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TECHNICAL FIELD 
       [0001]    This invention relates to ground drilling equipment. Specifically, this invention relates to connection designs for components of drill stems. 
       BACKGROUND 
       [0002]    Directional drilling is a useful technique for several procedures such as utility installation, etc. One common type of directional drilling is horizontal directional drilling, where a drill stem is extended essentially horizontally to form passages under structures such as roads for example. 
         [0003]    The drill stem typically includes multiple components, including a drill head, a sonde housing, sections of drill rod, etc. Drill heads in directional drilling typically have a feature which causes the drill head to steer in one direction when forced ahead by a drilling device. During a boring operation, pressure is applied through the drill stem from behind to the drill head. During a straight bore, the drill stem is typically rotated at a regular rate so that on average, only straight ahead drilling is accomplished. In order to steer a drill head, the rotation is temporarily stopped, and the drill head is allowed to steer in the desired direction. Once the steering maneuver is complete, the drill head is again rotated at a regular rate for straight ahead drilling. 
         [0004]    Ground drilling requires large amounts of forward linear force, as well as large amounts of torque, applied to the drill stem. The drill stem also experiences frictional forces due to the interaction of the drill stem with the medium (i.e., soil, rock, sand, clay, etc.) through which the drill stem is traveling during a boring operation. Therefore, for a successful boring operation, it is necessary that the components, as well as the couplings therebetween, be able to withstand the various drilling forces without failure. 
         [0005]    Various coupling designs and methods have been employed to connect drill stem components. One common method of connecting drill stem components is to threadingly couple one component to another, such that the linear and the rotational forces experienced during a drilling operation are transmitted from one component to the other through the threads of the adjoining components. Because of this, such threaded couplings are difficult to remove after the drilling operation is complete due to tightening of the threads during rotation of the drill stem in a drilling operation. Large tools, such as a pipe wrench, are frequently needed to disconnect the threaded-together drill stem components. Pipe wrenches or similar methods requiring large forces are inconvenient, and may be dangerous to the operator. 
         [0006]    What is needed is a drill stem component connection system and method that provides structural integrity for drilling operations, while providing ease of assembly and disassembly with an increased level of safety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows a drilling device according to an embodiment of the invention. 
           [0008]      FIG. 2  shows a drilling device according to an embodiment of the invention. 
           [0009]      FIG. 3  shows a threaded collar of a drilling device according to an embodiment of the invention. 
           [0010]      FIGS. 4A-4C  show views of a threaded collar of a drilling device according to an embodiment of the invention. 
           [0011]      FIG. 5  shows an adapter of a drilling device according to an embodiment of the invention. 
           [0012]      FIGS. 6A-6C  show views of an adapter of a drilling device according to an embodiment of the invention. 
           [0013]      FIG. 7  shows a drill stem section of a drilling device according to an embodiment of the invention. 
           [0014]      FIG. 8  shows a drill stem section of a drilling device according to an embodiment of the invention. 
           [0015]      FIGS. 9A-9C  show views of a drill stem section of a drilling device according to an embodiment of the invention. 
           [0016]      FIG. 10  is a cross-sectional view of the drill stem section of  FIG. 9C  taken along line  10 - 10 . 
           [0017]      FIG. 11  is an exploded view of a drilling device according to an embodiment of the invention. 
           [0018]      FIG. 12  shows a drill stem component of the drilling device of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, or logical changes, etc. may be made without departing from the scope of the present invention. In the following descriptions, a drill stem is defined to include any component that is advanced from a drilling device. A drill rod is defined as a section of pipe, solid material, etc. where sections of drill rod are coupled together to form a main part of a drill stem. Various drill stem components such as a drill head, a drilling blade holder, a sonde housing, etc. can be attached to the front end of a number of drill rods during one embodiment of a typical drilling operation. 
         [0020]    Referring to  FIGS. 1 and 2 , there is shown a drilling device. Although an example of a directional drill stem portion  10  is used in the following descriptions, other drilling devices utilizing a number of sections of drill stem are also contemplated to be within the scope of the invention. It is noted that, while the drill stem portion  10  of  FIGS. 1 and 2  is shown in isolation, it is intended that in use the drill stem portion  10  be attached to an end of a drill rod (not shown) at least during directional drilling. Additionally, typically, the drill stem portion  10  will be drivingly coupled to a drilling apparatus (not shown) during directional drilling. In this example, the drill stem portion  10  includes a threaded collar  20 , an adapter  30 , and an end portion  40 . The end portion  40 , in at least this example, includes a sonde housing  42  and a drill head  44 . 
