The present invention relates to a four-stage boom device for a live-wire operations vehicle, and more particularly, to a four-stage
cantilever device for a live working vehicle, which minimizes the telescopic length of the boom device to improve the
utilization rate of a vehicle position space by independently leading out and leading in an insulating
cantilever. The insulating
cantilever is telescoped through the telescopic device which converts straight movement into rotary movement, so that the insulating range of the insulating cantilever is maximized, and the insulating performance is improved. The four-stage boom device for the live-wire operations vehicle comprises a first-stage boom, a second-stage boom, a third-stage boom, a linkage device, an insulating boom and an insulating boom telescopic device, and the insulating boom telescopic device comprises a second driving cylinder, a pair of rotating
pulley wheels and a pair of transmission mechanisms. When the
piston rod of the second driving cylinder moves straightly, the rotating
pulley wheels rotate, and meanwhile, the transmission mechanism leads the insulating cantilever out of or into the third-stage cantilever.