| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that a hydraulic cylinder is arranged in parallel with an axle, parts around the axle become complicated and a large arranging space is required around the axle as the axle is conventionally constituted to extend and contract by using the hydraulic cylinder. SOLUTION: A screw body 20 is constituted of a male screw body and a female screw body, either one of them is provided on the axle side, the other is provided on the movable flange body side, a stopper is formed on an end part of either one of them, the other end is constituted to make contact with the stopper at the time when it is contracted the smallest, the screw body 20 is constituted of two sets of first screw bodies 31 and second screw bodies 32, and an end part of the male screw body of the first screw body is connected to and fixed on an end part of the female screw body of the second screw body through a connecting member 24 in constitution free to change a tread by revolution of the screw body by arranging the movable flange body 30 on which a wheel 36 is fixed free to slide on the axle 22 and connecting the screw body 20 to the movable flange body.
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