Abstract:
A drill string with a bit at one end is used to dig an underground borehole. When the drill string exits the borehole at a surface exit point, a pullback adapter is used to interconnect the bit with an above-ground utility line. A drilling rig retracts the drill string from the borehole. As the drill string is pulled back through the borehole, the trailing utility line follows along its underground path. As the utility line is pulled through the borehole, the connector biases the utility line to the center of the borehole. Such biasing reduces the risk of ensnaring of the connector and utility line by the borehole walls during the pulling process.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/281,399 tiled on Jan. 21, 2016, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The invention relates to tools and methods for pulling a utility line through a borehole. 
       SUMMARY 
       [0003]    An assembly is formed from a bit and a connector. The bit has a body and a plurality of hardened cutting elements supported on the body. The body has an internal passage extending therethrough. The connector extends through the passage. The connector is formed from a first member and a second member. The first member has an elongate neck and an enlarged head formed at one end of the neck. The second member is pivotally connected to the neck. 
         [0004]    A kit is formed from a bit, a first connector element, and a second connector element. The bit has a body and a plurality of hardened cutting elements supported on the body. The body has an internal passage extending therethrough. The first connector element has an elongate neck and an enlarged head formed at one end of the neck. The elongate neck is sized to be closely received within the passage, The second connector element is configured for pivotal connection to the neck. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of a pullback adapter formed from a shackle pivotally connected to a connector member. 
           [0006]      FIG. 2  is a side elevation view of the connector member of  FIG. 1 . 
           [0007]      FIG. 3  is a perspective view of the connector member of  FIG. 1 . 
           [0008]      FIG. 4  is a perspective view of a bit. 
           [0009]      FIG. 5  is an exploded view of a pullback assembly formed from the pullback adapter of  FIG. 1  attached to the bit of  FIG. 4 . 
           [0010]      FIG. 6  is a perspective view of the pullback assembly of  FIG. 5  in which an upper side of the bit is shown. 
           [0011]      FIG. 7  is a perspective view of the pullback assembly of  FIG. 5  in which a lower side of the bit is shown. 
           [0012]      FIG. 8  is a side elevation view of the pullback assembly with an alternate bit. 
           [0013]      FIG. 9  is a side elevation view of a beacon connected to the pullback assembly of  FIG. 8 . 
           [0014]      FIG. 10  is a perspective view of the beacon and assembly of  FIG. 9 . 
           [0015]      FIG. 11  is a front elevation view of the pullback assembly of  FIG. 5 . 
           [0016]      FIG. 12  is a system for pulling a utility line through a borehole using the pullback adapter, bit, and beacon shown in  FIG. 9 . 
           [0017]      FIG. 13  is an enlarged view of a portion of the system of  FIG. 12 , showing the connection between the utility line and the pullback adapter. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Shown in  FIG. 12  is a system  10  for pulling a utility line  12  through a borehole  14 . The system  10  comprises a drilling rig  16 , a drill string  18 , a beacon  20 , a bit  22 , a pullback adapter  24 , and the utility line  12 . The utility line  12  may be a pipe, a cable, or any structure suitable for pulling through a borehole. Prior to installation, the utility line  12  may be stored on a spool  26 . 
         [0019]    The drill string  18  begins drilling the borehole  14  at a surface entrance point  28  and follows a path underground to a surface exit point  30 . At the exit point  30  the pullback adapter  24  is connected to the bit  22  and the utility line  12 . The drilling rig  16  pulls the drill string  18  back through the borehole  14 . Since the pullback adapter  24  connects the utility line  12  to the drill string  18 , the utility line  12  is pulled through the borehole  14  as the drill string  18  is retracted by the drilling rig  16 . 
         [0020]    With reference to  FIGS. 1-3 , the pullback adapter  24  comprises a first connector member  32 . The first connector member  32  is formed from a strong and durable material, such as steel. The first connector member  32  has an elongate neck  34  and an enlarged head  36 . 
         [0021]    The elongate neck  34  has opposed first and second ends  38 ,  40 . A passage  42  is formed in the first end  38  of the elongate neck  34  opposite the enlarged head  36 . The first end  38  of the elongate neck  34  may terminate in a free end  44  that is curved, as shown in  FIGS. 1-3 . In another embodiment, the elongate neck  34  may terminate in a free end  44  having a planar surface. In the embodiment of  FIGS. 1-3 , the elongate neck  34  has the shape of a rectangular prism. However, in another embodiment the elongate neck  34  may have the shape of prism formed from a non-rectangular polygonal base, such as a triagonal prism, a pentagonal prism, or a hexagonal prism. In yet another embodiment, the elongate neck  34  may have the shape of a cylinder or a shape formed from a partial cylindrical base, such as a semicylinder. 
