Dual-tube drill string for sample drilling

Claim 1

IN A ROTARY DRILLING RIG PROVIDED WITH A DUAL TUBE DRILL STRING ADAPTED TO BRING CORE SAMPLES TO THE SURFACE AS DRILLING PROGRESSES AND INCLUDING A CORE BIT, CONCENTRIC OUTER AND INNER STRINGS OF TUBING DEFINING AN ANNULAR PASSAGE LEADING FROM THE SURFACE TO SAID BIT, MEANS FOR INTRODUCING A PRESSURE FLUID INTO SAID PASSAGE NEAR THE UPPER END THEREOF, AND CORE RECOVERY MEANS AT THE UPPER END OF THE INNER STRING OF TUBING, THE IMPROVEMENT COMPRISING A PACKER SEAL RING CONCENTRICALLY SWIVELED ON AND OUTWARDLY OF THE OUTER DRIVE STRING OF TUBING ABOVE BUT NEAR THE BIT, FOR SEALING OFF THE UPPER PORTION OF THE EARTH BORE PASSAGE FROM THE LOWERMOST PORTION THEREOF DURING DRILLING, SAID OUTER STRING HAVING PASSAGES THERETHROUGH, BELOW BUT ADJACENT SAID PACKER SEAL RING AND ESTABLISHING COMMUNICATION BETWEEN SAID ANNULAR PASSAGE AND THE BORE HOLE, AND SAID BIT HAVING PASSAGES THERETHROUGH ALSO ESTABLISHING COMMUNICATION BETWEEN SAID ANNULAR PASSAGE AND THE BORE HOLE, THE SAID PASSAGES IN BOTH INSTANCES BEING SO INCLINED AS TO ESTABLISH LOCALIZED CIRCULATION OF SAID PRESSURE FLUID THROUGH SAID LOWERMOST PORTION OF THE EARTH BORE PASSAGE.