Patent Publication Number: US-11396778-B2

Title: Telescopic drill rod

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a continuation-in-part of U.S. application Ser. No. 16/091,382 filed Oct. 4, 2018 which is a National Stage Entry of PCT/US17/26184 filed Apr. 5, 2017 which claims priority from PPA 62/318,252 filed Apr. 5, 2016. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to drill rods for ground (soil and rock) drilling equipment, and more particularly, to drill rods comprising a number of members extendable in the manner of a telescope. The rods can be used with non-telescoping rods or with additional telescoping rods to allow ground drilling connecting a drilling rig to a drilling bit to allow for drill hole advancement. 
     2. Description of the Background 
     Mobile drill rigs are typically used for earth drilling in various geologic drilling applications. The mobile drill rig typically includes a drill mast mounted onto a truck chassis. A rotatable drill head is slideably mounted on the drill mast and can be driven up or down along the length of the erected drill mast. The drill head screws a drill string into the ground, gripping and turning the uppermost section of drill pipe of the string. 
     Drill pipe, is hollow, thin-walled, steel piping and comes in a variety of sizes, strengths, and weights but are typically within a range of from 5 to 40 feet in length. They are hollow to allow drilling fluid to be pumped through them, down the hole, and back up. 
     In practice, the drill string is extended by drilling in each drill rod sequentially and by attaching the next rod to the trailing end of the drill string, and repeating. This changeover is difficult, time consuming and sometimes dangerous. 
     It would be highly desirable to provide a drill rod that can be used for drilling a bore and also limit the number of assembly iterations required to advance the drill hole The present invention does this with a telescopically extendable drill rod that may be extended during the actual drilling operation thereby avoiding any need to assemble further sections to the drill rod in order to extend it. The present invention also allows the use of a shorter drill mast, which in turn requires fewer tooling additions and smaller and more economical equipment. Also, the shorter drill masts facilitates drilling in limited access conditions that would preclude the use of large equipment with longer drill masts. 
     One skilled in the art will understand that Kelly drilling employs “telescopically extendable” drill attachments in a loose sense. Kelly drilling is often used for oil drilling and for the production of foundation piles for buildings. In this case, the rotary drive of the drill turns a Kelly rod arrangement, which comprises several nested tubular Kelly rods of square cross-section. The rotational movement of one rod is transmitted to the adjacent Kelly rod. Kelly rod attachments can be added down the hole. Kelly drilling is good for larger holes and rocky formations but is not well-suited for “tieback” (micropile) drill rigs and other small hole drilling rigs, A tieback is a horizontal wire, rod, or helical anchor used to reinforce retaining walls for stability. With one end of the tieback secured to the wall, the other end is anchored to a micropile anchored in the earth. The tieback-pile structure resists forces that would otherwise cause the wall to lean. What is needed is a telescopically extendable drill rod more suitable for use with tieback drill rigs (alternately known as micropile drill rigs) suitable for use in a wide range of small-hole drilling applications including anchor drilling, micropiles, soil nailing, water wells and jet grouting, and other such smaller hole drilling. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a telescopic drill rod which is of the simplest possible construction but which is nevertheless able to transmit drilling pressure when in the extended position. A further object of the invention is to enable the individual members of the rod, while in the extended position, to be easily connected together and also easily disconnected using standard rotary tieback drilling equipment for installations substantially similar to those as described above. 
     The invention comprises a telescopic drill rod comprising at least two rod members disposed coaxially to one another, including an inner rod member and an outer rod member axially slidable relative to each other in a telescoping manner between an extended position and a retracted position. Both the inner rod member and outer rod member are equipped with joints at each end for connection to a drill head and/or another section of drill pipe. The joints also lock the inner and outer rod members in either the extended or retracted positions, and this is accomplished with a unique frusto-conical threaded engagement that is well-suited for transmitting pressure forces. 
     The invention makes it possible for the members of a telescopic drill rod to be coupled together in the extended position, without further aids or additional devices, in a simple, convenient manner which is particularly suitable for practical operation, in such a manner that rotational and axial drilling forces with or without drilling fluid use can be applied. 
     For a more complete understanding of the invention, its objects and advantages, refer to the remaining specification and to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof, in which: 
         FIG. 1  is a side cross-section of a telescopic drill rod  2  in its unsecured intermediate position according to an embodiment of the invention with enlarged insets of some components. 
         FIG. 2  shows the telescopic drill rod  2  secured in its fully-retracted position. 
