Mow Circuit - Toro GroundsmasterR 4300-D Service Manual

Mow Circuit

A four section gear pump is coupled to the piston (trac-
tion) pump. Gear pump sections (P1) and (P2) supply
hydraulic flow for the mow circuit. These gear pumps
take their suction from the hydraulic reservoir.
The deck control manifold contains two (2) independent
control circuits for the front and rear cutting decks. Each
circuit is supplied by its own pump section. Pump sec-
tion (P1) supplies hydraulic power to the rear cutting
decks with circuit control by proportional relief valve
(PRV1), relief valve (RV1) and logic cartridge (LC1) in
the deck control manifold. Pump section (P2) supplies
the front cutting decks with circuit control by proportional
relief valve (PRV2), relief valve (RV2) and logic cartridge
(LC2) in the deck control manifold. Both circuits share
manifold port T, which drains to the oil cooler, oil filter and
hydraulic reservoir.
Cutting deck motors are equipped with a cross over re-
lief valve to prevent hydraulic component damage in
case a single cutting deck should stall.
The machine controller uses inputs from various ma-
chine switches to determine when the solenoids for pro-
portional relief valves (PRV1) and (PRV2) are to be
energized. The controller also provides a slight delay in
activation of rear cutting decks.
PTO Not Engaged
When proportional relief valves (PRV1) and (PRV2) are
not energized (PTO switch in the OFF position or cutting
decks raised), flow from pump sections (P1) and (P2) is
directed through the unshifted proportional relief valves,
out the mow control manifold port T and then returns to
the hydraulic reservoir through the oil filter and oil cooler,
bypassing the deck motors. The manifold logic car-
tridges (LC1 and LC2) remain in the unshifted position
to prevent any return flow from the deck motors so the
motors will not rotate.
PTO Engaged (Fig. 11)
When proportional relief valve (PRV1) is energized by
the controller (PTO switch in the ON position and cutting
decks lowered), the proportional relief valve shifts and
prevents pump section (P1) flow through the valve.
Pump flow that entered deck control manifold port P1 is
then directed toward the rear cutting deck motors. Be-
cause logic cartridge LC1 is unshifted, circuit pressure
increases until manifold relief valve (RV1) is opened by
a manifold pilot piston. The shifted relief valve allows a
small amount of hydraulic flow to return to tank through
Groundsmaster 4300--D
a manifold sensing line. This flow passes through an ori-
fice which causes a pressure differential that shifts logic
cartridge LC1. The shifted LC1 allows circuit flow to ro-
tate the rear cutting deck motors. Return oil from the
deck motors is directed through the shifted logic car-
tridge (LC1), manifold port T, oil cooler, oil filter and then
to the reservoir. Deck motor case drain leakage returns
directly to the hydraulic reservoir.
Mow circuit pressure for the rear cutting decks (pump
section P1) can be measured at deck control manifold
port G1.
The front cutting deck circuit operates the same as the
rear cutting deck circuit. Deck control manifold propor-
tional relief (PRV2), relief valve (RV2) and logic car-
tridge (LC2) are used to control the front cutting deck
circuit. Mow circuit pressure for the front cutting decks
(pump section P2) can be measured at deck control
manifold port G2.
Cutting Deck Circuit Relief
Maximum cutting deck circuit pressure is limited by the
proportional relief valves in the hydraulic control man-
ifold. The front deck circuit valve (PRV2) is set at 3500
PSI (241 bar) and the rear deck circuit valve (PRV1) is
set at 2500 PSI (175 bar).
When increased circuit resistance is met (e.g. a cutting
blade should strike an object), the pressure increase is
felt at the proportional relief valve. If circuit pressure
should exceed the relief setting, the valve will open to al-
low circuit flow to return to tank through manifold port T.
When circuit pressure lowers, the valve closes to allow
flow to return to the deck motors.
GROUNDSMASTER
4300- -D CUTTING
DECK LOCATIONS
Page 4 - - 13
#4 #1 #5
#2 #3
Figure 12
Hydraulic System