Abstract:
The present disclosure relates to a fiberglass rod with connectors on each end. Each connector has a rod-receiving receptacle having an open end, a closed end, and axially spaced annular wedge shaped surfaces such that the compressive forces between the rod and the respective connector are defined by the shape of the wedged surfaces.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation-in-part application of the application of Russell P. Rutledge, Russell P. Rutledge, Jr. and Ryan B. Rutledge, U.S. Ser. No. 13/136,715, filed Aug. 9, 2011 now U.S. Pat. No. 8,851,162, entitled Sucker Rod Apparatus and Method. 
    
    
     FIELD 
     The present disclosure relates generally to oil well sucker rods. In particular, the disclosure relates to oil well sucker rods made of fiberglass with end fittings or connectors on each end and the manufacture thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the disclosure and together with the general description of the disclosure and the detailed description of the preferred embodiments given below, serve to explain the principles of the disclosure. 
         FIG. 1  illustrates a typical pumping system for use with the technology of the present disclosure. 
         FIG. 2  is a cross-sectional view of an embodiment of a sucker rod and an associated end fitting within the scope of the present disclosure. 
         FIG. 2A  is an exploded view of the blow-up section  2 A as illustrated in  FIG. 2  illustrating the angles between the leading edge and the trailing edge of a wedged-shaped portions of the wedge system. 
         FIG. 3  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 2  taken along the section line  3 - 3 . 
         FIG. 4  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 2  taken along the section line  4 - 4 . 
         FIG. 5  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 2  taken along the section line  5 - 5 . 
         FIG. 6  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 2  taken along the section line  6 - 6 . 
         FIG. 7  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 2  taken along the section line  7 - 7 . 
         FIG. 8  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 2  taken along the section line  8 - 8 . 
         FIG. 9  is a graph of the relationship between the length on the ordinate of the leading edge and trailing edge of each wedged-shaped portion on the abscissa in the wedge system of the present disclosure. 
         FIG. 10  is a cross-sectional view of another embodiment of a sucker rod and an associated end fitting within the scope of the present disclosure. 
         FIG. 11  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 10  taken along the apogee of one of the wedge portions of the wedge system within the scope of the present disclosure. 
         FIG. 12  is a sectional view of the sucker rod and end fitting combination illustrated in  FIG. 10  taken along the vortex of the wedge portion of the wedge system illustrated in  FIG. 11  within the scope of the present disclosure. 
     
    
    
     The depicted embodiments of the sucker rod and associated connectors are described below with reference to the listed Figures. 
     The above general description and the following detailed description are merely illustrative of the generic disclosure, and additional modes, advantages, and particulars of this disclosure will be readily suggested to those skilled in the art without departing from the spirit and scope of the disclosure. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In many oil wells, the pressure in the oil reservoir is not sufficient to lift the oil to the surface. In such cases, it is conventional to use a sub-surface pump to force the oil from the well. A pumping unit located at the surface drives the sub-surface pump. The pumping unit is connected to the sub-surface pump by a string of sucker rods. The pumping unit moves the sucker rod string up and down to drive the sub-surface pump. 
     Originally, a sucker rod was a special steel pumping rod. A sucker rod is, typically, a steel rod that is used to make up the mechanical assembly between the surface and the down hole components of a rod pumping system. Several sucker rods were screwed together to make up the mechanical link, or sucker rod string, from a beam-pumping unit on the surface to the subsurface pump at the bottom of a well. The sucker rods were threaded on each end and manufactured to dimension standards and metal specifications set by the petroleum industry. Typically, sucker rods have been in the lengths of 25 or 30 feet (7.6 or 9.1 meters), and the diameter varies from ½ to 1⅛ inches (12 to 30 millimeters). 
     Thus, sucker rod pumping is a method of artificial lift in which a subsurface pump located at or near the bottom of the well and connected to a string of sucker rods is used to lift the well fluid to the surface. The weight of the rod string and fluid is counterbalanced by weights attached to a reciprocating beam or to the crank member of a beam-pumping unit or by air pressure in a cylinder attached to the beam. 
