A sectional drive and coupling system for transmitting rotational power to an output, which system includes multiple, splined drive and receiving segments that are connected, nested and interlocked in the ends of successive segment housings to define a drive string that is rotatable in a selected straight or curved path. The top one of the segments cooperates with a drive mechanism to effect rotation of the drive string in concert and the bottom one of the segments connects to an output such as a drill bit. Multiple, tapered and truncated exterior splines on the drive segments mesh with complementary interior splines on the adjacent receiving segments in the segment housings to enable slight angular positioning of the sets of drive and receiving segments on each other and facilitate dampening of drive vibration and bending of the drive string in or out of the chosen path in any desired direction as the drive string transmits rotational power in a curved path of desired magnitude from the drive mechanism to the output. The drive and receiving segments are typically connected internally by a bolt, nuts and belleville springs at the ends of the housings to form the drive string. In one embodiment a drill bit is mounted on the bottom one of the segments on the drive string for interval drilling. In another embodiment a selected number of drive and receiving segments and connected segment housings replace the flexible drive shaft coupling in a mud motor.

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and incorporates by reference U.S. Provisional Application Ser. No. 61/003,584, Filed Nov. 19, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
     Summary of the Invention 
       [0002]    Conventional techniques for effecting the transmission of rotational power between a power source and an output under circumstances where the power is to be transmitted in an offset or curved manner, includes the use of coupling mechanisms such as a universal or “CV” joints which are well known to those skilled in the art. For example, many devices have been designed for lowering into an oil or gas well for the purpose of boring and drilling holes at right angles to the well bore at the production interval, but many problems have been encountered using these systems. Typically, the relatively low bit rotational speed generally necessitated by using curved shafts of various design sometimes requires excessive time to achieve significant penetration, and increasing the bit rotational speed and torque load frequently causes failure of the shafts. Accordingly, these conventional horizontal drilling devices have not proved capable of sustaining the high compressive loads necessary to penetrate the well casing, concrete sheath, rock and producing interval in a well within an economical time frame without failure. Other problems have been encountered, such as impediments to bit retrieval and reduced freedom of rotation of the drill string in such application. 
         [0003]    This invention relates to drive and coupling systems for transmitting rotational power to an output and more particularly, to a sectional drive and coupling system which is characterized by connected multiple, splined, interlocking drive and receiving segments seated in the facing ends of a string of linearly-aligned segment housings. The interior-tapered drive segments include truncated and tapered exterior splines extending from a segment base and the receiving segments have interior splines extending from a companion segment base for receiving the exterior splines of the drive segment in a series or string of the segment housings. Interior spline seats on the receiving segments are located between the interior splines and are substantially complementary to the configuration of the exterior splines on the opposed sets of drive segments. The drive and receiving segments are thusly nested and interlocked at the ends of the respective linearly-aligned segment housings by inserting the exterior splines of one set of drive segments in the respective congruent interior spline seats between adjacent interior splines of the adjacent sets of receiving segments and bolting the segment sets together in the ends of the drive housings using spherical bearings and belleville springs. The resulting drive system can be rotated as a drive string in a selected path in one embodiment, to drill openings in down-hole oil and gas intervals. The drilling path may be straight or curved and in the latter case, the interlocking drive and receiving segments and associated segment housings are capable of slight angular shifting on each other against the tension in the belleville springs, while maintaining a drive configuration of high integrity. In another embodiment, this mechanical arrangement allows the segmented drive string to dampen drive vibration, as in a mud motor, for example, and to define a chosen curved drive path and facilitate transmission of rotation from a drive mechanism to an output device, with the application of considerable torque and thrust. The respective nested drive and receiving segment sets are typically threaded in the ends of the respective linearly-aligned segment housings and are interconnected by the bolt, nuts, spherical bearings and belleville springs in a selected compressive force. The resulting tool string can therefore be used as a drive train in any application in which a transfer of rotation is required in a straight line or at an angle or deviation from a straight line. The sectional drive and coupling system is therefore ideally suited to effect horizontal drilling or coring of producing hydrocarbon intervals in oil and gas wells, utilizing the multiple, stacked and tapered, housing-mounted interlocking drive segments, driven by a downhole drilling motor, power swivel, top drive or rotary table at one end of the drive string to operate a drill bit connected to the opposite end of the drive string. Retrieval of the drive string from the interval is facilitated by the connection of the respective interlocking drive and receiving segments together at the respective bolts. Consequently, the sectional drive and coupling system of this invention can be used in a downhole drilling apparatus to more efficiently effect drilling deviation in a controlled manner from a vertical well bore and provide a primary horizontal deviation or a lateral deviation from an existing vertical well bore. In one application a drill bit is mounted on the bottom one of the drive segments on the drive string and is characterized by multiple interior splines which engage the companion exterior splines of the drive segment. 
