Extensible boom construction for self-propelled aerial work platforms

Claim 1

An axially extensible boom assembly, comprising: a tubular outer boom section, a tubular intermediate boom section, and a tubular inner boom section supported in a telescoping relationship and movable between a retracted position and an extended position and providing a forward end portion and a rearward end portion of the boom assembly; power means interconnected with the boom sections for moving the intermediate boom section within and relative to the outer boom section and for moving the inner boom section within and relative to the intermediate boom section; at least one elongate, flexible power conducting line extending through the boom assembly and accessible adjacent the forward and rearwards ends thereof; and an articulated, hollow track member extending axially within the boom section, which receives and guards said power conducting line from damage during relative movement of the boom sections, the forward end of the track member being fastened to the inner boom section and the rear portion of the track member being doubled-back in the forward direction with the rear end thereof fastened to the outer boom section, whereby when the assembly is moved to the retracted position the amount of said doubling-back is increased and when the assembly is moved to the extended position the amount of the doubling-back is decreased.