Ground borers

Claim 1

APPARATUS FOR BORING IN A STEP-BY-STEP MANNER A HOLE OF LARGE DIAMETER IN HARD GROUND COMPRISING A VERTICALLY-ARRANGED HOLLOW GUIDE MEMBER OPEN AT ITS LOWER END, CLAMPING MEANS CONNECTED TO SAID GUIDE MEMBER FOR RELEASABLY CLAMPING SAID GUIDE MEMBER TO THE WALLS OF SAID HOLE, A CARRIER MEMBER MOUNTED IN SAID GUIDE MEMBER FOR LONGITUDINAL DISPLACEMENT RELATIVE THERETO, A HOLLOW BORER HEAD COLINEARLY ARRANGED BELOW AND ROTATABLY CONNECTED TO THE LOWER END OF SAID CARRIER MEMBER, THE LOWER END OF SAID HOLLOW BORER HEAD TERMINATING IN A CONVERGING CONICAL PORTION HAVING A CENTRAL OPENING AT THE APEX THEREOF, A HAMMER TYPE DRILL MOUNTED WITHIN SAID BORER HEAD AND HAVING A BIT PORTION EXTENDING THROUGH SAID CENTRAL OPENING TO BORE A CENTRAL PILOT HOLE IN THE GROUND, A GUIDE COLLAR SURROUNDING SAID CENTRAL OPENING AND WHICH EXTENDS INTO SAID PILOT HOLE FOR GUIDING THE LOWER END OF SAID BORER HEAD DURING ROTATION THEREOF, A PLURALITY OF OTHER HAMMER-TYPE DRILLS MOUNTED WITHIN SAID BORER HEAD AND HAVING BIT PORTIONS EXTENDING OUTWARDLY THROUGH AXIALLY-SPACED OPENINGS IN THE CONICAL PORTION OF SAID BORER HEAD, MEANS INTERCONNECTING SAID GUIDE MEMBER AND SAID CARRIER MEMBER AND WHICH PROVIDE FOR LIMITED LONGITUDINAL MOVEMENT OF SAID CARRIER MEMBER RELATIVE TO SAID GUIDE MEMBER WHEN SAID GUIDE MEMBER IS CLAMPED TO THE WALLS OF SAID HOLE, MOTOR MEANS SECURED TO SAID CARRIER MEMBER FOR ROTATING SAID BORER HEAD RELATIVE TO SAID CARRIER MEMBER, AND MEANS FOR AXIALLY RECIPROCATING SAID DRILLS RELATIVE TO THE OPENINGS IN SAID BORER HEAD COMPRISING AN ELECTRIC MOTOR SECURED TO SAID CARRIER MEMBER AND HAVING A ROTARY OUTPUT SHAFT EXTENDING INTO SAID HOLLOW BORER HEAD, CAM MEANS IN SAID BORER HEAD CONNECTED TO SAID MOTOR SHAFT FOR ROTATION THEREBY, AND LINKAGE MEANS IN SAID BORER HEAD OPERABLE BY SAID CAM MEANS TO AXIALLY RECIPROCATE SAID DRILLS.