         [0021]    Referring to FIGS.  5  and  6 A- 6 C, the adapter  30  is generally cylindrical in shape, having a side wall  30   a  disposed between a first end  30   b  and a second end  30   c.  The first end  30   b  of this example includes interior adapter threads  36  configured to selectively engage conical threads (not shown) of an end of a drill rod (not shown). In other examples, it is contemplated that engagement structures other than conical adapter threads  36  are used at the first end  30   b.  The adapter  30  further includes a central passage  30   d  therethrough disposed between the first and second ends  30   b,    30   c  through which fluid (not shown), such as bentonite fluid or other drilling fluid, optionally travels. Proximate the second end  30   c,  the central passage  30   d  includes a radial passage  38  that extends through the side wall  30   a  for fluid connection with a fluid passage within the end portion  40 , which will be described in greater detail below. Although the end of the central passage  30   d  is shown as extending through the second end  30   c  of the adapter  30 , in one example, it is intended that the end be closed off in a known way, such as by welding, inserting a stopper, etc., so that the fluid flows through the radial passage  38  and does not flow out of the second end  30   c  of the adapter  30 . Although only one radial passage  38  is shown, it is within the spirit and scope of the present invention that there be more than one passage to facilitate the passage of fluid from the central passage  30   d  to the fluid passage of the end portion  40 . An exterior of the side wall  30   a  of one example of the adapter  30  includes O-ring slots  35  on either longitudinal side from the radial passage  38  for accepting O-rings (not shown) for sealingly engaging the adapter  30  within the end portion  40  to inhibit fluid leakage into the interior of the end portion  40 . 
         [0022]    The adapter  30 , in one example, further includes an engagement feature in the form of exterior adapter splines  32  disposed proximate the second end  30   c  of the adapter  30 . In one embodiment, the adapter splines  32  are generally longitudinally oriented with respect to the adapter  30 . The adapter  30 , in one example, further includes a raised shoulder  34  optionally including a generally circumferential channel  34   a,  as shown in  FIG. 5 , for engagement with the threaded collar  20 , as will be described below. In another example, the adapter  30  includes only a raised shoulder  34 , as shown in  FIGS. 6A and 6B , and does not include a circumferential channel. The shoulder  34  and optional circumferential channel  34   a  are configured for engagement with the threaded collar  20 , as will be described in greater detail below. 
         [0023]    Referring to  FIGS. 7-10 , the end portion  40  is generally cylindrical and includes a side wall  40   a  disposed between a first end  40   b  and the drill head  44 . At least the sonde housing  42  of the end portion  40  includes a generally hollow interior  40   c  extending from the first end  40   b  to the drill head  44 . In this example, the hollow interior  40   c  is configured to optionally accept a sonde (not shown) for sensing and sending drilling environment data to a user in a manner that is generally known to those skilled in the art. The side wall  40   a  in the area of the sonde housing  42  includes windows  40   d  therethrough to allow radio waves or other such sensing signals emitted from the sonde to exit the sonde housing  42 . In one example, the end portion  40  includes three windows  40   d,  although it is within the spirit and scope of the present invention that there be more or less than three windows  40   d  through the side wall  40   a,  provided the sensing signals of the sonde are able to exit the sonde housing  42  in order to sense drilling environment characteristics. Additionally, although not shown in the figures, the windows  40   d  are intended to be covered or filled with epoxy or other such material that is permeable with respect to radio waves or other such signals emitted by the sonde. By filling or otherwise covering the windows  40   d,  fluid can be prevented or at least inhibited from entering the interior  40   c  of the end portion  40 , thereby at least reducing the likelihood that the sonde inside the sonde housing  42  will become damaged by fluids, soil, mud, and other drilling-related contaminates encountered by the drill stem portion  10  during directional drilling. 
         [0024]    In one example, the end portion  40  further includes end portion threads  46  on end exterior surface of the side wall  40   a,  disposed proximate the first end  40   b.  The end portion threads  46  are configured to engage the threaded collar  20 , as described in more detail below. End portion splines  48  are disposed on an interior surface of the side wall  40   a  proximate the first end  40   b.  The end portion splines  48  are configured, in this example, to mate with and engage the adapter splines  32 , such that, when engaged with the adapter splines  32 , relative rotational motion of the adapter  30  with respect to the end portion  40  is inhibited thereby. Although a plurality of end portion splines  48  are shown disposed around the entire interior circumference of the end portion  40  and a plurality of adapter splines  32  are shown disposed around the entire exterior circumference of the adapter  30 , it is within the spirit and scope of the present invention that the adapter and end portion splines  32 ,  48  be configured differently. For instance, the adapter splines  32  could be configured around an interior circumference of the adapter  30  and the end portion splines  48  could be configured around an exterior circumference of the end portion  40 . Also, the adapter splines  32  could be disposed only around a portion of the circumference of the adapter  30  with the end portion splines  48  disposed around a corresponding portion of the circumference of the end portion  40 . Additionally, one of the adapter  30  and the end portion  40  could have as few as one spline forming a projection and the other of the adapter  30  and the end portion  40  could have as few as two splines forming a slot for engagement of the projection therewith. Although not expressly shown or described herein, further engagement variations are contemplated in the present invention. 