         [0004]    While capable of being operated in an efficient manner to permit horizontal or angular drilling of drain hole perforations in oil wells, the sectional drive and coupling system of this invention can also be implemented to transmit rotational power from substantially any drive system to an output apparatus, drive or other system, such as a mud motor, under circumstances where the rotational power is to be transmitted in an offset or a curved line. Accordingly, the sectional drive and coupling system is preferably designed with truncated drive and receiving segments and is capable of being used to transmit rotation from an engine, motor or other power source to automobiles, mud motors and like apparatus and equipment, as well as to dental drills, various robotic devices and material-handling equipment, in non-exclusive particular. 
         [0005]    Accordingly, the invention includes a new and improved sectional drive and coupling system for transmitting rotational power from a drive source or apparatus of selected character to an output device of selected design under circumstances where the drive apparatus and the output device are misaligned or can become misaligned. The multiple, internally tapered, splined and interlocking drive segments typically include eight, spaced-apart, asymmetrical, tapered and truncated exterior splines extending from one surface of a round base, each having an exterior spline seat, a drive face and an angular spline support face of unequal area and enclosed in one end of respective aligned segment housings. Interior splines extend from the base of the companion receiving segments secured in the opposite ends of the aligned segment housings and define interior spline seats between the interior splines for receiving the congruent or complementary exterior splines of the facing adjacent drive segments in driving relationship to facilitate articulation between the respective housing segments. The drive and receiving segments are typically bolted together in sets in the aligned ends of the corresponding segment housings, typically with associated spherical bearings and cupped belleville springs in a concave surface-to concave surface, single or stacked configuration, to create a desired tension. This spherical bearing and belleville spring configuration, together with the internal taper in the drive segments, facilitates a selected degree of articulation at each joint in the segment housings as a selected number of the segments are stacked and nested in spaced-apart, rotatable relationship to define a rotatable drive string, one end of which drive string is attached to a drive mechanism and the opposite end to an output device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention will be better understood by reference to the accompanying drawings, wherein: 
           [0007]      FIG. 1  is a side view of a drive string of a typical sectional drive and coupling system of this invention which may be connected at one end to a suitable drive apparatus for rotating the entire segment string and a drill bit provided on the opposite end of the drive string; 
           [0008]      FIG. 2  is a side view of a typical pair of connected sectional drive and coupling system components, more particularly illustrating drive and receiving segments of the drive string partially enclosed in respective aligned segment housings; 
           [0009]      FIG. 3  is a sectional view taken along line  3 - 3  of the drive and receiving segments illustrated in  FIG. 2 ; 
           [0010]      FIG. 4  is a perspective view of the top drive segment illustrated in  FIG. 2 , more particularly illustrating the exterior splines and intervening exterior spline seats and the segment aperture of the drive segment; 
           [0011]      FIG. 5  is a perspective view of the drive segment 180-degrees reversed from the position illustrated in  FIG. 4 , more particularly illustrating the threaded segment base and segment aperture of the drive segment; 
           [0012]      FIG. 6  is a perspective view of the bottom receiving segment 180-degrees reversed from the position illustrated in  FIG. 2 ; 
           [0013]      FIG. 7  is a reverse perspective view of the sectional drive system illustrated in  FIG. 6 , more particularly illustrating the segment aperture therein; 
           [0014]      FIG. 8  is an exploded view of the sectional drive system drive and receiving segment components illustrated in  FIG. 2 , including bolt, connecting nuts and belleville spring components; 
