Retrievable drill bit

Claim 1

IN APPARATUS ADAPTED FOR OPERATION IN A WELL BORE: A TUBULAR MEMBER ADAPTED TO FORM PART OF A STRING OF PIPE TO BE LOWERED IN THE WELL BORE AND HAVING A SUBSTANTIALLY SMALLER OUTSIDE DIAMETER THAN THE DIAMETER OF THE WELL BORE, SAID MEMBER HAVING FIRST STOP MEANS THEREIN: A COUPLING BODY ADAPTED TO MOVE THROUGH THE STRING OF PIPE INTO SAID TUBULAR MEMBER, SAID BODY HAVING SECOND STOP MEANS ENGAGING SAID OTHER STOP MEANS TO LIMIT DOWNWARD MOVEMENT OF SAID BODY IN SAID TUBULAR MEMBER; SAID TUBULAR MEMBER HAVING AN INNER CIRCUMFERENTIAL GROOVE INTERMEDIATE ITS LENGTH AND CIRCUMFEREITIALLY SPACED RECESSES LATERALLY OUTWARDLY OF AND OPENING RADIALLY INTO SAID GROOVE; COUPLING MEMBERS MOUNTED ON SAID BODY FOR LATERAL MOVEMENT WITH RESPECT THERETO AND DISPOSED IN THE HORIZONTAL PLANE OF SAID GROOVE AND RECESSES WHEN SAID SECOND STOP MEANS ENGAGES SAID FIRST STOP MEANS; A TUBULAR MANDREL SLIDABLY MOUNTED IN SAID BODY AND ENGAGEABLE WITH SAID COUPLING MEMBERS FOR EXPANDING SAID COUPLING MEMBERS INTO SAID GROOVE AND RECESSES, WHEREBY ROTATION OF SAID TUBULAR MEMBER IS TRANSMITTED THROUGH SAID COUPLING MEMBERS TO SAID BODY; OUTER CUTTER MEANS SECURED TO THE LOWER END OF SAID TUBULAR MEMBER TO CUT THE OUTER PORTION OF THE BOTTOM OF THE BORE HOLE; THE LOWER PORTION OF SAID BODY HAVING A CONNECTION FOR ATTACHMENT THERETO OF A DRILL BIT TO CUT THE INNER PORTION OF THE BOTTOM OF THE BORE HOLE; AND MEANS FOR RETRACTING SAID COUPLING MEMBERS FROM SAID RECESSES AND GROOVE TO ENABLE SAID BODY TO BE ELEVATED FROM SAID TUBULAR MEMBER AND THROUGH THE PIPE TO THE TOP OF THE WELL BORE TO LEAVE AN UNOBSTRUCTED PASSAGE THROUGH THE PIPE AND ITS TUBULAR MEMBER.