Apparatus for gripping a down hole tubular for rotation

An apparatus for engaging a down hole tubular for rotation in a drilling machine of the type comprising a rotatable quill having a threaded lower end, means for rotating the quill, means for vertically positioning the quill, and means for vertically moving an additional element beneath the rotating means with respect to the quill, said apparatus comprising:

• a support member defining an axis and having a threaded upper end configured to threadedly engage the threaded lower end of the quill;
• a plurality of guides mounted to the support member around the axis and oriented at an angle with respect to the axis;
• a plurality of engaging members, each mounted to move in a respective one of the guides to move into engagement with a down hole tubular when positioned toward a first end of the respective guide and to move out of engagement with a down hole tubular when positioned toward a second end of the respective guide, said engaging members adapted to transmit torque from the guides to the engaged down hole tubular;
• a linkage coupled to the engaging members and comprising an actuating member exposed at an upper portion of the support member and movable along the axis between a closed position, in which the linkage urges the engaging members toward the first ends of the guides, and an open position, in which the linkage urges the engaging members toward the second ends of the guides;
• said actuating member shaped and positioned to bear against the additional element such that vertical movement of the additional element with respect to the quill moves the actuating member along the axis and therfore the engaging elements along the guides;
• wherein the guides and engaging members are dimensioned to engage a down hole tubular substantially larger in diameter than the threaded upper end of the support element.

An apparatus for engaging a down hole tubular for rotation in a drilling machine of the type comprising a rotatable quill having a threaded lower end, means for rotating the quill, means for vertically positioning the quill, and means for vertically moving an additional element beneath the rotating means with respect to the quill, said apparatus comprising:

• a support member defining an axis and having a threaded upper end configured to threadedly engage the threaded lower end of the quill;
• a plurality of guides mounted to the support member around the axis and oriented at an angle with respect to the axis;
• a plurality of engaging members, each mounted to move in a respective one of the guides to move into engagement with a down hole tubular when positioned toward a first end of the respective guide and to move out of engagement with a down hole tubular when positioned toward a second end of the respective guide, said engaging members adapted to transmit torque from the guides to the engaged down hole tubular;
• a linkage coupled to the engaging members and comprising an actuating member exposed at an upper portion of the support member and movable along the axis between a closed position, in which the linkage urges the engaging members toward the first ends of the guides, and an open position, in which the linkage urges the engaging members toward the second ends of the guides;
• said actuating member shaped and positioned to bear against the additional element such that vertical movement of the additional element with respect to the quill moves the actuating member along the axis and therefore the engaging elements along the guides;
• wherein the guides and engaging members are entirely positioned at a spacing from the axis greater than that of the threaded upper end of the support member.