     Due to the heavy weight of the steel sucker rods, large pumping units were required and pumping depths were limited. It is now preferable to use sucker rods made of fiberglass with steel connectors. The fiberglass sucker rods provide sufficient strength, and weigh substantially less than steel rods. 
     Since the development of the fiberglass sucker rod, there have been continued efforts to improve the sucker rod, and particularly, the relationship between the steel connectors and the successive rods. 
       FIG. 1  illustrates a generic pumping system  20 . The pumping system  20  includes a pump drive  22 , which is a conventional beam pump, or pump jack and is connected to a down hole pump  26  through a sucker rod string  24  inserted into wellbore  28 . The sucker rod string  24  can comprise a continuous sucker rod  10 , which extends from the down hole pump  26  to the pumping system  20 , a series of connected sucker rods  10 , a series of conventional length rods connected together, or any combination thereof. The pump drive  22  includes a horsehead  22 A, a beam  22 B, a gearbox  22   c  and a motor  22 D. Preferably, the sucker rod  10  is a fiberglass, composite or rod having similar characteristics. As described herein, the sucker rod string  24  may be the same as the continuous sucker rod  10  when the continuous sucker rod  10  is a one-piece rod that extends substantially between the pump drive  22  and the sub-surface pump  26 . 
       FIG. 2  is a cross-sectional view of an embodiment of the sucker rod  10  comprising a fiber composite rod  200  and associated end fitting  100  within the scope of the present disclosure. The sucker rod  10  comprises one or more end fittings  100  and the fiber composite rod  200 . The fiber composite rod  200  has a first end  202  and a second end (not illustrated). 
     Typically, there are end fittings  100  on each end of the fiber composite rod  200  for coupling together a plurality of fiber composite rods  200 . The end fitting  100  comprises an exterior surface  102 , a closed end  104 , an open end  106 , and an interior surface  108 . The interior surface  108  comprises a wedge system  110 . The present disclosure provides that the wedge system  110  can have any number of wedges from one to multiple wedges. The embodiment illustrated in  FIG. 2  has three wedges. The wedge system  110  defines a cavity  112  in the end fitting  100  for receiving the fiber composite rod  200 . 
     Further, the wedge system  110  comprises a plurality of wedged-shaped portions  114 . Each wedged-shaped portion  114  has an apogee  116 , a perigee  124 , a leading edge  118  and a trailing edge  120  extending from and between the apogee  116  and the perigee  124 . Each apogee  116  forms a perimeter  122  within the cavity  112  that is the narrowest part of the cavity  112  associated with each wedge shaped portion  114 . Each perigee  124  is the widest part of the cavity  112  associated with each wedge shaped portion  114 . The leading edge  118  is longer than the trailing edge  120  with the leading edge  118  facing the open end  106  and the trailing edge  120  facing the closed end  104  with respect to each wedge shaped portion  114  of the end fitting  100 . 
     The first wedge shaped portion  114 A is proximate to the closed end  104  for receiving compressive forces that are greater than the compressive forces associated with the other wedged-shaped portions  114 B,  114 C. Particularly, the first wedged-shaped portion  114 A receives greater compressive forces than the compressive force for which a second wedge shaped portion  114 B receives that is proximate to the first wedged-shaped portion  114 A. A third wedge shaped portion  114 C between the second wedge shaped portion  114 B and the open end  106  receives compressive forces that are less than the compressive forces associated with the first and second wedge shaped portions  114 A,  114 C. Therefore, the compressive forces create a force differential along each wedge shaped portion  114  greater at the closed end  104  of the end fitting  100  and decreasing toward the open end  106  of the end fitting  100 . 
     As the compressive forces associated with the first wedged-shaped portion  114 A deteriorate the structural integrity of the first wedged-shaped portion  114 A, then, it has been found that the uncompensated for compressive forces of the first wedged-shaped portion  114 A are transferred to and accepted by the second wedged-shaped portion  114 B. Similarly, as the compressive forces associated with the second wedged-shaped portion  114 B deteriorate the structural integrity of the second wedged-shaped portion  114 B, then it has been found that the uncompensated for compressive forces of the second wedged-shaped portion  114 B are transferred to and accepted by the third wedged-shaped portion  114 C. 
