| 摘要 |
<p>A thread structure for use in coupling percussion drilling extension rods minimizes the torque necessary to disconnect such extension rods. This is accomplished by beveling the crest portions of the cooperating thread structures. The direction of the bevel is such that the greatest intrusion of the crest portions into the complementary portions of the cooperating thread structure occurs immediately adjacent the abutting flanks thereof. The abutting flanks then wear in such a way that wedging is substantially avoided. Additionally, the root portions are defined by a continuously curved surface that smoothly extends into a flat surface defining the thread flanks so that fatigue stresses are minimized.</p> |
