Toro Groundsmaster 4000-D, Service Manual

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Groundsmaster 4000--D Hydraulic System Page 4 -- 20
PTO Mow Circuit Cutting Deck Blade Braking
When the operator turns the PTO switch OFF or if a deck
is raised with the PTO switch ON, PTO control manifold
solenoid valve (S) is de--energized causing logic car-
tridge (LC1) to shift (refer to information in PTO Mow Cir-
cuit in this section). This shifted cartridge allows oil
return out manifold port P2. At the same time, solenoid
valve (S) in its neutral position prevents any sense line
flow through the spool which causes the logic cartridge
LC2 to shift to its neutral position blocking return flow
from the deck motor and slowing the cutting blades (Fig.
10).
The inertia of the rotating cutting blades, however, effec-
tively turns the deck motor into a pump causing an in-
crease in pressure as the flow from the motor comes up
against the closed logic cartridge (LC2). When this pres-
sure builds to approximately 600 PSI (41 bar), relief
valve (RV2) opens which allows a small amount of hy-
draulic flow to return to tank through a manifold sensing
line (Fig. 11). This flow causes a pressure increase that
shifts logic cartridge LC2 to once again allow oil flow
from the motor (Fig. 12). When return pressure drops
below 600 PSI (41 bar), relief valve (RV2) reseats and
causes LC2 to close again blocking return flow from the
deck motor to further slow the cutting blades. This action
of the brake 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, logic cartridge LC2 remains in the neutral
position to keep the deck motor from rotating.
Figure 10
PTO MANIFOLD
MOTOR
CD
DECK
G
RV1
RV2
LC2
LC1
S
P1
P2
M1
M2
Figure 11
PTO MANIFOLD
MOTOR
CD
DECK
G
RV1
RV2
LC2
LC1
S
P1
P2
M1
M2
Figure 12
PTO MANIFOLD
MOTOR
CD
DECK
G
RV1
RV2
LC2
LC1
S
P1
P2
M1
M2