Toro Groundsmaster 5900 Series Service Manual page 129

PTO Not Engaged
PTO Engaged
Groundsmaster ® 5900 & 5910
16227SL Rev B
Each of the three (3) cutting decks is controlled by a hydraulic control manifold
equipped with a proportional relief valve (PRV), logic valves (LC1) and (LC2), a
sequence valve (SQ) and a brake relief cartridge (RV). The proportional relief
valve is a solenoid operated valve that also functions as the circuit relief valve
when the valve is energized by the slave Toro Electronic Controller (TEC). Mow
circuit pressure can be measured at port (G1) of the hydraulic manifold for each
cutting deck.
Note: To engage the mow circuit, the operator must be in the operator seat, the
traction speed must be in the LOW speed (mow) position, the PTO switch must
be ON and the cutting deck(s) must be fully lowered.
When the PTO switch is OFF or if the deck is raised with the PTO switch ON, the
PTO manifold proportional relief valve (PRV) is not energized by the slave TEC
which allows a small amount of hydraulic flow through the valve. As this hydraulic
flow returns to the hydraulic reservoir, a circuit pressure increase shifts logic
valve LC1. The pump flow is routed through shifted LC1 and out manifold port
P2 bypassing the cutting unit motor. Sequence valve (SQ), pilot direction valve
(PD) and relief valve (RV) remain in the unshifted position to prevent any flow to
or from the deck motor which keeps the motor and cutting blades from rotating.
Return flow from the front and right deck control manifolds is routed through the
oil cooler, oil filter and then to the gear pump input. Return flow from the left deck
control manifold provides supply for the right deck.
When the PTO switch is turned ON and the decks are lowered, the PTO manifold
proportional relief valve (PRV) is energized by the slave TEC. This shifted
solenoid valve prevents any flow through the valve which allows the logic valve
LC1 to be in its neutral position directing circuit flow toward the cutting deck
motor. Gear pump flow entering the manifold is routed out manifold port M1 and
to the cutting deck motor. As circuit pressure increases, the sequence valve
(SQ) and then the logic valve (LC2) shift to allow the motor and cutting blades to
rotate and to provide a return path for circuit flow. The return flow from the deck
motor re−enters manifold port M2, is routed through shifted logic valve (LC2) and
out manifold port P2. Return flow from the front and right deck control manifolds
is routed through the oil cooler, oil filter and then to the gear pump input. Return
flow from the left deck control manifold provides supply for the right deck. Flow for
the deck motor continues as long as proportional relief valve (PRV) is energized.
Deck motor case drain leakage returns directly to the hydraulic reservoir.
Page 5–29 Hydraulic System: Hydraulic Flow Diagrams