Patent ID: 8151906

Claim:
A backreaming apparatus comprising: a plurality of intermediate drill rods configured to connect together to form a string of intermediate drill rod units, each intermediate drill rod unit including a drive shaft rotatably mounted within a casing assembly, the casing assemblies of the intermediate drill rod units being connected together by connections that allow a pull-back load to be transferred through the casing assemblies of the intermediate drill rod units, and the drive shafts of the intermediate drill rod units being connected by connections that allow torque to be transferred through the string of intermediate drill rod units; a backreamer having a rearwardly facing cutting face positioned adjacent to and facing a first end of the string of intermediate drill rod units; and an external drive positioned at a second end of the string of drill rod units for applying a pull-back load to the string of intermediate drill rod units and for applying torque to the string of intermediate drill rod units, the torque being transferred to the backreamer by the drive shafts of the intermediate drill rod units and the pull-back load being transferred to the backreamer by the casing assemblies of the intermediate drill rod units, wherein the intermediate drill rod units define a vacuum channel for removing slurry from a hole being backreamed, the vacuum channel having an inlet adjacent the backreamer and an outlet connected to a source of vacuum.