Lift Circuit (Lower) - Toro Groundsmaster 7200 Service Manual

Lift Circuit (Lower)

A single section gear pump is directly coupled to the
transmission which is driven by the engine. This gear
pump supplies hydraulic flow for raising and lowering
the cutting deck (or implement). The pump takes its suc-
tion from the hydraulic tank.
Circuit operation for lowering the cutting deck (or imple-
ment) is similar to raising it. However, hydraulic flow is
used to contract the lift cylinder and this action allows the
cutting deck (or implement) to lower.
During conditions of not raising or lowering the cutting
deck (or implement), flow from the gear pump by- pass-
es the lift circuit and is routed directly to the oil cooler and
transmission. Flow then returns to the hydraulic tank.
Manual Lift Control
313000000)
Machines with serial numbers below 313000000 have
a manual lift control valve that uses a lever to lower the
cutting deck (or implement).
When the cutting deck (or implement) is to be lowered,
the lift control valve spool is shifted by moving the lift
control lever to LOWER. This shifted spool allows gear
pump flow to unseat the pilot check valve in the lift con-
trol valve and then to the barrel end of the lift cylinder.
The lift cylinder contracts, causing the cutting deck (or
implement) to lower. The fluid displaced from the barrel
end of the lift cylinder is routed to the oil cooler, transmis-
sion and hydraulic tank. An orifice fitting at the barrel end
of the lift cylinder controls the contracting speed of the
lift cylinder while lowering the cutting deck (or imple-
ment).
Load on the lift cylinder causes lift circuit pressure to in-
crease. If lift circuit pressure reaches implement relief
valve pressure (3000 PSI/207 bar), the relief valve in the
gear pump shifts allowing pump flow to return to the hy-
draulic tank. This condition occurs in both the raise and
lower modes.
Groundsmaster 7200/7210
(Serial Number Below
Page 4 - 15
When the lift control lever is released from LOWER,
spring action returns the spool to its original, centered
position, stopping lift cylinder movement. Gear pump
flow is again bypassed through the oil cooler, transmis-
sion and to the hydraulic tank. The pilot check valve in
the control valve will be reseated to lock the lift cylinder
in place.
Electrical Lift Control (Serial Number Above
313000000)
NOTE: On machines with electrical lift control, the en-
gine must be running to allow the cutting deck to be low-
ered. When the bottom of the lift/lower switch is pressed
(detent position), the deck will lower fully and then enter
the float position.
When the bottom of the lift/lower switch is pressed (det-
ent position), solenoid valve A/S1 in the deck lift man-
ifold is energized to cause the valve to shift. Energized
solenoid valve A/S1 allows a path for oil flow from the
barrel end of the lift cylinder. The weight of the cutting
deck causes the lift cylinder to retract, allowing the cut-
ting deck to lower to the ground. An orifice fitting at the
barrel end of the lift cylinder controls the retracting
speed of the lift cylinder while lowering the cutting deck.
Cutting Deck Float
Cutting deck float allows the fully lowered cutting deck
to follow ground surface contours. Deck lift manifold so-
lenoid valve A/S1 stays energized for deck float when
the deck is fully lowered. This energized solenoid pro-
vides an oil passage to and from the lift cylinder to allow
cylinder and cutting deck movement while mowing.
Rev. A
Hydraulic System