Patent ID: 7452177

Claim:
A working mechanism for a construction machine having a first boom mounted on a vehicle body of a construction machine as to be rotatable to upper and lower sides; a second boom mounted on a distal end of said first boom as to be swingable to left and right sides; a third boom mounted on a distal end of said second boom to be swingable to the left and right sides; an arm mounted on said third boom to be rotatable to the upper and lower sides and having a working tool mounted on the distal end thereof; and an offset cylinder which is arranged between said first boom and said second boom to swing said second boom to the left and right sides at the distal end of said first boom, characterized in that said working mechanism for a construction machine comprises: a parallel support member formed by a pair of links, which are connected between said first boom and said third boom and which are respectively arranged at left and right positions, provided on on opposite sides of said second boom, and said third boom is supported by said parallel support member so as to be parallel to said first boom when said offset cylinder is extended or retracted; each of said links that constitute said parallel support member has a base end rotatably connected to said first boom by use of a first joint pin and a distal end rotatably connected to said third boom by use of a second joint pin; a first pin hole into which said first hole joint pin is inserted is formed in said base end of said link, and a second pin hole into which said second joint pin is inserted is formed in said distal end of said link, and wherein one of said first and second pin holes is formed as an oversized hole that said first or second joint pin is inserted into whereby said first or second pin is movable in the longitudinal direction of said link.