Toro Groundsmaster 4500-D Series Service Manual page 127

Cutting Deck Lower (continued)
Cutting Deck Float
Counterbalance
Groundsmaster ® 4500-D/4700-D
19245SL Rev A
flow from the rod ends of the center five (5) deck lift cylinders. The weight of the
cutting decks cause the lift cylinders to extend and the center decks to lower.
An orifice in the lift control manifold restricts oil flow from the lift cylinders to
control deck drop speed. Additionally, an orifice in the junction manifold further
controls the lowering speed of the #1 deck.
To lower a side cutting deck on the Groundsmaster 4700-D (deck #6 or #7), the
front of the appropriate lift switch is depressed. The switch acts as an input to
the TEC controller (T2) which then provides electrical output to the appropriate
solenoid valves in the lift control manifold: S1, S3 and S4 for deck #6 or S1, S8
and S9 for deck #7. The energized solenoid valves shift to allow pump flow to
the barrel end of the deck lift cylinder and a passage for oil from the rod end of
the cylinder. The cylinder extends to lower the side cutting deck. An orifice in the
lift manifold restricts oil flow from the lift cylinder to control side deck drop speed.
Cutting deck float allows the fully lowered cutting decks to follow ground surface
contours. On a Groundsmaster 4700-D, S6 (center decks), S4 (left deck #6)
and S9 (right deck #7) are energized for deck float. These energized solenoids
provide 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 (T1) is provided to the proportional relief valve
(TS) to maintain counterbalance pressure.
Page 5–25 Hydraulic System: Hydraulic Flow Diagrams