US Patent 7290623 Welded joints for rotary-vibratory drills having reduced stress

A drill string for a rotary-vibratory drill comprises a plurality of drill pipes. Each of the drill pipes has a longitudinal axis and at least one end. A female connector member and a male connector member are between the ends of adjacent said drill pipes, the female connector member having a first portion mating with a first of the adjacent drill pipes and a second portion extending away from the first of the drill pipes. The male connector member has a first portion mating with a second of the adjacent drill pipes and a second portion extending away from the second of the drill pipes, the second portion of the female connector threadedly engaging the second portion of the male connector. One of said each drill pipe and the connectors has a plurality of spaced-apart slots adjacent to the end of the drill pipe and communicating outwardly at the end. The slots are parallel to the longitudinal axis. Each of the connectors is connected to one of the adjacent drill pipes by welding extending about an adjacent said end of the one drill pipe and along the slots.