Service Manual

Groundsmaster 4300--DHydraulic System Page 4 -- 14
Mow Circuit Cutting Deck Blade Braking
When the operator turns the PTO switch OFF or if the
decks are raised with the PTO switch ON, the deck con-
trol manifold proportional relief valves (PRV1 and
PRV2) are de--energized causing circuit flow to bypass
the deck motors and return to the reservoir out manifold
portT(referto information in Mow Circuitinthissection).
Without circuit flow, the manifold relief valve (RV1 or
RV2)returns toitsneutralpositionwhichcausesthelog-
ic cartridge (LC1 or LC2) to shift to its neutral position,
blocking return flow from the deck motors and slowing
the cutting blades (Fig. 13).
Theinertiaoftherotating cutting blades, however, effec-
tively turns the deck motors into pumps causing an in-
crease in pressure as the flow from the motor comes up
against the closed logic cartridge (LC1 or LC2). When
this pressure builds to approximately 1500 PSI (105
bar), the relief valve (RV1 or RV2) re--opens which al-
lows a small amount of hydraulic flow to return to tank
through a manifold sensing line (Fig. 14). This flow
causes a pressure differential that shifts the logic car-
tridge (LC1 or LC2) to once again allow oil flow from the
motors (Fig. 15). When return pressure drops below
1500 PSI (105 bar), the relief valve (RV1 or RV2) re-
seats and causes the logic cartridge (LC1 or LC2) to
close again, blocking return flow from the deck motors
to further slow thecutting 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 fi-
nally come to a stop. Once the blades have stopped, the
logic cartridge (LC1 or LC2) remains in the neutral posi-
tion to keep the deck motors from rotating.
Figure 13
DECK
CONTROL
MANIFOLD
FROM
GEAR
PUMP
TO
OIL
COOLER
FROM
FRONT
MOW
CIRCUIT
ORIFICE
DECK
CONTROL
MANIFOLD
FROM
GEAR
PUMP
TO
OIL
COOLER
FROM
FRONT
MOW
CIRCUIT
ORIFICE
Figure 14
DECK
CONTROL
MANIFOLD
FROM
GEAR
PUMP
TO
OIL
COOLER
FROM
FRONT
MOW
CIRCUIT
ORIFICE
Figure 15
DECK
CONTROL
MANIFOLD
FROM
GEAR
PUMP
TO
OIL
COOLER
FROM
FRONT
MOW
CIRCUIT
ORIFICE