| 摘要 |
<p>A length measuring tool, concretely to a high protective machinery ruler with meter that has invisible rack (203) and can prevents outside matter dropping into inter-tooth space. The engaging piece of a gear (304) and a rack (203) is provided in mobile protective space to keep it in protection state all the ways. And wherever the protective space moves, the rack (203) out of the protective space is always covered by one sheet band (204), which keeps in stretching state.</p> |
