Subsurface drilling tool

Abstract

An improved subsurface drill bit includes two rotatable cutters disposed between two ear portions of a shank, each of the rotatable cutters having an arcuate face and cutting elements. Cutting edges of the cutting elements, outer surfaces of the ear portions, and protrusions extending outwardly from the shank collectively define a circular configuration to prevent backflow of drilling debris and to prevent wobble of the drill bit in operation. The two rotatable cutters can have an on-load configuration in which each of the cutters is in contact with each other, and an off-load configuration in which each of the cutters is in contact with one of the ear portions. Several improved rotatable cutters are provided. The rotatable cutters can be interchangeable. The drill bit can further include an improved fluid delivery system, including multiple fluid passageways and reverse jets.

What is claimed is: 
     
         1 . A drill bit configured to drill a drill bore, the drill bit comprising:
 a shank having a first end configured to operably connect to a drill string;   two ear portions integrally formed to and extending from a second end of the shank, each of the two ear portions having an arcuate outer surface;   two rolling cutters disposed between the two ear portions, each of the two rolling cutters having an arcuate face;   a plurality of cutting elements operably connected to each of the two rolling cutters, each of the plurality of cutting elements having a cutting edge; and   wherein the cutting edges of a portion of the plurality of cutting elements define a circular configuration.   
     
     
         2 . The drill bit of  claim 1  wherein the circular configuration is further defined by the arcuate outer surfaces of the two ear portions. 
     
     
         3 . The drill bit of  claim 1  further comprising:
 a plurality of protrusions extending outwardly from the shank, wherein the plurality of protrusions further define the circular configuration, and further wherein the plurality of protrusions is configured to prevent wobble of the drill bit in operation. 
 
     
     
         4 . The drill bit of  claim 3  wherein an exposed surface of each of the plurality of protrusions is hemispherical. 
     
     
         5 . The drill bit of  claim 4  wherein the circular configuration corresponds to a circumference of the drill bore and configured to prevent backflow of drilling debris. 
     
     
         6 . The drill bit of  claim 1  further comprising at least one milling course extending longitudinally along an outer surface of the shank and configured to urge drilling debris in a direction opposite a cutting direction of the drill bit within the drill bore. 
     
     
         7 . The drill bit of  claim 6  wherein the at least milling course further comprises two milling courses; wherein a portion of the plurality of protrusions is disposed on a ridge disposed between the two milling courses. 
     
     
         8 . A drill bit comprising:
 a generally cylindrical bit body having a first end configured to operably connect to a drill string;   two ear portions associated with the bit body, each of the two ear portions having a planar inner surface;   an axle extending between the two ear portions;   two rotatable cutters disposed on the axle, each of the two rotatable cutters having a planar inner surface, a planar outer surface, and an arcuate face extending between the inner surface and the outer surface;   wherein the outer surface of each of the two rotatable cutters directly abuts the inner surface of one of the two ear portions, and further wherein the inner surface of each of the two rotatable cutters directly abuts one another.   
     
     
         9 . The drill bit of  claim 8  wherein the two rotatable cutters have an on-load configuration comprising:
 a gap disposed between the outer surface of each of the two rotatable cutters and one of the ear portions; and 
 wherein the inner surfaces of each of the two rotatable cutters are in contact. 
 
     
     
         10 . The drill bit of  claim 8  wherein the two rotatable cutters have an off-load configuration comprising:
 a gap disposed between the inner surfaces of each of the two rotatable cutters; and 
 wherein the outer surface of each of the two rotatable cutters and one of the ear portions are in contact. 
 
     
     
         11 . The drill bit of  claim 10  wherein centripetal forces force the outer surface of each of the two rotatable cutters into contact with one of the ear portions in the off-load configuration. 
     
     
         12 . The drill bit of  claim 9  wherein the on-load configuration is associated with pulverization of rock within a drill bore. 
     
     
         13 . A drill bit configured to drill a drill bore, the drill bit comprising:
 a shank having a first end configured to operably connect to a drill string;   two ear portions integrally formed to and extending from a second end of the shank;   an axle extending between the two ear portions;   two rolling cutters disposed between the two ear portions and operably mounted on the axle, each of the two rolling cutters having an arcuate cutting face between an inner surface and an outer surface.   
     
     
         14 . The drill bit of  claim 13  further comprising:
 a plurality of cutting elements operably connected to the arcuate cutting faces of each of the two rolling cutters, wherein the plurality of cutting elements are arranged about more than one circumference of each of the arcuate cutting faces. 
 
     
     
         15 . The drill bit of  claim 14  wherein the plurality of cutting elements are equally spaced about more than one circumference of each of the arcuate cutting faces. 
     
     
         16 . The drill bit of  claim 13  wherein each of the two rolling cutters further comprises:
 a plurality of ridges and a plurality of grooves in an alternating configuration, associated with the arcuate cutting face, and extending between the inner surface and the outer surface of each of the two rolling cutters; and 
 one or more notches disposed within the plurality of ridges. 
 
     
     
         17 . The drill bit of  claim 13  wherein each of the two rolling cutters further comprises a plurality of three-sided cutting elements and a plurality of four-sided cutting elements associated with the arcuate cutting face. 
     
     
         18 . The drill bit of  claim 13  further comprising:
 a fluid course extending axially within the shank, the fluid course having an inlet proximate to the first end of the shank and at least one outlet proximate to the second end of the shank; and 
 wherein fluid exiting the outlet of the fluid course contacts the two rolling cutters opposite a drill face of the drill bore. 
 
     
     
         19 . The drill bit of  claim 14  wherein the fluid course further comprises a bifurcated portion comprising two fluid passageways in fluid communication with the inlet, and further wherein the at least one outlet comprises two outlets, each of the two outlets associated with one of the two fluid passageways of the bifurcated portion. 
     
     
         20 . The drill bit of  claim 14  wherein the fluid course further comprises a plurality of fluid passageways in fluid communication with the inlet, and further wherein the at least one outlet comprises a plurality of outlets, each of the plurality of outlets associated with one of the plurality of fluid passageways. 
     
     
         21 . The drill bit of  claim 18  further comprising:
 one or more reverse jets within the shank and in fluid communication with the fluid course; and 
 wherein the one or more reverse jets are configured to urge drilling debris in a direction opposite a cutting direction of the drill bit within the drill bore. 
 
     
     
         22 . The drill bit of  claim 14  further comprising a plurality of protrusions extending outwardly from the shank and configured to prevent wobble of the drill bit in operation. 
     
     
         23 . The drill bit of  claim 14  further comprising a plurality of cutting elements disposed on the shank.