Percussive drill bit with multiple sets of front cutting inserts

Abstract

A percussive rock drill bit includes a head provided with an elongate shank. A plurality of front cutting inserts are distributed at a front face of the head and are grouped into a plurality of sets, with each set being positioned at a different radial distance from a central axis. Each set of inserts includes the same number of inserts to maximize drilling rate and service lifetime of the drill bit.

1 . A percussive rock drill bit comprising:
 a head provided at one end of an elongate shank, the head having a forward facing front face defined by a perimeter edge; and   a plurality of front cutting inserts distributed at the front face at different radial positions between a central axis extending through the drill bit and the perimeter edge of the front face, wherein the front cutting inserts are grouped into a plurality of sets, each set including an equal number of inserts positioned at a different radial distance from the axis, each insert of each respective set of inserts being positioned at substantially the same radial distance and positioned circumferentially between a pair of inserts of a neighbouring radially outer and/or radially inner set inserts, such that the positions of the inserts of neighbouring sets are staggered circumferentially.   
     
     
         2 . The drill bit as claimed in  claim 1 , wherein each set includes from three to six inserts ( 104 ). 
     
     
         3 . The drill bit as claimed in  claim 2 , wherein each set includes four inserts. 
     
     
         4 . The drill bit as claimed in  claim 1 , further comprising from two to eight sets of front cutting inserts. 
     
     
         5 . The drill bit as claimed in  claim 1 , wherein a diameter of the inserts within at least some of the sets increases in a direction radially outward from the axis. 
     
     
         6 . The drill bit as claimed in  claim 1 , wherein a central region of the front face is positioned axially forward of the perimeter edge. 
     
     
         7 . The drill bit as claimed in  claim 1 , wherein the front face is generally convex such that a central region of the front face is positioned axially forward of the perimeter edge. 
     
     
         8 . The drill bit as claimed in  claim 1 , wherein the inserts of at least two sets overlap radially. 
     
     
         9 . The drill bit as claimed in  claim 1 , wherein one of the sets represents a radially innermost set of the front cutting inserts, the innermost set comprising having the same number of inserts as the radially outer sets. 
     
     
         10 . The drill bit as claimed in  claim 1 , further comprising a radially innermost group of front inserts that include a number of inserts being less than the number of inserts within each of the sets that are positioned radially outside the sets. 
     
     
         11 . The drill bit as claimed in  claim 1 , further comprising:
 a first inner set of inserts positioned radially innermost at or towards the axis relative to other sets; and   a first intermediate set of inserts positioned radially between the first inner set and a gauge group of cutting inserts positioned at or towards the perimeter edge.   
     
     
         12 . The drill bit as claimed in  claim 11 , further comprising a second intermediate set of inserts positioned radially intermediate the first intermediate set and the gauge group of inserts. 
     
     
         13 . The drill bit as claimed in  claim 12 , further comprising a second inner set of inserts positioned radially intermediate the first inner set and the first intermediate set of inserts. 
     
     
         14 . The drill bit as claimed in  claim 13 , wherein the inner and intermediate sets are positioned at different axial positions with the first inner set ( 205 ) of inserts positioned axially forwardmost and the second intermediate set of inserts positioned axially rearwardmost, the gauge group of inserts being positioned axially rearward of the second intermediate set. 
     
     
         15 . Percussive drilling apparatus comprising:
 a drill bit, the drill bit including a head provided at one end of an elongate shank, the head having a forward facing front face defined by a perimeter edge, and a plurality of front cutting inserts distributed at the front face at different radial positions between a central axis extending through the drill bit and the perimeter edge of the front face, wherein the front cutting inserts are grouped into a plurality of sets, each set including an equal number of inserts positioned at a different radial distance from the axis, each insert of each respective set of inserts being positioned at substantially the same radial distance and positioned circumferentially between a pair of inserts of a neighbouring radially outer and/or radially inner set inserts, such that the positions of the inserts of neighbouring sets are staggered circumferentially