| 摘要 |
A side stowable swing-around boom extension is pinned on the nose of a telescoping crane boom in a first use position nearly coaxial with the center line of the boom but tilted or offset therefrom at a small angle. Two larger angularly offset use positions of the boom extension are obtained with convenience and with complete safety while the crane boom and boom extension are at a near ground level position. Two slotted tension links are connected between the upper side of the boom extension and the boom nose and are allowed to support the boom extension in either of two major offset use positions automatically as the crane boom is elevated from the near ground level position. In such operation, the boom extension is allowed to rotate around the axis of its lower side pivotal connection with the boom nose while its upper side connection with the nose is released. The lower side connection is biased toward a position corresponding to the nearly coaxial use position of the boom extension. |
