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BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This technology relates to oil and gas wells, and in particular to pipe connectors within the wells. 
         [0003]    2. Brief Description of Related Art 
         [0004]    Typical oil and gas wells include strings of pipe that extend into the well in conjunction with drilling, casing, and production operations. These strings of pipe generally consist of discrete pipe segments that are joined together by pipe connectors as the pipe is run into the well. The pipe connectors may be threaded, with adjacent connectors having male and female threads configured to engage and join the pipe. Generally, the pipe end having the male thread is known as the pin, and the pipe end having the female thread is known as the box. When joining the pipe segments, it is desirable to limit circumferential movement between the connectors so that the connectors remain firmly attached. To limit such circumferential movement, a lock key may be employed. 
         [0005]    Some known lock keys require corresponding grooves in the pin and the box that align when the pin and the box are threaded together. The key is then inserted into the aligned grooves to prevent relative circumferential movement between the pin and the box. However, many pipe connectors that are threaded together cannot be repeatedly assembled to the same relative angle to each other due to manufacturing variations in the thread, as well as changes to the thread of connectors previously used under load. This is because the pipe connectors must be fully torqued to ensure that the joint properly seals, regardless of the relative positions of the locking grooves on the pin and box. 
         [0006]    Additionally, some threaded connectors have small overall wall thickness (e.g., subsea drill pipe and casing), thereby requiring a key that is low profile. Furthermore, under some circumstances there is not enough space surrounding the pipe connectors to incorporate large external mechanisms to drive locking pins or keys into place, as required for many types of locking keys. 
       SUMMARY OF THE INVENTION 
       [0007]    Disclosed herein is a system for locking adjacent pipe connectors. In an example, the system includes a first pipe connector, or box, a second pipe connector, or pin, and a locking key. The first and second pipe connectors have male and female connecting ends, and are configured to thread together. Either the first pipe connector or the second pipe connector has a recess in its connecting end, and the locking key is inserted into the recess to prevent further relative circumferential movement between the first and second pipe connectors. 
         [0008]    In this example, the key includes inner and outer surfaces. When the key is inserted into the recess, the inner surface is positioned radially inward, and the outer surface is positioned radially outward relative to the pipe connectors. The key also includes upper and lower surfaces. The upper surface and the lower surface extend from the inner surface to the outer surface. The key also includes locking protrusions positioned on at least the lower surface. In some embodiments, these locking protrusions are ridges that are pressed into, and become embedded in the first or second pipe connectors when the key is inserted into the recess. In other embodiments, some of the locking protrusions may be splines that correspond to notches or grooves in the first or second pipe connectors and are received by the notches when the key is inserted. In either instance, the locking protrusions prevent relative circumferential movement of the pipe connectors. 
         [0009]    Also disclosed herein is a method of locking adjacent threaded pipe connectors to prevent relative rotational movement between the pipe connectors. The pipe connectors have threaded male and female connecting ends. In addition, the end of one of the pipe connectors has a recess. According to the method, the pipe connectors are first threaded together. Then, a key is radially inserted into the recess. The key has locking protrusions, as described above, to prevent relative circumferential movement of the pipe connectors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present technology will be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawings, in which: 
           [0011]      FIG. 1  is a perspective view of a pipe connector locking system having a key according to an example embodiment of the present technology; 
           [0012]      FIG. 2A  is an enlarged sectional view of a portion of the connector locking system of  FIG. 1 , with a key disengaged from pipe connectors; 
           [0013]      FIG. 2B  is an enlarged sectional view of a portion of the connector locking system of  FIG. 1 , with a key inserted between pipe connectors; 
           [0014]      FIG. 2C  is an enlarged sectional side view of a portion of the connector locking system of  FIG. 1 , with a key disengaged from pipe connectors; 
           [0015]      FIG. 2D  is a perspective view of the key according to one embodiment of the present technology; 
           [0016]      FIG. 3A  is an enlarged sectional view of a portion of the connector locking system according to another embodiment of the present technology, with the key disengaged from the pipe connectors; 
           [0017]      FIG. 3B  is an enlarged sectional view of a portion of the connector locking system of  FIG. 3A , with the key inserted between the pipe connectors; 
           [0018]      FIG. 3C  is a perspective view of a key according to an alternate embodiment of the present technology. 