         [0025]    In one example, the drill head  44  of the end portion  40  includes a plurality of holes  44   a  for optional engagement of additional components such as steering blades (not shown), etc. with the drill head  44 . In one example, the holes  44   a  are threaded for receiving fasteners (not shown). Additionally, the drill head  44  of this example includes a slot  44   b  for insertion and retention of a fluid port (not shown) or other tool and/or component suitable for use with a directional drill. The use of a steering blade is generally known in the art and, for this reason, will not be described in detail herein. The drill head  44  further includes a drill fluid outlet  44   c  ( FIG. 7 ) for discharging drill fluid (not shown) into the fluid port within the slot  44   b  or otherwise discharging drill fluid within the drill hole during directional drilling. Fluid is often used to loosen the soil in the vicinity of the steering blade, thus making the drilling operation easier. In one example, the drilling fluid includes a bentonite lubricant. The drill fluid outlet  44   c  is fluidly coupled to the passage  38  of the adapter  30  with a drill fluid passageway  43  (see  FIG. 10 ) in the side wall  40   a  of the end portion  40 . 
         [0026]    Referring now to FIGS.  3  and  4 A- 4 C, the threaded collar  20  in one example includes a generally cylindrical side wall  20   a  disposed between first and second ends  20   b,    20   c.  The threaded collar  20  is configured to fit over the adapter  30  and at least a portion of the end portion  40  to act to couple the adapter  30  to the end portion  40 . In one example, the threaded collar  20  includes collar threads  26  on an interior surface of the side wall  20   a  configured to threadingly engage the end portion threads  46  described above. The collar threads  26  are configured to inhibit if not prevent loosening of the threaded collar  20  during rotation of the drill stem portion  10  during directional drilling. In one embodiment, the collar threads  26  are configured to be left-hand tightening threads so that rotation of the drill stem portion  10 , which is intended to be rotated in a right-hand rotational direction, and, more specifically the frictional interaction of the drill stem portion  10  with respect to the material being drilled causes further tightening of the threaded collar  20 . 
         [0027]    Tightening of the collar threads  26  with the end portion threads  46  causes compression of a collar shoulder  20   d  of the threaded collar  20  against the shoulder  34  of adapter  30  to engage the adapter  30  with the end portion  40 . In this way, tightening of the collar threads  26  with the end portion threads  46  inhibits axial movement of adapter  30  with respect to the end portion  40 . Through holes  28  of the threaded collar  20  are configured to accept set screws (not shown) for optional engagement within channel  34   a  to further affix the threaded collar  20  to the adapter  30 . Two holes  28  are shown in this example, although it is contemplated that there be more or less than two holes  28 . 
         [0028]    In one example, the collar threads  26  include one continuous thread with the end portion threads  46  including a corresponding thread. In another example, the collar threads  26  and the end portion threads  46  include more than one thread. In yet another example, the collar threads  26  and the end portion threads  46  include multiple, interlaced threads. For instance, the collar threads  26  could include two, three, or more interlaced threads with the end portion threads  46  including a corresponding number of threads. Multiple threads provide the same engagement surface area between the end portion threads  46  and the threaded collar threads  26  as a single thread. However, fewer rotations of the threaded collar  20  are required with multiple threads than are required for a single thread, leading to faster engagement/disengagement of the threaded collar  20  with the end portion  40 . 
         [0029]    The threaded collar  20  further includes end holes  24  disposed around the first end  20   b  configured to accept carbide blades to scrape away drill residue, i.e., caked on mud, rock, etc. during loosening of the collar  20 . Although four end holes  24  are shown, it is contemplated that there be more or less than four end holes  24 . Spanner features  22 , such as holes, flats, etc., are located in an exterior of the side wall  20   a.  The spanner features  22  in this example only partially extend through the side wall  40   a  and are configured for engagement with a spanner (not shown) or other such tool configured to be used to tighten and/or loosen the threaded collar  20 . In this example, there are two diametrically opposed spanner features  22 , although it is within the spirit and scope of the present invention that there be more or less than two spanner features and/or that the spanner features not be diametrically opposed, provided a tool such as a spanner is still capable of being used to tighten and/or loosen the collar threads  26  of the threaded collar  20 . 
