Down-the-hole motor for rotary drill rod and process for drilling using

Abstract

The motor is adapted to be used to drive a rotary drill rod of the type comprising an elongated pipe having a longitudinally extending bore therethrough, a percussive bit at the distal end thereof, and an abutment thereon relatively transverse the bore adjacent the bit. The motor comprises a cylindrically outlined piston member which is adapted to be slidably engaged in the bore of the pipe and has a fluid operated hammer mechanism thereon for applying hammer blows to the rod through the abutment. It also comprises an anvil member which is coaxially interconnected with the piston member at a position relatively forwardly of the hammer mechanism and has a diameter no greater than that of the piston member so that it can be inserted in the bore ahead of the piston member and engaged with the abutment to receive and transmit the hammer blows into the abutment. In addition, the motor comprises fluid transmission means for operating the hammer mechanism, means on the relatively rear end portion of the piston member for admitting fluid to the same from the bore of the pipe when the motor is engaged in the bore, and means for discharging the fluid from the motor including means for passing fluid through the anvil member from the piston member. The motor also includes means on the piston member for causing a pressure drop in the fluid as it discharges from the motor, whereby a pressure differential can be generated across the motor axially of the members when the motor is engaged with the abutment and transmitting hammer blows thereto.