Abstract:
The apparatus, system and method is capable of providing power from a directional or vertical drilling apparatus at an origin above the ground to an electronic device located in a drill head of the directional or vertical drilling apparatus located below the ground. The apparatus, system and method is also capable of providing an electrical signal from below ground back to the origin, above ground, from the electronic device. Accordingly, the mechanism for feeding electrical power down a hole to the electronic device located in the drill head and transmitting a signal back to the origin, greatly enhances the drilling process making it faster, more reliable and more efficient.

Description:
BACKGROUND 
     The present invention relates generally to directional or horizontal drilling devices. More particularly, the present invention relates to an electrical transmission line for use with directional or horizontal drilling machines. 
     Directional or horizontal drilling machines are used to drill holes along a generally horizontal path beneath the ground. After a hole is drilled, the hole is back reamed and then a length of cable or the like can be passed through the hole. Such directional drilling machines eliminate the need for digging a long trench to lay a length of cable or the like. 
     A typical directional drilling machine includes an elongated track that can be aligned at an inclined orientation relative to the ground. A drill head is mounted on the track so as to be moveable along the length of the track. The drill head includes a drive member that is rotated about a drive axis that is generally parallel to the track. The drive member is adapted for connection to a length of pipe, or drill stem. For example, the drive member can include a threaded end having either female or male threads. 
     To drill a hole using the directional drilling machine, the track is oriented at an inclined angle relative to the ground, and the drill head is retracted to an upper end of the track. Next, a length of drill stem is unloaded from a magazine and is coupled to the drive member of the drill head. Once the drill stem is connected to the drill head, the drill head is driven in a downward direction along the inclined track. As the drill head is driven downward, the drive member is concurrently rotated about the drive axis. Typically, a cutting element or drilling/boring member, is mounted at the distal end of the drill stem on the drill head. Consequently, as the drill head is driven down the track, the rotating drill stem is pushed into the ground thereby causing the drill stem to drill or bore a hole. By stringing multiple drill stems together, it is possible to drill holes having relatively long lengths. 
     After drilling a hole, it is common for a back reamer to be connected to the end of the drill string. Once the back reamer is connected to the end of the drill string, the directional drilling apparatus is used to pull the string of drill stems back toward the drilling machine. As the string of drill stems is pulled back toward the drilling machine, the reamer enlarges the pre-drilled hole, and the drill stems are individually uncoupled from the drill string and loaded back into the magazine of the directional drilling machine. 
     In order to accurately guide the drill string, an operator must monitor the position of the drill head. The principal means for locating the position of the drill head for guiding it is to equip the drill head with an electronic device that emits electromagnetic energy. Typically, the electronic device is a radio transmitter or sonde mounted within the drill head. The sonde emits electromagnetic energy at radio frequencies which can be detected above the ground by an operator using an electromagnetic wave detection device, or the like, tuned to the same radio frequency emitted by the sonde. Accordingly, by providing feedback of the drill head&#39;s position, the drilling machine operator can make the required adjustments such that the hole is bored at the proper depth and in the proper direction. 
     Electrical power required to operate the sonde has typically been supplied via a conventional wire line, or a battery placed within the drill head. Several problems are associated with the conventional wire line in that it is cumbersome to feed the wire line through the drill stem. In order to extend the drill string, sections of drill stem are added at the drive head of the drilling machine. Therefore, a new length of wire must be spliced or connected to a previous length or wire in the drill string. This takes time and is not generally an efficient process, thus reducing the overall productivity and slowing down the drilling process. 
     Providing power to the sonde via a battery is problematic in that the energy delivered to the sonde is limited to the energy capacity of the battery. Therefore, the output signal strength emitted by the sonde is practically limited to the battery&#39;s energy capacity. Since electromagnetic waves are emitted from a source (the sonde) beneath the ground, they are greatly attenuated by the time they reach the detection device above ground. Accordingly, it is desirable to increase the energy or power delivered to the sonde to increase the strength of the electromagnetic waves emitted therefrom. 
     For the foregoing reasons, there is a need for an apparatus, system and method capable of providing electrical power to an electronic device located within a drill head of a drilling machine that greatly enhances the productivity of the drilling process. Furthermore, there is a need for providing power to the electronic device that is not limited by the energy capacity of a battery. 
