Center tube retention

Abstract

A center tube retention system of a down-the-hole tool includes a casing having an inner wall, a feed tube centrally disposed within the casing, the feed tube having an upper end and a tapered outer surface at the upper end, and a tube holder arranged to receive the top end of the feed tube, the tube holder having a tapered inner surface, the tapered surface of the feed tube matching the taper of the tube holder to form a tapered seat. The tube holder is formed as a collet having a plurality of machined slits aligned radially to a central axis of the casing. The slits are arranged to allow the tube holder to expand outward and press against the inner wall of casing ensuring alignment and retention of the feed tube within the casing.

What is claimed is: 
     
         1 . A center tube retention system of a down-the-hole tool, the system comprising:
 a casing having an inner wall;   a feed tube centrally disposed within the casing, the feed tube having an upper end and a tapered outer surface at the upper end;   a tube holder arranged to receive the top end of the feed tube, the tube holder having a tapered inner surface, the tapered surface of the feed tube matching the taper of the tube holder to form a tapered seat.   
     
     
         2 . The center tube retention system of  claim 1 , wherein a top sub is disposed within an upper end of the casing. 
     
     
         3 . The center tube retention system of  claim 2 , wherein a make-up ring is positioned between and end of the top sub and a guide member. 
     
     
         4 . The center tube retention system of  claim 3 , wherein the upper end of the feed tube communicates with the guide member, wherein pressure from the top sub forces the make-up ring, which in turn forces the guide member to push the feed tube into the tube holder at the tapered seat. 
     
     
         5 . The center tube retention system of  claim 1 , wherein the tube holder is formed as a collet having a plurality of machined slits aligned radially to a central axis of the casing, the slits being arranged to allow the tube holder to expand outward and press against the inner wall of casing ensuring alignment and retention of the feed tube within the casing. 
     
     
         6 . The center tube retention system of  claim 4 , wherein the guide member is a check valve guide. 
     
     
         7 . The center tube retention system of  claim 4 , wherein the guide member is a choke tube guide. 
     
     
         8 . A method of retaining a center tube in a down-the-hole tool, the method comprising the steps of:
 providing a center tube retention system of  claim 1 ;   moving the top sub to compress the makeup ring, which in turn forces the guide member to push the feed tube into the tapered seat formed in the tube holder to expand the tube holder into the casing wall.