     Thus, a force transfer continuum is created by the wedge system  110 . The force transfer continuum provides for a constant effectiveness between the end fitting  100  and the fiber composite rod  200  as the wedge system  110  deteriorates from one wedged-shaped portion  114  to the next wedged-shaped portion  114  of the wedge system  110 . The present structure of the sucker rod  10  including specifically the end fitting  100  does not distribute the compressive forces throughout the end fitting  100 , but rather focuses the compressive forces on each wedge shaped portion  114  of the wedge system  110  of the present disclosure. 
     The sucker rod  10  has a plurality of longitudinal cross-sections of the wedged-shaped portions  114 , which forms a plurality of frustro-conical shapes within the cavity  112 . 
     The wedge shaped portions  114  of the sucker rod  10  create different compressive forces on each respective edge  118 ,  120  thereof with the compressive force being approximately proportional to a length of each edge  118 ,  120 . In one embodiment, the compressive force on each edge  118 ,  120  is directly proportional to the length of each edge  118 ,  120 . Further, the plurality of wedge shaped portions  114  are determined by the angles associated between the leading edge  118  and the trailing edge  120 . 
     An adhesive or epoxy  130  is used to sufficiently bond with the fiber composite rod  200  and engage with the end fitting  100 . It is appreciated that any adhesive substance that will sufficiently bond with the fiber composite rod  200  and engage with the end fitting  100  may be used. The adhesive or epoxy  130  is placed in the cavity  112  and cured to bond with the fiber composite rod  200  in the cavity  112  for fixedly securing the end fitting  100  with the fiber composite rod  200 . 
       FIG. 2A  is an exploded view of the blow-up section  2 A as illustrated in  FIG. 2  illustrating the angles between the leading edge and the trailing edge of a wedged-shaped portion of the wedge system. In one embodiment, the angle A between the leading edge  118  and the trailing edge  120  of each wedge shaped portion is obtuse having an angle greater than 90 degrees.  FIG. 2  illustrates an angle A associated with each wedged-shaped portion  114  of the wedge system  110 . 
       FIG. 2A  is an exploded view of the blow-up section  2 A as illustrated in  FIG. 2  illustrating the angles between the leading edge  118 B and the trailing edge  120 B of a wedged-shaped portion  114 B of the wedge system  110 . The fiber composite rod  200  is illustrated in the end fitting  100 . The end fitting  100  defines the leading edge  118 B and the trailing edge  120 B to form the cavity  112  to be filled by the epoxy  130 . The angle between the leading edge  118 B and the trailing edge  120 B defines the angle A. The angle A is obtuse having an angle greater than 90 degrees. Generally, the leading edge  118 , the trailing edge  120  and the fiber composite rod  200  form a scalene triangle with the longest side of the scalene triangle being along the fiber composite rod  200 , the shortest side of the scalene triangle being along the trailing edge  120 , and the intermediate side of the scalene triangle being along the leading edge  118 . 
       FIG. 2A  also illustrates the angle B between the trailing edge  120 B of the wedge shaped portion  114 B and the leading edge  118 A of the wedge shaped portion  114 A. Thus, the angle B defines the relationship between the trailing edge  120  of the wedge shaped portion  114  and the leading edge  118  of an adjacent wedge shaped portion  114 . The angle B is a reflex angle. A reflex angle is an angle that exceeds 180 degrees. 
       FIG. 3  is a sectional view of the fiber composite rod  200  and end fitting  100  combination illustrated in  FIG. 2  taken along the section line  3 - 3 . The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 3 . It is appreciated with respect to practicing the innovation of the present disclosure that the gap can be of any dimension, for example, from as small as zero or no gap to as large a gap as required to achieve the efficacy of the present disclosure. 
       FIG. 4  is a sectional view of the fiber composite rod  200  and end fitting  100  combination illustrated in  FIG. 2  taken along the section line  4 - 4 . The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 4 . The gaps G 3  and G 4  are associated with the first wedged-shaped portion  114 A of the wedge system  110 . 
