JLG 4013PS Service Manual - Manual (Page 41)

3-9 3508PS, 3509PS, 3512PS, 3513PS, 4008PS, 4009PS, 4012PS, 4013PS, 4017PS, 40.8, 40.9
Boom
3.5 BOOM SYSTEM - FOUR SECTION
BOOM
3.5.1 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.
3.6 BOOM ASSEMBLY MAINTENANCE -
FOUR SECTION BOOM
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.
3.6.1 Boom Removal
1. Remove any attachment from the quick switch
assembly. Refer to Section 3.11.1, “Connecting with
a Mechanical Quick Switch Device.”
Note: If replacing the innermost boom section, remove
the quick switch assembly. Refer to Section 3.11.4,
“Quick Switch Removal.”
2. 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.
3. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel, stating that the
machine should not be operated.
4. Open the engine cover. Allow the system fluids to
cool.
5. Properly disconnect the battery.
6. Label, disconnect 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. Cap all fittings to prevent dirt and debris
from entering the hydraulic system.
7. Remove the Extend/Retract cylinder support at the
top front of the first boom section.
8. Support the Extend/Retract cylinder and remove the
clip and pin from rod end of extend/retract cylinder.
Remove the clip and pin from barrel end of extend/
retract cylinder and remove the extend/retract
cylinder.
9. Disconnect the boom angle indicator rod from switch
at the inside left rear corner of the main boom
section and frame.
10. Support the front of the boom by placing a sling
behind the boom head. Support the Lift/Lower
cylinder and remove the lock bolt and then the rod
end pin. Lower the Lift/Lower cylinder onto the frame
rails.
11. Remove the lock bolt and pin from Compensation
cylinder on each side of first boom section. Remove
the lock bolt and pivot pin from rear of first boom
section.
12. Lower the boom to a level position and place a
suitable support under the boom head. Reposition
the slings to each end of the boom.