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Groundsmaster 4500--D/4700--DHydraulic System Page 4 -- 26
Cutting Deck Blade Braking
When the operator turns the PTO switch OFF (or if the
decks are raised), deck manifold solenoid valves
(PRV1, PRV2, SV1 and SV2) are de--energized. The
valves will shift to direct oil away from the deck motors
and toward the oil cooler and filter. Hydraulic pressure
is reduced to the cutting deck motors which slows the
cutting blades and also allows the deck manifold relief
valve (RV) to shift. The shifted relief valve removes the
flow path from the orifice at the logic cartridge, causing
the logic cartridge to shift and block the return oil path
from the d eck motors (Fig. 20).
The inertia of the rotating cutting blades, however,effec-
tively turns the deck motors into pumps causing an in-
crease in pressure as the flow from the motors comes
up against the closed logic cartridge (LC). When this
pressure builds to approximately 1500 PSI (104 bar),
the relief valve opens whichallows a smallamount of hy-
draulic flow past the relief valve (Fig. 21). This flow
causes apressure increase that shifts the logic cartridge
to once again allow oil flow from the deck motors (Fig.
22). When return pressure drops below 1500 PSI (104
bar), the relief valve reseats and causes the logic car-
tridge to close again, blocking return flow from the deck
motors to further slow the cutting blades. This action of
the relief valve opening and the logic cartridge shifting
occurs several times in a very short time frame as the
blades finally come to a stop. Once the blades have
stopped, the logic cartridge remains in the neutral posi-
tion to keep the deck motors from rotating.
Figure 20
3500
PSI
1500
PSI
P2
PRV2
LC2
M3
M4
RV09
FRONT
LEFT
1.16
CID
1.16
CID
G4
G3
FRONT
CENTER
#1
#4
TO OIL
FROM
COOLER
GEAR
PUMP
ORIFICE
DECK CONTROL
MANIFOLD
Figure 21
3500
PSI
1500
PSI
P2
PRV2
LC2
M3
M4
RV09
FRONT
LEFT
1.16
CID
1.16
CID
G4
G3
FRONT
CENTER
#1
#4
TO OIL
FROM
COOLER
GEAR
PUMP
ORIFICE
DECK CONTROL
MANIFOLD
Figure 22
3500
PSI
1500
PSI
P2
PRV2
LC2
M3
M4
RV09
FRONT
LEFT
1.16
CID
1.16
CID
G4
G3
FRONT
CENTER
#1
#4
TO OIL
FROM
COOLER
GEAR
PUMP
ORIFICE
DECK CONTROL
MANIFOLD