       FIG. 5  is a sectional view of the fiber composite rod  200  and end fitting  100  combination illustrated in  FIG. 2  taken along the section line  5 - 5 . The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 5 . 
       FIG. 6  is a sectional view of the fiber composite rod  200  and end fitting  100  combination illustrated in  FIG. 2  taken along the section line  6 - 6 . The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 6 . The gaps G 5  and G 6  are associated with the second wedged-shaped portion  114 B of the wedge system  110 . 
       FIG. 7  is a sectional view of the fiber composite rod  200  and end fitting  100  combination illustrated in  FIG. 2  taken along the section line  7 - 7 . The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 7 . 
       FIG. 8  is a sectional view of the fiber composite rod  200  and end fitting  100  combination illustrated in  FIG. 2  taken along the section line  8 - 8 . The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 8 . The gaps G 7  and G 8  are associated with the second wedged-shaped portion  114 C of the wedge system  110 . 
       FIG. 11  is a sectional view of the sucker rod  10  including the end fitting  100  combination illustrated in  FIG. 10  taken along the apogee  116  of one of the wedge portions  114  of the wedge system  110  within the scope of the present disclosure. The end fitting  100  is exterior of and engaged with the fiber composite rod  200  with no cavity  112  there between. The lack of a cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a zero gap G 9 . It is appreciated with respect to practicing the innovation of the present disclosure that the gap can be of any dimension, for example, from as small as zero or no gap, as illustrated in  FIG. 11 , to as large a gap as required to achieve the efficacy of the present disclosure. 
       FIG. 12  is a sectional view of the sucker rod  10  and including the end fitting  100  combination illustrated in  FIG. 10  taken along the vortex  124  of the wedge portion  114  of the wedge system  110  illustrated in  FIG. 11  within the scope of the present disclosure. The end fitting  100  is exterior of the fiber composite rod  200  with the cavity  112  there between. The cavity  112  between the fiber composite rod  200  and the end fitting  100  forms a gap G 10 . It is appreciated with respect to practicing the innovation of the present disclosure that the gap can be of any dimension, for example, from as small as zero or no gap to as large a gap as required to achieve the efficacy of the present disclosure. 
     The smaller gaps G 3 , G 5 , G 7 , G 9  associated with each wedged-shaped portion  114  are substantially constant having essentially the same dimension. Similarly, the larger gaps G 4 , G 6 , G 8 , G 10  associated with each wedged-shaped portion  114  are substantially constant having essentially the same dimension. The symmetry provided by the relationship of the minimum gaps G 3 , G 5 , G 7 , G 9  and the maximum gaps G 4 , G 6 , G 8 , G 10  provides unforeseen results. Particularly, the symmetry provided by the relationship of the minimum gaps G 3 , G 5 , G 7 , G 9  and the maximum gaps G 4 , G 6 , G 8 , G 10  greatly enhances the stability and ability of the fiber composite rod  200  and end fitting  100  combination to accept enhanced compressive and back pressure forces associated with the reciprocating environment in which the sucker rods  10  are used. 
       FIG. 9  is a graph of the relationship between the length on the ordinate (x-axis) of the leading edge  118  and the trailing edge  120  of each wedged-shaped portion  114  on the abscissa (y-axis) in the wedge system  110  of the present disclosure. As illustrated in  FIG. 2 , the leading edge  118  is progressively longer from the closed end  104  of the end fitting  100  to the open end  106  of the end fitting  100 . Similarly, the trailing edge  120  is progressively longer from the closed end  104  of the end fitting  100  to the open end  106  of the end fitting  100 . The functions defined by these relationships are illustrated in  FIG. 9 . Particularly, a line having a slope or gradient defines the function associated with the trailing edge  120 , and a line having a slope or gradient defines the function associated with the leading edge  118 . 