     SUMMARY 
     The invention is directed to an apparatus, system and method that satisfies the need identified above. The apparatus, system and method having features of the invention is capable of providing power from an origin above the ground to an electronic device located below the ground. The apparatus, system and method having features of the invention is also capable of providing electrical signals between the origin (above ground) and the electronic device located below ground. Having these capabilities greatly enhances the drilling process, thus making it faster, more reliable and more efficient. 
     One aspect of the invention relates to a drill head that forms a portion of a drill string for boring a hole through the ground. The drill head has a member that has a generally longitudinally extending housing and includes an outer surface, an inner surface defining a hollow passage therethrough and further defining a chamber, a first end adapted and configured for boring through the ground and a second end adapted and configured to be coupled to a starter rod or a drill stem. An electrically conductive ring is radially disposed about a distal end of the second end and an electrically insulative ring is radially disposed about the second end and located proximate to the electrically conductive ring. An electrical conductor encapsulated by an electrically insulative material is disposed within the hollow passage. The electrical conductor is electrically connectable between the conductive ring and an electronic device disposed within the chamber. The electrically insulative ring provides electrical isolation between the conductive ring and the outer surface of the drill head. The electrically insulative material provides electrical isolation between the electrical conductor and the inner surface of the hollow passage. 
     Another aspect of the invention relates to a drill pipe that forms a portion of a drill string for boring a hole through the ground. The drill pipe has a member having a generally longitudinally extending housing including an outer surface, an inner surface defining a hollow passage therethrough and first and second ends adapted and configured to be coupled to a second member. The drill pipe also includes first and second electrically conductive rings that are radially disposed about first and second distal ends of the member. The drill pipe also includes first and second electrically insulative rings that are radially disposed about the first and second ends and proximate to the first and second electrically conductive rings and an electrical conductor encapsulated by an electrically insulative material. The electrical conductor is disposed within the hollow passage and is electrically connectable between the first and second conductive rings and the first and second electrically insulative rings. The electrically insulative rings provide electrical isolation between the first and second conductive rings and the outer surface of the starter rod. The electrically insulative material provides electrical isolation between the electrical conductor and the inner surface of the hollow passage. 
     A further aspect of the invention relates to a drill string for boring a hole through the ground having one end adapted and configured to be coupled to a drilling apparatus. The drill string includes one or more members having generally longitudinally extending housings, each of the housings including an outer surface and an inner surface defining a hollow passage therethrough and first and second ends adapted and configured to be coupled to a drill head, a drill stem or a starter rod. The drill string also includes electrical connection means between each end of the members. Electrical insulation means between the electrical connections and the outer surfaces of each the members and one or more electrical conductors encapsulated by an electrically insulative material, each electrical conductor being disposed within the hollow passage of each of the members and are electrically connected through the electrical connection means to an electrical conductor of an adjacent member throughout the length of the drill string. 
     Yet another aspect of the invention relates to a drilling apparatus for boring a hole through the ground. The drilling apparatus includes a frame having a longitudinal axis extending from a first frame end to a second frame end, a drill string having a first end adapted and configured to be coupled to the drilling apparatus and a second end adapted and configured for boring a hole through the ground. The drill string further includes one or more adjacently disposed members including electrical connection means disposed therebetween. The electrical connection means provide electrical continuity between the members. The drilling apparatus also includes a drive mechanism mounted on the frame for movement along the longitudinal axis and the drill string is connected to the drive mechanism for the drive mechanism to rotate the drill string and to longitudinally advance and retract the drill string in response to the drive mechanism moving along the longitudinal axis. The drilling apparatus also includes means for providing electrical continuity between a first and second ends of the drill string. 
     Still a further aspect of the invention relates to drilling apparatus for boring a hole through the ground. The drilling apparatus includes a frame having a longitudinal axis extending from a first frame end to a second frame end, a drill string having a first end adapted and configured to be coupled to the drilling apparatus and a second end adapted and configured for boring a hole through the ground. The drill string further includes one or more adjacently disposed members and signal flow path connection means disposed therebetween. The signal flow path connection means providing signal continuity between the members. The drilling apparatus also includes a drive mechanism mounted on the frame for movement along the longitudinal axis and the drill string is connected to the drive mechanism for the drive mechanism to rotate the drill string and to longitudinally advance and retract the drill string in response to the drive mechanism moving along the longitudinal axis. The drilling apparatus also includes one or more signal flow path means disposed within the drill string. The signal flow path means providing electrical signal continuity between first and second ends of each member and first and second ends of the drill string. 
