Reverse circulation hammer spline arrangement improvements

Abstract

A down-the-hole hammer drill that delivers fluid to a cutting face has particular application, but not limited, to a reverse-circulation (RC) down-hole face sampling hammer drill is tailored to the design of the cutting face to improve flushing of the cutting face. An associated drill bit and drive sub are also disclosed.

1 . A down-the-hole hammer comprising:
 a drill bit, the drill bit including a shank and a head having a cutting face; and   a drive sub, the drive sub surrounding at least a portion of the shank and cooperating with the drill bit to form fluid passages extending lengthwise along the shank to direct fluid to the cutting face to flush the cutting face, wherein each of the passages initially direct fluid to a different portion of the cutting face, and at least one of the passages delivering a greater flow rate of fluid than the others, thereby directing more fluid to at least one portion of the cutting face in preference to other portions thereof.   
     
     
         2 . The down-the-hole hammer of  claim 1 , wherein the drive sub includes a plurality of inwardly directed driving splines, and the shank of the bit includes a plurality of outwardly directed driven splines which are so spaced and numbered as to form with the driving splines spline pairings having abutting cutting faces, the bit and the drive sub cooperatively defining between adjacent spline pairings said passages for directing fluid to the cutting face. 
     
     
         3 . The down-the-hole hammer of  claim 2 , wherein said at least one passage is larger than other passages. 
     
     
         4 . The down-the-hole hammer of  claim 3 , wherein said at least one passage is wider than other passages. 
     
     
         5 . The down-the-hole hammer  claim 3 , wherein the fluid passages include larger passages and smaller passages, the larger passages being primary passages and the smaller passages being secondary passages. 
     
     
         6 . The down-the-hole hammer of  claim 5 , wherein each of the primary passages is defined between two adjacent spline pairings spaced so that the width between these is greater than the width between any other two adjacent spline pairings. 
     
     
         7 . The down-the-hole hammer of  claim 5 , wherein at least one of the splines defining a primary channel is dissimilar to other splines of its type. 
     
     
         8 . The down-the-hole hammer of  claim 7 , wherein each dissimilar spline has a different thickness than the other splines. 
     
     
         9 . The down-the-hole hammer of  claim 1 , wherein said at least one portion of the cutting face is a portion having increased flushing needs. 
     
     
         10 . The down-the-hole hammer of  claim 1 , wherein said at least one portion of the cutting face is at or near to a-cutting inserts under high load. 
     
     
         11 . The down-the-hole hammer of  claim 1 , wherein the hammer is a reverse circulation (RC) hammer 
     
     
         12 . The down-the-hole hammer of  claim 1 , wherein the hammer is pneumatic and the fluid is air. 
     
     
         13 . The down-the-hole hammer of  claim 12 , wherein said at least one portion of the cutting face is positioned between an outlet from the passage and an inlet for an inner tube which returns air carrying entrained flushed cuttings to the surface. 
     
     
         14 . A drill bit for a down-the-hole hammer comprising:
 a shank;   a head having a cutting face; and   fluid passages extending lengthwise along the shank to direct fluid to the cutting face to flush the same, each of the fluid passages directing fluid to a different portion of the cutting face, at least one of the fluid passages delivering a greater flow rate of fluid than the others, thereby directing fluid to at least one portion of the cutting face in preference to other portions thereof.   
     
     
         15 . The drill bit of  claim 14 , wherein the shank of the bit comprises includes a plurality of outwardly directed splines defining passages between adjacent pairs thereof, and said at least one passage is defined between two adjacent splines spaced so that the distance between these is greater than the distance between other adjacent splines. 
     
     
         16 . The drill bit of  claim 15 , wherein at least one of the splines defining said at least one passage is dissimilar to other splines of its type. 
     
     
         17 . A drive sub for a down-the-hole hammer having a drill bit, the drill bit comprising:
 a shank; and   a head having a cutting face, the drive sub surrounding at least a portion of the shank and cooperating with the drill bit to form fluid passages extending lengthwise along the shank to direct fluid to the cutting face to flush the same, each of the fluid passages directing fluid to a different portion of the cutting face, and at least one of the fluid passages delivering a greater flow rate of fluid than the others, thereby directing fluid to at least one portion of the cutting face in preference to other portions.   
     
     
         18 . The drive sub of  claim 17 , wherein the drive sub includes a plurality of inwardly directed driving splines defining passages between adjacent pairs thereof, and said at least one passage is defined between two adjacent splines spaced so that the distance between these is greater than the distance between other adjacent splines. 
     
     
         19 . The drive sub of  claim 18 , wherein at least one of the splines defining said at least one passage is dissimilar to other splines of its type.