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CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Division of pending U.S. patent application Ser. No. 10/430,734 “Loaded Transducer for Downhole Drilling Components” filed on May 6, 2003, by David R. Hall, et al, and incorporated by reference herein for all it discloses. 
     
    
     STATEMENT OF GOVERNMENT INTEREST  
       [0002]     This invention was made with government support under Contract No. DE-FC26-01NT41229 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. The Field of the Invention  
         [0004]     This invention relates to oil and gas drilling, and more particularly to apparatus and methods for reliably transmitting information between downhole drilling components.  
         [0005]     2. The Relevant Art  
         [0006]     For the past several decades, engineers have worked to develop apparatus and methods to effectively transmit information from components located downhole on oil and gas drilling strings to the ground&#39;s surface. Part of the difficulty of this problem lies in the development of reliable apparatus and methods for transmitting information from one drill string component to another, such as between sections of drill pipe. The goal is to provide reliable information transmission between downhole components stretching thousands of feet beneath the earth&#39;s surface, while withstanding hostile wear and tear of subterranean conditions.  
         [0007]     In an effort to provide solutions to this problem, engineers have developed a technology known as mud pulse telemetry. Rather than using electrical connections, mud pulse telemetry transmits information in the form of pressure pulses through fluids circulating through a well bore. However, data rates of mud pulse telemetry are very slow compared to data bandwidths needed to provide real-time data from downhole components.  
         [0008]     For example, mud pulse telemetry systems often operate at data rates less than 10 bits per second. At this rate, data resolution is so poor that a driller is unable to make crucial decisions in real time. Since drilling equipment is often rented and very expensive, even slight mistakes incur substantial expense. Part of the expense can be attributed to time-consuming operations that are required to retrieve downhole data or to verify low-resolution data transmitted to the surface by mud pulse telemetry. Often, drilling or other procedures are halted while crucial data is gathered.  
         [0009]     In an effort to overcome limitations imposed by mud pulse telemetry systems, reliable connections are needed to transmit information between components in a drill string. For example, since direct electrical connections between drill string components may be impractical and unreliable, converting electrical signals to magnetic fields for later conversion back to electrical signals offers one solution for transmitting information between drill string components.  
         [0010]     Nevertheless, various factors or problems may make data transmission unreliable. For example, dirt, rocks, mud, fluids, or other substances present when drilling may interfere with signals transmitted between components in a drill string. In other instances, gaps present between mating surfaces of drill string components may adversely affect the transmission of data therebetween.  
         [0011]     Moreover, the harsh working environment of drill string components may cause damage to data transmission elements. Furthermore, since many drill string components are located beneath the surface of the ground, replacing or servicing data transmission components may be costly, impractical, or impossible. Thus, robust and environmentally-hardened data transmission components are needed to transmit information between drill string components.  
       SUMMARY OF THE INVENTION  
       [0012]     In view of the foregoing, it is a primary object of the present invention to provide robust transmission elements for transmitting information between downhole tools, such as sections of drill pipe, in the presence of hostile environmental conditions, such as heat, dirt, rocks, mud, fluids, lubricants, and the like. It is a further object of the invention to maintain reliable connectivity between transmission elements to provide an uninterrupted flow of information between drill string components.  
         [0013]     Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, an apparatus is disclosed in one embodiment of the present invention as including a transmission element having a communicating surface mountable proximate a mating surface of a downhole drilling component, such as a section of drill pipe.  
         [0014]     By “mating surface,” it is meant a surface on a downhole component intended to contact or nearly contact the surface of another downhole component, such as another section of drill pipe. For example, a mating surface may include threaded regions of a box end or pin end of drill pipe, primary or secondary shoulders designed to come into contact with one another, or other surfaces of downhole components that are intended to contact or come into close proximity to surfaces of other downhole components.  
         [0015]     A transmission element may be configured to communicate with a corresponding transmission element located on another downhole component. The corresponding transmission element may likewise be mountable proximate a mating surface of the corresponding downhole component. In order to close gaps present between communicating surfaces of transmission elements, transmission elements may be biased with respect to the mating surfaces they are mounted on.  