           [0015]      FIG. 9  is a longitudinal sectional view of a typical well casing, more particularly illustrating a typical tool body and internal whipstock, along with a drill bit on the drive string of the sectional drive and coupling system interposed inside the tool body in a drilling configuration of the invention; and 
           [0016]      FIG. 10  is a sectional view of a typical mud motor, more particularly illustrating application of the sectional drive and coupling system of this invention to the power transmission section of the mud motor. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring initially to  FIGS. 1-8  of the drawings, the sectional drive and coupling system of this invention is generally illustrated by reference numeral  1 . The sectional drive and coupling system  1  is characterized by a drive and coupling string  10 , formed by mounting multiple, splined drive segments  17  and receiving segments  23  in facing sets in the ends of respective segment housings  2 , as illustrated in  FIGS. 1 and 2 . Each of the drive segments  17  includes a flat, disc-shaped segment base  18  and multiple tapered, truncated, asymmetrical exterior splines  19  extending from a flat front base surface  19   c  of the segment base  18 , as illustrated in  FIGS. 4 and 8 . In a typical embodiment of the invention each of the drive segments  17  is shaped to include eight exterior splines  19 , each having a drive face  19   a  and an angular spline support face  19   b.  The exterior splines  19  define eight intervening exterior spline seats  20  in a repetitive, geometric pattern which resembles an eight-point star when viewed from the front, as further illustrated in  FIG. 4 . The segment base  18  defines a segment base shoulder  18   b,  lying adjacent to the segment base threads  18   a,  as illustrated in  FIG. 5 . The exterior splines  19  taper from the front base surface  19   c  to a flat, truncated tip  21 , which is coplanar with the converging sets of exterior splines  19 , and a tapered tip aperture  22  is typically provided in the center of the tip  21 , and extends through the segment base  18 , as illustrated in  FIGS. 3 ,  4  and  5 . A segment base cavity  18   c  and lower spring washer seat  8   b  are provided inside the receiving segment threads  23   a,  as illustrated in  FIG. 5 . 
         [0018]    Referring again to  FIGS. 6 ,  7  and  8  of the drawings, the receiving segments  23  include multiple interior splines  25 , extending from a flat tip seat  26  of the receiving segment base  23   c,  to define a central segment interior  22   a.  As illustrated in  FIG. 6 , each of the interior splines  25  is typically characterized by a flat drive face  25   a  and a flat spline wall  25   b.  An interior spline seat  24  is defined between adjacent interior splines  25  and the interior splines  25  of the receiving segments  23  substantially conform to the taper angle of the exterior splines  19  in the companion drive segments  17 . Moreover, the exterior splines  19  of the drive segments  17  are complementary in shape to the interior spline seats  24  of the nesting receiving segments  23  and the interior splines  25  are complementary in shape to the exterior spline seats  20 , respectively. Accordingly, the drive segments  17  will nest in, stack and interlock with the companion receiving segments  23  and yet are capable of being positioned at an angle alpha on each other in driving relationship to shape the drive string  10  as illustrated in  FIGS. 1 and 2 , with the respective nested exterior splines  19  of one drive segment  17  inserted in the interior spline seats  24  respectively, of respective adjacent and facing drive receiving segments  23 . This interlocking registration of the drive segments  17  and receiving segments  23  is not rigid, but permits a pivoting or rocking movement of the drive segments  17  and receiving segments  23  in the interlocking and nested configuration, such that the drive and coupling string  10  can easily bend to conform to the curvature illustrated in  FIG. 1  and yet maintain an interlocking, driving relationship of high integrity due to matching of the drive faces  19   a  of the exterior splines  19  in the drive segments  17 , to the interior drive faces  25   a  of the interior splines  25  in the companion receiving segments  23 . This articulating and interlocking registration of the drive segments  19  and receiving segments  23  also serves to dampen any excessive vibration of such devices as mud motors (not illustrated) or other drive mechanisms (not illustrated) at the input of the drive string  10 , as hereinafter further described. 
