Rock bit having cuttings channels for flow optimization

Abstract

A rock bit for blast hole drilling includes a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side and a ported boss, and a plurality of roller cones. Each roller cone is secured to the respective bearing shaft for rotation relative thereto. A row of crushers is mounted around each roller cone. Each leading side and each trailing side are recessed relative to the respective shirttail. Each side has a cuttings channel formed therein. The rock bit further having a nozzle disposed at each ported boss. wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle.

1 . A rock bit for blast hole drilling, comprising:
 a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side, and a ported boss;   a plurality of roller cones, each roller cone secured to the respective bearing shaft for rotation relative thereto;   a row of crushers mounted around each roller cone, wherein each leading side and each trailing side are recessed relative to the respective shirttail, and each side has a cuttings channel formed therein; and   a nozzle disposed in each ported boss, wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle.   
     
     
         2 . The rock bit of  claim 1 , wherein each leading cuttings channel and the respective trailing cuttings channel are asymmetric. 
     
     
         3 . The rock bit of  claim 1 , wherein each outward angle ranges between five and twenty-five degrees. 
     
     
         4 . The rock bit as claimed in  claim 3 , wherein the outward angle is between eight to fifteen degrees. 
     
     
         5 . The rock bit as claimed in  claim 3 , wherein the outward angle is between ten to thirteen degrees or between eleven to twelve degrees. 
     
     
         6 . The rock bit of  claim 1 , wherein each leading side is concave and each trailing side is faceted. 
     
     
         7 . The rock bit of  claim 6 , wherein each leading cuttings channel has a cross-sectional shape of a circular segment, each trailing cuttings channel has a fillet, and a radius of each leading cuttings channel is at least twice a radius of each trailing cuttings channel. 
     
     
         8 . The rock bit of  claim 7 , wherein each leading side further has a first bevel extending from an edge thereof adjacent to the respective shirttail to the respective leading cuttings channel, and each leading side further has a second bevel extending from the respective leading cuttings channel to an edge thereof adjacent to an adjacent other leg. 
     
     
         9 . The rock bit of  claim 7 , wherein each trailing cuttings channel further has a first face extending from an edge of the respective trailing side adjacent to the respective shirttail to the respective fillet, and a second face extending from the fillet to a bevel, each trailing side having a respective bevel extending to either an edge thereof or to the respective ported boss. 
     
     
         10 . The rock bit of  claim 1 , wherein each leading cuttings channel has an inlet located at a lower edge of the respective leading side and an outlet located at an upper edge thereof adjacent to the respective base, and each trailing cuttings channel has an inlet offset from a lower edge of the respective trailing side and an outlet located at an upper edge thereof adjacent to the respective base. 
     
     
         11 . The rock bit of  claim 10 , wherein a longitudinal centerline of each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit, and a longitudinal centerline of each trailing cuttings channel is slightly curved extending from the inlet thereof for a short portion of the length and is then straight along the rest thereof and inclined relative to the longitudinal axis of the rock bit. 
     
     
         12 . The rock bit of  claim 11 , wherein each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between ten and thirty degrees, and the straight portion of each trailing cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between two and fifteen degrees. 
     
     
         13 . The rock bit of  claim 10 , wherein longitudinal centerlines of each leading and the respective trailing cuttings channels converge toward each other from the respective inlets thereof to the respective outlets thereof. 
     
     
         14 . The rock bit of  claim 1 , wherein each leg has a lubricant reservoir formed therein and a pressure compensator disposed therein. 
     
     
         15 . The rock bit of  claim 14 , wherein each lubricant reservoir is located adjacent to the respective trailing cuttings channel.