     The relationship of the function associated with the trailing edge  120  and the function associated with the leading edge  118  provides insight to the unforeseen effectiveness of the wedge system  110  of the present disclosure. It has been found that the rate of increase of the length of the leading edge  118  with respect to the rate of increase of the length of the trailing edge  120 , as defined by the slope or gradient of each associated function, provides an enhanced sucker rod  10  and sucker rod system. The slope of the leading edge  118  associated with the wedge system  110  of the present disclosure is greater than the slope of the trailing edge  120  associated with the wedge system  110  of the present disclosure. 
     The wedge system  110  of the present disclosure as applied to a sucker rod  10  provides unforeseen effectiveness not before appreciated. The combination of the wedged-shaped portions  114 , the relationship of the leading edge  118  to the trailing edge  120 , the symmetry of the minimum gaps G 3 , G 5 , G 7 , G 9  and the maximum gaps G 4 , G 6 , G 8 , G 10  result in a wedge system  110  that provides improved and unpredicted functionality. Particularly, the improved and unpredicted functionality of the sucker rod  10  having the wedge system  110  of the present disclosure greatly enhances the stability of the sucker rod  10  and ability of the fiber composite rod  200  and end fitting  100  combination to accept enhanced compressive and back pressure forces associated with the reciprocating environment in which the sucker rods  10  are used. 
     The change of the length of the leading edge increases from the inner wedge to the outer wedge. However, the rate of change of the length of the leading edge is greater than the rate of change of the trailing edge. This is evidenced by the slope of the line for the leading edge  1  and the slope of the line for the trailing edge  2  illustrated in  FIG. 9 . For another example, if the slope of the line representing the trailing edge was  1 , then the line would be horizontal in  FIG. 9 . Then, the slope of the line representing the leading edge would be any value greater than 1, and would be angled upward from left to right in  FIG. 9 . 
     It has not been know before that such an arrangement would provide the unexpected results achieved by the present disclosure. Particularly, the unexpected results achieved by the present end fitting design distributes the stresses to the interior wedge first, and thereafter to the next successive wedges in the wedge system. The prior art teaches away from achieving such results. The prior art describes wedge systems that distribute the stresses along the entire length of the wedge system. 
     Further, the relationship of the rate of change of the lengths of the leading edge to the trailing edge illustrated in  FIG. 9  is not described in or anticipated by the prior art. The increased rate of change of the length of the leading edge relative to the trailing edge provides enhanced and unexpected characteristics with respect to the effectiveness of the end fitting of the present disclosure. Particularly, the present end fitting design concentrates the compressive forces in the strongest part of the end fitting, the interior wedge. Thus, there is an increased cohesion between the end fitting and the rod. This results in a more secure engagement of the rod within the end fitting. Still further, this results in reduced strain or deformation as a result of the forces caused by stress associated with the use of the fiberglass rod. 
       FIG. 10  is a cross-sectional view of another embodiment of a sucker rod  10  and associated end fitting  100  within the scope of the present disclosure. The sucker rod  10  comprises one or more end fittings  100  and a fiber composite rod  200 . The fiber composite rod  200  has a first end  202  and a second end (not illustrated). 
     Typically, there are end fittings  100  on each end of the fiber composite rod  200  for coupling together a plurality of fiber composite rods  200 . The end fitting  100  comprises an exterior surface  102 , a closed end  104 , an open end  106 , and an interior surface  108 . The interior surface  108  comprises a wedge system  110 . The present disclosure provides that the wedge system  110  can have any number of wedges as indicated by the broken line between the first wedged-shaped portion  114 A and the second wedged-shaped portion  114 B. The wedge system  110  defines a cavity  112  in the end fitting  100 . 
     The wedge system  110  comprises a plurality of wedged-shaped portions  114 . Each wedged-shaped portion  114  has an apogee  116 , a perigee  124 , a leading edge  118  and a trailing edge  120  extending from the apogee  116  and/or the perigee  124 . Each apogee  116  forms a perimeter  122  within the cavity  112  that is the narrowest part of the cavity  112  associated with each wedge shaped portion  114 . Each perigee  124  forms the widest portion of the cavity  112  associated with each wedge shaped portion  114 . The leading edge  118  is longer than the trailing edge  120  with the leading edge  118  facing the open end  106  and the trailing edge  120  facing the closed end  104  with respect to each wedge shaped portion  114 . 
