Patent ID: 7694753

Claim:
A drill rod assembly, comprising: a) an outer drill rod having a first externally threaded end and a second internally threaded end, the outer drill rod including: i) a first inner diameter and a second inner diameter, the second inner diameter being greater than the first inner diameter; and ii) an internal shoulder located at a transition between the first and second inner diameters; b) an inner drill rod having first and second hexagonal ends, the inner drill rod being positioned within the outer drill rod such that an annular fluid flow path is defined between the inner and outer drill rods, the inner drill rod including an external shoulder sized to engage the internal shoulder of the outer drill rod to limit movement of the inner drill rod relative to the outer drill rod in a first longitudinal direction; c) a coupling attached to the second end of the inner drill rod, the coupling having an outer diameter at a first end that exceeds the first inner diameter of the outer drill rod to limit movement of the inner drill rod relative to the outer drill rod in a second opposite longitudinal direction; and d) wherein the coupling defines fluid flow passages that are in fluid communication with the annular fluid flow path when the coupling is seated against the outer drill rod.