| 摘要 |
A mine bolt has an anchor device 25 including an expansible shell 29 surrounding a cone member 27 in threaded engagement with a bolt rod 23. Axial movement of the shell 29, as the cone 27 moves into the shell 29, is blocked by a thrust member 28 having a limited resistance to thrust. On exceeding the thrust limit, the thrust member 28 strips out of its threaded engagement with the rod 23, and slides over the unthreaded portion of the rod 23 on continued rotation of the bolt rod 23. During this continued rotation, the cone 27 and shell 29 remain relatively fixed, with the rod 23 advancing axially in its threaded engagement to tighten the head 24 of the bolt against a surface plate 31. The method provides for setting an anchor bolt to a limit pressure controlled by this stripping action. <IMAGE> |
