Earth boring apparatus

Claim 1

APPARATUS FOR USE IN EARTH BORING INCLUDING IN COMBINATION WITH A TUBULAR STEEL MANDREL HAVING AN UPPER END AND A LOWER END AND HAVING A SLEEVE COAXIALLY MOUNTED THEREON AND STOP MEANS AT THE LOWER END OF THE MANDREL TO PREVENT DOWNWARD MOVEMENT OF THE SLEEVE RELATIVE TO THE MANDREL BEYOND SAID STOP MEANS, THE INNER SURFACE OF THE SLEEVE HAVING AN ELASTOMERIC PORTION, THE OUTER SURFACE OF THE MANDREL AND SAID ELASTOMERIC PORTION OF THE INNER SURFACE OF THE SLEEVE PROVIDING COOPERATING STEEL AND ELASTOMER BEARING MEANS CONSTRAINING THE RELATIVE MOTION OF THE MANDREL AND SLEEVE SUBSTANTIALLY TO SLIDING OF THE ELASTOMERIC PORTION OF THE INNER SURFACE OF THE SLEEVE UPON THE STEEL OUTER SURFACE OF THE MANDREL, THE IMPROVEMENT COMPRISING ELASTOMERIC DETRITUS EXCLUSION MEANS ON THE INNER SURFACE OF THE SLEEVE ADJACENT THE UPPER END OF THE ELASTOMERIC PORTION THEREOF COOPERATING WITH SAID MANDREL TO EXCLUDE DETRITUS OF LARGER SIZE THAN WILL PASS BETWEEN SAID COOPERATING BEARING MEANS, SAID DETRITUS EXCLUSION MEANS AND MANDREL MAKING A CLOSER FIT THAN SAID COOPERATING BEARING MEANS EXTENDING THEREBELOW FROM SAID UPPER END THROUGH THE MID PORTION OF SAID ELASTOMERIC PORTION TO THE LOWER END THEREOF, WHEREBY DETRITUS THAT CAN ENTER BETWEEN THE SLEEVE AND MANDREL AT THE UPPER END OF THE SLEEVE PAST SAID ELASTOMERIC EXCLUSION MEANS WILL BE OF A SIZE THAT CAN FALL THROUGH THE CLEARANCE SPACE BETWEEN SAID COOPERATING STEEL AND ELASTOMER BEARING MEANS AT THE OUTER SURFACE OF THE MANDREL AND INNER SURFACE OF THE SLEEVE WITHOUT SPOILING THE SLIDING FIT THEREBETWEEN.