| 摘要 |
Apparatus for injecting and withdrawing a length of flexible cylindrical tubing into and from a well bore comprises first and second sets of gripper shoes that a re moved around first and second endless paths, respectively. The paths include first and second parallel sections disposed on opposite sides of a length of the tubing, the gripper shoes being pressed against the tubing with sufficient force to hold the tubing therebetween. Ea ch gripper shoe includes: a base portion and at least two gripper elements each having cylindrical gripping surfaces. Each cylindrical surface has a radius of curvature corresponding t o the outer surface of the tubing. At least one of the gripper elements is connected to the base member in a manner permitting movement of the element relative to the base portion between a closed position where the cylindrical gripping surface engages the tubing an d an open position that facilitates engagement and disengagement of the gripping shoe elements with the tubing.
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