Seal Ring With Auxiliary Ring for Earth-Boring Bit

Abstract

An elastomeric seal ring is located between each bearing pin and each cone of an earth-boring bit. An auxiliary ring or band is imbedded within an annular recess formed in the inner diameter of the seal ring. A portion of the inner diameter of the seal ring as well as the auxiliary ring are in dynamic contact with the bearing pin. The auxiliary ring has a geometric feature that enhances radial flexibility but prevents it from sealing. The geometric feature may be a transverse cut, notches in either the inner or outer diameters, or holes extending between the sides of the auxiliary ring. The auxiliary ring has lubricating properties.

1 . An earth boring bit having a body with a depending bearing pin, and a cone rotatably mounted to the bearing pin, the cone having a plurality of cutting elements, the improvement comprising:
 an elastomeric seal ring having an outer portion in sealing engagement with a seal surface on the cone and an inner portion in sealing engagement with a seal surface on the bearing pin;   an annular recess extending around one of the portions of the seal ring;   an auxiliary ring carried in the annular recess and having a face urged by the seal ring into contact with one of the sealing surfaces;   said one of the portions of the seal ring has sections on opposite lateral sides of the auxiliary ring that sealingly engage said one of the seal surfaces; and   a geometric feature in the auxiliary ring that enhances radial flexibility of the auxiliary ring and prevents it from sealing.   
     
     
         2 . The bit according to  claim 1 , wherein the geometric feature comprises a fluid communication path extending from one of the lateral sides to the other of the lateral side of the auxiliary ring. 
     
     
         3 . The bit according to  claim 1 , wherein the geometric feature comprises:
 a skive cut extends from one of the lateral sides to the other of the lateral sides, completely severing the auxiliary ring; and   the skive cut is formed at an acute angle relative to the lateral sides of the auxiliary ring.   
     
     
         4 . The bit according to  claim 1 , wherein the geometric feature comprises:
 at least one hole extending through the auxiliary ring from one its lateral sides to the other of its lateral sides.   
     
     
         5 . The bit according to  claim 1 , wherein:
 the auxiliary ring has an inner diameter and an outer diameter; and the geometric feature comprises   at least one recess on at least one of the diameters that extends from one of its lateral sides to the other of its lateral sides.   
     
     
         6 . The bit according to  claim 1 , wherein:
 the annular recess is located in the inner portion of the seal ring, and the auxiliary ring is in sliding engagement with the seal surface on the bearing pin; and   the auxiliary ring is formed of a self-lubricating material.   
     
     
         7 . The bit according to  claim 1 , wherein the auxiliary ring is formed of a material that consists essentially of PTFE. 
     
     
         8 . The bit according to  claim 1 , wherein the auxiliary ring is formed of a material consisting essentially of PTFE and a filler material selected from one or more of the following: carbon graphite, glass fibers, and metallic particles. 
     
     
         9 . The bit according to  claim 1 , wherein the auxiliary ring is formed of PEEK with a filler of PTFE. 
     
     
         10 . An earth boring bit, comprising:
 a body having a depending bearing pin;   a cone having a cylindrical cavity mounted rotatably on the bearing pin, the cone having an exterior containing a plurality of cutting elements, the cone and the bearing pin defining bearing spaces filled with a lubricant;   a seal ring of nitrile rubber, having an outer diameter in sealing contact with the cavity of the cone and an inner diameter in sealing contact with the bearing pin, the seal ring having an exterior side exposed to drilling fluid during operation and an interior side exposed to lubricant within the bearing spaces;   an annular recess formed in the inner diameter of the seal ring between the interior and exterior sides;   at least one thermoplastic auxiliary ring having an interior side and an exterior side and located in the annular recess, the auxiliary ring having an inner diameter urged by the seal ring into dynamic contact with the bearing pin; and   at least one pathway extending from the interior side to the exterior side of the auxiliary ring to increase radial flexibility of the auxiliary ring.   
     
     
         11 . The bit according to  claim 10 , wherein the pathway comprises a cut that severs the auxiliary ring. 
     
     
         12 . The bit according to  claim 10 , wherein the auxiliary ring has an outer diameter in contact with a base of the annular recess, and said at least one pathway comprises a plurality of recesses formed on one of the diameters of the auxiliary ring. 
     
     
         13 . The bit according to  claim 10 , wherein said at least one pathway comprises a plurality of holes in the auxiliary ring, each extending from the interior side to the exterior side. 
     
     
         14 . The bit according to  claim 10 , wherein
 the inner diameter of the auxiliary ring after the seal ring and auxiliary ring are installed in the groove of the cone and prior to installing the cone on the bearing pin are less than an outer diameter of the bearing pin; and   the pathway allows the auxiliary ring to rapidly expand during installation of the cone on the bearing pin.   
     
     
         15 . The bit according to  claim 10 , wherein the auxiliary ring is formed of a material that consists essentially of PTFE. 
     
     
         16 . The bit according to  claim 10 , wherein the auxiliary ring is formed of a material consisting essentially of PTFE and a filler material selected from one or more of the following: carbon graphite, glass fibers, and metallic particles. 
     
     
         17 . The bit according to  claim 10 , wherein the auxiliary ring is formed of PEEK with a filler of PTFE. 
     
     
         18 . An earth boring bit, comprising:
 a body having a depending bearing pin;   a cone having a cylindrical cavity mounted rotatably on the bearing pin, the cone having an exterior containing a plurality of cutting elements;   an annular groove in the cylindrical cavity of the cone;   a seal ring of elastomeric material and having an outer portion in sealing contact with the groove and an inner portion;   an annular recess extending around the inner portion of the seal ring, defining segments of the seal ring on each side of the recess that are in dynamic sealing contact with the bearing pin;   an auxiliary ring within the annular recess of the seal ring, the auxiliary ring having an outer diameter in contact with a base of the annular recess and an inner diameter in contact with the bearing pin, the auxiliary ring having an interior side and an exterior side;   the inner diameter of the auxiliary ring after the seal ring and auxiliary ring are installed in the groove of the cone and prior to installing the cone on the bearing pin being less than an outer diameter of the bearing pin; and   a cut extending from the interior side to the exterior side of the auxiliary ring,, severing and providing radial flexibility to the auxiliary ring to allow the auxiliary ring to rapidly expand during installation of the cone on the bearing pin.   
     
     
         19 . The bit according to  claim 18 , wherein prior to installation of the auxiliary ring and the seal ring in the annular recess in the cone, the inner diameter of the auxiliary ring is greater than the outer diameter of the bearing pin. 
     
     
         20 . The bit according to  claim 18 , wherein the auxiliary ring is formed of a material that has less elasticity than the seal ring.