           [0019]      FIG. 4A  is an enlarged exploded sectional view of a portion of an alternate embodiment of the connector locking system according to an embodiment of the present technology; 
           [0020]      FIG. 4B  is an enlarged side view of a portion of the connector locking system of  FIG. 4A , with the key inserted between the pipe connectors; 
           [0021]      FIG. 4C  is an outer perspective view of a key according to an embodiment of the present technology; and 
           [0022]      FIG. 4D  is an inner perspective view of the key of  FIG. 4C . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    The foregoing aspects, features, and advantages of the present technology will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein like reference numerals represent like elements. In describing the preferred embodiments of the technology illustrated in the appended drawings, specific terminology will be used for the sake of clarity. However, the technology is not intended to be limited to the specific terms used, and it is to be understood that each specific term includes equivalents that operate in a similar manner to accomplish a similar purpose. 
         [0024]      FIG. 1  is a perspective view of one example of a pipe connector locking system  10  according to the present technology, including a first pipe connector  12 , a second pipe connector  14 , and a key  16 . The first and second pipe connectors  12 ,  14  are configured to engage one another and become attached. For example, the first pipe connector  12  may be a male pipe connector, or pin, having external threads (not shown), and the second pipe connector  14  may be a female pipe connector, or box, having internal threads (not shown). In such an embodiment, the first pipe connector  12  may engage the second pipe connector  14  by connecting the threaded end of the first pipe connector  12  with the threaded end of the second pipe connector  14 , and rotating the pipe connectors  12 ,  14  relative to one another until the threads are engaged. With the threads engaged, and the pipe connectors  12 ,  14  attached, the key  16  may be inserted between the first and second pipe connectors  12 ,  14  to limit or substantially prevent relative circumferential movement between the pipe connectors  12 ,  14 . In this embodiment, the key  16  may include a material that is harder than the material of first and second pipe connectors  12 ,  14 . 
         [0025]    The structure and function of the key  16  is shown in detail in  FIGS. 2A-2D . For example, the key  16  has an inner surface  18  (best shown in  FIGS. 2C and 2D ), and an outer surface  20 . The inner surface  18  may be configured so that, upon insertion between the first and second pipe connectors  12 ,  14 , it is positioned radially inward from the outer surface  20 . The key  16  also has an upper surface  22  and a lower surface  24  (best shown in  FIGS. 2C and 2D ). In some embodiments, the upper surface  22  may be tapered axially upward relative to the pipe connectors  12 ,  14  from the inner surface  18  to the outer surface  20 . Similarly, the lower surface  24  may be tapered axially downward relative to the pipe connectors  12 ,  14 . Thus, the thickness the distance between upper and lower surfaces  22 ,  24 ) increases with distance from the inner surface  18 . In the embodiment of  FIGS. 2A-2D , the key  16  include locking ridges  26  protruding therefrom and extending radially from the inner surface  18  to the outer surface  20  of the key  16 . Locking ridges  26  each have a generally triangular cross-section with opposing lateral sides that depend towards one another and join a distance from the main body to form a peak. In an example, the key  16  is an elongate member and is set lengthwise along a portion of a circumference of an interface between the first and second connectors  12 ,  14 . 
         [0026]      FIGS. 2A and 2C  further show a recess  28  in the first pipe connector  12 . The recess  28  has outer edges  46 . Although the recess  28  is shown in the first pipe connector  12 , it may alternately be located in the second pipe connector  14 . As best shown in  FIG. 2C , the height of the recess  28  is greater than or equal to the height of the inner surface  18  of the key  16 , but smaller than the height of the outer surface  20  of the key  16 . Thus, when the key  16  is inserted into the recess, the inner surface  18  of the key  16  initially enters the recess, but the locking ridges  26  on the tapered upper and lower surfaces  22 ,  24  of the key  16  contact the edge  46  of the recess  28  and the outer surface of the adjacent pipe connector, and resist further entry of the key  16  into the recess  28 . The position of the recess  28  entirely in one pipe connector is advantageous because it allows use of the key  16  regardless of the relative circumferential positions of the pipe connectors when they are fully joined, thereby allowing for clocking independence. 
