| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an efficient simultaneous extension boom of four steps or more which generates no dead space at the base end of the boom in the most contracting time. SOLUTION: The first pulley 21 for contraction is provided to the tip of the first hydraulic cylinder which is installed to the first step boom 2, while the second pulley 22 for contraction and the third pulley 23 are provided at the base end of the second step boom 3. A tip pulley 24 is provided at the tip of the fourth step boom 5, one end of a contraction wire rope 25 is locked to the fourth lock member 26 at the tip of the third boom 4, it is hung around the first to the third contraction pulleys 21, 22, and 23, through the tip pulley 24, and the other end is locked to the fifth lock member 27 at the tip of the first hydraulic cylinder 6. The rope tension applied to the contraction wire rope 25 is made as F/4 to the force F of the second hydraulic cylinder 7, the diameters of the second and the third contraction pulleys 22 and 23 are made smaller, and the dead space is eliminated.</p> |
