Mow Circuit Cutting Deck Blade Braking - Toro Groundsmaster 4000-D Service Manual

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 propor-
tional relief valve (PRV) is de--energized causing logic
valve (LC1) to shift (refer to information in Mow Circuit
in this section). This shifted cartridge directs oil return
out of manifold port P2. As circuit pressure decreases,
pilot direction valve PD is shifted to it's neutral position,
preventing return flow from the deck motor and slows
the cutting blades (Fig. 12).
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 relief valve (RV). When this pressure
builds to approximately 600 PSI (41 bar), relief valve
(RV) opens which allows hydraulic flow to flow from the
motor (Fig. 13). When return pressure drops below 600
PSI (41 bar), relief valve (RV) reseats to once again
block return flow from the deck motor to further slow the
cutting blades. This action of the brake relief valve open-
ing occurs several times in a very short time frame as the
blades finally come to a stop. Once the blades have
stopped, relief valve (RV) remains seated to keep the
deck motor from rotating.
Hydraulic System
M1
1.17 CID
M2
RETURN
M1
1.17 CID
M2
RETURN
Page 4 - - 22
3000 PSI
.025
PD
PRV
RV
600 PSI
RIGHT DECK
CD
PTO SWITCH OFF
PRV NOT ENERGIZED
LC1 SHIFTED
Figure 12
3000 PSI
.025
PD
PRV
RV
600 PSI
RIGHT DECK
CD
PTO SWITCH OFF
PRV NOT ENERGIZED
LC1 AND RV SHIFTED
Figure 13
Groundsmaster 4000--D/4010--D
PUMP
FLOW
P1
G
LC1
P2
RETURN
PUMP
FLOW
P1
G
LC1
P2
RETURN