JLG 4017 Service Manual - Manual (Page 27)

3.3 4017
Boom
3.2 BOOM SYSTEM
3.2.1 Boom System Operation
The four section boom consists of the first, second, third
and fourth assemblies with double third and fourth
section extend chains, a double third section retract
chains and a single fourth section retract chain.
As the extend/retract cylinder, which is anchored at the
front of the second boom section, and the rear of the first
boom section begins to extend, it forces the second boom
section out of the first boom section.
The first, second, third and fourth boom sections are
connected by extend and retract chains. These chains
are routed around sheaves on the second and third boom
sections. As the second and third boom sections are
forced out, the extend chain pulls the fourth boom section
out of the third boom section.
As hydraulic pressure is applied to the retract port on the
extend/retract cylinder, the second boom section is pulled
back into the first boom section, and the retract chain
pulls the third and fourth boom sections back into the
second boom section.
This mechanical linkage formed by the chains and
supporting hardware, extends and retracts the third and
fourth boom sections at the same rate.
The first boom section does not extend or retract, but lifts
and lowers via action of the lift cylinder.
3.3 BOOM ASSEMBLY MAINTENANCE
The boom assembly consists of the first, second, third
and fourth boom sections and supporting hardware.
IMPORTANT: Before removing the boom, the carriage
or any other attachment must be removed from the quick
switch assembly.
These instructions must be completed in sequence. The
second, third and fourth boom sections are removed from
the first boom section.The third and fourth boom sections
are removed from the second boom section.The fourth
boom section is removed from the third boom section.
Before beginning, conduct a visual inspection of the
machine and work area, and review the task about to be
undertaken. Read, understand and follow these
instructions.
3.3.1 Boom Removal
1. Remove any attachment from the quick switch
assembly. (Refer to Section 3.8.1, “Connecting with
a Mechanical Quick Switch Device.”)
2. Set the quick attach assembly in a vertical position
and set on a hard level surface. Refer to Section
3.8.4, “Quick Switch Removal,” for disassembly
instructions.
3. Park the machine on a firm, level surface. Be sure
there is enough room in front of the machine to allow
the boom sections to be removed. Fully retract the
boom then raise the boom to access the rod end pin
of lift cylinder. Place the transmission control lever in
(N) NEUTRAL, engage the park brake and shut the
engine OFF.
4. Open the engine cover. Allow the system fluids to
cool.
5. Place an Accident Prevention Tag on both the
ignition key switch and the steering wheel, stating
that the machine should not be operated.
6. Relieve any trapped pressure in the tilt hydraulic
system by installing the handle (1) (located in the
toolbox) or using an 9mm wrench and move the
double nut on the side of the actuator module on the
tilt valve section back and forth. Repeat on the
auxiliary valve section and on the extend/retract
valve section.
7. Disconnect, label and cap both hoses from the
extend/retract cylinder, tilt hoses and both auxiliary
hoses from tubes at left rear corner of first boom
section to prevent dirt and debris from entering
hydraulic system.
8. Remove the extend/retract cylinder support at the
top front of the first boom section.
MZ0420
EXT/RET
LIFT
TIL
T AU
X
SW
AY
L.
O/R
R.
O/R
FRONT OF
MA
CHINE
1