         [0030]    In this way, once engaged in a securing position (see  FIGS. 1 and 2 ), the threaded engagement of the threaded collar  20  with the end portion  30  maintains the end portion  40  in engagement with the adapter  30  and, thereby, maintains mating engagement of the adapter splines  32  with the end portion splines  48  to transmit torque between the adapter  30  and the end portion  40 . The engagement of the collar threads  26  with the end portion threads  46  transmits axial forces along the drill stem portion  10  but does not transmit torque forces due to the above-described interaction of the end portion splines  48  and the adapter splines  32 . By isolating the torque forces and the axial forces in this way, the threaded collar  20  does not become over-tightened by rotation of the drill stem portion  10  during a drilling operation and, therefore, requires relatively little force by a user to remove the threaded collar  20  from the end portion threads  46 , when it is desired to disassemble the drill stem portion  10  after a drilling operation. 
         [0031]    The threaded collar  20 , when engaged with the adapter  30  and the end portion  40 , not only acts to maintain connection of the adapter  30  and the end portion  40 , but also protects a joint between the adapter  30  and the end portion  40  by at least partially covering the joint. In one example, the threaded collar  20  completely covers the joint to inhibit encroachment of drilling byproducts, such as fluid, soil, rocks, etc., within the joint. 
         [0032]    In operation, the threaded collar  20  is slidably disposed between the first end  30   b  and the shoulder  34  of the adapter with the second end  20   c  of the threaded collar  20  facing in the direction of the second end  30   c  of the adapter  30 . The adapter threads  36  of the adapter  30  are then threadably engaged with an end (not shown) of a generally known drill rod (not shown). The first end  40   b  of the end portion  40  is then slipped over the second end  30   c  of the adapter  30  so that the adapter splines  32  engage with the mating end portion splines  48 , with the first end  40   b  of the end portion  40  abutting the shoulder  34  of the adapter  30  in one example. The treaded collar  20  is passed along the adapter  30  toward the end portion  40  and into engagement with the end portion threads  46 , at which point the collar threads  26  are engaged therewith. Optionally, a spanner (not shown) can be engaged with the spanner features  22  of the threaded collar  20  to gain a mechanical advantage in order to further tighten the threaded collar  20  onto the end portion threads  46 , thereby compressing the joint between the end portion  40  and the adapter  30 . Optionally, set screws (not shown), such as allen bolts, hex bolts, screws, and the like, can be threaded into the through holes  28  in the threaded collar  20 , such that ends of the set screws become disposed within the channel  34   a,  further optionally biting into an exterior of the adapter  30  within the channel  34   a.  In this way, the threaded collar can be optionally further engaged with the drill stem portion  10  to lessen the likelihood that the threaded collar  20  becomes dislodged from its engagement with the end portion  40 . The drill stem portion  10  can then be used in a directional drilling operation to bore through soil, rock, clay, etc. in order to create a directional drilling hole in a manner generally known to those skilled in the art. It is further contemplated that the collar threads  26  be left-handed, such that frictional interaction of the threaded collar  20  with the drill bore causes further tightening of the threaded collar  20  onto the end portion threads  46  to further lessen the likelihood of disengagement of the end portion  40 . This promotes a secure attachment of the end portion  40  and the adapter  30  during a drilling operation. Because the threaded collar  20  at least partially covers the joint between the end portion  40  and the adapter  30 , the joint is protected from the incursion of drilling byproducts, such as soil, rocks, fluid, etc. 
         [0033]    After performing a desired drilling operation, the drill stem portion  10  can be removed from within the drill bore, either by backing the drill stem portion  10  out or by passing the drill stem portion  10  completely through the drill bore. At this point, if desired, the end portion  40  can be removed from the adapter  30  by loosening the threaded collar  20 . If used, the set screws of the threaded collar  20  are loosened to disengage the set screws from within the channel  34   a  of the adapter  30 . The threaded collar  20  is then loosened and removed from engagement with the end portion threads  46 . As discussed above, because the collar threads  26  are only tightened due to friction, are not tightened due to drill stem rotation, a lower amount of force is required to loosen the threaded collar  20 . Optionally, the spanner is engaged within the spanner features  22  and is used to gain a mechanical advantage in loosening the thread collar  20  from engagement with the end portion  40 . Use of the spanner in this way eliminates the unsafe and relatively common practice of using pipe wrenches (not shown) or other such devices to loosen the sections of the drill stem. 