         FIG. 3  shows the telescopic drill rod  2  secured in its fully-extended position 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is a telescopic drill rod comprising two or more rod members: at least including an inner rod member and an outer rod member axially slidable relative to each other in a telescoping configuration between an extended position and a retracted position. 
       FIG. 1  is a side cross-section of a telescopic drill rod  2  according to an embodiment of the invention shown in an intermediate (unsecured) position. The telescopic drill rod generally comprises the inner rod member  30  and outer rod member  20 , inner rod member  30  being slidably carried in telescoping manner within the outer rod member  20 . The outer rod member  20  is configured for attachment to a drill rig and the inner rod member  30  is configured for attaching a drill bit, albeit multiple drill rods  2  may be coupled together end-to-end. In either case the outer rod member  20  can be secured in a fully retracted position (shown and described below with reference to  FIG. 2 ), unsecured as shown in  FIG. 1  for free telescoping extension or retraction, or fully extended and secured in the fully extended position (shown and described below with reference to  FIG. 3 ). 
     The inner rod member  30  further comprises an elongate hollow pipe section  32  of uniform or variable cross-section d 1  extending from a flared joint  33  at one end that widens progressively along a threaded surface  37  to a raised collar  39  of diameter d 2  at the upper end or top of the drill rod  2 . Inner rod member  30  extends to an opposing lower flared joint  34  at the other end terminating at a raised collar  35  of diameter d 2 . Pipe section  32  preferably has a uniform cross-section along its length symmetric about a central axis, and subject to that constraint may be cylindrical, hexagonal, octagonal or otherwise. 
     As seen in the enlarged right inset to  FIG. 1  lower flared joint  34  comprises a pronounced bulbous tip of larger cross-section than d 1  and flared gradually along a frusto-conical threaded surface  38  expanding outward and distally to a raised medial collar  35  of diameter d 2 , and continuing to a bulbous distal socket  40 . In the preferred embodiment threaded surface  38  is left-hand screw-threaded along its length. The frusto-conical shape provides a wedging effect. The collar  35  is of slightly greater diameter d 2  than the largest threads of surface  38  and presents a smooth flat surface to serve as a bushing for slidable engagement with the inner surface of outer rod member  20 . The smallest threads of surface  38  are of slightly greater width/diameter d 1  than the hollow pipe section  32 . The inner rod member  30  has a hollow center channel that extends continuously through the entire inner rod member  30  and maintains a uniform cross-section through a majority of its length to approximately the socket  40  of lower flared joint  34 . At that point it expands into a receptacle within socket  40  that is shaped, dimensioned and threaded for screw-insertion of a conventional drill head (not shown) or, alternatively, for screw-insertion of another drill rod  2 . A length of larger pipe section  43  is carried on the lower flared joint  34  for telescoping engagement with the outer rod member  20 . 
     The outer rod member  20  further comprises an elongate hollow pipe section  22  of uniform or variable cross-section with an internal diameter d 2  extending from a cap  24  at one end to a double-female joint  26  that is compression and/or screw-threaded into the end of pipe section  22 . Pipe section  22  preferably has a uniform cross-section along its length symmetric about a central axis, and subject to that constraint may be cylindrical, hexagonal, octagonal or otherwise. 
     As seen in the enlarged center inset to  FIG. 1  double-female joint  26  is compression fit and/or screw-threaded into the end of pipe section  22 , and remains attached thereto, and slidably engages pipe section  43 . In the illustrated embodiment double-female joint  26  is a hollow tubular cylindrical section having a two-tier exterior dimension for flush insertion into the pipe section  22 . The interior of the double-female joint  26  is a double-conical frustum constricted mid-length, and flared and threaded outward on both sides. The top end receptacle of double-female joint  26  is shaped, dimensioned and threaded to conform to the frusto-conical threaded surface  37  of upper flared joint  33  for screw-insertion therein. The bottom end receptacle of double-female joint  26  is shaped, dimensioned and threaded to conform to the frusto-conical threaded surface  38  of lower flared joint  33  for screw-insertion therein. The mid-point presents a cylindrical lip having a diameter slightly more than d 1 . Once more, tapered-conical or non-tapered threads may be used. 