         [0019]    Referring again to  FIGS. 1-8  of the drawings, each set of the drive segments  17  and interlocking receiving segments  23 , fitted with spherical bearings  47  inserted in spherical bearing seats  46  ( FIG. 7 ) are seated in corresponding ends of linearly-aligned segment housings  2  of selected length and wall thickness. In a typical embodiment the drive segments  17  are fitted with segment base threads  18   a  that thread into corresponding segment housing threads  3  provided in each end of each segment housing  2 , as illustrated in  FIG. 8 . In similar manner, each of the receiving segments  23  is fitted with receiving segment threads  23   a  that lie adjacent to a receiving segment base shoulder  23   d,  and fit in opposite ends of the segment housings  2  from the drive segments  17 , at the corresponding segment housing threads  3 . In this manner, opposing and interconnecting sets of the drive segments  17  and the receiving segments  23  can be mounted in the ends of complimentary segment housings  2  as illustrated in  FIG. 3 , to facilitate interlocking, yet articulating connection of the respective segment housings  2 . Securing of the respective sets of drive segments  17  and receiving segments  23  together in the respective aligned segment housings  2  at the respective segment housing ends  6  is typically effected by connecting bolts  12 , each having a connecting bolt head  13 , positioned in the segment housing bore  4  of one of the segment housings  2 . The connecting bolt shank  14  of each connecting bolt  12  extends through the aligned tapered tip aperture  22  and receiving segment aperture  23   b  provided in the respective engaged drive segments  17  and receiving segments  23 , respectively. A pair of connecting bolt nuts  11  are typically threaded on the connecting bolt threads  13   a  of the connecting bolt shank  14  against each spherical bearing  47  seated in the corresponding receiving segment  23  in the adjacent aligned segment housing  2 , as further illustrated in  FIG. 3 . An O-ring seat  15  is typically provided on the connecting bolt head  13  to receive a companion O-ring  16  and seal the connecting bolt head  13  ( FIG. 8 ) in the segment housing  2 . The second or outside one of the connecting bolt nuts  11  typically serves as a lock nut to facilitate securing both of the connecting bolt nuts  11  on the connecting bolt threads  13   a  and the inside connecting bolt nuts  11  against the respective spherical bearings  47 . Interposed between the connecting bolt head  13  and the segment base  18  in the segment base cavity  18   c  of each of the drive segments  17  are several belleville springs  7  ( FIG. 3 ), that typically fit against a corresponding upper spring washer  8  and a larger lower spring washer  8   a,  as illustrated in  FIGS. 3 and 8  of the drawings. In a preferred arrangement, the belleville springs  7  are positioned such that the concave or cupped faces of one or more outside springs lie against the flat, typically hardened, ground and polished faces of the corresponding upper spring washer  8  and lower spring washer  8   a,  respectively, to facilitate a reduced friction contact between the concave side of each of the outside belleville springs  7  and the corresponding upper spring washer  8  and lower spring washer  8   a.  The upper spring washer  8  is seated against the belleville springs  7  and on the lower spring washer seat  8   b  ( FIGS. 3 and 5 ) in the segment base  18  of each drive segment  17 . The lower spring washer  8   a  is seated against the connecting bolt head  13  of the connecting bolt  12  and the belleville springs  7 , adjacent to a shoulder space  5   a  at the segment shoulders  5 , as illustrated in  FIG. 3 . This mechanical arrangement allows selective flexure of the belleville springs  7  upon tightening of the connecting bolt nuts  11  on the connecting bolt threads  13   a  of the corresponding connecting bolt shank  14  to a selected torque, thus varying the clearance in the shoulder space  5   a,  as further illustrated in  FIG. 3  of the drawings. The interior belleville springs  7  are fitted against each other in sets of two or more in selected assemblies at the respective cupped or concave faces, to allow flexure and facilitate the desired spring tension in the segment connection. The segment shoulder  5  on each of the drive segments  17  creates a stop surface for the lower spring washer  8   a  that is seated against the connecting bolt head  13  in a spaced-apart clearance from the bottom end of the segment base  18  of the adjacent drive segment  17  at the shoulder space  5   a.  The shoulder space  5   a  allows variable tensioning of the belleville springs  7  by selectively tightening and loosening the connecting bolt nuts  11  to a desired torque, and thus facilitates adjusting the degree of articulation or flexure of the drive segment-receiving segment interconnection at the respective ends of the segment housings  2 . 
