Percussion-rotary drill

Claim 1

A RAPID, PORTABLE, LIGHT-WEIGHT, LOW-THRUST LOW-POWER, HOLLOW ROTATING DRILL HEAD, ADAPTED FOR DRILLING A SUBSTANTIALLY HORIZONTAL HOLE THROUGH GROUND-AND-ROCK STRATA OR SIMILAR MATERIAL, UNDER A ROADWAY OR THE LIKE; SAID DRILL HEAD COMPRISING: AN ELONGATED HOLLOW BODY-SECTION PORTION HAVING A PERIPHERAL HELIX; A HOLLOW END HEAD PORTION HAVING ITS REAR END RIGIDLY CARRIED BY THE FRONT END OF SAID HOLLOW BODY SECTION PORTION; A NARROW FORWARDLY EXTENDING CUTTING BIT, RIGIDLY CARRIED BY THE FRONT END OF SAID END HEAD PORTION, SAID CUTTING BIT HAVING A FORWARD CUTTING EDGE IN SUCH POSITION AS TO PLANE OR PARE OFF SHAVINGS OR CUTTINGS, WHICH RESULT IN A NARROW PERIPHERAL CIRCULAR CUT OUT OF THE MATERIAL THROUGH WHICH A HOLE IS BEING DRILLED, LEAVING UNCUT SOLID MATERIAL INSIDE OF SAID NARROW CIRCULAR CUT; A RECIPROCATING PERCUSSION BIT HEAD, HAVING A REAR STEM HAVING A SLIDABLE MOUNTING WITHIN THE HOLLOWS OF THE END HEAD AND BODY SECTION PORTIONS, SAID SLIDABLE MOUNTING PROVIDING FREEDOM FOR LONGITUDINAL MOVEMENT, BUT SUBSTANTIALLY NO ROTATIONAL MOVEMENT, OF SAID PRECUSSION BIT HEAD WITH RESPECT TO SAID DRILL HEAD, THE FRONT END OF SAID PRECUSSION BIT HEAD HAVING FORWARDLY FACING PRECUSSION BIT MEANS, DISPOSED IN SUCH MANNER AS TO CHOP CLOSE TO THE PERIPHERY OF SAID UNCUT SOLID MATERIAL, BUT WITHOUT INTEREFERENCE WITH SAID DRAG BIT MEANS; THE REARWARD LIMIT OF SAID LONGITUDINAL MOVEMENT BEING SUCH THAT THE FRONT OF THE PERCUSSION BIT HEAD IS THEN BACK OF THE FRONT OF THE CUTTING BIT; AND A RECIPROCATING HAMMER MEMBER AND A SEPARATELY CONTROLLABLE POWER MEANS FOR SAID HAMMER MEMBER, BOTH MOUNTED WITHIN A REAR PART OF THE HOLLOW BODY SECTION PORTION, FOR CAUSING THE RECIPROCATION OF SAID HAMMER MEMBER TO DELIVER A PLURALITY OF BLOWS TO THE REAR END OF THE REAR STEM OF THE RECIPROCATING PRECUSSION BIT HEAD DURING EACH ROTATION OF THE DRILL HEAD.