| 摘要 |
<p>In coal mining, tunnel engineering or potash mining use is made of a spreading anchor as known in previous practice. The spreader nut is provided with grooves, and the spreader wedges with tongues. The new system gives better guidance for the wedges when the nut is tightened with the aid of the anchor rod, and prevents any lateral wandering off course. The grooves and tongues may not run right through, thus preventing the nut from being drawn through.</p> |