     Still another aspect of the invention relates to a method of providing an electrical connection throughout the length of a drill string. The drill string includes one or more members having generally longitudinally extending housings. Each housing member includes an outer surface and an inner surface defining a hollow passage therethrough. The first and second ends of each member are adapted and configured to be coupled to a drill head, a drill stem or a starter rod. The drill string also includes electrical connection means between ends of each of the members and electrical insulation means between the electrical connection means and the outer surfaces of each of the members. The drill string also includes one or more electrical conductors encapsulated by an electrically insulative material and each electrical conductor is disposed within the hollow passage of each of the members and are electrically connected through the electrical connection means to an electrical conductor of an adjacent member throughout the length of the drill string. The method includes moving a first member into coaxial alignment with a drill axis, coupling a second member to the first member and engaging electrical connection means between adjacent ends of the members while coupling the first member to the second member. 
     Yet another aspect of the invention relates to a system for locating a drill head located below the ground from a location above the ground. The system includes a drilling apparatus, a drill string arranged and configured to be coupled to the drilling apparatus at one end and coupled to a drill head at another end, said drill string further including one or more members having generally longitudinally extending housings, each of the housings include an outer surface and an inner surface defining a hollow passage therethrough and first and second ends adapted and configured to be coupled to a drill head, a drill stem or a starter rod. The drill string also includes electrical connection means between each of the members and electrical insulation means between the electrical connection means and the outer surfaces of each of the members. The drill string also includes one or more electrical conductors encapsulated by an electrically insulative material. Each electrical conductor is disposed within the hollow passage of each of the members and are electrically connected through the electrical connection means to an electrical conductor of an adjacent member throughout the length of the drill string. The system also includes an electronic transmitter disposed within the drill head, the transmitter emitting electromagnetic energy. The system also includes an electronic receiver disposed above ground, the electronic receiver receiving the electromagnetic energy. 
     Another aspect of the invention relates to a drill head that forms a portion of a drill string for boring a hole through the ground. The drill head includes a member having a generally longitudinally extending housing including an outer surface, an inner surface defining a first hollow passage therethrough. The housing further defining a chamber, a first end adapted and configured for boring through the ground and a second end adapted and configured to be coupled to any one of a starter rod and a drill stem. An electrically insulative ring radially disposed about said second end, and one or more second hollow passages defined through said member, said one or more second hollow passages forming one or more access tunnels for providing a signal flow path. 
     Yet another aspect of the invention is a drill pipe that forms a portion of a drill string for boring a hole through the ground. The drill pipe includes a member having a generally longitudinally extending housing including an outer surface, an inner surface defining a first hollow passage therethrough and first and second ends adapted and configured to be coupled to a second drill pipe. An electrically insulative ring radially disposed about said second end, and one or more second hollow passages defined through said member, said one or more second hollow passages forming one or more access tunnels for providing a signal flow path. 
     Still a further aspect of the invention is a drill string for boring a hole through the ground having a first end adapted and configured to be coupled to a drilling apparatus and a second send adapted and configured for boring a hole through the ground. The drill string includes one or more members having generally longitudinally extending housings, each of said housings including an outer surface and an inner surface defining a hollow passage therethrough and first and second ends adapted and configured to be coupled to any one of a drill head, a drill stem and a starter rod. Electrical insulation means between said members, and one or more second hollow passages defined through said member, said one or more second hollow passages forming one or more access tunnels for providing a signal flow path. 
     Another aspect of the invention is a method for providing an electrical connection between first and second pipes in a drill string, the pipes including electrical conductors that extend through the pipes, the electrical conductors including electrical contact locations attached to the pipes adjacent the ends of the pipes, the electrical contact locations including a first electrical contact location corresponding to the first pipe and a second electrical contact location corresponding to the second pipe, the first and second electrical contact locations being positioned such that when the first and second pipes are threaded together, the first electrical contact location contacts the second electrical contact location. The method including electrically connecting the electrical conductors of the first and second pipes by threading the first and second pipes together thereby causing the first electrical contact location to be brought into contact with the second electrical contact location. 
