| 摘要 |
<p>A shank (10) connects to a drive mechanism and supports a flexible tapered spike (14), at the bottom end of which there fastens the bottom end of a bell-shaped operating head (20) made out of ribbed metal mesh. The operating head's top open edge is set with a gap from the spike so that, under radial load, the operating head can tilt at its bottom end and mold into itself.</p> |
