Drill bit bearing contact pressure reduction

Abstract

A method of reducing contact pressure between bearing surfaces of a drill bit can include constructing a structure which supports one bearing surface in contact with the other bearing surface, and reducing contact pressure between the bearing surfaces by relieving strain energy in the structure. A drill bit can include one bearing surface which contacts another bearing surface. There is a transition between contact and lack of contact between the bearing surfaces. A structure supporting one of the bearing surfaces has a reduced stiffness, whereby a contact pressure between the bearing surfaces is reduced at the transition.

1 . A method of reducing contact pressure between first and second bearing surfaces of a drill bit, the method comprising:
 constructing a structure which supports the first bearing surface in contact with the second bearing surface, the structure being part of at least one of a cone and a journal of the drill bit; and   reducing contact pressure between the first and second bearing surfaces by relieving strain energy in the structure.   
     
     
         2 . The method of  claim 1 , wherein constructing the structure comprises forming the structure as part of the cone of the drill bit. 
     
     
         3 . The method of  claim 1 , wherein constructing the structure comprises forming the structure as part of the journal of the drill bit. 
     
     
         4 . The method of  claim 1 , wherein the reduced contact pressure is due to a lack of material supporting the structure in the contacting step. 
     
     
         5 . The method of  claim 4 , wherein the lack of material is disposed adjacent a wall of a seal groove. 
     
     
         6 . The method of  claim 4 , wherein the lack of material is selected from one or more of the group consisting of a recess, a hole and a void. 
     
     
         7 . The method of  claim 4 , wherein the structure constructing step further comprises positioning the structure between the lack of material and the first bearing surface. 
     
     
         8 . The method of  claim 1 , wherein the reduced contact pressure is due to a reduced stiffness of the structure. 
     
     
         9 . The method of  claim 1 , wherein the reduced contact pressure is due to a reduced elastic modulus material of the structure. 
     
     
         10 . The method of  claim 1 , wherein the structure comprises a functionally gradient material. 
     
     
         11 . The method of  claim 1 , wherein the structure comprises a graduated elastic modulus material. 
     
     
         12 . The method of  claim 1 , wherein the structure comprises nano structures therein. 
     
     
         13 . The method of  claim 1 , wherein the structure comprises a first material having a reduced stiffness relative to a second material which supports the first bearing surface in contact with the second bearing surface. 
     
     
         14 . A drill bit, comprising:
 a first bearing surface which contacts a second bearing surface;   a transition between contact and lack of contact between the first and second bearing surfaces; and   a structure which supports one of the first and second bearing surfaces, the structure being part of at least one of a cone and a journal of the drill bit, and the structure having a reduced stiffness, whereby a contact pressure between the first and second bearing surfaces is reduced at the transition due to deflection of the structure.   
     
     
         15 . The drill bit of  claim 14 , wherein the transition is at a tangent formed on the first bearing surface. 
     
     
         16 . The drill bit of  claim 14 , wherein the transition is positioned adjacent a wall of a seal groove. 
     
     
         17 . The drill bit of  claim 14 , wherein the reduced stiffness of the structure is due to a lack of material supporting the structure. 
     
     
         18 . The drill bit of  claim 17 , wherein the lack of material is disposed adjacent a wall of a seal groove. 
     
     
         19 . The drill bit of  claim 17 , wherein the lack of material is selected from one or more of the group consisting of a recess, a hole and a void. 
     
     
         20 . The drill bit of  claim 14 , wherein the reduced stiffness of the structure is due to a reduced elastic modulus material of the structure. 
     
     
         21 . The drill bit of  claim 14 , wherein the deflection of the structure is increased due to the reduced stiffness when forces are transmitted between the first and second bearing surfaces. 
     
     
         22 . The drill bit of  claim 14 , wherein the structure comprises a functionally gradient material. 
     
     
         23 . The drill bit of  claim 14 , wherein the structure comprises a graduated elastic modulus material. 
     
