Toro Groundsmaster 4300-D - Page 85

MowCircuitCuttingDeckBladeBraking(continued)
g186192
Figure34
WhentheoperatorturnsthePTOswitchOFF(orifthedecksareraised),thedeck
controlmanifoldproportionalreliefvalves(PRV1andPRV2)arede-energized.
Thevalveswillshifttodirectuidawayfromthedeckmotorsandtowardtheoil
coolerandlter.Hydraulicpressureisreducedtothecuttingdeckmotorswhich
slowsthecuttingbladesandalsoallowsthedeckcontrolmanifoldreliefvalves
(RV1andRV2)toshift.Theshiftedreliefvalvesremovestheowpathfromthe
oricebeforethelogiccartridge,causingthelogiccartridgetoshiftandblock
thereturnoilpathfromthedeckmotors(Figure32).
Theinertiaoftherotatingcuttingblades,however,effectivelyturnsthedeck
motorsintopumpscausinganincreaseinpressureastheowfromthemotors
comesupagainsttheclosedlogiccartridges(LC1andLC2).Whenthispressure
buildstoapproximately10,340kPa(1,500psi),thereliefvalvesopenwhich
allowsasmallamountofhydraulicowpastthereliefvalve(Figure33).This
owcausesapressureincreasethatshiftsthelogiccartridgetoonceagainallow
uidowfromthedeckmotors(Figure34).Whenreturnpressuredropsbelow
10,340kPa(1,500psi),thereliefvalvere-seatsandcausesthelogiccartridgeto
closeagain,blockingreturnowfromthedeckmotorstofurtherslowthecutting
blades.Thisactionofthereliefvalveopeningandthelogiccartridgeshifting
occursseveraltimesinaveryshortperiodasthebladesnallycometoastop.
Oncethebladeshavestopped,thelogiccartridgeremainsintheclosedposition
tokeepthedeckmotorsfromrotating.
Groundsmaster
®
4300-D
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HydraulicSystem:HydraulicFlowDiagrams
16226SLRevC