         [0016]     By “biased,” it is meant, for the purposes of this specification, that a transmission element is urged, by a biasing member, such as a spring or an elastomeric material, or by a “spring force” caused by contact between a transmission element and a mating surface, in a direction substantially orthogonal to the mating surface. Thus, the term “biased” is not intended to denote a physical position of a transmission element with respect to a mating surface, but rather the condition of a transmission element being urged in a selected direction with respect to the mating surface. In selected embodiments, the transmission element may be positioned flush with, above, or below the mating surface.  
         [0017]     Since a transmission element is intended to communicate with another transmission element mounted to another downhole tool, in selected embodiments, only a single transmission element is biased with respect to a mating surface. For example, transmission elements may be biased only in “pin ends” of downhole tools, but may be unbiased or fixed in “box ends” of the same downhole tools. However, in other embodiments, the transmission elements are biased in both the pin ends and box ends.  
         [0018]     In selected embodiments, a gap may be present between mating surfaces of downhole tools due to variations in tolerances, or materials that may become interposed between the mating surfaces. In other embodiments, the mating surfaces are in contact with one another. In selected embodiments, a biasing member, such as a spring or elastomeric material may be inserted between a transmission element and a corresponding mating surface to effect a bias therebetween.  
         [0019]     A mating surface may be shaped to include a recess. A transmission element may be mounted or housed within the recess. In selected embodiments, a recess may include a locking mechanism to retain the transmission element within the recess. In certain embodiments, the locking mechanism is a locking shoulder shaped into the recess. A transmission element, once inserted into the recess, may slip past and be retained by the locking shoulder.  
         [0020]     A transmission element and corresponding recess may have an annular shape. In selected embodiments, a transmission element may snap into the recess and be retained by the locking mechanism. In selected embodiments, angled surfaces of the recess and the transmission element may create a “spring force” urging the transmission element in a direction substantially orthogonal to the mating surface. This “spring force” may be caused by the contact of various surfaces of the transmission element and the recess, including the outside diameters, the inside diameters, or a combination thereof.  
         [0021]     In selected embodiments, a transmission element on a downhole component communicates with a transmission element on a separate downhole component by converting an electrical signal to a magnetic field or current. The magnetic field or current induces an electrical current in a corresponding transmission element, thereby recreating the original electrical signal. In other embodiments, a transmission element located on a downhole component may communicate with a transmission element on another downhole component due to direct electrical contact therebetween.  
         [0022]     In another aspect of the present invention, a method for transmitting information between downhole tools located on a drill string includes mounting a transmission element, having a communicating surface, proximate a mating surface of a downhole tool. Another transmission element, having a communicating surface, may be mounted proximate a mating surface of another downhole tool, the mating surfaces of each downhole tool being configured to contact one another. The method may further include biasing at least one transmission element with respect to a corresponding mating surface to close gaps present between communicating surfaces of the transmission elements.  
         [0023]     In certain instances, a gap may be present between the mating surfaces. In other instances, mating surfaces may be in direct contact with one another. The method may further include providing a biasing member, such as a spring, elastomeric material, or the like, to effect the bias between a transmission element and a mating surface.  
         [0024]     A method may further include shaping a mating surface to include a recess such that the transmission element substantially resides in the recess. Within the recess, a locking mechanism may be provided to retain the transmission element within the recess. The locking mechanism may be a locking shoulder and the transmission element may be retained within the first recess by slipping by and engaging the locking shoulder.  
         [0025]     A method in accordance with the invention may further include forming a transmission element and a recess into an annular shape. Furthermore, biasing of the transmission element may be provided by angled surfaces of the recess and the transmission element to create a “spring force,” thereby urging the transmission element in a direction substantially orthogonal to a mating surface. This “spring force” may be caused by contact between various surfaces of the transmission element and the recess, including the outside diameters, the inside diameters, or a combination thereof. The method may further include communicating between transmission elements due to direct electrical contact or by transfer of magnetic energy therebetween.  
         [0026]     In another aspect of the present invention, an apparatus for transmitting data between downhole tools may include a loaded annular housing. By “loaded,” it is meant, for the purposes of this specification, providing a “spring force” between a mating surface and an annular housing mounted thereon. In selected embodiments, the annular housing may include at least one substantially U-shaped element disposed within the loaded annular housing.  
