Rock-bit seals with asymmetric contact profiles

Abstract

Sealing arrangements for a rotary cone rock-bit comprising a leg extending from a bit body and a cone rotatably mounted to the leg. A seal is disposed radially between the cone and the leg. A footprint defines an area of contact between the seal and the leg. Compression of the seal generates a contact pressure between the seal and the leg. An axial centerline evenly bisects the footprint into a mud side and a grease side. A contact pressure profile defines the contact pressure over the footprint, wherein the contact pressure on the mud side of the footprint is greater than the contact pressure on the grease side of the footprint.

1 . A rotary cone rock-bit comprising 
 a bit body;    a leg extending from said bit body;    a cone rotatably mounted to said leg;    a first seal disposed radially between said cone and said leg;    a footprint defining an area of contact between said first seal and said leg, wherein compression of said first seal generates a contact pressure between said first seal and said leg;    an axial centerline that evenly bisects said footprint into a mud side and a grease side; and    a contact pressure profile defining the contact pressure over said footprint, wherein the contact pressure on the mud side of said footprint is greater than the contact pressure on the grease side of said footprint.    
   
   
       2 . The rotary cone rock-bit of  claim 1  wherein the contact pressure on the grease side of said footprint is less than 95% of the contact pressure on the mud side of said footprint.  
   
   
       3 . The rotary cone rock-bit of  claim 1  wherein the contact pressure on the grease side of said footprint is less than 75% of the contact pressure on the mud side of said footprint.  
   
   
       4 . The rotary cone rock-bit of  claim 1  wherein the maximum contact pressure is on the mud side of said footprint.  
   
   
       5 . The rotary cone rock-bit of  claim 1  wherein said first seal further comprises: 
 a body constructed from a first resilient material; and    a first end portion constructed from a second resilient material, wherein said first end portion is connected to said body along a first interface.    
   
   
       6 . The rotary cone rock-bit of  claim 5  wherein said first end portion has an asymmetrical outer surface arranged such that a greater volume of the second resilient material is disposed on the mud side of said seal.  
   
   
       7 . The rotary cone rock-bit of  claim 1  further comprising a second seal disposed radially between said cone and said leg, wherein said second seal is adjacent to and on the mud side of said first seal.  
   
   
       8 . A bit for drilling a borehole into earthen formations, the bit comprising: 
 a bit body;    a journal shaft extending from said bit body;    a rolling cone cutter mounted on said journal shaft and being adapted to rotate about a cone axis;    a seal gland between said shaft and said cone and comprising a first seal engaging surface on said shaft and a second seal engaging surface on said cone;    an annular seal disposed in said gland, said annular seal comprising: a radially inner surface sealingly engaging said first seal engaging surface; a radially outer seal surface sealingly engaging said second seal engaging surface; and    a seal footprint on one of said seal engaging surfaces, said footprint being defined by the portion of said seal contacting said one seal engaging surface, said footprint having a footprint length measured axially relative to said cone axis and being bisected by a footprint centerline that is perpendicular to said cone axis;    wherein said seal creates a pressure profile on one of said seal engaging surface axially along said footprint, said pressure profile being asymmetric relative to said centerline.    
   
   
       9 . The drill bit of  claim 8  wherein said seal divides a lubricant side from a drilling fluid side, and wherein said pressure profile includes a maximum pressure peak located on said drilling fluid side.  
   
   
       10 . The drill bit of  claim 9  wherein a curve representing the pressure profile on the lubricant side defines an area that is less than 95% of an area defined by a curve representing the pressure profile on the frilling fluid side.  
   
   
       11 . The drill bit of  claim 9  wherein a curve representing the pressure profile on the lubricant side defines an area that is less than 75% of an area defined by a curve representing the pressure profile on the frilling fluid side.  
   
   
       12 . The drill bit of  claim 8  wherein said seal further comprises: 
 a body constructed from a first resilient material; and    a first end portion constructed from a second resilient material, wherein said first end portion is connected to said body along a first interface.    
   
   
       13 . The drill bit of  claim 12  wherein said first end portion has an asymmetrical outer surface arranged such that a greater volume of the second resilient material is disposed on the drilling fluid side of said centerline.  
   
   
       14 . The drill bit of  claim 12  wherein the first interface is asymmetric.  
   
   
       15 . The drill bit of  claim 8  wherein said seal creates a pressure profile on said second seal engaging surface.  
   
   
       16 . A rotary cone rock-bit seal comprising: 
 a first seal in contact with a rotating surface along a first footprint;    a first centerline through the midpoint of the first footprint, wherein said first centerline divides said first seal into a drilling fluid side and a lubricant side; and    a first contact pressure profile formed between said first seal and the rotating surface, wherein said first contact pressure profile is asymmetric about said first centerline.    
   
   
       17 . The rotary cone rock-bit of  claim 16  wherein said first contact pressure profile on the drilling fluid side of said first seal defines an area larger than an area defined by said first contact pressure profile on the lubricant side of said first seal.  
   
   
       18 . The rotary cone rock-bit of  claim 16  wherein said first contact pressure profile comprises a peak contact pressure that is located on the drilling fluid side of said first centerline.  
   
   
       19 . The rotary cone rock-bit seal of  claim 16  wherein said first seal is constructed of a resilient material, wherein a majority of the resilient material is located on the drilling fluid side of said first seal.  
   
   
       20 . The rotary cone rock-bit seal of  claim 16  wherein said first seal is constructed of a first material and a second material bonded along a boundary that is asymmetric about the first centerline.  
   
   
       21 . The rotary cone rock-bit seal of  claim 16  wherein said first seal has an asymmetric surface profile in contact with the rotating surface.  
   
   
       22 . The rotary cone rock-bit seal of  claim 16  further comprising: 
 a second seal in contact with a rotating surface along a second footprint, wherein said second seal is adjacent to the drilling fluid side of said first seal;    a second centerline through the midpoint of the second footprint, wherein said second centerline divides said second seal into a drilling fluid side and a lubricant side; and    a second contact pressure profile formed between said second seal and the rotating surface.    
   
   
       23 . The rotary cone rock-bit seal of  claim 22  wherein said second contact pressure profile is asymmetric about said second centerline.  
   
   
       24 . The rotary cone rock-bit of  claim 23  wherein said second contact pressure profile on the drilling fluid side of said second seal defines an area larger than an area defined by said second contact pressure profile on the lubricant side of said second seal.  
   
   
       25 . The rotary cone rock-bit of  claim 23  wherein said second contact pressure profile comprises a peak contact pressure that is located on the drilling fluid side of said second centerline.  
   
   
       26 . The rotary cone rock-bit seal of  claim 23  wherein said second seal is constructed of a resilient material, wherein a majority of the resilient material is located on the drilling fluid side of said second seal.  
   
   
       27 . The rotary cone rock-bit seal of  claim 23  wherein said second seal is constructed of a first material and a second material bonded along a boundary that is asymmetric about the second centerline.  
   
   
       28 . The rotary cone rock-bit seal of  claim 22  wherein said second contact pressure profile is symmetric about said second centerline.