Surgical bur with anti-chatter flute geometry

Abstract

A surgical bur including a shaft with a bur head. A number of flutes are formed on the bur head. Each flute has a cutting edge. Chamfer surfaces form the front, distally directed faces of some of the burs. The flutes without chamfer surfaces having cutting edges emerge from the bur head at locations relatively close to the distal end tip of the head. The flutes over which the chamfer surfaces extend have cutting edges that start, extend proximally rearward, from locations that are, spaced proximal from the distal end tip.

1 . A surgical bur, said bur
 an elongated shaft having opposed proximal and distal ends;   a coupling feature associated with the proximal end of the shaft, the coupling featured shaped to engage a drive unit of a surgical handpiece so that the handpiece can rotate the shaft;   a bur head attached to the distal end of the shaft, the bur head having: a body with a distal end tip; and a plurality of flutes that emerge from said body at locations proximal to the distal end tip, wherein each said flute has a rake surface and a clearance surface that meet to define a cutting edge wherein:
 a single pair of first flutes that are symmetric to each other around the body distal end tip emerge from the body distal end tip emerge from said body so as to have cutting edges that extends rearward from a distal position that is located proximal to the distal end tip and the first flutes are separated from each other by opposed arcuate spaces; 
 in each arcuate space between the flutes forming the first flutes, a plurality of second flutes extend out from said bur head body; 
 in each arcuate space between the flutes forming the first flutes, a first chamfer surface extends proximal from the body distal end tip so as to form a distal end face of each of the second flutes so that each of the second flutes has a cutting edge that extends rearward from a distal position that is spaced from the body distal end tip. 
   
     
     
         2 . The surgical bur of  claim 1 , wherein:
 a longitudinal center axis extends through the shaft and the bur head body distal end tip;   the first chamfer surfaces have a first pitch angle relative to longitudinal center axis;   said bur head is formed so that in each arcuate space between the flutes forming the second set of flutes there is a second chamfer surface, the second chamfer surfaces in the opposed arcuate spaces being, relative to the bur head body distal end tip symmetric relative to each other, each second chamfer surface extending over one of the second flutes in the arcuate space and extending proximally beyond the first chamfer surface in the arcuate space and having a second pitch angle relative to the longitudinal center axis, the second pitch angle being less than the first pitch angle wherein, within each arcuate space there is at least one second flute over which a second chamfer surface does not extends so that the cutting edge of the second flutes over which the second chamfer surfaces extend extends rearward from a distal position that is spaced proximal to the position from which the cutting edges of the second flutes over which the second chamfer do not extend extends rearwardly.   
     
     
         3 . A surgical bur, said bur
 an elongated shaft having opposed proximal and distal ends;   a coupling feature associated with the proximal end of the shaft, the coupling featured shaped to engage a drive unit of a surgical handpiece so that the handpiece can rotate the shaft;   a bur head attached to the distal end of the shaft, the bur head having: a body with a distal end tip; a longitudinal axis that through the body including through the distal end tip; and a plurality of flutes that emerge from said body at locations proximal to the distal end tip, wherein each said flute has a rake surface and a clearance surface that meet to define a cutting edge wherein:   a single pair of first flutes that are symmetric to each other around the body distal end tip emerge from the body distal end tip emerge from said body so as to have cutting edges that extends rearward from a distal position that is located proximal to the distal end tip and the first flutes are separated from each other by opposed arcuate spaces;   a single pair of second flutes that are symmetric to each other around the body distal end tip emerge from the body, each of the second flutes extending into one of the arcuate spaces;   two pairs of third flutes that are symmetric to each other around the body distal end tip emerge from the body and extend into the arcuate space, each third flute being located between one of the first flutes and one of the second flutes;   first chamfer surfaces extends proximally from adjacent the bur head body distal end tip, each said first chamfer surface forming a distal end face of one of the second flutes and the third flutes adjacent the second flute so that the each second flute has cutting edge that extends rearwardly from a position along the bur head that is spaced proximal to the distal end tip, and the first chamfer surfaces have a first pitch angle relative to the longitudinal axis; and   a second chamfer surface extends over each third flute, the second chamfer surfaces extending proximally rearward of the first chamfer surfaces and having second pitch angle relative to the longitudinal axis, the second pitch angle being less than the first pitch angle so that each third flute has a cutting edge that extends distally from a position along the bur head that is spaced proximal to the position from which the cutting edges of the second flutes extend distally.   
     
     
         4 . The surgical bur of  claim 3 , wherein each second chamfer surface abuts one of the first chamfer surfaces. 
     
     
         5 . The surgical bur of  claim 3 , wherein within each arcuate space between the first flutes:
 a first one of the second chamfer surfaces extends over a first one of the third flutes and the first one of the second chamfer surfaces extends rearward from a position proximal to the bur head body distal end tip; and   a second one of the second chamfer surfaces extends over a second one of the third flutes and extends rearward from a position that is spaced away from the bur head body distal end tip.