Rolling cone drill bit having non-uniform legs

Abstract

A drill bit for drilling through earthen formations. In an embodiment, the drill bit comprises a bit body having a bit axis. In addition, the drill bit comprises a first rolling cone cutter mounted on the bit body at a first journal angle and adapted for rotation about a first cone axis. Further, the drill bit comprises a second rolling cone cutter mounted on the bit body at a second journal angle and adapted for rotation about a second cone axis, wherein the second journal angle differs from the first journal angle.

1 . A drill bit for drilling through earthen formations comprising: 
 a bit body having a bit axis;    a first rolling cone cutter mounted on the bit body at a first journal angle and adapted for rotation about a first cone axis;    a first plurality of cutter elements mounted to the first rolling cone cutter;    a second rolling cone cutter mounted on the bit body at a second journal angle and adapted for rotation about a second cone axis, wherein the second journal angle differs from the first journal angle;    a second plurality of cutter elements mounted to the second rolling cone cutter, wherein at least one of the second plurality of cutter elements intermeshes with the first plurality of cutter elements.    
   
   
       2 . The drill bit of  claim 1  wherein the first rolling cone cutter is mounted on the bit body at a first cone offset and the second rolling cone cutter is mounted on the bit body at a second cone offset that is different than the first cone offset.  
   
   
       3 . The drill bit of  claim 2  wherein the first cone offset is greater than the second cone offset, and wherein the first journal angle is less than the second journal angle.  
   
   
       4 . The drill bit of  claim 2  wherein the first cone offset is positive and the second cone offset is negative.  
   
   
       5 . The drill bit of  claim 3  wherein the first and second plurality of cutter elements each include a circumferential row of gage inserts, wherein the number of gage inserts mounted to the first rolling cone cutter is different than the number of gage inserts mounted to the second rolling cone cutter.  
   
   
       6 . The drill bit of  claim 2  wherein the first cone offset is less than the second cone offset and wherein the first journal angle is less than the second journal angle.  
   
   
       7 . The drill bit of  claim 1  wherein the first rolling cone cutter is mounted on a first journal pin extending from the bit body and the second rolling cone cutter is mounted on a second journal pin extending from the bit body, wherein the diameter of the first journal pin is different than the diameter of the second journal pin.  
   
   
       8 . A drill bit for drilling through earthen formations comprising: 
 a bit body having a bit axis;    at least three rolling cone cutters mounted on the bit body and adapted for rotation about a different cone axis, each of the cone cutters including a circumferential row of gage cutter elements and at least one circumferential row of inner row cutter elements spaced apart from the row of gage cutter elements, wherein at least one of the inner row cutter elements of one rolling cone cutter intermeshes with the inner row cutter elements of a different rolling cone cutter; 
 wherein each of the rolling cone cutters defines a journal angle and a cone offset; and  
   wherein the journal angle of a first of the cone cutters differs from the journal angle of a second of the cone cutters.    
   
   
       9 . The drill bit of  claim 8  wherein at least one cone cutter has an offset that is different from the offset of another of the cone cutters.  
   
   
       10 . The drill bit of  claim 9  wherein at least one of the cone cutters has a positive offset and at least one of the cone cutters has negative offset.  
   
   
       11 . The drill bit of  claim 8  wherein each of the cone cutters is mounted on a different journal pin extending from the bit body, and wherein the diameter of at least one journal pin is different from the diameter of another journal pin.  
   
   
       12 . The drill bit of  claim 8  wherein each of the cone cutters is mounted on a different journal pin and wherein the journal pin of at least one cone cutter differs from the journal pin of another of the cone cutters in at least one characteristic selected from the group consisting of journal length and journal diameter.  
   
   
       13 . The drill bit of  claim 8  wherein at least one of the cone cutters is mounted with roller bearings and at least a second cone cutter is mounted with journal bearings.  
   
   
       14 . The drill bit of  claim 8  wherein the bit includes at least one cone seal disposed between each cone and the journal pin upon which it is mounted, and wherein the bit includes cone seals of differing types.  
   
   
       15 . The drill bit of  claim 8  wherein a first cone cutter is disposed between and immediately adjacent a second cone cutter and a third cone cutter, wherein the first cone cutter is separated from the second cone cutter by a first separation angle and separated from the third cone cutter by a second separation angle that is different than the first separation angle.  
   
