionfromthehydraulictankthroughasuction
strainer.Maximumcircuitpressureof7998kPa(1160PSI)islimitedbythe
reliefvalvelocatedinthesteeringvalve.
Duringcuttingunithold(notraisingorlowering)conditions,owfromtherear
gearpumpsectionisby-passedthroughthesteeringvalveandde-energized
solenoidvalve(S2)inthemowermanifolddirectlytothetractionsystemcharge
circuit.Chargecircuitowinexcessofclosed-loopsystemrequirementsreturns
tothehydraulictankviathetraction(piston)pumpcasedrain.
RaiseCuttingUnits
WhentheRasie/LowerMowcontrolismovedforward,themowermanifold
solenoidvalves(S2andS3)areenergized;refertoFigure20.Energized
solenoidvalve(S2)blockstheowofuidtothetractionsystemchargecircuit,
anddirectstheowtoenergizedsolenoidvalve(S3).Theowcontinuesthrough
de-energizedsolenoidvalve(S4)andontotheliftcylinders.Hydraulicpressure
atthebarrelendoftheliftcylinderextendsthecylinderscausingthecuttingunits
toraise.Atthesametime,thecylinderpistonspushhydraulicuidoutofthe
rodendofthecylinder,throughenergizedsolenoidvalve(S3)andbackintothe
tractionsystemchargecircuit.Raisespeedforthefrontcuttingunitsiscontrolled
byapairor0.055inchoricesinthemowermanifold.A0.030inchoriceinthe
mowermanifoldcreatesaslightdelayinraisingthecentercuttingunit.
Whensolenoidvalves(S2)and(S3)de-energize,springactionreturnsthe
valvestotheiroriginalpositionandowisdirectedbacktothetractioncharge
circuitstoppingliftcylindermovement.Theliftcylinderspositionisheldinplace
bythecheckvalvefeatureofde-energizedsolenoidvalve(S4),blockingany
returnowfromthecylinders.
LowerCuttingUnits
WhentheRasie/LowerMowcontrolismovedrearwardtolowerthecuttingunits,
mowermanifoldsolenoidvalves(S2andS4)areenergized;refertoFigure21.
Energizedsolenoidvalve(S2)blockstheowofuidtothetractionsystem
chargecircuit,anddirectstheowthroughde-energizedsolenoidvalve(S3)
andontotheliftcylinders.Hydraulicpressureattherodendoftheliftcylinder
retractsthecylinderscausingthecuttingunitstolower.Atthesametime,the
cylinderpistonspushhydraulicuidoutofthebarrelendofthecylinder,through
energizedsolenoidvalve(S4),de-energizedsolenoidvalve(S3)andbackinto
thetractionsystemchargecircuit.Lowerspeedforthefrontcuttingunitsis
controlledbyapairor0.055inchoricesinmowermanifold.Anadjustable
owcontrolvalveinthemowermanifoldcreatesaslightdelayinloweringthe
centercuttingunit.
Reliefvalve(R2)inthemowermanifoldisincorporatedintotheloweringcircuit
incasethecuttingunitsareobstructedduringlowering.Thereliefvalveisset
to1,724kPa(250psi)atthefactory.Oncethecuttingunitsarefullylowered,
solenoidvalve(S2)and(S4)de-energize,springactionreturnsthevalvestotheir
originalpositionandowisdirectedbacktothetractionchargecircuitstopping
liftcylindermovement.
Greensmaster3120
Page4–17
HydraulicSystem:HydraulicFlowDiagrams
17230SLRevC