         [0027]    To complete insertion of the key  16  into the recess  28 , an external force may be applied to the outer surface  20  of the key  16 . For example, the key  16  may be pressed into the recess  28  using a press tool, or hammered in with hand tools. Because the material of the key  16  is harder than the material of the first and second pipe connectors  12 ,  14 , the locking ridges  26  become embedded in the first and second pipe connectors  12 ,  14  as the key  16  is driven into the recess  28 . Thus, when fully inserted, the ridges  26  of the key are engaged with, and may be embedded in, the first and second pipe connectors  12 ,  14 , as shown in  FIG. 2B . Thus embedded, the locking ridges  26  prevent relative rotational movement between the first and second pipe connectors  12 ,  14 . Furthermore, the key  16  will act bi-directionally, preventing both over-tightening and un-tightening of the pipe connectors  12 ,  14 . 
         [0028]    In an alternate embodiment, a portion of the outer edge  46  of the recess  28  may have pre-cut grooves (not shown) configured to accept some of the locking ridges  26 . In such an embodiment, the number of locking ridges  26  that become embedded in the first or second pipe connectors  12 ,  14  would be reduced, thereby reducing the amount of force required to press the key  16  into the recess  28 . The key  16  may be removed using a specialty tool or hand tools, for example, by inserting a screw driver or pry bar into a notched area  42  at either end of the key  16 . The ability to insert and remove the key  16  using hand tools or other small tools is advantageous because it allows use of the key  16  in circumstances where there is little space surrounding the pipe connectors  12 ,  14 , a circumstance that tends to limit or prevent the use of large external pressing mechanisms or removal tools. 
         [0029]    Referring to  FIG. 2B , there are shown optional fasteners  30  that may be inserted into the surface of the first pipe connector  12 . The fasteners may be, for example, screws or bolts, each with threaded elongate shafts and a larger diameter head attached to an end of the shaft. The fasteners  30  are positioned so that a portion of the head of each fastener  30  overlaps a portion of the key  16 . Thus, the fasteners  30  may help to secure the key  16  radially relative to the pipe connectors  12 ,  14 , thereby preventing the key  16  from backing out due to, for example, vibrations, or torsional loads. In the embodiments shown, the fasteners are inserted into holes  32  (shown in  FIG. 2A ) in the first pipe connector  12 . Use of screws or other fasteners may be beneficial to prevent debris from entering removal notch areas  42 . In addition, the fasteners may double as anchors for attaching a press tool (for pressing the key  16  into the recess) using external bolts or screws. 
         [0030]    Optionally, the fasteners  30  may be countersunk, so that the heads of the fasteners  30  do not protrude beyond the surface of the first pipe connector  12  when the fasteners  30  are fully inserted into the holes  32 . Thus, a countersink  40  may be drilled or otherwise bored into the surface of the first pipe connector  12  and a portion of the key  16 , In certain embodiments, the heads of the fasteners  30  may be configured to accept a fastener insertion tool, such as, for example, a screwdriver, or a hexagonal alien wrench. For example, the fasteners  30  of the present technology are shown to have hexagonal sockets  34  for accepting such an alien wrench. In an embodiment where the recess  28  is in the second pipe connector  14 , the fasteners  30  may correspondingly be inserted into the second pipe connector  14 , rather than the first pipe connector  12 . In such an embodiment, the holes  32  and countersinks  40  would also be drilled into the second pipe connector  14 . Although the fasteners shown in  FIG. 2B  are bolts, any appropriate mechanism may be used to retain the key  16  radially in place relative to the first and second pipe connectors  12 ,  14 . For example, the key  16  could be retained using flexible tabs, clips, spring mechanisms, or any other appropriate mechanism. In addition, any number of fasteners or retaining mechanisms could be used, including a single fastener or retaining mechanism. 