         [0020]    Accordingly, referring again to  FIGS. 1 and 3  of the drawings, when a selected number of the segment housings  2  of the sectional drive and coupling system  1  are connected in a drive and coupling string  10  as illustrated in  FIGS. 1 and 3 , the entire sectional drive and coupling system  1  is able to flex and define a curvature such as that illustrated in  FIG. 1 , because of the selected flexure provided in each of the joints at the corresponding shoulder spaces  5   a  in the respective interconnection of the corresponding drive segments  17  and receiving segments  23 . Aiding this flexure are the respective spherical bearings  47  and the tapered tip apertures  22  in the drive segments  17 . As described above, this curvature can be adjusted by controlling the tension applied to the respective belleville springs  7  in each of the interconnected drive segments  17  and receiving segments  23 , at the shoulder spaces  5   a,  which tension is selectively adjusted by tightening and loosening the connecting bolt nuts  11  on the connecting bolt threads  13   a  of the corresponding connecting bolt shanks  14 . 
         [0021]    Referring now to  FIG. 9  of the drawings, in one embodiment the sectional drive and coupling system  1  of this invention can be utilized to drill production openings in various oil and gas intervals by initialing placing the segment housing  2  string in a tool body  33 , typically fitted with a whipstock  32 , having a concave surface  32   a  of selected curvature. The tool body  33  is lowered into a casing  27  using suitable equipment known to those skilled in the art, including a top drive shaft  30  and a length of tubing  28 . An anchor body  34  may be fitted with anchor slips  35  and an anchor bar  36  is typically suspended from the anchor body  34  and is attached to the tool body  33 . The top drive shaft  30  is typically connected to the tubing  28  at a coupling  29  and a top lock  31  serves to secure the tool body  33  to the top drive shaft  30 . A top lock assembly  37  is typically provided on the top end of the sectional drive and coupling system  1  for engaging a catch mandrel  40 , secured to the tool body  33 , to stabilize the sectional drive and coupling system  1  inside the tool body  33 . Accordingly, the tubing  28  can be rotated by a suitable drive system known to those skilled in the art to also rotate the sectional drive and coupling system  1  inside the tool body  33 . When downward weight is applied to the tubing  28  and the top drive shaft  30 , the drive and coupling string  10  is forced outwardly against the casing  27  by contact with the concave surface  32   a  at the whipstock  32 , as illustrated in phantom. Continued rotation of the drill bit  51  causes the drill bit  51  to cut through the casing  27  and facilitates extension of the drive and coupling string  10  of the sectional drive and coupling system  1  outwardly into an interval (not illustrated) at a selected predetermined curvature, as illustrated in  FIG. 1  and  FIG. 9 . Accordingly, a borehole can be drilled through the interval at a selected angle with respect to the casing  27  by continued downward rotatable pressure applied to the drive and coupling string  10  at the tubing  28 . Retrieval of the drive and coupling string  10  from the interval and into the tool body  33  can be achieved by pulling the tubing  28  upwardly, while rotating it in the clockwise direction when viewed from above and applying steady tension to the tubing  28  and thus to the top drive shaft  30  and the drive and coupling string  10 , to lift the sectional drive and coupling system  1 , including the tool body  33 , from the casing  27 . 
         [0022]    It will be further appreciated by those skilled in the art that other applications of the sectional drive and coupling system  1  may include the application of torque and thrust in a straight line or along a deviation from a straight line up to or even beyond ninety degrees, wherein the drive segments  17  and companion receiving segments  23  shift or pivot on each other in any desired direction. Torque may also be applied to the drive segments  17  and interlocking receiving segments  23  as the latter lie in a curved guide tube or path (not illustrated), as desired. Accordingly, typical of these applications, include replacement of the “CV” joints and mechanical couplings in mud motors and other applications involving misaligned drive and driven systems. Application of the invention to dental drills may also be effected under circumstances where the dental drill drive train must be curved over a selected adjustable or fixed radius from the drive motor to the application or drill end. The device may also be used in tools such as flexible-shaft screwdrivers and similar applications, in non-exclusive particular. 
