Patent ID: 7458308

Claim:
Multistaged telescope boom, in particular for a loading crane on a truck, where a hydraulic unit, comprising a piston ( 16 ) and a cylinder ( 9 - 12 ), is arranged between successive, telescopic arms ( 2 - 7 ), said boom comprising a hydraulic system connecting to said hydraulic units for the operation thereof and arranged to force the hydraulic units of at least the two innermost arms for filling a cylinder chamber ( 27 ) of one of these cylinders at a time, starting from the innermost arm and moving outwardly in the order of the arms when extending the booms, and draining said cylinder chambers in the opposite order when retracting the boom, wherein at least the hydraulic unit of said innermost arm is provided with an arrangement structured and arranged to isolate and block the cylinder chamber ( 27 ) of that first cylinder from communication with said hydraulic system when that cylinder is fully extended, and re-establish said communication upon full retraction of the cylinder next to said first cylinder.