   
       16 . A drill bit for drilling through earthen formations, comprising: 
 a bit body having a bit axis;    at least three rolling cone cutters mounted on the bit body and adapted for rotation about a different cone axis;    wherein each of the cone cutters includes a circumferential row of gage cutter elements and at least one circumferential row of inner row cutter elements spaced apart from the row of gage cutter elements, wherein at least one of the inner row cutter elements of one rolling cone cutter intermeshes with the inner row cutter elements of a different rolling cone cutter;    wherein a first of the cone cutters differs from a second of the cone cutters in at least one characteristic selected from the group consisting of cone offset, journal angle, seal type, journal length, and journal diameter.    
   
   
       17 . The drill bit of  claim 16  wherein a first cone cutter has a first cone offset and a second cone cutter has a second cone offset that is different from the first cone offset, and wherein the first cone cutter is mounted having a first journal angle that differs from the journal angle of at least one other of the cone cutters.  
   
   
       18 . The drill bit of  claim 17  wherein each of the cone cutters differs in cone offset and journal angle from each of the other cone cutters.  
   
   
       19 . The drill bit of  claim 17  wherein the second cone cutter is mounted having a second journal angle, and wherein first cone offset is greater than the second cone offset and the first journal angle is less than the second journal angle.  
   
   
       20 . The drill bit of  claim 17  wherein the second cone cutter is mounted having a second journal angle, and wherein the first cone offset is less than the second cone offset and the first journal angle is less than the second journal angle.  
   
   
       21 . A drill bit for drilling through earthen formations comprising: 
 a bit body having a bit axis;    a plurality of bit legs, each of the legs including a rolling cone cutter mounted thereon and adapted for rotation about a different cone axis;    wherein each of the cone cutters includes at least one circumferential row of inner row cutter elements, wherein at least one of the inner row cutter elements of one cone cutter intermeshes with the inner row cutter elements of a different cone cutter;    wherein at least a first of the cone cutters differs from a second of the cone cutters in at least one characteristic selected from the group consisting of journal angle, cone offset, seal type and bearing configuration.    
   
   
       22 . The drill bit of  claim 21  wherein the first of the cone cutters has a first cone offset and the second of the cone cutters has a second cone offset that is different from the first cone offset, and wherein the first of the cone cutters is mounted having a first journal angle that differs from the journal angle of at least one other of the cone cutters.  
   
   
       23 . The drill bit of  claim 22  wherein the second of the cone cutters is mounted having a second journal angle, and wherein first cone offset is greater than the second cone offset and the first journal angle is less than the second journal angle.  
   
   
       24 . A drill bit for drilling through earthen formations comprising: 
 a bit body having a bit axis;    at least three rolling cone cutters mounted on the bit body and adapted for rotation about a different cone axis, each of the cone cutters including a circumferential row of gage cutter elements and at least one circumferential row of inner row cutter elements spaced apart from the row of gage cutter elements, wherein at least one of the inner row cutter elements of one rolling cone cutter intermeshes with the inner row cutter elements of a different rolling cone cutter; 
 wherein each of the cone cutters defines a journal angle and a cone offset; and  
   wherein the cone offset of at least one cone cutter is different from the cone offset of another of the cone cutters.    
   
   
       25 . The drill bit of  claim 24  wherein the journal angle of a first of the cone cutters differs from the journal angle of a second of the cone cutters.  
   
   
       26 . The drill bit of  claim 24  wherein at least one of the cone cutters has a positive offset and at least one of the cone cutters has negative offset.  
   
   
       27 . The drill bit of  claim 24  wherein each of the cone cutters is mounted on a different journal pin and wherein the journal pin of at least one cone cutter differs from the journal pin of another of the cone cutters in at least one characteristic selected from the group consisting of journal length and journal diameter.  
   
   
       28 . The drill bit of  claim 24  wherein at least one of the cone cutters is mounted with roller bearings and at least a second cone cutter is mounted with journal bearings.  
   
   
       29 . The drill bit of  claim 24  wherein the bit includes at least one cone seal disposed between each cone and the journal pin upon which it is mounted, and wherein the bit includes at least two cone seals of differing types.  
   
   
       30 . The drill bit of  claim 24  wherein a first cone cutter is disposed between and immediately adjacent a second cone cutter and a third cone cutter, wherein the first cone cutter is separated from the second cone cutter by a first separation angle and separated from the third cone cutter by a second separation angle that is different than the first separation angle.