Patent ID: 6685038
Filing Date: 2004-02-03
Classification: B66C

Abstract:
An extendible boom comprising:(A) a base; (B) first and second extendible boom sections which are supported on said base; (C) a hydraulic lift cylinder which has a lower end and which has arm upper end operatively coupled to said first section so as to raise said first section relative to said second section upon lift cylinder extension; and (D) a locking mechanism including (1) first and second locking devices which are mounted on respective first and second pivot shafts located on opposite sides of said boom and each of which is pivotable, relative to said boom a) from a disengaged position permitting lowering of said first section, b) to an engaged position in which said locking devices engage said first section to prevent said first section from being lowered, (2) a hydraulic release cylinder having opposite ends connected to said first and second pivot shafts and movable between a) an extended position when said locking devices are in said disengaged position and b) a retracted position when said locking devices are in said engaged position, and (3) a rigid equalizer bar which is connected to both of said first and second pivot shafts and which mechanically couples said pivot shafts to one another so that both of said pivot shafts always pivot through at least essentially the same stroke at least at essentially at the same time.