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Groundsmaster 4100--D/4110--D Hydraulic SystemPage 4 -- 19
Mow Circuit
A four section gear pump is coupled to the piston (trac-
tion) pump. Hydraulic flow for the m ow 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 wings of the cutting deck, while the
next gear pump section supplies the center section of
the cutting deck.
Each cutting deck section 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). The proportional relief valve is
a solenoid operated valve that also functions as the cir-
cuit 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 traction speed must be in the
LOW speed (mow) position, the PTO switch must be ON
and the wing decks must be fully lowered and in float.
PTO Not Engaged
When the PTO switch is OFF or if the deck or wing deck
is raised with the PTO switch ON, the PTO manifold pro-
portional relief valve (PRV) is not energized which al-
lows a small amount of hydraulic flow through the valve.
As this hydraulic flow returns to the hydraulic reservoir,
a circuit pressure increase shifts logic valve LC1. The
pump flow is routed through shifted LC1 and out man-
ifold port P2 bypassing the cutting deck motors. Pilot dir-
ection valve PD and relief valve RV remain in the
unshifted position to prevent any return flow from the
deck motor which keeps the deck section motor and cut-
ting blades from rotating.
Return flow from the center a nd right PTO manifolds is
routed through the oil cooler, oil filter and then to the 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 deck is low-
ered, 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 position directing
circuit flow toward the cutting deck motors. Gear pump
flow entering the manifold is routed out manifold port M1
and to the cutting deck motor to cause the motor and cut-
ting blades to rotate. As circuit pressure increases, pilot
direction valve PD shifts to provide a return path for cir-
cuit flow. The return flow from the deck motor re--enters
manifold port M2, is routed through shifted PD, out man-
ifold port P2, through the oil cooler and filter and then is
routed to the gear pump input. The deck motor contin-
ues 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
section by p roportional relief valve (PRV) in the PTO
manifold. The center and left wing deck relief valves are
set at 3000 PSI (207 bar) and the right wing deck relief
valve is set at 2000 PSI (138 bar).
Proportional relief valve (PRV) and logic valve (LC1)
work together as a t wo stage circuit relief. When in-
creased circuit resistance is met (e.g. a cutting blade
strikes an object), thepressure increase is felt atthe 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 sec tion 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