Bearing seal with improved contact width

Abstract

A high aspect ratio seal is provided for large roller cone drill bit having a diameter of greater than about 12¼ inches wherein the contact width is narrowed, relative to the width of the seal, to provide a desired contact width.

1 . An drill bit having a diameter of greater than about 12¼ inches, comprising:
 a bit body having a depending bearing pin;   a cone having a plurality of cutting elements for engaging a bore hole, the cone having a cavity that rotatably engages the bearing pin; and   a groove formed in the cavity of the cone;   a ring shaped elastomeric seal in the groove between the bearing pin and the cone;   the seal having an inner diameter that sealingly engages the bearing pin, an outer diameter that sealingly engages the cone, and two side surfaces, the distance between the inner and outer diameter defining a radial dimension of the seal and the distance between the side surfaces defining a seal width, the seal having a radial dimension greater than the seal width;   wherein an inner diameter contact width is defined as the width of a surface of the inner diameter of the seal that sealingly engages the bearing pin when installed in the drill bit and an outer diameter contact width is defined as the width of a surface of the outer diameter of the seal that sealingly engages the cone when installed in the drill bit; and   wherein the ratio of the installed inner diameter contact width to the uninstalled seal width is less than 0.5.   
   
   
       2 . The drill bit of  claim 1  wherein the seal is compressed to an amount between about 5 and 15% when installed in the seal groove. 
   
   
       3 . The drill bit of  claim 1  wherein the drill bit has a diameter of at least about 16 inches. 
   
   
       4 . The drill bit of  claim 1  wherein the side surfaces comprise at least one protuberance protruding from at least one of the side surfaces of the seal ring for contact with one of the side walls of the groove. 
   
   
       5 . The drill bit of  claim 1  wherein the seal has an inner diameter contact width of between about 0.09 and 0.12 inches. 
   
   
       6 . The drill bit of  claim 1  wherein the seal has an inner diameter contact width of between about 0.1 and 0.11 inches. 
   
   
       7 . At least two drill bits comprising:
 first and second drill bits each having a diameter of greater than about 12¼ inches, the second drill bit having a diameter greater than the diameter of the first drill bit, each drill bit comprising;   a bit body having a depending bearing pin;   a cone having a plurality of cutting elements for engaging a bore hole, the cone having a cavity that rotatably engages the bearing pin, the cone and the bearing pin having a seal area defined by two annular surfaces, one of which rotates relative to the other;   an elastomeric seal ring comprising:
 a forward side surface, a rearward side surface and positioned between the bearing pin and the cone cavity in sealing engagement with the annular surfaces of the seal area; 
 an inner diameter surface contacting the bearing shaft at an inner diameter contact width when installed and an outer diameter surface contacting the cutter cone at an outer diameter surface contact width when installed, and two side surfaces, the distance between the two side surfaces defining a seal width; 
 a radial dimension of each seal defined by the distance between the inner and outer diameter of each seal, the radial dimension of the seal of the second drill bit being greater than the radial dimension of the seal of the first drill bit; and 
   the inner diameter contact width of the first drill bit and the inner diameter contact width of the second drill bit vary no more than 33% from each other.   
   
   
       8 . The drill bits of  claim 7  wherein the second drill bit has a diameter of at least 22 inches. 
   
   
       9 . The drill bits of  claim 7  wherein the inner diameter contact widths of the seals of the first and second drill bits are each less than about 0.12 inches. 
   
   
       10 . The drill bits of  claim 7  wherein the inner diameter contact widths of the first and second drill bits are each between about 0.09 inches and about 0.12 inches. 
   
   
       11 . The drill bits of  claim 7  wherein the inner diameter contact widths of the first and second drill bits are each between about 0.1 inches and about 0.11 inches. 
   
   
       12 . The drill bits of  claim 7  wherein a ratio of the inner diameter contact width of the first drill bit is less than 50% of the seal width of the seal of the first bit. 
   
   
       13 . The drill bits of  claim 7  wherein the seals of the first and second drill bits are each compressed to an amount between about 5 and 15% when installed in a seal groove. 
   
   
       14 . The drill bits of  claim 7  wherein the contact widths of the seals of the first and second drill bits are substantially equal. 
   
   
       15 . A method for designing seals for a rotating cone drill bit having a diameter of greater than about 12¼ inches, comprising:
 (a) determining a seal width based upon the drill bit diameter, with drill bits of larger diameters in the range having greater seal widths than drill bits of smaller diameters in the range;   (b) selecting a seal radial dimension of the seal between the inner and outer diameters of the seal to achieve a desired seal squeeze; and   (c) configuring the seal for the drill bit such that regardless of the bit diameter in the range and regardless of the seal width selected and seal radial dimension selected, the contact widths for the seals are within 33% of each other for all drill bits in the range.   
   
   
       16 . The method of  claim 15  wherein step (c) comprises making the contact widths for the seals less than 0.12 inches. 
   
   
       17 . The method of  claim 15  wherein step (c) comprises making the contact widths for the seals between about 0.09 and about 0.12 inches. 
   
   
       18 . The method of  claim 15  wherein step (c) comprises making the contact widths for the seals between about 0.1 and about 0.11 inches. 
   
   
       19 . The method of  claim 15  wherein a ratio of the inner diameter contact width of a seal is less than 50% of the seal width. 
   
   
       20 . The method of  claim 15  wherein step (b) comprises selecting a seal squeeze between about 5% and about 15%. 
   
   
       21 . The method of  claim 15  wherein step (b) comprises providing greater radial dimensions for seals of larger diameter bits in the range than for smaller diameter bits in the range.