         [0031]    Referring now to  FIGS. 3A-3C , there is shown an alternate embodiment of the present technology, including a first pipe connector  112 , a second pipe connector  114 , and a key  116 . The key  116  has an inner surface  118 , an outer surface  120 , an upper surface  122 , and a tapered lower surface  124 . The inner surface  118  may be configured so that, upon insertion between the first and second pipe connectors  112 ,  114 , it is positioned radially inward relative to outer surface  120 . Conversely, the outer surface  120  may be configured so that, upon insertion between the first and second pipe connectors  112 ,  114 , it is positioned radially outward from inner surface  110 . The lower surface  124  may be tapered axially downward relative to the pipe connectors  112 ,  114 . In addition, the key  116  includes locking ridges  126  protruding from the lower surface  124  and extending radially from the inner surface  118  to the outer surface  120 . Furthermore, in the embodiment of  FIGS. 3A-3C , the first pipe connector  112  has a recess  128  configured to at least partially accept the key  116 , and holes  132  for accepting fasteners  130 . The recess  128  has notches  136  in the upper surface thereof which may be pre-machined into the pipe connector. Notches  136  extend radially into connector  112  and have generally rectangular outer peripheries. 
         [0032]    In the embodiment of  FIGS. 3A-3C , the upper surface  122  of the key  116  has rectangular splines  138  with rectangular outer peripheries that extend transverse to the elongate side of the key  116 , so that when the key  116  is inserted into the recess  128 , the rectangular splines  138  are received by the notches  136 . The locking ridges  126  of the bottom surface  124  contact, and become embedded into, the second pipe connector  114  when the key  116  is pressed into the recess  128 , as described above. A fully inserted key  116 , according to this embodiment, is shown in  FIG. 3B . Thus configured, with the key  116  fully inserted, the first and second pipe connectors  112 ,  114  are restrained from rotating relative to one another. One advantage of the key  116 , is that it will act bi-directionally, preventing both over-tightening and un-tightening of the pipe connectors  112 ,  114 , The key  116  may be removed using a specialty tool or hand tools, for example, by inserting a screw driver or pry bar into a notched area  142  at either end of the key  116 . 
         [0033]    It is to be understood that variations of the embodiment shown in  FIGS. 3A-3C  are also contemplated. For example, the recess  128  could be in the second pipe connector  114  instead of the first pipe connector  112 , as shown. Alternately, the rectangular splines  138  could be positioned on the bottom surface  124  of the key, and the locking ridges  126  on the top surface  122 . In such an embodiment, the notches  136  of the recess  128  would be cut into the portion of the second pipe connector  114  adjacent to the recess  128 . 
         [0034]    Referring to  FIG. 3B , there are shown optional fasteners  130  that may be inserted into the surface of the first pipe connector  112 . The fasteners may be, for example, screws or bolts. The fasteners  130  are positioned so that a portion of the head of each fastener  130  overlaps a portion of the key  116 . Thus, the fasteners  130  may help to secure the key  116  radially relative to the pipe connectors  112 ,  114 , thereby preventing the key  116  from backing out due to, for example, vibrations, or torsional loads. In the embodiments shown, the fasteners  130  are inserted into holes  132  (shown in  FIG. 3A ) in the first pipe connector  112 . Use of screws of other fasteners may be beneficial to prevent debris from entering removal notch areas  142 . In addition, the fasteners may double as anchors for attaching a press tool (for pressing the key  116  into the recess) using external bolts or screws. 
