Toro Groundsmaster 4300-D - Lift Cylinder Circuit: Raise the Cutting Decks

LiftCylinderCircuit:RaisetheCuttingDecks
A4-sectiongearpumpiscoupledtothepiston(traction)pump.Thegearpump
section(P4)supplieshydraulicowtotheliftcontrolmanifoldandliftcylinders.
Thegearpumptakesitssuctionfromthehydraulicreservoir.
Theliftcontrolmanifoldincludes3electricallyoperatedvalves.Thesolenoid
valve(S1)isusedtodirectuidowtoextendtheliftcylinders(lowerthe
cuttingdecks)whenenergizedorretractthem(raisethecuttingdecks)when
de-energized.Thesolenoidvalve(S2)allowshydraulicowfromtherodend
oftheliftcylinderswhenenergized,andpreventshydraulicowfromthelift
cylinderswhende-energized.UsingsolenoidvalveS2inthismanneralso
helpskeepthecuttingdeckselevatedoncethemachineisswitchedOFF.The
proportionalreliefvalve(PRV)isusedtocontroltheoperationofthelogic
cartridge(LC)andactsasacircuitreliefvalve.
RaisetheCuttingDecks
Whenthejoystickismovedtotheraiseposition,thecontrollerenergizesthe
proportionalreliefvalve(PRV)(Figure35).Theenergizedreliefvalve(PRV)
preventsowthroughthevalvewhichallowslogiccartridgeLCtoreturntoits
unshifted(closed)position.Withthevalvesinthisposition,thepumpowis
directedtotherodendofallliftcylinderstoretractthecylindersandraiseallthe
cuttingdecks.Theowtotheliftcylindersbypassesthe4controlmanifoldxed
oricestopreventtheowrestrictionduringdeckraising.
Whilethecuttingdecksarebeingraised,theproportionalreliefvalve(PRV)
hasasecondaryfunctionasacircuitrelieftolimitliftcylindercircuitpressure
to13,800kPa(2,000psi).Theliftcylindercircuitpressurecanbemonitoredat
liftcontrolmanifoldportG4.
WhenthecuttingdeckisfullyraisedorthejoystickisreturnedtotheNEUTRAL
(center)position,theproportionalreliefvalve(PRV)andsolenoidvalvesS1and
S2arede-energized.Thede-energizedreliefvalve(PRV)allowshydraulicow
toreturntotankthroughthemanifold.Thisowthroughtheproportionalrelief
valvecausesapressuredifferentialthatshiftsthelogiccartridge(LC)which
allowsthemajoritypumpowtobypasstheliftcylinders.Theliftcylindersand
cuttingdecksareheldintheraisedpositionbythede-energizedvalveS2.
Groundsmaster
®
4300-D
Page4–25
HydraulicSystem:HydraulicFlowDiagrams
16226SLRevC