| 摘要 |
A crane boom comprises plural extensible and retractable telescoping sections each of which is trapezoidal in cross section. The trapezoidal cross sectional shape imparts to a boom of given weight greater lifting capacity or longitudinal rigidity and greater lateral stability than any other cross sectional shape. The trapezoidal cross section allows for a much more efficient placement of wear pads between boom sections and web stiffeners on the sides and bottoms of the sections. Adequate internal space is provided for boom extending and retracting means whether hydraulic or mechanical. |
