| 摘要 |
<p>The connector which screws into the end of the drill string, has a spherical head clamped between two shell pieces, the lower one carrying a sleeve onto which a drive pinion is keyed. This construction protects the head from forces conveyed back from the drill string. A plug on the top can be removed for connection of a flushing head so that flushing mud can be passed through and down the hollow drill string.</p> |