         [0035]    Optionally, the fasteners  130  may be countersunk, so that the heads of the fasteners  130  do not protrude beyond the surface of the first pipe connector  112  when the fasteners  130  are fully inserted into the holes  132 . Thus, a countersink  140  may be drilled or otherwise bored into the surface of the first pipe connector  112  and a portion of the key  116 . In certain embodiments, the heads of the fasteners  130  may be configured to accept a fastener insertion tool, such as, for example, a screwdriver, or a hexagonal alien wrench. For example, the fasteners  130  of the present technology are shown to have hexagonal sockets  134  for accepting such an alien wrench. In an embodiment where the recess  128  is in the second pipe connector  114 , the fasteners  130  would correspondingly be inserted into the second pipe connector  114 , rather than the first pipe connector  112 . In such an embodiment, the holes  132  and countersinks  140  would also be drilled into the second pipe connector  114 . Although the fasteners shown in  FIG. 3B  are bolts, any appropriate mechanism may be used to retain the key  116  radially in place relative to the first and second pipe connectors  112 ,  114 . For example, the key  116  could be retained using flexible tabs, clips, spring mechanisms, or any other appropriate mechanism. In addition, any number of fasteners or retaining mechanisms could be used, including a single fastener or retaining mechanism. 
         [0036]    Referring now to  FIGS. 4A-4D , there is shown another embodiment of the present technology, including a first pipe connector  212 , a second pipe connector  214 , and a key  216 . The key  216  has an inner surface  218 , an outer surface  220 , an upper surface  222 , and a tapered lower surface  224 . The inner surface  218  may be configured so that, upon insertion between the first and second pipe connectors  212 ,  214 , it is positioned radially inward relative to the pipe connectors  212 ,  214 . Conversely, the outer surface  220  may be configured so that, upon insertion between the first and second pipe connectors  212 ,  214 , it is positioned radially outward relative to the pipe connectors  212 ,  214 . The tower surface  224  may be tapered axially downward relative to the pipe connectors  212 ,  214 . In addition, the key  216  includes locking ridges  226  protruding from the lower surface  224  and extending radially from the inner surface  218  to the outer surface  220 , Furthermore, in the embodiment of  FIGS. 4A-4D , the first pipe connector  212  has a recess  228  configured to at least partially accept the key  216 , and holes  232  for accepting fasteners  230 . The recess has grooves  236  in the upper surface thereof which may be pre-machined into the pipe connector. 
         [0037]    In the embodiment of  FIGS. 4A-4D , the upper surface  222  of the key  216  has radially extending splines  238 , each with an upper surface that is curved about an axis of each spline  238 . Splines  238  are positioned so that when the key  216  is inserted into the recess  228 , the curved splines  238  are received by the grooves  236 . Splines  238  have ridges shown extending radially from the front surface  220  to the rear surface  218 . The locking ridges  226  of the bottom surface  224  contact, and become embedded into, the second pipe connector  214  when the key  216  is pressed into the recess  228 , as described above. A fully inserted key  216 , according to this embodiment, is shown in  FIG. 4B . Thus configured, with the key  216  fully inserted, the first and second pipe connectors  212 ,  214  are restrained from rotating relative to one another. 
         [0038]    One advantage to the key  216 , is that it will act hi-directionally, preventing both over-tightening and un-tightening of the pipe connectors  212 ,  214 . Moreover, the curved splines  238  can be either symmetric, as shown in  FIGS. 4A ,  4 C, and  4 D, or asymmetric, as shown in  FIG. 4B . If symmetric, the curved splines  238  will have a substantially equal capacity to prevent relative circumferential rotation of the pipe connectors  212 ,  214  in both directions. If asymmetric, the curved splines  238  will have additional load bearing capacity in one direction, depending on the orientation of the curved splines  238 . Another advantage to the key  216  having curved splines  238 , is that as the surfaces of the curved splines absorb the forces F (shown in  FIG. 4B ) exerted on the key  216  by the first pipe connector  212 , the locking ridges  226  are driven deeper into the second pipe connector  214 . Accordingly, the ability of the key  216  to prevent relative circumferential rotation between the pipe connectors  21   214  is increased. The key  216  may be removed using a specialty tool or hand tools, for example, by inserting a screw driver or pry bar into a notched area  242  at either end of the key  216 . 
         [0039]    It is to be understood that variations of the embodiment shown in  FIGS. 4A-4D  are also contemplated. For example, the recess  128  could be in the second pipe connector  214  instead of the first pipe connector  212 , as shown. Alternately, the curved splines  238  could be positioned on the bottom surface  224  of the key, and the locking ridges  226  on the top surface  222 . In such an embodiment, the grooves  236  of the recess  228  would be cut into the portion of the second pipe connector  214  adjacent to the recess  228 . 
