luffing crane

Description of luffing crane:
he Luffing crane boom is hinged to a frame on which is mounted a winch operating the boom through a pulley tackle. The fixed pulleys of the boom tackle are mounted on the crane frame and the movable pulleys thereof are linked to the boom head. The boom tackle has auxiliary pulleys mounted on symmetrically positioned brackets pivoted to the crane frame parallel to the boom luffing crane plane. The rope is reeved so that its parts connecting the movable and fixed pulleys run parallel to the boom luffing plane and the auxiliary pulleys are each connected to the movable pulleys by the same number of rope parts. Another winch mounted on the frame raises and lowers the load. The drums of both winches are kinematically interconnected so that they simultaneously rotate in opposite directions, whereby the boom is elevated while the load is lowered. Thus, the load is moved in a true horizontal path while the reach of the crane boom is varied.