         [0027]     The U-shaped element may be composed of a magnetically conductive and electrically insulating material, such as ferrite, thereby enabling magnetic current to be retained therein and channeled in a desired direction. An electrical conductor may be disposed within the U-shaped element to carry electrical current. The electrical conductor may be electrically insulated to prevent shorting of the conductor to other electrically conductive components.  
         [0028]     The loaded annular housing may be formed such that it is mountable in a recess of a mating surface of a downhole tool. The annular housing may be flush with the mating surface, below the mating surface, above the mating surface, or a combination thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The foregoing and other features of the present invention will become more fully apparent from the following description, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments in accordance with the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which:  
         [0030]      FIG. 1  is a perspective view illustrating one embodiment of sections of downhole drilling pipe using transmission elements, in accordance with the invention, to transmit and receive information along a drill string;  
         [0031]      FIG. 2  is a cross-sectional view illustrating one embodiment of gaps that may be present between a pin end and box end of downhole drilling components, thereby causing unreliable communication between transmission elements;  
         [0032]      FIG. 3  is a perspective cross-sectional view illustrating one embodiment of an improved transmission element retained within a recess of a box end or pin end of a downhole drilling component;  
         [0033]      FIG. 4A  is a perspective cross-sectional view illustrating one embodiment of a shoulder formed along both the inside and outside diameters of a loaded annular transmission element;  
         [0034]      FIG. 4B  is a perspective cross-sectional view illustrating one embodiment of a shoulder formed along the inside diameter of a loaded annular transmission element; and  
         [0035]      FIG. 4C  is a perspective cross-sectional view illustrating one embodiment of a shoulder formed along the outside diameter of a loaded annular transmission element. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]     It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of embodiments of apparatus and methods of the present invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of various selected embodiments of the invention.  
         [0037]     The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. Those of ordinary skill in the art will, of course, appreciate that various modifications to the apparatus and methods described herein may easily be made without departing from the essential characteristics of the invention, as described in connection with the Figures. Thus, the following description of the Figures is intended only by way of example, and simply illustrates certain selected embodiments consistent with the invention as claimed herein.  
         [0038]     Referring to  FIG. 1 , drill pipes  10   a,    10   b,  or other downhole tools  10   a,    10   b,  may include a pin end  12  and a box end  14  to connect drill pipes  10   a,    10   b  or other components  10   a,    10   b  together. In certain embodiments, a pin end  12  may include an external threaded portion to engage an internal threaded portion of the box end  14 . When threading a pin end  12  into a corresponding box end  14 , various shoulders may engage one another to provide structural support to components connected in a drill string.  
         [0039]     For example, a pin end  12  may include a primary shoulder  16  and a secondary shoulder  18 . Likewise, the box end  14  may include a corresponding primary shoulder  20  and secondary shoulder  22 . A primary shoulder  16 ,  20  may be labeled as such to indicate that a primary shoulder  16 ,  20  provides the majority of the structural support to a drill pipe  10  or downhole component  10 . Nevertheless, a secondary shoulder  18  may also engage a corresponding secondary shoulder  22  in the box end  14 , providing additional support or strength to drill pipes  10  or components  10  connected in series.  
         [0040]     As was previously discussed, apparatus and methods are needed to transmit information along a string of connected drill pipes  10  or other components  10 . As such, one major issue is the transmission of information across joints where a pin end  12  connects to a box end  14 . In selected embodiments, a transmission element  24   a  may be mounted proximate a mating surface  18  or shoulder  18  on a pin end  12  to communicate information to another transmission element  24   b  located on a mating surface  22  or shoulder  22  of the box end  14 . Cables  27   a,    27   b,  or other transmission medium  27 , may be operably connected to the transmission elements  24   a,    24   b  to transmit information therefrom along components  10   a,    10   b.    
         [0041]     In certain embodiments, a recess may be provided in the secondary shoulder  18  of the pin end  12  and in the secondary shoulder  22  of the box end  14  to house each of the transmission elements  24   a,    24   b.  The transmission elements  24   a,    24   b  may have an annular shape and be mounted around the radius of the drill pipe  10 . Since a secondary shoulder  18  may contact or come very close to a secondary shoulder  22  of a box end  14 , a transmission element  24   a  may sit substantially flush with a secondary shoulder  18  on a pin end  12 . Likewise, a transmission element  24   b  may sit substantially flush with a surface of a secondary shoulder  22  of a box end  14 .  
