Reverse circulation sub

Claim 1

APPARATUS FOR DRILLING WELLS AND THE LIKE, COMPRISING: A ROTARY BIT HAVING A HEAD WITH AN AXIAL OPENING THERETHROUGH, SAID HEAD HAVING DEPENDING ARMS, CUTTER ELEMENTS OPERABLY MOUNTED ON SAID ARMS, AND AN EXTERNALLY THREADED PIN EXTENDING UPWARDLY FROM THE UPPER END OF SAID HEAD AND HAVING AN UPWARDLY OPENING RECESS THEREIN; AN UPWARDLY EXTENDING TUBE SECURED IN THE OPENING IN THE BIT HEAD AND PROJECTING UPWARDLY OF THE UPPER END OF THE PIN, THE EXTERNAL DIAMETER OF SAID TUBE BEING SUBSTANTIALLY LESS THAN THAT OF THE RECESS IN THE PIN; AND A TUBULAR SUB ADAPTED TO BE CONNECTED TO THE LOWER END OF A PIPE STRING AND HAVING AN INTERNALLY THREADED BOX AT THE LOWER END IN WHICH SAID PIN IS THREADABLY RECEIVED, THE EXTERNAL DIAMETER OF SAID SUB BEING SUBSTANTIALLY UNIFORM THROUGHOUT ITS LENGTH, THE PASSAGE THROUGH THE SUB BEING OF SUBSTANTIALLY THE SAME DIAMETER AS THE DIAMETER OF THE RECESS OF SAID PIN, SAID SUB HAVING A PLURALITY OF ANNULARLY SPACED OPENINGS IN THE WALL THEREOF UPWARDLY OF THE BOX AND IN THE SAME PLANE RELATIVE TO EACH OTHER, SAID TUBE EXTENDING UPWARDLY INTO THE PASSAGE OF THE SUB AND SAID OPENINGS BEING INCLINED INWARDLY AND UPWARDLY WITH THE INNER ENDS THEREOF SPACED DOWNWARDLY OF THE UPPER END OF SAID TUBE, GASEOUS FLUID PASSING DOWNWARDLY IN THE WELL AT THE OUTER SIDES OF THE SUB FLOWING UPWARDLY THROUGH THE TUBE AND ALSO THROUGH THE OPENINGS IN THE SUB AND PASSING UPWARDLY ABOUT THE TUBE TO EFFECT REDUCED PRESSURE AT THE UPPER END OF SAID TUBE.