Starter rod for use in back reaming

Abstract

An improved starter rod connects a back reamer to the distal end of a drill string. The starter rod is an elongated body having a front end portion which has a first connecting portion configured for connecting the starter rod to the back reamer, a rear end portion having a second connecting portion configured for connecting the starter rod to the drill string, a fluid passage configured for conveying fluid from the drill string through the starter rod from the rear end to the front end, and a branch passage extending from the fluid passage to a side surface of the starter rod configured to pass part of the fluid in the fluid passage outside the starter rod. Generally, the front end portion of the starter rod is also used to connect to a drill head and thus has an outer diameter greater than the rear end which connects to the drill string. In a preferred embodiment, the branch passage opens rearwardly of the large diameter front end portion so that the lubricating fluid is injected in the hole ahead of it. The lubricant provided ahead of the large diameter portion of the starter rod reduces wear and the chance of breakage at this location during back reaming.

1 . A starter rod for connecting a back reamer to the distal end of a drill string, comprising an elongated body having: 
 a front end portion having a first connecting portion configured for connecting the starter rod to a back reamer;    a rear end portion having a second connecting portion configured for connecting the starter rod to a drill string;    a fluid passage configured for conveying fluid from the drill string through the starter rod from the rear end to the front end;    a branch passage extending from the fluid passage to a side surface of the starter rod configured to pass part of the fluid in the fluid passage outside the starter rod.    
     
     
         2 . The starter rod of  claim 1 , wherein the front end portion has an outer diameter greater than the outer diameter of the rear end portion.  
     
     
         3 . The starter rod of  claim 2 , wherein the branch passage opens rearwardly of the front end portion.  
     
     
         4 . The starter rod of  claim 3 , wherein the branch passage opens on a midportion of the starter rod that spans the front and rear end portions.  
     
     
         5 . The starter rod of  claim 4 , wherein the branch passage opens on a rearwardly tapering shoulder of the midportion of the starter rod.  
     
     
         6 . The starter rod of  claim 1 , further comprising a removable plug that fits into the branch passage.  
     
     
         7 . The starter rod of  claim 6 , wherein the plug is solid and blocks the flow of fluid through the branch passage.  
     
     
         8 . The starter rod of  claim 6 , wherein the plug comprises a nozzle having a hole therethough through which the fluid passes.  
     
     
         9 . The starter rod of  claim 1 , further comprising: 
 a first removable plug that fits into the branch passage, which plug is solid and blocks the flow of fluid through the branch passage; and    a second removable plug that fits into the branch passage, which plug comprises a nozzle having a hole therethough through which the fluid passes, wherein the first and second plugs are interchangeable.    
     
     
         10 . The starter rod of  claim 1 , wherein the branch passage is angled away from the front end of the starter rod so that it ejects fluid towards the rear end of the starter rod.  
     
     
         11 . A method for back reaming using a back reamer mounted on a drill string driven by a directional boring machine, wherein the back reamer is connected to the drill string by a starter rod, the starter rod including an elongated body having a front end portion having a first connecting portion configured for connecting the starter rod to the back reamer, a rear end portion having a second connecting portion configured for connecting the starter rod to the drill string, a fluid passage configured for conveying fluid from the drill string through the starter rod from the rear end to the front end, and a branch passage extending from the fluid passage to a side surface of the starter rod configured to pass part of the fluid in the fluid passage outside the starter rod, comprising the steps of: 
 connecting the back reamer to the front end portion of the starter rod and connecting the drill string to the rear end portion of the starter rod; and    pulling the back reamer through an existing hole through which the drill string extends while rotating the back reamer with the drill string and injecting a fluid through the drill string so that fluid is ejected through the branch passage and lubricates the outer surface of the starter rod.    
     
     
         12 . The method of  claim 11 , further comprising ejecting about 5 to 50 percent of the drill fluid entering the starter rod through the drill string through the branch passage.  
     
     
         13 . The method of  claim 11 , further comprising installing a nozzle in the branch passage, which nozzle has a hole therethrough which regulates the amount of fluid ejected from the branch passage.  
     
     
         14 . The method of  claim 11 , further comprising installing a solid plug in the branch passage prior to using the starter rod for forward drilling.