| 摘要 |
<p>A downhole device (10), such as a cement dart, having a body (12) comprising a male end portion (14), a female end portion (16) and a mandrel portion (18) disposed between the male end portion (14) and the female end portion (16). A recess (28, fig 3) is disposed in the outer surface (30) of the male end portion 14, which may be threaded, and is configured to receive a retainer (38) for securing the downhole device (10) to another downhole device (10a).</p> |
