Hydraulic Circuit Operation - Locked Mode - JLG sky trak mmv Service Manual

Stabil-TRAK™ System
11.4.16 Hydraulic Circuit Operation -
Locked Mode
Note: The electrical schematic shown in illustration on
page 26, shows the Stabil-TRAK™ system in the
LOCKED MODE.
a. Conditions:
• Boom angle is above 40°
• Park brake ON, or service brake ENGAGED, or travel
select lever in [N] NEUTRAL
b. Operation:
Note: Refer to Section 11.4.21, Electrical Schematic -
Locked Mode, for the electrical schematic for this circuit.
When the conditions are met, solenoids 4A (1), 4B (2),
12A (3), and 12B (4) are de-energized and solenoid 3 is
energized. In the LOCKED MODE, oil is prevented from
flowing through the Stabil-TRAK™ manifold due to check
valves in solenoid-operated valves 4A (1), 4B (2), 12A (3),
and 12B (4).
11.20
11.4.17 Hydraulic Circuit Operation -
Locked Mode, Frame Sway Right
When the joystick control is placed in the frame sway
mode, the frame sway solenoid-operated valve in the pilot
select manifold is energized. As the joystick is moved to
the right, oil flows through the solenoid-operated valve in
the pilot select manifold, and then flows to the frame sway
spool valve section in the main control valve.
This pilot pressure causes the spool valve to shift position,
allowing oil to flow through the valve to the Stabil-TRAK™
manifold, port V.
Oil entering the Stabil-TRAK™ manifold at port V flows
through solenoid cartridge valve 3 (5), through a .030" ori-
fice (6) and check valve 2A (7), to the base end of the sta-
bilizer cylinder (8). The orifice slows the movement of the
frame sway.
Some of this oil is diverted to the pilot line of check valve
2B (9), opening the valve.
Rod end oil from the stabilizer cylinder flows through
check valve 2B (9), opened by pilot pressure in the Stabil-
TRAK™ manifold. The oil then flows through cartridge
valve 3 (5), out of the Stabil-TRAK™ manifold at port FTR,
through a check valve (10), to the rod end of the frame
sway cylinder (11).
Oil from the base end of the frame sway cylinder flows
through a piloted-open check valve (12) and back
through the frame sway spool valve in the frame sway
section of the main control valve, dumping the returned
oil to the reservoir.
Pressurized oil entering the Stabil-TRAK™ manifold at
port P is stopped at the four closed solenoid-operated
valves 4A (1), 4B (2), 12A (3), and 12B (4). At this time
pilot pressure will cause the 100 psi relief valve (13) to
change position, allowing the excess oil to vent to the res-
ervoir.
Model MMV Rev. 12/04