Groundsmaster 4000--D/4010--D Hydraulic SystemPage 4 -- 21
Mow Circuit
A four section gear pump is coupled to the piston (trac-
tion) pump. Hydraulic flow for the mow circuit is supplied
by two sections of the gear pump. The gear pump sec-
tion closest to the piston (traction) pump supplies hy-
draulic flow to the side cutting decks, while the next 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).Theproportional r elief valve is a solenoid op-
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 o perator seat, the traction speed must be in the
LOW speed (mow) position, the PTO switch must be ON
and the cutting deck(s) must be fully lowered and in float.
PTO Not Engaged
When the PTO switch is OFF or if the deck is raised with
the PTO switch ON, the PTO manifold proportional relief
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 logic valve LC1. The pump flow
is routed through shifted LC1 and out manifold port P2
bypassing the cutting unit motor. Pilot direction valve PD
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
routed through the oil cooler, oil filter and then to the gear
pump input. Return flow f rom 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.
Gear pump flow entering the manifold is routed out man-
ifold port M1 and to the cutting deck motor to cause the
motor and cutting blades to rotate. As circuit pressure 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 pressur e is limited for each deck
by proportional relief valve (PRV) in the PTO manifold.
The center and left deck relief valves are set a t 3000 PSI
(207 bar) and the right deck relief valve is set at 2000 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
strikes an object), the pressure increase is felt at the pro-
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
manifold port P2 (Fig. 11). When circuit pressure lowers,
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
3000 PSI
CD
RIGHT DECK
1.17 CID
600 PSI
.025
PUMP
RETURN
FLOW
RETURN
G
Hydraulic
System
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