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Groundsmaster 4000--D/4010--D Hydraulic SystemPage 4 -- 21
Mow Circuit
A four section gear pump is coupled to the piston (trac-
tion) pump. Hydraulicflow for the mowcircuit issupplied
by two sections of the gear pump. The gear pump sec-
tion closest to the piston (traction) pump supplies hy-
draulic flow tothe side cutting decks, while thenext gear
pump section supplies the front cutting deck.
Each cutting deck is controlled by a hydraulic manifold
equipped with a proportional relief valve (PRV), a pilot
directional valve (PD), a logic valve (LC1) and a relief
valve(RV).Theproportionalreliefvalve isa solenoidop-
erated valve that also functions as the circuit relief valve
when energized. Circuit pressure can be measured at
port (G) of the hydraulic manifold for each cutting deck.
NOTE: To engage the mow circuit, the operator must
be in the operator seat, the tractionspeed must bein the
LOW speed (mow)position, thePTOswitch mustbe ON
andthecutting deck(s)must befullylowered andinfloat.
PTO Not Engaged
When the PTO switch is OFF or if the deck is raised with
the PTOswitch ON, the PTO manifoldproportionalrelief
valve (PRV) is not energized which allows a small
amount of hydraulic flow through the valve. As this hy-
draulic flow returns to the hydraulic reservoir, a circuit
pressure increase shifts logicvalve LC1. The pump flow
is routed through shifted LC1 and out manifold port P2
bypassingthe cuttingunit motor. Pilotdirection valvePD
and relief valve RV remain in the unshifted position to
prevent any return flow from the deck motor which
keeps the motor and cutting blades from rotating.
Return flow from the front and right PTO manifolds is
routedthroughtheoilcooler,oilfilterandthen tothe gear
pump input. Return flow from the left PTO manifold pro-
vides supply for the right deck.
PTO Engaged
When the PTO switch is turned ON and the decks are
lowered, the PTO manifold proportional relief valve
(PRV) is energized by the TEC controller. This shifted
solenoid valve prevents any flow through the valve
which allows the logic valve LC1 to be in its neutral posi-
tion directing circuit flow toward the cutting deck motor.
Gearpump flow enteringthemanifoldis routedoutman-
ifold port M1 and to the cutting deck motor to cause the
motorand cutting blades to rotate.As circuitpressure in-
creases, pilot direction valve PD shifts to provide a re-
turn path for circuit flow. The return flow from the deck
motor re--enters manifold port M2, is routed through
shifted PD, out manifold port P2, through the oil cooler
and filter and then is routed to the gear pump input. The
deck motor continues to rotate as long as proportional
relief valve (PRV) is energized.
Deck motor case drain leakage returns to the hydraulic
reservoir.
PTO Circuit Relief
Maximum mow circuit pressure is limited for each deck
by proportional relief valve (PRV) in the PTO manifold.
The centerand leftdeck relief valves areset at3000 PSI
(207bar)andt he rightdeck reliefvalve isset at2 000 PSI
(138 bar).
Proportional relief valve (PRV) and logic valve (LC1)
work together as a two stage circuit relief. When in-
creased circuit resistance is met (e.g. a cutting blade
strikesan object),the pressureincreaseis feltat thepro-
portional relief valve. If the pressure should exceed the
relief valve setting, the relief valve will open, allowing a
small amount of hydraulic flow through the valve. This
flow causes a pressure increase that shifts logic valve
LC1 and diverts circuit flow away from the deck motor to
manifoldport P2(Fig. 11). When circuit pressurelowers,
proportional relief valve (PRV) closes which returns lo-
gic valve LC1 back to its neutral position allowing flow
to return to the deck motor.
Figure 11
PRV ENERGIZED
PRV AND LC1 SHIFTED
DECK MOTOR STALLED
P1
P2
M1
M2
LC1
PRV
PD
RV
3000PSI
CD
RIGHTDECK
1.17CID
600PSI
.025
PUMP
RETURN
FLOW
RETURN
G
Hydraulic
System