TB20J Plus Maintenance Manual 49
© Feb. 2023
6 BOOM AND PLATFORM ASSEMBLY
6.1 BOOM AND PLATFORM
SYSTEM
Broken Wire Rope Detection System
This machine is equipped with 3-section proportionally-
driven telescopic boom tube. The first telescopic boom
is directly driven by a telescopic cylinder. The second
telescopic boom is driven by a separate wire rope sys-
tem which is equipped with a spare wire rope, allowing
the operator to continue using the machine in the event
of one wire rope broken. The retracting wire rope is
mounted on the outside of the boom for easy detection
of failure. While the extending wire rope depends on the
broken rope detection system to warn the operator of
wire rope failure in time. The system uses proximity sen-
sors to detect unwanted movement of the wire rope to
determine whether the wire rope is faulty. When the
proximity sensor detects unwanted movement of the
wire rope, the broken rope detection result will be dis-
played on the display of the ground controller, and an
alarm will be triggered. Then the boom will be restricted
from extending and raising, but be allowed to retract
and lowering. The operator should take necessary
measures to correct the fault.
Platform Control Enable System
The platform control system uses time-dependent sup-
port circuits to limit the time availability of active or en-
abled controllers. The foot switch must be depressed
before any movement can be performed. When the foot
switch is depressed, the controller will be activated and
the operator can perform any movements within 7s. The
controller will remain enabled as long as the operator
keeps operating any functions until 7s after the last func-
tion stops. When the controller is active, the indicator on
the platform display panel will light up. After the set time,
the illuminated indicator will turn off and the controller
will turn off or be disabled. To continue to operate the
machine, the controller must be re-enabled to start the
timing system again. To activate the timing system
again, follow these steps: release all control buttons,
handles, and foot switch, and then depress the foot
switch again.
Transport Position Sensing System
The transport position sensing system detects the posi-
tion of the boom tube by means of the angle sensor and
length sensor on the boom head (near the turntable).
When the angle sensor detects that the boom tube is
raised more than 15° above the horizontal, or the length
sensor detects that the boom tube extends more than
1.2m (3.9ft), the machine is considered as in operating
position, otherwise, it is considered as in non-operating
position. The position of the jib boom is not taken into
account.
This system is used to control the drive speed reduction
system.
Load Sensing System
The load sensing system on this machine detects the
load on the platform through the load cell installed at the
connection between the platform and the boom tube.
The overload indicator on the platform display panel in-
dicates if the platform load has exceeded the rated load.
When the load sensing system detects that the platform
load exceeds the rated load, the overload indicator will
flash, and all movements of the machine will be re-
stricted in the KG (overload limit) mode; while in other
modes, the telescopic boom will be allowed to retract,
the turntable can rotate slowly, and the boom can be
lowered after the telescopic boom is fully retracted. After
the excess load is removed, the overload indicator will
go out and all machine movements will be resumed.
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