Patent Grant
8122979
The present invention relates in general to earth boring bits, and in particular to offset rock bits for use in horizontal directional drilling for installing underground utilities.
Horizontal Directional Drilling (“HDD”) continues to grow as a construction alternative to open trenching for installation of conduit and pipelines for underground utilities. One discipline of the HDD industry is the delivery of fiber optic and high speed telecommunication transmission lines to homes and businesses, which is commonly called “Fiber to the Home” (“FTTH”) or “Fiber to the Premises” (“FTTP”). With a majority of the primary fiber lines installed connecting major population areas across the United States, there is now a push to install optical fiber from local distribution hubs to each home. HDD is playing a large role in installing fiber to homes or businesses with as little disruption as possible to streets, sidewalks, driveways and landscapes. One aspect of this type of drilling is hole size. In most other HDD projects, an initial hole or “pilot hole” is made and a reamer or “hole opener” is pulled back and forth through the hole until an adequate size is achieved to allow passage of a selected size pipe or conduit. For FTTP projects the pilot hole is typically of adequate size for receiving one inch diameter conduit for passing a fiber line to an individual home or small premises. These bores are usually short and shallow and drilled with a small HDD rig, with FTTP boring contractors often making a number of these bores a day.
FTTP contractors who use rock bits to drill these short bores consider speed as being critical to profitability. Upon completing the pilot hole for an FTTP project, the end of a drilling tool string will exit the terminal end of the borehole and be pushed outward to expose a drill bit. The drill bit is then often removed and a separate device is secured to the end of the tool string to which a fiber conduit is connected for pulling back through the borehole with the tool string. Removal of the drill bit and installation of a pull back device is time consuming, and repeated removal and installation of the drill bit provides opportunity for damage to threaded connections and seals. Some HDD paddle bits have included a hole in the end of the paddle bits for attaching a shackle to connect pull back attachments for the conduit. Some offset rock bits have had a removable cutting tooth insert replaced by a tooth-like insert having an eye for attaching a shackle. However, these pull back attachment solutions result in securing pull back attachment devices to the drill string at points which are offset from a central longitudinal axis of the drill string, resulting in fiber conduit cutting into the wall of the borehole and becoming stuck during pull back.
An offset rock bit with a pull back adapter for use in horizontal directional drilling is disclosed. The offset rock bit is connected in a drill string having a longitudinal axis which is centrally disposed with the offset rock bit and the drill string. A cutting face provides a forward portion of the offset rock bit. A connection member is provided on a rearward portion of the offset rock bit for securing to other portions of the drill string. A heel extends from an intermediate portion of the offset rock bit. A steering face is defined to extend intermediate the cutting face and the heel at an acute angle to the longitudinal axis. The cutting face and the heel are spaced apart along the longitudinal axis, offset on opposite sides of the longitudinal axis. A shoe is provided by a recess formed into the steering face, with an enlarged forward portion located adjacent the cutting face and tapering to a narrow rearward portion located adjacent to the heel, with the shoe preferably being centrally disposed within the steering face. A slot is formed into the shoe, centrally disposed with the shoe and the steering face, and extending in a general direction of the longitudinal axis. A bolt hole is formed into the offset rock bit adjacent the heel and spaced apart from the steering face, and passes through the slot in a direction which is perpendicular to the longitudinal axis. A pull back adapter has a rearward portion for fitting within the slot, a first aperture extending through a first end thereof for aligning in registration with the bolt hole and adjacent the shoe, and a second aperture defining a pull back eye disposed on an opposite end of the pull back adapter from the first aperture. The pull back eye is adapted for receiving a shackle, such that when the pull back adapter is fully inserted into the slot the first aperture is disposed in registration with the bolt hole and the second aperture defining the pull back eye is disposed along the longitudinal axis.