     A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various aspects of the invention and together with the description, serve to explain the principles of the invention. These and other features, aspects and advantages of the invention will become better understood with regard to the following description, appended claims and accompanying drawings where: 
     FIG. 1 is a side elevational view of one example of a directional drilling or boring machine constructed in accordance with the principles of the present invention; 
     FIG. 2 is a side elevational view of a one example of a directional drilling or boring machine including a drill string constructed in accordance with the principles of the present invention; 
     FIG. 3 illustrates one example of a system for locating a drill head located below the ground from a location above the ground; 
     FIG. 4 is a longitudinal cross-sectional view of one example of a drill head and starter rod; 
     FIG. 5 is a longitudinal cross-sectional view of one example of mechanically coupled drill stems; 
     FIG. 6 is a longitudinal cross-sectional view of one example of mechanically coupled drill stems; 
     FIGS. 7A-C are cross-sectional end views of several examples of drill stems; 
     FIGS. 8A-B is a longitudinal cross-sectional view of one example of mechanically coupled drill stems; 
     FIG. 9 is a longitudinal cross-sectional view of one example of mechanically coupled drill stems; and 
     FIG. 10 is functional block diagram of a system for locating a drill head. 
    
    
     DESCRIPTION 
     Reference will now be made in detail to exemplary aspects of the present invention which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIG. 1 shows one embodiment of a drilling apparatus  20  (e.g., a directional boring machine) constructed in accordance with the principles of the present invention. The drilling apparatus  20  includes a pair of drive tracks  22  (only one shown) for propelling the drilling apparatus  20  along the ground. A frame  24  is pivotally mounted above the drive tracks  22 . A magazine  26  for holding one or more drill stems  40 ,  40 ′ and  40 ″ (FIG. 2) is supported on the frame  24 . An elongated track  30  is also supported on the frame  24 . A drive head  32  is mounted on a carriage  42  that is coupled to the elongated track  30 . The drive head  32  includes a drive member  34  adapted to be coupled to a drill stem (e.g., the drive member  34  includes a threaded end that can be threaded within a drill stem). A drive mechanism  38  is provided for rotating the drive member  34  about a longitudinal drive axis X—X that is generally parallel with respect to the elongated track and a drive mechanism  44  is provided for moving the carriage  42  back and forth along the elongated track  30 . A pair of drill stem transfer members  46  are used to convey drill stems between the magazine  26  and the drive head  32 . 
     The drilling apparatus  20  is used to push a drill string  28  (FIG. 2) formed of several drill pipes. The drill string  28  comprises at least one drill stem, a starter rod and a drill head, into the ground to bore a hole. To start the drilling sequence, the frame  24  is pivoted relative to the drive tracks  22  such that the elongated track  30  is inclined relative to the ground (shown generally at FIG.  3 ). Also, the carriage  42  is moved to a start position as shown in FIG. 1. A first drill stem is then removed from the magazine  26  by the drill stem transfer members  46  and placed in coaxial alignment with the drive axis X—X of the drive head  32 . With the drill stem aligned along the drive axis X—X, one end of the drill stem is coupled to the drive member  34  of the drive head  32 . Preferably, a cutting or boring member, e.g., a drill head  36  (FIG.  2 ), is positioned at the other end of the drill stem. Once the drill stem has been coupled to the drive member  34 , the drive mechanism  38  is used to rotate the drill stem about the drive axis X—X. Concurrently, a push stroke is initiated such that the rotating drill stem is drilled into the ground. During the push stroke, the drive mechanism  44  moves the carriage  42  in a direction  48  along the track  30 . As is conventionally known in the art, drilling fluids can be used to facilitate drilling operations. 