         [0042]     In selected embodiments, a transmission element  24   a  may communicate with a corresponding transmission element  24   b  by direct electrical contact therewith. In other embodiments, the transmission element  24   a  may convert an electrical signal to a magnetic flux or magnetic current. A corresponding transmission element  24   b,  located proximate the transmission element  24   a,  may detect the magnetic field or current. The magnetic field may induce an electrical current into the transmission element  24   b  that may then be transmitted from the transmission element  24   b  to the electrical cable  27   b  located along the drill pipe  10  or downhole component  10 .  
         [0043]     As was previously stated, a downhole drilling environment may adversely affect communication between transmission elements  24   a,    24   b  located on successive drill string components  10 . For example, materials such as dirt, mud, rocks, lubricants, or other fluids, may inadvertently interfere with the contact or communication between transmission elements  24   a,    24   b.  In other embodiments, gaps present between a secondary shoulder  18  on a pin end  12  and a secondary shoulder  22  on a box end  14  due to variations in component tolerances may interfere with communication between transmission elements  24   a,    24   b.  Thus, apparatus and methods are needed to reliably overcome these as well as other obstacles.  
         [0044]     Referring to  FIG. 2 , for example, as was previously stated, a gap  28  may be present between the secondary shoulders  18 ,  22  of the pin end  12  and box end  14 . This gap  28  may be the result of variations in manufacturing tolerances between different sections  10   a,    10   b  of pipe. In other embodiments, the gap  28  may be the result of materials such as dirt, rocks, mud, lubricants, fluids, or the like, interposed between the shoulders  18 ,  22 .  
         [0045]     If transmission elements  24   a,    24   b  are designed for optimal function when in direct contact with one another, or when in close proximity to one another, materials or variations in tolerances leaving a gap  28  may cause malfunction of the transmission elements  24   a,    24   b,  impeding or interfering with the flow of data. Thus, apparatus and methods are needed to improve reliability of communication between transmission elements  24   a,    24   b  even in the presence of gaps  28  or other interfering substances.  
         [0046]     In accordance with the present invention, a transmission element  24   a,    24   b  may be provided such that it is moveable with respect to a corresponding shoulder  18 ,  22 . Thus, transmission elements  24   a,    24   b  may be translated such that they are in closer proximity to one another to enable effective communication therebetween. In selected embodiments, direct contact between transmission elements  24   a,    24   b  may be required.  
         [0047]     In other embodiments, only a specified separation may be allowed between transmission elements  24   a,    24   b  for effective communication. As illustrated, transmission elements  24   a,    24   b  may be mounted in secondary shoulders  18 ,  22  of the pin end  12  and box end  14  respectively. In reality, the transmission elements  24   a,    24   b  may be provided in any suitable surface of the pin end  12  and box end  14 , such as in primary shoulders  16 ,  20 .  
         [0048]     Referring to  FIG. 3 , in selected embodiments, a transmission element  24  may include an annular housing  30 . The annular housing  30  may include a magnetically conducting electrically insulating element  32  therein, such as ferrite or some other material of similar electrical and magnetic properties. The element  32   a  may be formed in a U-shape and fit within the housing  30 . Within the U-shaped element  32   a,  a conductor  34  may be provided to carry electrical current therethrough. In selected embodiments, the electrical conductor  34  is coated with an electrically insulating material  36 .  
         [0049]     As current flows through the conductor  34 , a magnetic flux or field may be created around the conductor  34 . The U-shaped element  32  may serve to contain the magnetic flux created by the conductor  34  and prevent energy leakage into surrounding materials. The U-shape of the element  32  may also serve to transfer magnetic current to a similarly shaped element  32  in another transmission element  24 . Since materials such as ferrite may be quite brittle, the U-shaped elements  32  may be provided in segments  32   a,    32   b  to prevent cracking or breakage that might otherwise occur using a single piece of ferrite.  
