Toro Groundsmaster 3500 30807 Service Manual page 79

Cutting Unit Blade Braking (Unit Serial No.
314000001 & Up)
When the solenoid valve (S) is de−energized, the flow
to the cutting deck motors and the relief valve (RV) is re-
moved allowing relief valve (RV) to shift. The shifted re-
lief valve removes flow from the orifice at the logic
cartridge (LC2), causing a balanced pressure condition
which shifts the logic cartridge, blocking the return oil
path from the deck motors (Fig. 21).
The inertia of the rotating cutting blades, however, effec-
tively turns the deck motors into pumps immediately
causing an increase in return pressure against the
closed relief valve (RV) and logic cartridge (LC2). When
this pressure builds to approximately 1500 PSI (104
bar), the relief valve (RV) opens which allows a small
amount of hydraulic flow past the relief valve (Fig. 22).
This returning flow is restricted by the orifice in the logic
cartridge (LC2) creating a pressure imbalance that
shifts the logic cartridge to allow oil flow from the deck
motors to pass through the manifold (Fig. 23). When re-
turn pressure drops below 1500 PSI (104 bar), the relief
valve reseats blocking flow through the orifice in the lo-
gic cartridge. The loss of flow causes the logic cartridge
to close again, stopping the cutting blades. Once the
blades have stopped, the logic cartridge remains in the
closed position to keep the deck motors from rotating.
TO DECK
MOTORS
RV
1500
psi
3200
psi
FROM
GEAR PUMP (P1)
Figure 21
Groundsmaster 3500
FROM DECK
MOTORS
ORIFICE
BLANCED
PRESSURE
LC2
S
TO
FLUID COOLER
Page 5 − 21
TO DECK
MOTORS
ORIFICE
RV
1500
psi
S
3200
psi
FROM
GEAR PUMP (P1) FLUID COOLER
Figure 22
TO DECK
MOTORS
ORIFICE
RV
PRESSURE
1500
IMBALANCE
psi
S
3200
psi
FROM
GEAR PUMP (P1) FLUID COOLER
Figure 23
FROM DECK
MOTORS
LC2
TO
FROM DECK
MOTORS
LC2
TO
Hydraulic System