DRILL STEM TUBULAR CONNECTION WITH INTERNAL STIFFENER RING
A threaded pipe coupling is shown for a drill pipe used in horizontal boring operations utilizing a special form of a threaded connection with an internal stiffener ring which eliminates the need for hot forging operations. The pipe coupling is used for joining an upset region of a first tubular member to a further tubular member of lesser external diameter. The internal stiffener ring is received within the internal bore of the pin end of the coupling and underlies and extends along a portion of its length. The stiffener ring having an innermost extent terminating in an exposed end which is received upon an internal shoulder provided in the mating internally threaded box end. The stiffener ring also has an external shoulder formed at the innermost extent thereof which traps the pin face between the ring exterior and the box threaded interior.