Flow restrictor and drilling assembly

Abstract

A flow restrictor comprising a body adapted to restrict a flow of fluid through a drill rod passage, the body having a coupling for coupling said body into the drill rod passage, said body defining an upstream fluid receiving passage, a downstream fluid egress passage, and a passage of restrictive diameter between said passages to limit the flow of fluid in the drill rod passage.

1 . A flow restrictor comprising a body adapted to restrict a flow of fluid through a drill rod passage, the body having a coupling for coupling said body into the drill rod passage, said body defining an upstream fluid receiving passage, a downstream fluid egress passage, and a passage of restrictive diameter between said upstream and downstream fluid passages to limit the flow of fluid in the drill rod passage. 
     
     
         2 . The flow restrictor according to  claim 1 , wherein said passages are concentrically aligned with one another along a central longitudinal axis of the drill rod passage. 
     
     
         3 . The flow restrictor according to  claim 1 , wherein the passage of restrictive diameter has a diameter from about 25% to about 50% of the diameter of the drill rod passage. 
     
     
         4 . The flow restrictor according to  claim 1 , wherein the passage of restrictive diameter has a circular cross-section. 
     
     
         5 . The flow restrictor according to  claim 1 , wherein the upstream fluid receiving passage inwardly tapers from an upstream end thereof to the passage of restrictive diameter. 
     
     
         6 . The flow restrictor according to  claim 5 , wherein the upstream end of said passage has a diameter greater than about 60% of the drill rod passage. 
     
     
         7 . The flow restrictor according to  claim 1 , wherein the downstream fluid egress passage has a polygonal cross-section. 
     
     
         8 . The flow restrictor according to  claim 7 , wherein the polygonal cross-section is hexagonal, star-shaped, square, or a rectangular slot. 
     
     
         9 . The flow restrictor according to  claim 7 , wherein the polygonal cross-section is adapted to receive a complementary shaped head of a rotary drive 
     
     
         10 . The flow restrictor according to  claim 5 , wherein the downstream fluid egress passage has a similar diameter to the upstream end of the upstream fluid receiving passage. 
     
     
         11 . The flow restrictor according to  claim 1 , wherein the coupling is a threading disposed on an external surface of the body, the threading being complementary to a threading on an internal wall of the drill rod defining the passage therethrough. 
     
     
         12 . A flow restrictor comprising a body adapted to restrict a flow of fluid through a drill rod passage, the body having an interior passage to enable fluid flow through the body and an external threading arranged to engage an internal thread disposed within the drill rod passage, said restrictor being configured in use to be disposed inboard of an end of the drill rod so as to allow connection of a drill bit to said drill rod end with a threaded stem of said drill bit engaging said internal thread of said drill rod. 
     
     
         13 . A drill rod assembly comprising a drill rod having a drill rod passage for passing a flow of fluid therethrough, and a flow restrictor disposed within the drill rod passage and comprising a body adapted to be restrict a flow of fluid through the drill rod passage. 
     
     
         14 . A drill rod assembly according to  claim 13 , wherein the flow restrictor is disposed inboard of an end of the drill rod and the drill rod includes a coupling at said drill rod end to engage with drill bit to connect the drill bit to said drill rod. 
     
     
         15 . A drill bit arrangement having a shank adapted to be closely engaged by a drill rod, said drill bit having at least one internal passage therein capable of communicating with a drill rod passage of said drill rod to receive a flow of fluid therefrom, said drill bit further comprising a flow restrictor comprising a body adapted to restrict a flow of fluid from said drill rod passage in, or entering, the drill bit passage. 
     
     
         16 . A drill bit arrangement according to  claim 15 , wherein the flow restrictor is formed separate to the drill bit and is coupled to the drill bit. 
     
     
         17 . A drill bit arrangement according to  claim 16 , wherein the flow restrictor is disposed within the drill bit passage. 
     
     
         18 . (canceled) 
     
     
         19 . (canceled)