         [0050]     As was previously stated, a recess  38  may be provided in a mating surface  18 , such as in a secondary shoulder  18 . Likewise, the transmission element  24  may be inserted into and retained within the recess  38 . In selected embodiments, the recess  38  may include a locking mechanism to enable the housing  30  to enter the recess  38  while preventing the exit therefrom. For example, in one embodiment, a locking mechanism may simply be a groove  40  or recess  40  formed within the larger recess  38 . A corresponding shoulder  42  may be formed in the housing  30  such that the shoulder  42  engages the recess  40 , thereby preventing the housing  30  from exiting the larger recess  38 .  
         [0051]     As was previously discussed, in order to close gaps  28  or space  28  present between transmission elements  24   a,    24   b,  in the pin end  12  and box end  14 , respectively, a transmission element  24  may be biased with respect to a mating surface  18 , such as a secondary shoulder  18 . That is, a transmission element  24  may be urged in a direction  46  with respect to a secondary shoulder  18 . In selected embodiments, angled surfaces  50 ,  52  of the recess  38  and housing  30 , respectively, may provide this “spring force” in the direction  46 .  
         [0052]     For example, each of the surfaces  50 ,  52  may form an angle  48  with respect to a direction normal or perpendicular to the surface  18 . This angle  48  may urge the housing  30  in a direction  46  due to its slope  48 . That is, if the housing  30  is in tension as it is pressed into the recess  38 , a spring-like force may urge the housing  30  in a direction  46 .  
         [0053]     In other embodiments, a biasing member, such as a spring or other elastomeric material may be inserted between the housing  30  and the recess  38 , in a space  56 , to urge the housing  30  in a direction  46 . In selected embodiments, the housing  30  may only contact a single surface  50  of the recess  38 . Gaps  54 ,  56  may be present between the recess  38  and the housing  30  along other surfaces. These may serve several purposes.  
         [0054]     For example, if the housing  30  were to contact both a surface  50  on one side of the recess  38 , as well as another surface  54  on the other side of the recess  38 , pressure on both sides of the housing  30  may create undesired stress on a U-shaped element  32  or elements  32   a,    32   b.  If an element  32  is constructed of ferrite, the stress may cause cracking or damage due to its brittleness. Thus, in selected embodiments, it may be desirable that only a single surface  50  of the housing  30  contact a surface  52  of the recess  38 .  
         [0055]     Nevertheless, a surface  50  in contact with the housing  38  may be along either an inside or outside diameter of the recess  38 , or a combination thereof. Other recesses  44   a,    44   b,  or spaces  44   a,    44   b,  may be provided between the housing  30  and U-shaped elements  32 . These recesses  44   a,    44   b  may be filled with an elastomeric or bonding material to help retain the U-shaped elements  32  within the housing  30 .  
         [0056]     Referring to  FIGS. 4A, 4B , and  4 C, while continuing to refer generally to  FIG. 3 , a transmission element  24  may include one or several shoulders  42  to engage one or several locking recesses  40  within the larger recess  38 . For example, referring to  FIG. 4A , a transmission element  24  may include multiple locking shoulders  42   a,    42   b  along both an inner and outer diameter of a housing  30 . These shoulders  42   a,    42   b  may interlock with corresponding grooves  40  or recesses  40  formed in the recess  38 .  
         [0057]     In another embodiment, referring to  FIG. 4B , a transmission element  24  may simply include a single locking shoulder  42   a  located along an inside diameter of the transmission element  24 . This locking shoulder  42   a  may engage a corresponding groove  40  or recess  40  located along the inside diameter of the larger recess  38 . Likewise, with respect to  FIG. 4C , a transmission element  24  may simply include a locking shoulder around an outside diameter of the transmission element  24 . A corresponding groove  40  may be included around the outside diameter of the recess  38  to retain the transmission element  24 .  
         [0058]     The present invention may be embodied in other specific forms without departing from its essence or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes within the meaning and range of equivalency of the claims are to be embraced within their scope.

Summary:
A robust transmission element for transmitting information between downhole tools, such as sections of drill pipe, in the presence of hostile environmental conditions, such as heat, dirt, rocks, mud, fluids, lubricants, and the like. The transmission element maintains reliable connectivity between transmission elements, thereby providing an uninterrupted flow of information between drill string components. A transmission element is mounted within a recess proximate a mating surface of a downhole drilling component, such as a section of drill pipe. To close gaps present between transmission elements, transmission elements may be biased with a “spring force,” urging them closer together.