     After the push stroke has been completed, the drive member  34  of the drive head  32  is uncoupled from the drill stem and a return/pull stroke is initiated such that the carriage  42  returns to the start position of FIG.  1 . During the return/pull stroke, the drive mechanism  44  moves the carriage  42  in a direction  50  along the track  30 . With the carriage  42  returned to the start position, a second drill stem is removed from the magazine  26  and placed in coaxial alignment with the drive axis X—X. As so aligned, the second drill stem is coupled to both the drive member  34  and the first drill stem to form a drill string. Thereafter, a push stroke is again initiated such that the entire drill string is pushed further into the ground. By repeating the above steps, additional drill stems can be added to the drill string thereby increasing the length of the hole that is being drilled by the drilling apparatus  20 . 
     Once the hole has been drilled to a desired length, it is common to enlarge the hole through a back reaming process. For example, a back reamer can be attached to the distal end of the drill string. Additionally, product desired to be placed in the hole (e.g., a cable, a duct or the like) can also be connected to the distal end of the drill string. The drill string is then rotated and pulled back toward the drilling apparatus by the drive head  32 . For example, the drive head  32  is connected to the drill string and then a return/pull stroke is initiated causing drill string to be pulled in the direction  50 . As the drill string is pulled back to the drilling apparatus  20 , the back reamer enlarges the previously drilled hole and the product is pulled into the enlarged hole. With each pull/return stroke of the drive head  32 , a drill stem is removed from the ground. A conventional scraper (not shown) can be used to remove earth residue from the drill stems as the drill stems are extracted. The extracted drill stems are then uncoupled from the drill string and the drill stem transfer members  46  are used to convey the drill stems back to the magazine  26 . Preferably, drill stem lifts  52  are used to push the drill stems from the drill stem transfer members  46  back into the magazine  26 . 
     FIG. 2 shows one embodiment of the drilling apparatus  20  with the drill string  28  attachment constructed according to the principles of the present invention. The drill string  28  comprises of multiple drill pipes or stems  40 ,  40 ′,  40 ″ coupled together at several points  54 ,  54 ′,  54 ″ and  54 ′″ (generally the drill stems are threaded together), a starter rod  56  and a drill head  36 . An important aspect of the present invention relates to providing electrical power from the drilling apparatus  20  located above ground to a sonde  58  (FIG. 4) located within the drill head  36  below ground, and providing electrical signals to and from the sonde and the drilling apparatus  20 . In one embodiment, the present invention provides electrical connections through the drill stems  40 ,  40 ′ and  40 ″ as they are mechanically coupled to each other, to the starter rod  56  and to the drill head  36 . Means for making an electrical contact at the mechanical coupling points  54 ,  54 ′,  54 ″ and  54 ′″ are provided between these members. During the mechanical coupling process the contacts at the coupling points  54 ,  54 ′,  54 ″ and  54 ′″ make an electrical connection with an electrical conductor disposed within the drill stems  40 ,  40 ′ and  40 ″, the starter rod  56  and the drill head  36 . 
     FIG. 3 shows a system  60  constructed according to the principles of the present invention for locating the drill head  36  located at a distal end of the drill string  28  which is located below the ground  62 . The position of the drill head  36  is located using a radio receiver  64  from a location above the ground  62 . The radio receiver  64  detects electromagnetic energy at radio frequencies emitted by the sonde  58  (FIG. 4) located within the drill head  36 . One advantage of the present invention is that electrical power is supplied to the sonde via an electrical conductor disposed within a hollow passage inside the drill string  28 . Thus providing as much electrical power as may be required to generate an electromagnetic signal to be detected above the ground  62 . This feature allows the sonde  58  to emit a stronger electromagnetic signal. This is desirable if there is excessive attenuation of the signal at a point above the ground  62 . 
     FIG. 4 shows one embodiment of a longitudinal cross sectional view of the drill head  36  and the starter rod  56  forming a portion of the drill string  28 , constructed according to the principles of the present invention. The drill head  36  includes a generally longitudinally extending housing  66  including an outer surface  68  and an inner surface defining a hollow passage  70 . The hollow passage  70  is generally used to pass drilling fluids to facilitate the drilling process. The housing  66  also includes a chamber  72  for placing a sonde  58  therein. The drill head  36  includes a first end  75  adapted and configured with a drilling or boring member  74 . The drill head  36  includes a second end  76  adapted and configured to be coupled to a starter rod  56  at mechanical coupling point  54 . The second end  76  of the drill head  36  is a male threaded end that couples into a female threaded end of the starter rod  56 . It will be appreciated that the coupling ends may be male or female threaded ends depending on the configuration of the invention. 
