| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of step dropping or slip during the expansion of pole. SOLUTION: A plurality of hollow unit poles 1 having different diameters respectively are mutually fitted in a relatively movable manner, one of the unit pole 1 of the maximum diameter or the minimum diameter is fixed, and the other is extended or shrunk freely by driving with a drive device so as to turn the one end of an advancing or retreating chuck chain 2 inside the unit pole 1 into a tip and is installed to the inside of the unit pole 1b, a chain slide member 12 of the outer periphery of the chuck chain 2 is provided near the end portion of each unit pole 1 positioned at the fixed end side of the fixed unit pole 1a, and the chuck chain 2 inside the unit pole 1 is made retainable almost to a straight line shape by the chain slide member 12. In this way, the chuck chain 2 is precisely interlocked by combining the chuck chain 2 to the sprocket thereby preventing the occurrence of step dropping or slipping during the expansion of the pole. |