         [0023]    Referring now to  FIG. 10  of the drawings, a typical mud motor  39  is illustrated and includes a top sub  40   a,  with an internal rotor  41  and external stator  42  enclosed in a stator housing  43 . Thrust bearings  44  are provided in conventional fashion and a bit box  45  is located at the bottom end of the mud motor  39  for attachment of a drilling bit (not illustrated). Three of the segment housings  2  are fitted inside the mud motor  39  as indicated and connect the drive shaft  39   a  to the rotating element of the mud motor  39 . Accordingly, the segment housings  2  and associated sets of the engaged drive segments  17  and receiving segments  23  serve to centralize eccentric motion due to the stator drive shaft  39   a,  the rotor  41  and the mud motor rotating component attached to the bit box  45 . Articulation of the respective engaged drive segments  17  and receiving segments  23  at the interfaces of the respective segment housings  2  compensates for this eccentricity and facilitates application of considerable torque to the drive shaft  39   a  for transmission to the rotating element of the mud motor  39  and the bit box  45 , over a long service life with minimum maintenance necessary to the mud motor  39 . 
         [0024]    It will be appreciated by those skilled in the art that the drive segments  17  and receiving segments  23  of this invention can be constructed of substantially any desired material, depending upon the desired application. Furthermore, the respective drive and receiving segments are typically applied where the deviation, offset or curve between the input and the output ends of the drive and coupling string  10  is significant. Moreover, the drive and coupling string  10  can be constructed to facilitate winding on a drum as in the case of coiled tubing, wherein the drive string  10  can be directed into a well from the drum in a quick and efficient manner. 
         [0025]    Referring again to  FIGS. 4-8  of the drawings, it will be further appreciated by those skilled in the art that substantially any number of exterior splines  19 , exterior spline seats  20 , interior spline seats  24  and interior splines  25  can be provided in the design of the drive segments  17  and receiving segments  23 , respectively. However, in a typical embodiment of the invention eight exterior splines  19  and exterior spline seats  20 , as well as eight matching interior spline seats  24  and interior splines  25  are provided in the drive segments  17  and receiving segments  23 , as illustrated. The taper of the respective eight exterior splines  19  and the configuration of the interior splines seats  24  are complementary, as heretofore described, and the exterior splines  19  are typically about two percent to about five percent smaller than the interior spline seats  24 , for optimum smoothness and meshing during bending of the drive and coupling string  10  while operating the sectional drive and coupling system  1  typically as illustrated in  FIGS. 1 and 9 . 
         [0026]    Referring to  FIGS. 3 and 8  of the drawings, it will be appreciated that the respective drive segments  17  and receiving segments  23  can be connected by the connecting bolts  12  without the use of belleville springs  7 . However, either belleville springs or coil springs may be used to adjust the flexure of the drive and coupling string  10  by varying the width of the shoulder space  5   a  due to the tension applied by the connection bolts  12 . 
         [0027]    It will be further appreciated by those skilled in the art that drilling fluid (not illustrated) can be continuously circulated through the drive string  10  and attached drill bit  51  during operation of the sectional drive system  1  in a drilling application, for purposes of cooling and preventing accumulation of drilling fragments in the drive string  10  and drill bit  51 . Accordingly, the drilling fluid (not illustrated) is injected into the drive and coupling string  10  in any convenient manner and flows through the respective connecting bolt apertures  12   a  of the corresponding connecting bolts  12  of the sets of top input drive sections  17  of the drive string  10  and then through the respective intervening segment housing bores  4  connecting the drive segments  17  and the respective corresponding interlocking receiving segments  23 . The drilling fluid then typically enters the multiple water course passages  57  in the drill bit base  59  ( FIG. 1 ) and flows from the drill bit head  52 , back to the surface through the well annulus (not illustrated). The drilling fluid is capable of removing particulate drilling fragments from the hydrocarbon-producing interval in the well as the drilling fluid flows between the drill bit head  52  and the interval, through the water course grooves  57  in the outer circumference of the drill bit head  52 . 
         [0028]    While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.