     The starter rod  56 , constructed according to the principles of the present invention, also includes a generally longitudinally extending housing  82  including an outer surface  84  and an inner surface defining a hollow passage  80 . As is conventionally known in the art, drilling fluids are passed through the hollow passage  80  to facilitate the drilling process. The starter rod  56  includes a first female threaded end to couple with the drill head  36  at coupling point  54 . The starter rod  56  also includes a female threaded end adapted and configured for coupling to the drill stem  40  at connection point  54 ′. 
     Whenever the starter rod  56  is mechanically coupled to the drill head  36 , means disposed at each corresponding mechanical coupling ends form an electrical connection between a segment of electrical conductor  81  disposed within the hollow passage  80  of the starter rod  56 , and a segment of electrical conductor  83  disposed within the hollow passage  70  of the drill head  36 . The segment of electrical conductor  83  disposed within the drill head  36  terminates at the sonde  58  for supplying power thereto and for carrying signals therefrom and thereto. Also, an electrical conductor segment (not shown) disposed within the drill stem  40  is electrically coupled to the electrical conductor  81  segment disposed within the hollow passage  80  of the starter rod  56 , whenever the drill stem  40  is mechanically coupled to the starter rod  56 . An electrical contact point similar to electrical contact point  102  (described in detail in the description of FIG. 5 below) is formed between the starter rod  56  and the drill head  36  to provide an electrical connection between the conductor segments  81 ,  83  disposed within the starter rod  56  and the drill head  36 , respectively. 
     FIG. 5 shows generally at  88  a longitudinal cross sectional view of portions of drill stems  40  and  40 ′ mechanically coupled at mechanical coupling point  54 ″. Drill stems  40  and  40 ′ include outer surfaces  108  and  110 , respectively, and inner surfaces defining hollow passages  90  and  92 , respectively. The first drill stem  40  includes a segment of electrical conductor  94  that is encapsulated in an electrically insulative material. Likewise, the second drill stem  40 ′ also includes a segment of electrical conductor  96  that is encapsulated in an electrically insulative material. The first drill stem  40  includes a conductive ring  98  disposed at one end. Adjacent to the conductive ring  98 , the first drill stem  40  also includes an insulative (non-electrically-conductive) ring  104 . The second drill stem  40 ′ also includes a conductive ring  100 , and an insulative ring  106  disposed adjacently to the conductive ring  100 . 
     The electrical conductor segments  94 ,  96  are cylindrical (e.g., tubular) in shape for allowing drilling fluids to pass through each conductor segments. The conductor segments are formed with end flanges that project radially outward to provide a piercing location. Those skilled in the art will appreciate that the conductor segments should not be limited to a cylindrical tubular shape and may be provided in various embodiments as long as the functionality of passing drilling fluids between the first and second drill stems  40 ,  40 ′, respectively, is preserved. For example, one or more electrical conductor segments may be provided whereby each conductor segment is formed with a flange that projects radially outward to provide a piercing location. 
     When the second drill stem  40 ′ is mechanically coupled to the first drill stem  40  at mechanical coupling point  54 ″ an electrical contact point  102  is formed between the conductive rings  98  and  100 . As the second drill stem  40 ′ is coupled to the first drill stem  40 , the conductive ring  98  forms an electrical contact with the electrical conductor segment  94  disposed within the hollow passage  90 . Likewise, the conductive ring  100  forms an electrical contact with the electrical conductor segment  96 . Accordingly, a continuous electrical connection is formed between the newly added second drill stem  40 ′ through the electrically conductive coupling point  102  and mechanical coupling point  54 ″ to the portion of the drill string  28  formed by the drill stem  40 , the starter rod  56  and the drill head  36 . The electrically insulative rings  104  and  106  electrically isolate the conductive rings  98  and  100 , respectively, from the outer surfaces  108  and  110 , respectively, of the drill stems  40 ,  40 ′, respectively. The electrically insulative material encapsulating the electrical conductors  94 ,  96  electrically isolate the electrical conductor segments  94  and  96 , from the outer surfaces  108 ,  110 , respectively. 
