JLG 1250AJP Service Manual - Manual (Page 242)

SECTION 4 - BOOM & PLATFORM
4-2 – JLG Lift – 3121171
4.5 JIB STOW SYSTEM
This machine is equipped with a full function side swing
rotator that is mechanically limited to 55 degree rotation to
the left and electrically limited to 70 degrees to the right
through the use of a positive action limit switch mounted
on the rotator assembly. The machines stowed length can
be reduced to facilitate transportation on standard trailers
by swinging the jib further to the right using the hydraulic
power of the side swing rotator. The control system will
prevent swinging the jib past the 70 degree position
unless the axles are retracted, the boom is in the transport
position (see Section 4.2, Transport Position Sensing Sys-
tem), and the jib stow override button on the platform con-
trol panel is held in combination with the jib swing function
switch. When the jib is stowed, automatic platform leveling
is disabled, the boom is restricted to the transport posi-
tion, and axle extension is disabled. This system is func-
tional only in the 500# (230 kg) mode of the Dual
Capacity System (see Section 4.13, Dual Capacity Sys-
tem).
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
4.6 ENVELOPE CONTROL SYSTEM
The Envelope Control System is the primary means of
controlling the working positions of the tower and main
boom within the stability and structural requirements of
the machine. Although the machine includes a load pin
capable of measuring the changing forces on the boom, it
is used exclusively for boom retrieval as described in the
electrical retrieval system (see Section 4.9, Electrical
Retrieval System) and is not used for controlling the stabil-
ity of the machine until a fault is detected within the pri-
mary envelope control system. The control system is
therefore not considering the load on the machine but
rather the measured position of the boom within the enve-
lope.
The main boom must be controlled in maximum angle
and minimum angle to avoid entering a position that could
compromise backward stability and avoid main boom to
tower boom interference. The tower boom must be con-
trolled by permitting only specific combinations of tower
length and tower angle to avoid entering a position that
could compromise forward and backward stability (see
Section 4.7, Tower Path Control System).
This system uses two gravitationally based angle sensors
and two length sensors to continuously measure the posi-
tion of the tower boom in addition to two rotary angle sen-
sors to continuously measure the position of the main
boom. Each pair of sensors are continuously monitored
for mutual agreement, proper response to command, and
for correlation to a main boom angle limit switch, a tower
boom length limit switch, and a tower rotary angle sensor.
Recognized faults within this system will result in control
by the Electrical Retrieval System (Section 4.9, Electrical
Retrieval System), reduced function speeds, and BCS
warning light illumination. After retrieval the boom will be
restricted from leaving the transport position (see Section
4.2, Transport Position Sensing System) until the fault is
resolved.
Boom position violations outside of the allowable enve-
lope will result in reduced function speeds, BCS warning
light illumination, restriction of functions, and sounding of
the platform alarm and the flashing of the BCS light with
attempts to operate restricted functions.
Normally, the tower lift function switch on the ground and
platform control panels automatically activates both tower
lift and tower telescope as described in the tower path
control system (see Section 4.7, Tower Path Control Sys-
tem). Violations of the tower envelope will result in the sus-
pension of this automatic feature. In an otherwise healthy
control system, violations of the tower envelope can be
corrected by actuating either of the tower lift up or tower
lift down directions of the tower lift switch regardless of the
direction of the violation. The control system will telescope
or lift the tower in a singular manner to correct the tower
position.
The restricted functions due to backward tower envelope
violations are disallowing automatic tower lift down with
tower lift down commands, automatic tower telescope out
with tower lift up commands, main lift up and down, main
telescope in, jib, swing, drive and steer.
The restricted functions due to forward tower envelope
violations are disallowing automatic tower lift up with
tower lift up commands, automatic tower telescope in with
tower lift down commands, main lift up and down, main
telescope out, jib, swing, drive and steer.
The restricted functions due to maximum main boom
envelope violations are disallowing tower lift up and down,
main lift up, main telescope in, jib, swing and drive.
The restricted functions due to minimum main boom
envelope violations are disallowing main lift down, swing
and drive.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.