Patent Publication Number: US-8978790-B2

Title: Retention of cutters in bore hole tools

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional patent application Ser. No. 61/398,370 filed Jun. 24, 2010 by Alan L. Nackerud, which is incorporated by reference herein. 
    
    
     BACKGROUND AND FIELD OF INVENTION 
     Most conventional down hole tools used in the drilling and completion of bore holes in the earth such as drill bits, underreamers, section mills and casing cutters have cutters, cutting discs, inserts or cutting structures of hardened materials placed in the body of the tools to enhance cutting ability and lengthen drilling or cutting wear time. However, many cutting inserts such as PDC (polycrystalline diamond compact) cutters become loose, damaged or lost due to the fact that typical braze material used to retain the cutters does not bond well with the diamond or other hardened cutting materials and is only placed in the void between the cutter pocket diameter and the outside diameter of the cutters. Thus, the tool becomes ineffective and the tool life is shortened. The present invention is an improvement to said tools where grooves or recesses are cut into each cutter pocket just above or partially above the top level of the cutter. When the cutter is placed in position, braze material is then heated and applied in a liquid state to the groove and top of the cutter whereupon the braze material fills the grooves and then pools or overlaps onto the top of the cutters whereupon the braze material quickly cools and hardens thereby enhancing retention of the cutters similar to a snap ring retention device but more secure. In prior art the braze material only filled the void between the cutters and the pockets with no grooves or recesses. The present invention therefore allows enhanced cutter retention and extended drilling or boring time of drill bits, underreamers, section mills hole openers, casing cutters or other down hole tools used in bore hole drilling and completion operations. This same enhanced cutter retention is described in the present Inventors&#39; patent application titled Drill bit with replaceable blade members, patent application Ser. No. 12/456,234, filed Jun. 11, 2009, wherefore a Terminal Disclosure has been filed with said provisional patent application Ser. No. 61/398,370 filed Jun. 24, 2010 by Alan L. Nackerud. 
     SUMMARY OF THE INVENTION 
     The above and other advantages and features will become more readily appreciated and understood from a consideration of the following detailed description taken together with the accompanying drawings in which: 
    
    
     
       DRAWINGS 
       Figures 
         FIG. 1  is a side view of an Underreamer tool with retained cutters in a closed position; 
         FIG. 2  is a side view of an Underreamer tool with retained cutters in a closed position rotated 90 degrees; 
         FIG. 3  is a side view of an Underreamer tool with retained cutters and blades in an open position; 
         FIG. 4  is a side view of blade one of an Underreamer tool with retained cutters; 
         FIG. 5  is a side view of blade two of an Underreamer tool with retained cutters; 
         FIG. 6  is a section end view of blade one of an Underreamer tool with retained cutters; 
         FIG. 7  is an enlarged section end view of blade one of an Underreamer tool with retained cutters showing grooves and braze material in grooves and on top of cutters; 
     
    
    
     DRAWINGS 
     Reference Numerals 
     
         
         
           
               10 . threaded connection 
               11 . body 
               12 . blade one 
               13 . blade two 
               14 . cutters 
               15 . braze material 
               16 . cutter pocket 
               17 . grooves 
           
         
       
    
     DETAILED DESCRIPTION 
     Referring to the drawings, there is illustrated in  FIGS. 1 through 7  one form of the present invention being an improved Underreamer with grooves  17  which contain braze material  15  which retains cutters  14  for retention of cutters  14  in blade one  12  and blade two  13 .  FIG. 1  and  FIG. 2  show the Underreamer tool in a closed and non-operating position and  FIG. 3  shows the Underreamer in an open and operating position. In  FIGS. 1 ,  2  and  3  the Underreamer has a top threaded connection to allow connection to a drill string. The cutters  14  are placed in cutter pockets  16  around the drilling area perimeter of blade one  12  and blade two  13 . Braze material  15  is heated and in a liquid state placed in grooves  17  near the top of cutters  14  wherein the braze material  15  fills grooves  17  and overlaps onto the tops of cutters  14  whereupon the braze material  15  hardens and retains cutters  14  in cutter pockets  16  for enhanced retention of cutters  14 . 
     It is therefore to be understood that even though numerous characteristics and advantages of the present embodiment have been set forth in the foregoing description, together with the details of the structure and function of the embodiment, the disclosure is illustrative only, and changes may be made within the principles of the embodiment to the full extent indicated by the broad general meaning of the terms in which the claims are expressed and reasonable equivalents thereof and various forms of the present invention can be applied to numerous drilling and completion tools of earth bores.