         [0022]    The enlarged head  36  is formed at the second end  40  of the elongate neck  34 . The enlarged head  36  has at least one flanged portion projecting radially outward from the elongate neck  34 . At the flanged portion, the enlarged head  36  has a width larger than the width of the elongate neck  34 . In the embodiment of  FIGS. 1-3 , the enlarged head  36  has a top surface  46  having the shape of a convex curve. However, the top surface  46  of the enlarged head  36  may have a shape that is flat or concave. 
         [0023]    The pullback adapter  24  further comprises a second connector member attached to the first connector member  32 . The second connector member is formed from a strong and durable material, such as steel. The second connector member may attach to the first connector member  32  through the passage  42  formed in the first end  38  of the first connector member  32 . Preferably, the second connecter member is pivotally connected to the first connector member 
         [0024]    As shown in  FIGS. 1 and 5 , the second connector member is a shackle  50  comprising a link  52  and a bolt  54 . The link  52  has two arms  56  each having an opening  58 . Preferably, the arms  56  are internally threaded within the openings  58 . 
         [0025]    Continuing with  FIGS. 1 and 5 , the bolt  54  has a shaft  60  and a head  62 . The shaft  60  is sized to be received within the openings  58  of the arms  56 . Preferably, the shaft  60  has a threaded portion  64  complementary to the arms&#39; internal threads so that the bolt  54  may be threaded onto the link  52 . Also preferably, the head  62  has a plurality of flat gripping surfaces  66  to facilitate threading the bolt  54  onto the link  52 . The gripping surfaces  66  facilitate threading by providing purchase for a hand or tool that will rotate the bolt  54 . The shackle  50  is assembled by passing the bolt  54  through the openings  58  of the arms  56 . The assembled shackle  50  has an aperture  68  defined by the space enclosed by the link  52  and the bolt  54 . 
         [0026]    Referring to  FIGS. 4-8 , the bit  22  is formed from a strong and durable material, such as steel. The bit  22  has an elongate body  70  having an upper side  72  and a lower side  74 . The bit  22  is characterized by a plurality of recessed areas  76  formed in the bit body  70 . The body  70  is formed from a first leg  78  and a second leg  80 . The first leg  78  has an upper surface  82 , a lower surface  84 , and a pair of tapering side surfaces  86 . Preferably, the tapering side surfaces  86  converge to a point  88  at the first leg&#39;s free end. The second leg  80  has an upper surface  90  and a lower surface  92 . 
         [0027]    The first leg  78  and the second leg  80  join at a bend  94 . The bend  94  creates a steering face so that the drilling direction can be changed. As shown in  FIGS. 7 and 8 , on the bit&#39;s lower side  74 , the first leg  78  bends away from the second leg  80 . The lower surface  84  of the first leg  78  and the lower surface  92  of the second leg  80  form an included angle θ measuring greater than 180 degrees and less than 220 degrees. Preferably, the included angle θ is 190 degrees. 
         [0028]    With reference to  FIGS. 4, 6 and 7 , a plurality of passages  96  are formed in the body  70  and extend between the bit&#39;s upper and lower sides  72 ,  74 . Preferably, the passages  96  are formed in both the first leg  78  and the second leg  80  of the bit body  70 . As best shown in  FIGS. 4 and 5 , at least one of the passages  96  is a first leg passage  98  that is sized to closely receive the elongate neck  34  of the first connector member  32 . The shape of the first leg passage  98  may be circular, or it may be complementary to the shape of the elongate neck  34 . In the embodiment of  FIG. 4 , the first leg passage  98  has an oblong shape and is sized to closely receive the elongate neck  34  characterized by the shape of a rectangular prism. 
         [0029]    Sizing the first leg passage  98  to closely receive the elongate neck  34  prevents the enlarged head  36  from entering the passage  98 . Moreover, the tight fit between the passage  98  and the neck  34  combined with the oblong shape of the passage  98  prevents rotation of the rectangular neck  34  within the passage  98 . Were the neck  34  permitted to rotate, the shackle  50  that it carries could move away from a centered position and toward the walls of the borehole  14 . The shackle  50  and the utility line  12  could become mired in the borehole walls as a result. 
         [0030]    Referring to  FIGS. 4-8 , the bit  22  further comprises a plurality of hardened cutting elements  100  supported on the body  70 . The cutting elements  100  are formed from a strong and durable material, such as diamond or carbide. Preferably, the cutting elements  100  are polycarbonate diamond compact (PDC) cutters. The cutting elements  100  may be situated in the recessed areas  76  of the bit body  70 . Preferably, the cutting elements  100  are positioned on both the first and second legs  78 ,  80  of the bit body  70 . 
         [0031]    As best shown in  FIG. 5 , a pullback assembly  102  is assembled by passing the elongate neck  34  of the first connector member  32  through the first leg passage  98  of the bit body  70 . The shackle  50  is positioned so that the openings  58  in the arms  56  overlay the passage  42  in the elongate neck  34 . The bolt  54  is passed through the openings  58  and the passage  42 . Preferably, the shackle  50  is pivotally connected to the neck  34 . Also preferably, the bolt  54  is threaded onto the link  52 . However, the bolt  54  may be attached to the link  52  using any suitable fastener, such as a nut or a pin. 
