| 摘要 |
The track assembly includes top plate 204, which incorporates the tracks 206. In FIG. 18, dashed lines have been added to show the portion of the top plate 204 that is used as the track 206 for the rollers 214. The interaction of the rollers 214 and track 216 is similar to the interaction of rollercoaster wheels and their associated track. In operation, small vertical rollers 214c ride against the side edge of top plate 204 (as can be seen in FIGS. 17a and 30a), small horizontal rollers 214b ride against the underside of top plate 204 (as can be seen in FIG. 30a), and the large horizontal roller 214a rides on the top of top plate 204 (as can be seen in FIG. 30a). This allows the moving tower 202 to travel from one end of the track assembly 200 to the other. As is described above, this rolling movement takes place when the platform 13 is folded and pulls the first vertical arm 42, and, therefore, the moving tower 202 inwardly.
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