Lull 1044C-54 Series II Service Manual - Manual (Page 259)

Boom and Transfer
31200079 6-117
Boom Extension Proximity Switch
Description
Fig. 6-119: Boom Extension Proximity Switch
(Ref. Fig. 6-119) The boom extension proximity switch is located on the left
side of the outer boom section on machines with a 4-section boom. The
boom extend/lockout circuit is designed to increase stability of the machine
by limiting how far the boom can be extended with the outriggers up. The
system will disable the boom extend and transfer extend functions and the
warning lamp will come on when the boom is extended to specified
distance (approximately 21 feet with tilting tower or 25 feet with standard
carriage). The proximity switch then opens as it no longer senses metal. At
this point, the left and right outriggers must both be lowered to the ground
to allow the boom or transfer carriage to be extended any further.
Normally-open differential pressure switches in the outrigger cylinders
close when the base end pressure exceeds the rod end pressure by
approximately 90–95 psi. When both pressure switches close, this
completes the circuit, allowing the boom and transfer carriage to be
extended, and the lamp turns off. The system is fail-safe in that it requires
an electrical signal to enable the boom to be extended beyond the
specified distance.
0
80
60
40
20
Proximity Switch
J
1146