         [0034]    Although the above description relates to the use of the threaded collar  20  with the end portion  40  and adapter  30 , it is within the spirit and scope of the present invention that the threaded collar  20  be used with other joints between other sections of the drill stem, including, but not limited to, between drill rods, between a drill rod and the sonde housing, between the sonde housing and the drill head, etc. Additionally, although the above description primarily relates to the adapter splines  32  and the end portion splines  48  as the engagement/mating features of the end portion  40  and the adapter  30 , it is within the spirit and scope of the present invention that other engagement/mating features be used in conjunction with the threaded collar  20 . 
         [0035]    For instance, in another example, referring to  FIGS. 11 and 12 , a sonde housing  142  includes at least one twist-and-lock slot  148 , and an adapter  130  includes at least one corresponding protruding lobe  132  for selective engagement within the twist-and-lock slot  148 . More information regarding this twist-and-lock configuration can be found in U.S. patent application Ser. No. 10/757,378 entitled Connection Design and Sonde Housing Assembly for a Directional Drill, which is incorporated by reference herein in its entirety. In one example, the twist-and-lock slot  148  is proximate a first end  140   b  of the sonde housing  148  and includes a first portion  148   a  generally longitudinally oriented with respect to the sonde housing  142  and a second portion  148   b  generally radially oriented with respect to the sonde housing  142 . In this way, the protruding lobe  132  is inserted within the first portion  148   a,  and the adapter  130  is twisted with respect to the sonde housing  142  to slide the protruding lobe  132  into the second portion  148   b  and locked into place using, for instance, an insert  145 . Once the protruding lobe  132  is engaged within the second portion  148   b  of the twist-and-lock slot  148 , a threaded collar (not shown, but substantially similar to the thread collar  20  discussed above) is threadably engaged with sonde threads  146  proximate the first end  140   b  of the sonde housing  142 . In a manner similar to that described above, the threaded collar, as it is tightened, abuts a shoulder  134  of the adapter  130  and compresses a joint between the adapter  130  and the sonde housing  142 . In this way, the threaded collar acts to couple the sonde housing  142  and the adapter  130  and provides at least some protection from drilling byproducts of the joint to facilitate disassembly after use. 
         [0036]    It is noted that the above-discussed examples of drill stem couplings including the threaded collar are merely exemplary and that other configurations not specifically discussed herein are considered to be within the spirit and scope of the present invention. For instance, the thread collar discussed herein could be used with other engagement/mating features of drill stem components, whether initially designed to be used with the threaded collar or whether existing drill stem components having engagement/mating features are retrofitted for use with the threaded collar. 
         [0037]    The above-described drill stem coupling of the drill stem portion  10 , namely, the threaded collar  20  used in conjunction with the adapter  30 ,  130  and the end portion  40  or sonde housing  142 , is intended to provide a robust coupling for use during drilling operations in which torque forces are isolated to lessen the likelihood of the drill stem components becoming overly tightened and, as a result, difficult to separate. Because torque forces do not act to further tighten the threaded collar  20  of the present invention, the threaded collar  20  is relatively easier to remove than previously known drill stem couplings. As such, the present invention decreases the need to use large pipe wrenches or other such tools, which can be dangerous for a user to try to use and/or restrain, especially when the user is within a confined area such as a drill pit. 
         [0038]    Additionally, as stated above, the threaded collar  20  in the secured position acts to at least partially cover the joint between the adapter  30 ,  130  and the end portion  40  or sonde housing  142 , which serves to protect the joint from incursion of dirt, fluid, and other drilling debris into and around the joint. In this way, the threaded collar  20  acts to inhibit such debris from becoming lodged in and around the joint, thereby facilitating disassembly of the adapter  30 ,  130  and the end portion  40  or sonde housing  142 . 
         [0039]    While a number of advantages of embodiments described herein are listed above, the list is not exhaustive. Other advantages of embodiments described above will be apparent to one of ordinary skill in the art, having read the present disclosure. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. It is to be understood that the above description is intended to be illustrative, and not restrictive. Combinations of the above embodiments, and other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention includes any other applications in which the above structures and fabrication methods are used. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Summary:
A drill stem connection assembly includes a first drill stem section and a second drill stem section. At least one engaging feature is located at an end of the first drill stem section. At least one mating feature accepts the at least one engaging feature. The at least one mating feature is located at an end of the second drill stem section. Coupling of the respective ends of the first and second drill stem sections forms a drill stem joint. A threaded collar engages with at least one of the coupled first and second drill stem sections. When placed in a securing position, the threaded collar holds the engaging feature securely mated with the mating feature and at least partially covers the drill stem joint.