| 摘要 |
A shaft part 51 is axially supported rotatably on the case body 21. A part of a traveling wheel part 52 is positioned around the shaft part 51. A coil spring 53 energizing the traveling wheel part 52 with respect to the shaft part 51 is interposed between the shaft part 51 and the traveling wheel part 52. When the traveling wheel part 52 collides with an obstacle, the traveling wheel part 52 moves with respect to the shaft part 51 and the case body 21 while energizing the traveling wheel part 52 by the coil spring 53 and absorbs an impact. Without lowering the traveling performance by, for example, making the traveling wheel part 52 softer and increasing the thickness thereof, the cushioning characteristics can be improved. |
