| 摘要 |
A locking device has a lower concave housing suitable to receive and hold an upper end of an element to be attached to a drill stem. The housing forms a conical surface. A number of blocks slides along the conical surface. Each block has an outside sliding surface that is parallel to the conical surface and has an inside surface suitable to engage the elements to be held. The blocks are mounted to slide along the conical surface. The blocks are moveable from a first, free position in which the blocks are pushed toward the lower, outside surface of the conical surface to a second, locked position in which the blocks are radially clamped against the element to be hold.
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