         [0032]    Shown in  FIGS. 6-8  is the assembled pullback assembly  102  comprising the pullback adapter  24  attached to the bit  22 . Preferably, the pullback adapter  24  is attached to the first leg  78  of the bit body  70 . Also preferably, the enlarged head  36  of the first connector member  32  is situated on the upper side  72  of the bit body  70 , and the shackle  50  is situated on the lower side  74  of the bit body  70 . By situating the shackle  50  on the lower side  74  of the bit body&#39;s first leg  78 , the shackle  50  is located on the side of the bit  22  that faces toward the surface exit point  30 , which is the point from which the utility line  12  is pulled. Such configuration allows the shackle  50  and the utility line  12  to be biased toward the center of the borehole  14  during the pulling process. Such centering is advantageous because a centered shackle  50  and utility line  12  are less likely to become caught or mired within the borehole walls during the pulling process. 
         [0033]    In  FIGS. 9, 10, and 12 , the pullback assembly  102  is shown attached to the beacon  20 . The beacon  20  is carried by the drill string  18  so that the position of a downhole drilling tool can be monitored and adjusted. The beacon  20  is configured to transmit a low frequency dipole magnetic field, which can be detected by an above ground tracker. A tracker operator follows above the beacon  20  and transmits steering information back to a drill rig operator. 
         [0034]    With reference to  FIGS. 6 and 9-12 , the beacon  20  has a housing  104  having an outer circumference  106  and opposed first and second ends  108 ,  110 . The beacon&#39;s first end  108  is threaded onto the drill string  18 . The beacon&#39;s second end  110  is connected to the bit body  70 . The beacon  20  may be fastened to the bit body  70  by a plurality of fasteners passing through the plurality of passages  96  formed in the bit body&#39;s second leg  80 . The bit body  70  may be positioned in oblique relationship to the longitudinal axis of the beacon  20 . 
         [0035]      FIG. 13  shows an enlarged view of the beacon  20 , pullback assembly  102 , and utility line  12  of  FIG. 12  positioned with respect to a pulling axis  112  of the drill string  18 . The pulling axis  112  is collinear with the force applied to the shackle  50  during the process of pulling the utility line  12  through the borehole  14 . An included angle a is formed between the pulling axis  112  and the second leg  80 . The bit body  70  may be positioned on the beacon  20  such that the included angle α is greater than 0 degrees and less than 25 degrees. Preferably, the included angle a is between about 8 and about 10 degrees. 
         [0036]    Continuing with  FIG. 13 , an included angle β is formed between the pulling axis  112  and the bit body&#39;s first leg  78 . The bit body  70  may be positioned so that the included angle β is greater than 0 degrees and less than 25 degrees. Preferably, the included angle is between about 18 and about 20 degrees. 
         [0037]    With reference to  FIGS. 6, 11, and 13 , the shackle  50  is situated in the borehole  14  in collinear relationship with the pulling axis  112 . The aperture  68  of the shackle  50  opens perpendicular to the pulling axis  112 . A coupler  114  may be passed through the shackle&#39;s aperture  68  in order to connect the utility line  12  to the pullback adapter  24 . The coupler  114  may be a shackle, a pulling grip, a pulling clevis, or any suitable pulling tool, such as a puller having a threaded portion configured for connection to the utility line. The coupler  114  may comprise a swivel. 
         [0038]      FIGS. 11 and 13  shows the position of the shackle  50  relative to the borehole  14  and the beacon  20 . The borehole  14  has a circumference  118  defined by the outermost reach of the bit&#39;s cutting elements  100 . Because of the position of the bit body  70  relative to the beacon  20 , the beacon&#39;s outer circumference  106  is not centered within the borehole&#39;s circumference  118 . By situating the shackle  50  on the lower side  74  of the bit body  70 , the shackle  50  is biased toward the center of the borehole  14 , even though the beacon  20  is not centered within the borehole  14 . 
         [0039]    Shown in  FIGS. 12 and 13  is the system  10  for pulling the utility line  12  through the borehole  14  in which the shackle  50  is positioned on the pulling axis  112 . The pullback adapter  24  is connected to the bit  22 , which is carried by the drill string  18 . The pullback adapter  24  is also connected to the utility tine  12 . As the drill string  18  is retracted, the utility line  12  is pulled through the borehole  14 . Since the shackle  50  is centered on the pulling axis  112 , the attached utility tine  12  is also biased to the pulling axis  112 . 
         [0040]    Changes may be made in the construction, operation and arrangement of the various parts, elements, steps and procedures described herein without departing from the spirit and scope of the invention as described in the following claims.