Blast hole drill pipe gripping mechanism

摘要

A mechanism for loosening the threaded joint between members of a blast hole drill string includes a wrench to hold one of the members while the other member is gripped between one arm and a jaw pivotally mounted on the arm. A hydraulic cylinder advances one end of the arm to engage the member and another cylinder pivots the jaw to engage the member. The one end of the arm is then further advanced while the other end of the arm is retracted by a cylinder to apply a moment. The wrench has a pair of wrench arms that are pivotally attached at their rear to a support. Pawls are mounted on the wrench arms to engage slots in a drill pipe. A hydraulic cylinder is mounted between the wrench arms to open and close the arms. One end of the cylinder is fixed to one wrench arm while the other end is connected to the second arm by a spring mechanism.