     One skilled in the art will understand that non-tapered threads are suitable, in which case the double-female joint  26  is of substantially uniform internal cross-section with non-tapered threads. The double-female joint  26  may optionally be internally grooved mid-length for holding a rubberized rod wiper, e.g., an O-ring or other such wiping device or mechanism, captive therein where wiping might be of advantage to the drilling. A rod wiper squeegees the inner pipe section  32  clean as is slides through. 
     As seen in the enlarged left inset to  FIG. 1 , cap  24  is compression fit and/or screw-threaded onto the end of pipe section  22 , remains attached thereto, and presents an internal flange  31  that constrains telescoping of the inner rod member  30 . The distal top end of cap  24  comprises a threaded male coupling  38  that is shaped, dimensioned and threaded exactly like a conventional drill head coupling (not shown) or, alternatively, for screw-insertion into the distal socket  40  of another drill rod  2 . 
     The length of outer rod member  20  is L 1 , and inner rod member  30  is L 2 , giving a sum component length of L 1 +L 2 . However, it should now be apparent that the invention makes it possible for the inner and outer members  30 ,  20  of the telescopic drill rod  2  to be securely coupled together in the retracted and/or extended position by screw-insertion, without aid from further devices, in a simple, convenient manner. The present configuration optimizes both extension and retraction without compromising strength and security when locked in either the fully extended or fully retracted position. 
       FIG. 2  shows the telescopic drill rod  2  in its fully-retracted position with the threaded surface  38  on the lower-flared joint  34  of inner rod member  30  screw-inserted into the lower receptacle of the double female joint  26  of outer rod member  20 . In this position the total length L 3  is greater than L 1  by about the length of cap  24 . 
       FIG. 3  shows the telescopic drill rod  2  in its fully-extended position with the threaded surface  37  on the upper-flared joint  33  of inner rod member  30  screw-inserted into the upper female receptacle of the double-female joint  26  of outer rod member  20 . In this position L 4  is slightly less than L 1 +L 2  by a bit more than the length of the double female joint  26 . 
     In the above-described embodiment both the leftside (upper) receptacle of double-female joint  26  and the threaded surface  37  are left-hand screw-threaded such that clockwise rotation of outer rod  20  relative to inner rod  30  turns the lower flared-joint  34  and drill bit clockwise. During assembly this tightens the threaded surface  37  into the upper receptacle of double female joint  26  to lock the inner rod  30  in its extended position relative to outer rod  20  (see  FIG. 3 ). The threaded surface  37  of the upper-flared joint  33  of inner rod member  30  continues screw-insertion into the upper (left) receptacle of double female joint  26  until the raised collar  39  of diameter d 2  at the upper (left) of inner rod  30  locks flush against the upper receptacle of double female joint  26 . Afterward, clockwise drilling applied from a drill rig to cap  24  and outer rod  20  will only tighten the threaded surface  37  into the upper receptacle of double-female joint  26 , securing the connection rather than unscrewing it. Were these threads not left handed, the inner rod  30  and outer rod  20  would come unthreaded as soon as one encountered any drilling resistance. All other threaded surfaces including that of the lower receptacle of the double female joint  26  and  38  of lower flared-joint  34  are right-handed. The collar  39  resists the axial force of threads  37  resulting in a compressive preload to the entire upper-flared joint  33  of inner rod member  30 , which substantially strengthens the upper-flared joint  33 . This is important because as the telescopic drill rod  2  drills down into the ground in its fully-extended position outer rod  20  pushes down in the inner rod  30  which exerts substantial axial and rotational force upon the mating threads  37 ,  26 . However, the compression of rods  20 ,  30  pulls the upper-flared joint  33  out of the upper receptacle of double female joint  26 . The axial tension from drilling offsets the compressive preload of collar  39  which strengthens the upper joint and increases useful life. 
     Alternately, one skilled in the art will understand that the invention may be adapted for unconventional counterclockwise drilling. In this case both the leftside (upper) receptacle of double-female joint  26  and the threaded surface  37  are right-hand screw-threaded such that clockwise rotation of outer rod  20  relative to inner rod  30  screws the threaded surface  37  into the upper receptacle of double female joint  26  to lock the inner rod  30  in its extended position relative to outer rod  20  (see  FIG. 3 ). Afterward, counter-clockwise drilling applied from a drill rig to cap  24  and outer rod  20  will only tighten the threaded surface  37  into the upper receptacle of double-female joint  26 , securing the connection rather than unscrewing it. All other threaded surfaces including that of the lower receptacle of the double female joint  26  and  38  of lower flared-joint  34  are left-handed. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth in the appended claims.