| 摘要 |
<p>A power tong or back-up tong has a jaw assembly (6) that is advanced into engagement with a pipe (13) through a cam follower that contacts the camming (10) surface on the inside circumference of a ring gear (9), the cam follower being in the form of a series of roller elements (14) arranged as a circulating bearing. In a preferred form, the roller elements are cylindrical roller bearings and the jaw assembly is mounted for sliding advancement towards the pipe to be engaged. In an alternate variant the cam follower includes an indexing guide (30) that maintains the cylindrical roller bearings in proper alignment.</p> |