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which
A slot 66 extends into the steering face 30 of the offset rock bit 12 for receiving the pull back adapter 50. The slot 66 preferably has a rearward end 74 which is perpendicular to the longitudinal axis 20 and an inward side 76 which is parallel to the longitudinal axis 20. The inward side 76 of the slot 66 is spaced apart from and disposed outward of the longitudinal axis 20. An outward side and a forward end of the slot 66 are open for receiving the pull back adapter 50 into the installed position shown in
A pull back adapter 50 is formed from a flat piece of steel having a rearward portion 51 for fitting in the slot 66, and a forward portion 53 which extends at an angle to the forward portion for aligning with the longitudinal axis 20. Wherein a centerline of said forward portion 53 extends at an angle of approximately one hundred and fifty degrees to a centerline of said rearward portion 51 and said longitudinal axis 20. A first aperture 64 extends into the rearward portion for aligning in registration with the bolt hole 46 for passing a bolt 48 to secure the pull back adapter into the forward end of the offset drill bit 12 when the pull back adapter 50 is fully inserted into the slot 66. A second aperture extends into the forward portion to define a pull back eye 52, which is adapted for receiving a shackle to connect a conduit for pulling back a conduit through a borehole formed using the offset drill bit 12. The pull back adapter 50 has an outer edge 54 defining a surface which, when the pull back adapter 50 is fully inserted into the slot 66, is located directly adjacent to the side of the periphery 24 of the offset rock bit 12. The pull back adapter 50 also has a sloped forward surface 56 to prevent the pull back adapter 50 from hanging up on the borehole when being pulled back through the borehole for retrieval of the tool string 10. An edge 58 extends opposite the outer edge 54 of the pull adapter 50 to an inwardly sloped surface 60. Pull back eye 52 has a centerline 62 which, when the pull back adapter 50 is fully inserted into the slot 66, preferably intersects the longitudinal axis 20 with the centerline 62 perpendicular to the longitudinal axis 20.
When the pull back adapter 50 is fully inserted within the slot 66, preferably the edge 58 is located adjacent to and flush with the inward side 76 of the slot 66 and the sloped surface 60 is located adjacent to and flush with the sloped surface 70 of the shoe 30. A rearward end 72 of the pull back adapter 50 is provided for butting up against and engaging an edge 74 of the slot 66. With the pull back adapter 12 installed and the bolt 48 secured through holes 46 and 64, the rear side 72 of the pull-back adapter 12, the bottom side 58 of the pull-back adapter 12, and the sloped surface 60 are positioned flush against the end 74 and inward side 76 of the slot 66, and the sloped surface 70 of the shoe 30 such that the pull back adapter 12 will not pivot on the bolt and the centerline 62 of the pull back eye 62 will remain in longitudinal alignment with the longitudinal axis 20 to remain in the “centered” position. That is, if a pullback line secured to the pull back adapter 50 becomes “slack” with the heel 44 of the offset rock bit 12 resting on the bottom of a borehole and the cutting face 26 at the 12 o'clock position in the borehole, the pull-back adapter 12 will not pivot on the bolt 48 and will remain in a centered position with the pull back eye 52 aligned with the longitudinal axis 20.
In operation, the tool string 10 with the offset rock bit 12 is used in normal fashion for horizontal direction drilling, such as for installing fiber to a premises. Once a borehole is drilled, the offset rock bit 12 is pushed out of the hole to expose the bolt 48 and the shoe 30. The bolt 48 is removed from the hole 46, and the slot 66 is cleaned to allow insertion of the pull back adapter 50. Then, the pull back adapter 50 is fully inserted into the slot 66 until the first aperture 64 aligns in registration with the bolt holes 46. The bolt hole 48 is inserted through the bolt holes 46 and the first aperture 64, and threadingly secured to at least one of the bolt holes 48 and the first aperture 64 to secure the pull back adapter 50 into the forward end of the offset rock bit 12. Then, the eye 52 of the pull back adapter 50 is used to secure a shackle for pulling back conduit, tubing, fiber conductors, or the like, through the borehole when the tool string 10 is retrieved with the offset rock bit 12. Preferably, the center line 62 of the pull back eye 52 is aligned with and perpendicular to the longitudinal axis 20 of the tool string 10 to center the pull back eye 52 in a central region of the earthen borehole and thereby prevent the conduit, or the like, being pulled back from pressing into a sidewall of the borehole and becoming hung. Centering the pull back eye 52 and the pull back conduit also reduces the forces required to be overcome to pull the drill string 10 and the attached conduit back through the borehole.
The present invention provides advantages of an offset rock bit with a pull back eye centrally located aligned with a centrally disposed longitudinal axis of the bit and a borehole in which the bit is used. The offset rock bit is first used without the pull back eye. When the offset rock bit is at the terminal end of the borehole at a ground surface, the pull back eye is inserted into and bolted to the bit for attaching conduit for pulling back through the borehole with the offset rock bit and the drill string. Locating the pull back eye concentric with a centrally disposed longitudinal axis of the drill string and the bit aids in preventing the conduit from hanging up on the borehole wall during pull back.
Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
The present application is related to and claims priority to U.S. Provisional Patent Application Ser. No. 61/139,269, filed Dec. 19, 2008, entitled “Earth Boring Bit With Pull Back Coupling,” and invented by Ronald (Riff) F. Wright, Jr.
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| Number | Date | Country | |
|---|---|---|---|
| 61139269 | Dec 2008 | US |
