JLG 4017PS Service Manual - Manual (Page 49)

3-11 3706PS, 3707PS, 4014PS, 4017PS, 33.7, 37.6, 37.7
Boom
3.5 BOOM SYSTEM - THREE SECTION
3.5.1 Boom System Operation
The 4014PS three section boom consists of the first,
second and third assemblies with first and second section
extend chains, and a single first and second section
retract chain.
As the extend/retract cylinder, which is anchored at the
rear of the second boom section, and the front of the third
boom section begins to extend, it pushes the third boom
section out of the second boom section.
The boom sections are connected by extend and retract
chains. These chains are routed around sheaves on the
front and the rear of the second boom section. As the
extend/retract cylinder is forced out hydraulically, the
second and third boom sections are pulled out by the
extend chains.
As hydraulic pressure is applied to the retract port on the
extend/retract cylinder, the retract chain pulls the second
and third boom sections back into the first boom section.
This mechanical linkage formed by the chains and
supporting hardware, extends and retracts the second
and third boom sections into the first boom section at the
same rate.
The boom section lifts and lowers via action of the lift
cylinder.
3.6 BOOM ASSEMBLY MAINTENANCE
These instructions must be completed in sequence. The
second and third boom sections are removed from the
first boom section.The third boom section is removed
from the second boom section or the complete boom
assembly can be removed from the machine.
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.The boom assembly consists of the first,
second and third section booms and supporting
hardware.
Note: Before removing the boom or boom section, the
carriage or any other attachment must be removed from
the quick coupler.
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.
During service of the boom, perform the following:
1. Check wear pads. (Refer to Section 3.17.1, “Wear
Pad Inspection.”)
2. Check hose sheaves and chain rollers.
3. Apply grease at all lubrication points (grease fittings).
(Refer to Section 2.7, “Lubrication Schedule.”)
4. Check for proper operation by operating all boom
functions through their full ranges of motion several
times.
Depending on your particular circumstance, the following
procedures explain the removal/installation of individual
boom sections or removal/installation of the complete
boom.
WARNING
NEVER weld or drill the boom unless approved in
writing by JLG. The structural integrity of the boom
will be impaired if subjected to any repair involving
welding or drilling.