Extensible boom structure

Claim 1

In a crane or the like: a ground traversing vehicle defining a support structure; an extensible boom including a proximal section, a distal section, and at least one intermediate section, said sections being positioned in telescoping relationship with respect to one another; means mounting one end of said proximal section on said support structure for pivotal movement about a horizontal axis between a horizontal position and positions inclined with respect thereto; first independent means for moving said intermediate section outwardly relative to said proximal section, said first independent means including at least one cable connected to said intermediate section adjacent the inner end thereof, a winch adjacent the outer end of said proximal section and receiving said cable therearound, and pulley means guiding said cable from said winch to said intermediate section; locking means for retaining said intermediate section at selected positions relative to said proximal section; second independent means for moving said distal section outwardly relative to said intermediate section, and second independent means including a cable connected adjacent the inner end of said distal section, a winch adjacent the outer end of said intermediate section and receiving said last-named cable therearound, and pulley means for guiding said last-named cable from said last-named winch to said distal section; locking means for retaining said distal section at selected positions relative to said intermediate section; and means for retracting said distal section relative to said intermediate section to place the outer end of said distal section adjacent the outer end of said intermediate section and for retracting said intermediate and distal sections relative to said proximal section to place the inner end of said intermediate section and the inner end of said distal section a substantial distance past the pivotal connection of said proximal section to said support structure, said boom in the retracted position extending outwardly a substantial distance on opposite sides of said pivotal connection, whereby a compact road-ready structure is produced wherein the center of gravity of said boom is substantially aligned with the center of gravity of said vehicle.