LIFTING EQUIPMENT HAVING TELESCOPIC BOOM WITH AUTOMATIC EXTENSION LIMITING

摘要

Mobile lifting equipment having a wheeled vehicle with a frame. The boom structure is mounted on the frame for rotation about a vertical axis, raising and lowering the same about a horizontal axis and for extension and retraction with respect to the vehicle. The boom structure includes an outer boom and an inner boom which is mounted for telescoping movement in the outer boom. First and second extension cylinders are carried by the outer boom for extending and retracting inner boom with respect to the outer boom. An elevation cylinder is connected to the outer boom and is provided for raising and lowering of the boom structure. An elevation control is provided for supplying hydraulic fluid to the elevation cylinder. Piping is provided for connecting the elevation cylinder to one of the first and second extension cylinders so that extension of said one of said first and second extension cylinders is limited by the amount of hydraulic fluid which has been supplied from the elevation cylinder.