Lift Circuit (Raise)
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 suction from the hydraulic tank.
During the conditions of not raising or lowering the cutting deck (or implement),
flow from the gear pump is bypassed by the lift-control manifold directly to the oil
cooler and then to the transmission. The flow then returns to the hydraulic tank.
Note:
To raise the cutting deck, the engine must be in running condition.
Electrical Lift Control
The lift-control manifold is equipped with the 2 solenoid valves for electrical
control of the lift circuit. A deck lift/lower switch on the right side traction lever is
used to raise the cutting deck (or implement).
When the top of the lift/lower switch is pressed (momentary position), both the
solenoid valves (A/S1 and B/S2) in the deck lift manifold are energized to cause
the valves to shift. The energized solenoid valve B/S1 prevents the gear pump
flow from bypassing the lift cylinder. The energized solenoid valve A/S1 allows
the hydraulic flow from the gear pump to the cylinder head of the lift cylinder. The
lift cylinder extends, causing the cutting deck to raise. The fluid displaced from
the rod end of the lift cylinder is routed to the oil cooler, transmission, and then to
the hydraulic tank. An orifice in the manifold controls the extending speed of the
lift cylinder while raising the cutting deck.
The load on the lift cylinder causes the lift circuit pressure to increase. If the lift
circuit pressure reaches the implement relief valve pressure 20,700 kPa (3,000
psi), the relief valve in the gear pump shifts to allow the pump flow to return to
the hydraulic tank. This condition occurs in both the raise and lower modes.
When the top of the lift/lower switch is released, both the solenoid valves (A/S1
and B/S2) in the deck lift manifold are de-energized. The de-energized solenoid
valve B/S2 allows the gear pump flow to bypass the lift cylinder, returning to
the oil cooler, transmission, and then to the hydraulic tank. The de-energized
solenoid valve A/S1 prevents the hydraulic flow to and from the lift cylinder to
keep the cutting deck in the raised position.
Hydraulic System: Hydraulic Schematics
Page 4–18
Groundsmaster 7210
16222SL Rev C
Summary of Contents for Groundsmaster 7210
Page 4: ...NOTES Revision History Page 4 Groundsmaster 7210 16222SL Rev C...
Page 32: ...Specifications and Maintenance Special Tools Page 2 16 Groundsmaster 7210 16222SL Rev C...
Page 60: ...Diesel Engine Service and Repairs Page 3 28 Groundsmaster 7210 16222SL Rev C...
Page 196: ...Hydraulic System Service and Repairs Page 4 136 Groundsmaster 7210 16222SL Rev C...
Page 304: ...Chassis Service and Repairs Page 6 42 Groundsmaster 7210 16222SL Rev C...
Page 327: ...Drawing 105 7260 Rev E Sheet 1 16222SL Rev C Page A 3 Hydraulic Schematic g186843...
Page 328: ...Page A 4 16222SL Rev C Drawing 119 4372 Rev C Sheet 1 Electrical Schematic Platform g186842...
Page 329: ...Drawing 119 4377 Rev C Sheet 1 16222SL Rev C Page A 5 Electrical Schematic Engine g186841...
Page 336: ...Page A 12 16222SL Rev C Drawing 119 4386 Rev A Sheet 1 Wire Harness Drawing Cab Power g186851...
Page 342: ......