     It will be appreciated by those skilled in the art that the conductive rings  98 ,  100  may be formed of copper and the electrically insulative rings  104 ,  106  may be formed of a polymer material. The insulative rings  104 , 106  may also be formed of polyurethane, ceramic or other suitable electrically insulative materials that are generally well known in the art, without departing from the principles of the present invention. Furthermore, it will be appreciated that since insulative rings  104 ,  106  may be constructed of various polymers or polyurethanes, they will be compressed during the mechanical coupling process of the drill stems  40 ,  40 ′ so as to ensure good electrical engagement between the conductive rings  98 ,  100  and the electrical conductor segments  94 ,  96 , respectively. 
     FIG. 6 shows a detailed longitudinal cross sectional view of the portions of the drill stems  40 ,  40 ′ that are mechanically coupled at mechanical coupling point  54 ″. Other drill stems forming the drill string  28  are coupled in a similar fashion. Means for electrically coupling the conductive rings to the electrical conductor segments  94 ,  96  are provided on a rear portion of the conductive rings  98 ,  100 , respectively, that faces inwardly toward the center of the drill stem  40 ,  40 ′, respectively. For example, in one embodiment, means  112 ,  114  for piercing the electrically insulative material encapsulating the electrical conductor segments  94 ,  96  are provided on the rear portion of the conductive rings  98 ,  100 , respectively. It will be appreciated that other means may be provided for electrically coupling the conductive rings  98 ,  100  to the electrical conductor segments  94 ,  96 , respectively, without departing from the principles of the invention. 
     In one embodiment, as the drill stems  40  and  40 ′ are mechanically coupled, the rear portions of conductive rings  98 ,  100 , forming surfaces  112 ,  114 , respectively, pierce through the insulative material encapsulating the electrical conductive segments  94 ,  96 , respectively. Thus, forming an electrically conductive coupling with the electrical conductor segments  94  and  96  through electrical coupling point  102 . Accordingly, the conductive rings  98 ,  100  are then electrically coupled to the electrical conductor segments  94 ,  96 , respectively. 
     FIG. 7A is a cross sectional view of the drill stem  40 ′ taken along section A—A (FIG.  6 ). The conductive ring  100  is disposed at one end of the drill stem  40 ′ with an insulative ring  106  disposed adjacent and to the rear of the conductive ring  100 . 
     As illustrated in FIG. 7B, in one embodiment, a drill stem  240 ′ includes conductive rings formed as ring portions  100 ′,  100 ″, electrically insulated from each other. The conductive half rings  100 ′,  100 ″ are disposed at one end of the drill stem  240 ′ with an insulative ring  206  disposed adjacent and to the rear of the conductive ring portions  100 ′,  100 ″. Each ring portion  100 ′,  100 ″ providing a conductive path from an electrical conductor segment in one drill stem to another electrical conductor segment in an adjacent drill stem, as described above. Accordingly, once the two drill stems are coupled, two separate continuous electrical connections may be formed between the drill stems forming a drill string. It will be appreciated that one or more conductive ring segments may be provided in a similar fashion for providing one or more continuous conductive paths along the drill string  28  from a point above the ground  62  to the drill head  36 . 
     FIG. 8A illustrates one embodiment of the invention where conductive rings  98 ′ and  100 ′ are provided with an electrically insulative coating  198 ′,  200 ′. The electrically insulative coating  198 ′,  200 ′ functions such that contact point  102 ′ will no longer be an electrically conductive connection between the rings  98 ′ and  100 ′. Rather, the electrically insulative coatings  198 ′ and  200 ′ will electrically isolate the conductive rings  98 ′,  100 ′ from each other. Thus, this configuration forms a capacitive coupling between the conductive rings  98 ′ and  100 ′. Accordingly, the electrical conductor segments  94 ′ and  96 ′ will be capacitively coupled to each other rather than being electrically conductively coupled. However, as described above, each ring  98 ′,  100 ′ provides an electrical connection between itself and a corresponding electrical conductor segment  94 ′ and  96 ′, respectively, disposed within drill stems  140 ,  140 ′, respectively. For example, means  112 ′,  114 ′ for piercing the electrically insulative material encapsulating the electrical conductor segments  94 ′,  96 ′ may be utilized. 