     
         24 . The drill bit of  claim 14 , wherein the structure comprises nano structures therein. 
     
     
         25 . The drill bit of  claim 14 , wherein the structure comprises a first material having a reduced stiffness relative to a second material which supports the one of the first and second bearing surfaces. 
     
     
         26 . A drill bit, comprising:
 a first bearing surface which contacts a second bearing surface, the first bearing surface being formed in a cone, the second bearing surface being formed on a journal, the cone being rotatably mounted on the journal, and there being a transition between contact and lack of contact between the first and second bearing surfaces; and   at least one of the cone and the journal including first and second structures which support the first and second bearing surfaces in contact with each other, the first structure having a reduced stiffness relative to a stiffness of the second structure.   
     
     
         27 . The drill bit of  claim 26 , wherein the reduced stiffness of the first structure reduces contact pressure between the first and second bearing surfaces at the transition. 
     
     
         28 . The drill bit of  claim 26 , wherein the transition is at a tangent on the first bearing surface. 
     
     
         29 . The drill bit of  claim 26 , wherein the transition is positioned adjacent a wall of a seal groove. 
     
     
         30 . The drill bit of  claim 26 , wherein the reduced stiffness of the first structure is due to a lack of material supporting the first structure. 
     
     
         31 . The drill bit of  claim 30 , wherein the lack of material is disposed adjacent a wall of a seal groove. 
     
     
         32 . The drill bit of  claim 30 , wherein the lack of material is selected from one or more of the group consisting of a recess, a hole and a void. 
     
     
         33 . The drill bit of  claim 26 , wherein the reduced stiffness of the first structure is due to a reduced elastic modulus material of the first structure. 
     
     
         34 . The drill bit of  claim 26 , wherein a deflection of the first structure is greater than a deflection of the second structure when forces are transmitted between the first and second surfaces. 
     
     
         35 . The drill bit of  claim 26 , wherein at least the first structure comprises a functionally gradient material. 
     
     
         36 . The drill bit of  claim 26 , wherein at least the first structure comprises a graduated elastic modulus material. 
     
     
         37 . The drill bit of  claim 26 , wherein at least the first structure comprises nano structures therein. 
     
     
         38 . The drill bit of  claim 26 , wherein the first structure comprises a first material, and the second structure comprises a second material, and wherein the first material has a reduced stiffness relative to the second material. 
     
     
         39 . A drill bit, comprising:
 a thrust bearing interposed between a cone and a journal of the drill bit;   a first bearing surface on the thrust bearing which contacts a second bearing surface on at least one of the cone and the journal;   a transition between contact and lack of contact between the first and second bearing surfaces; and   a structure which supports the first bearing surface, the structure having a reduced stiffness, whereby a contact pressure between the first and second bearing surfaces is reduced at the transition.   
     
     
         40 . The drill bit of  claim 39 , wherein the reduced stiffness of the structure is due to a lack of material supporting the structure. 
     
     
         41 . The drill bit of  claim 40 , wherein the lack of material is selected from one or more of the group consisting of a recess, a hole and a void. 
     
     
         42 . The drill bit of  claim 39 , wherein the reduced stiffness of the structure is due to a reduced elastic modulus material of the structure. 
     
     
         43 . The drill bit of  claim 39 , wherein a deflection of the structure is increased due to the reduced stiffness when forces are transmitted between the first and second bearing surfaces. 
     
     
         44 . The drill bit of  claim 39 , wherein the structure comprises a functionally gradient material. 
     
     
         45 . The drill bit of  claim 39 , wherein the structure comprises a graduated elastic modulus material. 
     
     
         46 . The drill bit of  claim 39 , wherein the structure comprises nano structures therein. 
     
     
         47 . The drill bit of  claim 39 , wherein the structure comprises a first material having a reduced stiffness relative to a second material which supports the first bearing surface.