Drilling tool and device for drilling with cryogenic cooling and method for drilling a stack of heterogeneous materials

Abstract

A drill bit having an interior canal for liquid nitrogen to pass longitudinally through the body of the drill bit. The canal has, on the side of a cutting edge of the drill bit, at least one liquid nitrogen ejection duct that opens near the cutting edge which is formed by an insert made with polycrystalline diamond fixed to the body of the drill bit. A device for drilling a metal-composite stack includes the drill bit, a liquid nitrogen production unit and a distribution network to distribute the liquid nitrogen. The device drills through a metal-composite stack in a single pass of the drill bit. The liquid nitrogen at cryogenic temperature is conveyed close to the cutting edge, at least while the cutting edge is in contact with the metallic material.

1 - 12 . (canceled) 
     
     
         13 . A drill bit for drilling a stack comprising at least one layer of a metal material and at least one layer of a composite material comprising fibers held in a hardened matrix, the drill bit comprising: a tail end configured to be held on a rotary driving machine; at least one cutting edge at an end, along a length of the drill bit, opposite the tail end, said at least one cutting edge being formed by an insert made with polycrystalline diamond and attached to a body of the drill bit; and a liquid nitrogen flow channel passing internally through the body of the drill bit, the liquid nitrogen flow channel comprising at least one liquid nitrogen ejection duct that opens close to said at least one cutting edge of the drill bit. 
     
     
         14 . The drill bit as claimed in  claim 13 , further comprising a plurality of cutting edges, each cutting edge comprising at least one liquid nitrogen ejection duct that opens close to said each cutting edge. 
     
     
         15 . The drill bit as claimed in  claim 14 , wherein said each cutting edge comprises at least one liquid nitrogen ejection duct that opens on a cutting face of said each cutting edge and at least one liquid nitrogen ejection duct that opens on a wear face of said each cutting edge. 
     
     
         16 . The drill bit as claimed in  claim 13 , wherein the liquid nitrogen flow channel is substantially axial in the body. 
     
     
         17 . The drill bit as claimed in  claim 13 , wherein the liquid nitrogen flow channel is insulated internally by a layer of a thermally insulating material over at least one portion of a length of the liquid nitrogen flow channel. 
     
     
         18 . The drill bit as claimed in  claim 13 , wherein the liquid nitrogen flow channel of the drill bit comprises an enlarged cross section that forms a reservoir in a region of the body located near said at least one cutting edge. 
     
     
         19 . The drill bit as claimed in  claim 13 , wherein the metal material of the stack comprises a titanium-based alloy; and wherein the liquid nitrogen flow channel and the liquid nitrogen ejection duct are sized to provide a flow rate of liquid nitrogen, substantially at a temperature of 77 kelvin to keep said at least one cutting edge at a temperature below a temperature for converting the polycrystalline diamond of the insert into a graphite. 
     
     
         20 . A drilling device, comprising the drill bit as claimed in  claim 13 , a liquid nitrogen production unit and a distribution system to distribute liquid nitrogen from the liquid nitrogen production unit to the drill bit. 
     
     
         21 . A drilling method for drilling a stack comprising at least one layer of a metal material and at least one layer of a composite material comprising fibers held in a hardened matrix, comprising the steps of:
 drilling the stack in one pass with a drill bit comprising at least one cutting edge formed by an insert made with polycrystalline diamond and attached to a body of the drill bit; and   transporting liquid nitrogen at cryogenic temperature close to said at least one cutting edge in contact with the metal material through a channel passing internally through the body of the drill bit and through at least one ejection duct that opens close to said at least one cutting edge.   
     
     
         22 . The drilling method as claimed in  claim 21 , further comprising the step of transporting the liquid nitrogen simultaneously on a cutting face and on a wear face of said at least one cutting edge. 
     
     
         23 . The drilling method as claimed in  claim 21 , further comprising the step of transporting the liquid nitrogen into the channel as a function of a measured or estimated position of the drill bit with respect to the stack. 
     
     
         24 . The drilling method as claimed in  claim 21 , wherein the metal material of the stack comprises a titanium-based alloy; and further comprising the step of transporting the liquid nitrogen with a flow rate sufficient to keep a temperature of the drill bit below a temperature for converting the polycrystalline diamond into graphite.