Drill steel centralizers

Claim 1

IN PRESSURE FLUID OPERATED DRILL STEEL CENTRALIZER APPARATUS OF THE CHARACTER DESCRIBED FOR MOUNTING ON THE FEED SHELL OF A ROCK DRILL AND HAVING A SUPPORT THEREFOR AND A SOURCE OF PRESSURE FLUID, THE COMBINATION WHICH COMPRISES A PAIR OF OPPOSED, AXIALLY ALIGNED GRIPPING JAWS MOVABLY DISPOSED ON SAID SUPPORT FOR MOVEMENT FROM A GRIPPING POSITION ADJACENT EACH OTHER TO A SEPARATED POSITION AWAY FROM EACH OTHER, GUIDE SURFACES DISPOSED ON THE OPPOSED PORTIONS OF SAID JAWS FORMING IN THE SAID GRIPPING POSITION THEREOF A GUIDE OPENING FOR DRILL RODS PASSING THERETHROUGH HAVING A DIAMETER LARGER THAN SAID DRILL RODS, GRIPPING SURFACES DISPOSED ON THE OPPOSED PORTIONS OF THE JAWS ADJACENT SAID GUIDE SURFACES AND FORMING IN THE GRIPPING POSITION OF SAID JAWS A GRIPPER OPENING LARGER THAN SAID GUIDE OPENING FOR POSITIVELY GRASPING A DRILL ROD COUPLING SLEEVE THEREIN, A SEPARATE PRESSURE FLUID OPERATED POWER CYLINDER AND PISTON CONNECTED TO EACH OF SAID JAWS AND DISPOSED ON SAID SUPPORT AND IN FLOW COMMUNICATION WITH SAID SOURCE FOR MOVING SAID JAWS TO SAID GRIPPING POSITION AND HOLDING THEM IN THAT POSITION AND FOR MOVING SAID JAWS FROM SAID GRIPPING POSITION TO SAID SEPARATED POSITION, AND CONTROL MEANS DISPOSED BETWEEN SAID SOURCE AND SAID POWER CYLINDERS FOR SELECTING THE POSITION OF SAID JAWS AND FOR HOLDING THE SAID JAWS IN THE SAID SELECTED POSITIONS.