| 摘要 |
The invention relates to a drill rod coupling comprising a pivot element whi ch presents a cone-shaped outer threaded section between an outer shoulder and a pivot fac e, and an unthreaded section between the outer shoulder and the outer threaded section and betwee n the outer threaded section and the pivot face. The coupling further comprises a sleeve element which can be screwed onto the pivot element and presents a cone-shaped inner threaded section between an inner shoulder and a sleeve face and an unthreaded section between the inner shoulder and the inner threaded section and between the inner threaded section and the sleeve face. The length of the unthreaded sections of the pivot element and sleeve element, which are situated opposite each other when the two elements are screwed together, in the area of the inner shoulder is different from the length of the unthreaded sections of the pivot element and sleeve element in the area of the outer shoulder. The inner shoulder (3, 10) is the primary shoulder and, after the drill rod coupling has been assembled and screwed together to 90 % of its yield resistance, the pivot face (10) tightens against the inner shoulder (3, 10) with a pressure exceeding any pressure exerted by the sleeve face (4) on the outer shoulder (9). The sleeve face (4) tightens primarily against the outer shoulder (9) when an additional torque is exerted during drilling and the unthreaded sections (7, 13) situated in the area of the inner should er (3, 10) are at least twice as long as the unthreaded sections (6, 12) in the area of the outer shoulder (9).
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