| 摘要 |
An internal wrench for an earth drilling machine of the type having a mast, a top head drive assembly mounted for movement along the mast and a quill rotated by the top head drive assembly includes a body having an upper end and a lower end sized to fit within a length of casing. The upper end of the body is mounted to the quill for rotation with the quill and several jaws are mounted to the lower end of the body to move between an extended position in which the jaws engage in interior surface of the casing to rotate the casing with the body, and a retracted position in which the jaws are out of engagement with the interior surface. The jaws are selectively moved between the extended and retracted positions in response to rotation of the body by a system which includes a drag ring which operates the jaws and a friction brake which engages the drag ring. A plug is mounted to an intermediate portion of the body to mate with threads at the upper end of the casing to seal off the casing. Followers on selected jaws automatically retract the jaws when the body is lowered into the casing to mate the plug with the threads at the upper end of the casing. |
