BORING HEAD FOR A DUO-DRILLING APPARATUS

摘要

A boring head for duo-pipe drilling apparatus comprises a body having a passage for material return extending therethrough from the cutting end to the coupling end, the passage having an inlet at the cutting end displaced from the axis of rotation of the head and extending substantially across the full radius thereof, and an exit at the coupling end co-axial with the axis of rotation. The cutting end comprises one or more teeth having attacking edges overlying the inlet and beveled for mechanically displacing material into the inlet upon rotation of the head. Fluid supply galleries open into the passage for directing pressurized fluid from the duo-pipe system towards the exit of the passage for flushing cut material to the exit. The coupling end of the boring head is adapted for connection to the duo-pipe system with the annular passage of the duo-pipe system in communication with the fluid supply galleries and with the inner tube of the duo-pipe system in communication with the exit of the passage. An improved valving arrangement for avoiding the backflow of fluids or solids into the annular passage of the duo-pipe system is also disclosed.