| 摘要 |
A platform 400 for, a drill is supported on four support members 420, 422, 424, 426 which are pivotally fixed to the platform (fig 3, 400) to alter the angle between opposite members. In one embodiment a stop 440 limits the movement of the support members so that the maximum angle between them can be controlled to suit the diameter of a pipe on which the apparatus is mounted. In another embodiment, the support members are attached by connecting rods 620 to a cross member 630 which is raised and lowered on a threaded rod 642 to pivot the members. |