     FIG. 8B is a detailed illustration of the capacitive coupling connection at  102 ′, showing electrically the insulative coating  198 ′ on conductive ring  98 ′ and the electrically insulative coating  200 ′ on conductive ring  100 ′. 
     In one embodiment, one conductor may be used for capacitively coupling electrical signals between adjacent drill segments  140 ,  140 ′ through the capacitive coupling joint formed at the coupling point  102 ′. In this configuration, the exterior portions  108 ′ and  110 ′ of drill segments  140 ,  140 ′, respectively, provide a return path for an electrical signal that is capacitively coupled along the length of the drill stem. In another embodiment, two conductors may be used. One conductor for providing a signal path and the other conductor for providing a return path. 
     FIG. 9 shows generally at  136  a longitudinal cross sectional view of portions of drill stems  116  and  116 ′ mechanically coupled at mechanical coupling point  134 . Drill stems  116  and  116 ′ include outer surfaces  120  and  118 , respectively, and inner surfaces defining first hollow passages  124  and  122 , respectively. Each drill stem  116 ,  116 ′ further includes second hollow passages  138  and  128 , respectively, forming access tunnels for feeding means for providing a signal flow path therethrough (e.g. an electrical conductor cable, fiber optic cable, acoustic conduit, and the like). 
     It will be appreciated that as drill stems are added, a continuous signal flow path is formed between the drill head  36  and to a point above the ground (e.g. the drilling apparatus  20 ). It will also be appreciated that other cables or conduits capable of providing an electrical power, and/or a signal flow path between the drill head  36  and a point above ground may be provided through the second hollow passages  138 ,  128 . For example, a fiber optic cable may be disposed within the second passages  138 ,  128  for providing a signal flow path capable of transferring pulses of light therethrough. 
     As shown in FIG. 9, electrical conductor  126 , encapsulated in an electrically insulative material, is disposed within the second passage  138  in drill segment  116 . Likewise, the electrical conductor  126  is disposed within the second passage  128  in drill segment  116 ′. Electrical power and/or signals may be transmitted by the electrical conductor  126  from a point above the ground (e.g. the drilling apparatus) to the sonde  58  (or other electronic device) located within a drill head below the ground. To provide electrical isolation between the drill stems  116 ,  116 ′, an insulated contact ring  130  is disposed between the drill stems  116 ,  116 ′. It will be appreciated that the drill segments  116  and  116 ′ may be provided with one or more hollow passages for providing one or more signal paths between the sonde  58  and a point above ground. 
     Electrical conductor segment  126  should not be limited to a single conductor segment passing through the drill stems  116  and  116 ′. For example, separate conductor segments may be utilized without departing from the principles of the invention. Accordingly, if separate conductor segments are provided within the drill stems  116  and  166 ′ an electrical contact point similar to electrical contact point  102  (described in detail in the description of FIG. 5 above) may be provided between drill stems  116  and  116 ′ thus providing an electrical connection between the separate conductor segments disposed therein. 
     FIG. 7C shows a cross sectional view of the drill stem  116 ′ taken along section B—B (FIG.  9 ). In one embodiment, a single hollow passage  128  is provided in the drill stem  116 ′. Insulative ring  130  being disposed on a distal end of the drill stem. 
     FIG. 7D is a cross sectional view of the drill stem  216 ′ provided with two hollow passages  128 ′,  128 ″ within a drill stem  216 ′. As described above, an electrically insulative ring  230  is disposed on a distal end of the drill stem  216 ′. 
     FIG. 10 illustrates a functional block diagram of a system  139  for determining the position of a sonde  144  that is located underground. In one embodiment electrical power and signals may be provided to and from the sonde  144  and a power/signal source  152  via power/signal paths  146 ,  150 . It will be appreciated that both power and signals may be provided along a single path. In one embodiment, electrical power may be provided to the sonde  144  from the power/signal source  152 . The sonde  144  may propagate electromagnetic energy  142  to be detected above ground using radio frequency receiver  140 . 
     It is to be understood that the present invention is not limited to the particular construction and arrangement of parts disclosed and illustrated herein, but embraces all such modified forms thereof as come within the scope of the following claims.