Toro Groundsmaster 4500-D Series Service Manual page 124

Cutting Deck Lower
Cutting Deck Float
Counterbalance
Hydraulic System: Hydraulic Flow Diagrams
To lower the five (5) cutting decks on a Groundsmaster 4500-D, the front of the
lift switch is depressed. The switch acts as an input to the TEC controller (T1)
which then provides an electrical output to solenoid valve S6 in the lift control
manifold. This energized solenoid valve shifts to allow a passage for oil flow from
the rod ends of the five (5) deck lift cylinders. The weight of the cutting decks
causes the lift cylinders to extend and lowers all of the cutting decks. An orifice
in the lift control manifold C2 port restricts oil flow from the lift cylinders to control
deck drop speed. An orifice in the junction manifold further controls the lowering
speed of the #1 deck. The junction manifold orifices leading to the #4 and #5
decks are bypassed during deck lowering.
Cutting deck float allows the fully lowered cutting decks to follow ground surface
contours. On a Groundsmaster 4500-D, lift control manifold solenoid valve S6
is energized for deck float when the decks are fully lowered. This energized
solenoid provides an oil passage to and from the lift cylinders to allow cylinder
and cutting deck movement while mowing.
Once the cutting decks are fully lowered, the lift control manifold proportional
relief valve (TS) maintains back pressure (counterbalance) on the deck lift
cylinders. This counterbalance pressure transfers cutting deck weight to the
machine to improve traction.
A pressure sensor located in the hydraulic tube between the front wheel and rear
axle motors is used by the TEC controller (T1) as an input to determine traction
circuit pressure. Based on this sensor input, a PWM (Pulse Width Modulation)
signal from the TEC controller is provided to the proportional relief valve (TS)
to maintain counterbalance pressure.
Page 5–22 Groundsmaster ® 4500-D/4700-D
19245SL Rev A