Enhanced Backup Ring Edge Features for Metal Face Seal in Roller Cone Drill Bits

Abstract

A backup ring for a face seal in a roller cone bit is configured to resist wear from drilling fluids present adjacent exposed faces of the backup ring. Portions are removed from an exposed end face in a variety of shapes while the hardness of the material is increased. The removal of material offsets an increase in force that would be transmitted through the backup ring on face seal assembly due to flexing. A spring can optionally be included in the removed material location. Another way is to increase the edge density of all or part of the exposed edges while leaving the interior portions unaffected by using electron beam radiation to increase the crosslink density or by other techniques that allow a unitary structure with a more durable edge region.

We claim: 
     
         1 . A backup ring for a face seal for an earth boring bit, comprising:
 a ring shaped member having an inner surface adjacent the face seal and an outer surface that is at least in part exposed to drilling fluids, said outer surface comprising an edge segment that is harder than the balance of said member.   
     
     
         2 . The ring of  claim 1 , wherein:
 said edge segment extends to at least two adjacent sides.   
     
     
         3 . The ring of  claim 1 , wherein:
 said edge segment has uniform thickness.   
     
     
         4 . The ring of  claim 1 , wherein:
 said edge segment has non-uniform thickness.   
     
     
         5 . The ring of  claim 1 , wherein:
 said edge segment runs continuously.   
     
     
         6 . The ring of  claim 1 , wherein:
 said edge segment is discontinuous.   
     
     
         7 . The ring of  claim 1 , wherein:
 said edge segment is made of the same material as the balance of said member but has altered properties to make said segment more durable to wear or tearing.   
     
     
         8 . The ring of  claim 1 , wherein:
 said edge segment is a different and harder material than the balance of said member.   
     
     
         9 . The ring of  claim 1 , wherein:
 said edge segment further comprises a projection.   
     
     
         10 . The ring of  claim 1 , wherein:
 the hardness of said edge segment is at least 46 durometer on the Shore A scale.