| 摘要 |
PROBLEM TO BE SOLVED: To freely expand/contract the right and left outer width of a traveling element comprising a pair of right and left traveling frames and a coupling frame for coupling the traveling frames, and to decrease and increase a distance between a lower surface of the coupling frame and the ground in proportion to the outer width. SOLUTION: A coupling frame 14 is laid between a pair of right and left traveling frames 12a, 12b through a coupling surface S. The traveling frames 12a, 12b and the coupling frame 14 are relatively moved and mounted on the coupling surface S, and the coupling surface S is tiltedθto an outward lower side in a width direction. COPYRIGHT: (C)2003,JPO
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