         [0040]    Referring to  FIG. 4A , there are shown optional fasteners  230  that may be inserted into the surface of the first pipe connector  212 . The fasteners may be, for example, screws or bolts. The fasteners  230  are positioned so that a portion of the head of each fastener  230  overlaps a portion of the key  216  when installed in recess  228 . Thus, the fasteners  230  may help to secure the key  216  radially relative to the pipe connectors  212 ,  214 , thereby preventing the key  216  from hacking out due to, for example, vibrations, or torsional loads. In the embodiments shown, the fasteners  230  are inserted into holes  232  (shown in  FIG. 4A ) in the first pipe connector  212 . In certain embodiments, the heads of the fasteners  230  may be configured to accept a fastener insertion tool, such as, for example, a screwdriver, or a hexagonal allen wrench. For example, the fasteners  230  of the present technology are shown to have hexagonal sockets  234  for accepting such an alien wrench. Use of screws or other fasteners may be beneficial to prevent debris from entering removal notch areas  242 . In addition, the fasteners may double as anchors for attaching a press tool (for pressing the key  216  into the recess) using external bolts or screws. 
         [0041]    Optionally, the fasteners  230  may be countersunk, so that the heads of the fasteners  230  do not protrude beyond the surface of the first pipe connector  212  when the fasteners  230  are fully inserted into the holes  232 . Thus, a countersink  240  may be drilled or otherwise bored into the surface of the first pipe connector  212  and a portion of the key  216 . Alternatively, the key  216  may include a flat retaining surface  244  instead of a curved countersink. Such a flat retaining surface  244  allows the fastener  230  to be recessed relative to the surface of the pipe connector, while at the same time allowing the key  216  to move slightly relative to the second pipe connector  214 , thereby increasing drive pressure and capacity of the locking ridges  226 . 
         [0042]    In an embodiment where the recess  228  is in the second pipe connector  214 , the fasteners  230  would correspondingly be inserted into the second pipe connector  214 , rather than the first pipe connector  212 . In such an embodiment, the holes  232  and countersinks  240  would also be drilled into the second pipe connector  214 . Although the fasteners shown in  FIG. 4B  are bolts, any appropriate mechanism may be used to retain the key  216  radially in place relative to the first and second pipe connectors  212 ,  214 . For example, the key  216  could be retained using flexible tabs, clips, spring mechanisms, or any other appropriate mechanism, In addition, any number of fasteners or retaining mechanisms could be used, including a single fastener or retaining mechanism. 
         [0043]    Providing multiple locking ridges  26 ,  126 ,  226  or splines  138 ,  238  on both the upper  22 ,  122 ,  222  and lower  24 ,  124 ,  224  surfaces of the key  16 ,  116 ,  216  is advantageous because such a structure helps to prevent unintentional decoupling of the first  12 ,  112 ,  212  and second  14 ,  114 ,  214  pipe connectors. Furthermore, such a structure allows the key  16 ,  116 ,  216  to be low profile because the bearing and shear areas that transfer the load across the key  16 ,  116 ,  216  are distributed across all the locking ridges  26 ,  126 ,  226  and/or splines  138 ,  238 . Thus, the key  16 ,  116 ,  216  of the present technology is compatible with very low profile connectors. 
         [0044]    While the technology has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. Furthermore, it is to be understood that the above disclosed embodiments are merely illustrative of the principles and applications of the present invention. Accordingly, numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Summary:
A system for joining pipe segments, the system including a first pipe connector connected to a first pipe segment, and a second pipe connector threadingly connectable to the first pipe connector, and connected to a second pipe segment. The system further includes a recess in the outer surface of the first pipe connector, and an elongated key having first and second lengthwise surfaces. One of the lengthwise surfaces has protrusions that embed into a transverse surface of the second pipe connector when the key is mounted into the recess. The thickness of the key decreases with distance radially inward from the outer surface.