Toro Groundsmaster 4000-D Service Manual page 58

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 manifold sole-
noid valve (S) is de--energized causing bypass cartridge
(LC1) to shift (refer to information in Mow Circuit in this
section). This shifted cartridge allows oil return out man-
ifold port P2. At the same time, solenoid valve (S) in its
neutral position prevents any sense line flow through the
spool which causes the brake cartridge (LC2) to shift to
its neutral position blocking return flow from the deck
motor and slowing the cutting blades (Fig. 11).
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 brake cartridge (LC2). When this
pressure 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. 12). This flow causes a pressure increase that
shifts brake cartridge (LC2) to once again allow oil flow
from the motor (Fig. 13). 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 brake cartridge
shifting occurs several times in a very short time frame
as the blades finally come to a stop. Once the blades
have stopped, brake cartridge LC2 remains in the neu-
tral position to keep the deck motor from rotating.
Hydraulic System
MANIFOLD
PTO
MANIFOLD
PTO
MANIFOLD
Page 4 - - 20
PTO
Figure 11
Figure 12
Figure 13
Groundsmaster 4000--D/4010--D