     The first wedge shaped portion  114 A is proximate to the closed end  104  for receiving compressive forces that are greater than the compressive forces associated with the other wedged-shaped portions  114 B, C, etc. Particularly, the first wedged-shaped portion  114 A receives greater compressive forces than the compressive forces for which a second wedge shaped portion  114 B receives that is proximate to the first wedged-shaped portion  114 A. A third wedge shaped portion  114 C between the second wedge shaped portions  114 B and the open end  106  receives compressive forces that are less than the compressive forces associated with the first and second wedge shaped portions  114 A,  114 C. Therefore, the compressive forces create a force differential along each wedge shaped portion  114  greater at the closed end  104  of the end fitting  100  and decreasing toward the open end  106  of the end fitting  100 . 
     As the compressive forces associated with the first wedged-shaped portion  114 A deteriorate the structural integrity of the first wedged-shaped portion  114 A, then it has been found that the uncompensated for compressive forces of the first wedged-shaped portion  114 A are transferred to and accepted by the second wedged-shaped portion  114 B. Similarly, as the compressive forces associated with the second wedged-shaped portion  114 B deteriorate the structural integrity of the second wedged-shaped portion  114 B, then it has been found that the uncompensated for compressive forces of the second wedged-shaped portion  114 B are transferred to and accepted by the third wedged-shaped portion  114 C. 
     Thus, a force transfer continuum is created by the wedge system  110  regardless of the number of wedged-shaped portions  114  comprise the wedge system  110 . The force transfer continuum provides for a constant effectiveness between the end fitting  100  and the fiber composite rod  200  as the wedge system  110  deteriorates from one wedged-shaped portion  114  to the next wedged-shaped portion  114  of the wedge system  110 . 
     The wedge shaped portions  114  of the sucker rod  50  create different compressive forces on each respective edge  118 ,  120  thereof with the compressive force being approximately proportional to a length of each edge  118 ,  120 . In one embodiment, the compressive force on each edge  118 ,  120  is directly proportional to the length of each edge  118 ,  120 . Further, the plurality of wedge shaped portions  114  are determined by the angles associated between the leading edge  118  and the trailing edge  120 . 
     An adhesive or epoxy  130  is used to sufficiently bond with the fiber composite rod  200  and for engagement with the end fitting  100 . It is appreciated that any adhesive substance that will sufficiently bond with the fiber composite rod  200  and engage with the end fitting  100  may be used. The adhesive or epoxy  130  is placed in the cavity  112  and cured to bond with the fiber composite rod  200  in the cavity  112  for fixedly securing the end fitting  100  with the fiber composite rod  200 . 
     In another embodiment, the angle A between the leading edge  118  and the trailing edge  120  of each wedge shaped portion is obtuse.  FIG. 2A  illustrates an angle A associated with each wedged-shaped portion  114  of the wedge system  110  with respect to the present disclosure.  FIG. 2A  also illustrates the angle B between the trailing edge  120 B of the wedge shaped portion  114 B and the leading edge  118 A of the wedge shaped portion  114 A. Thus, the angle B defines the relationship between the trailing edge  120  of the wedge shaped portion  114  and the leading edge  118  of an adjacent wedge shaped portion  114 . The angle B is a reflex angle. A reflex angle is an angle that exceeds 180 degrees. 
     The longitudinal cross sections of the concaved portions  110  form frustro-conical shapes. The concaved portions  110  create different compressive forces on each respective surface thereof with the compressive force being approximately proportional to the length of each surface. The compressive force on each surface increases toward the closed end  104  and decreases toward the open end  106 . The compressive force on each first surface  118  is proportional to the length of each surface. The compressive force on each second surface  120  is proportional to the length of each second surface. 
     The plurality of concaved portions  110  are determined by the angle associated between the first surface  118  and the second surface  120  of each concaved surface  110 . The angle between the first surface  118  and the second surface  120  of each concaved surface  110  is obtuse. Further, each wedge shape portion  114  may have a length proportional to the compressive force applied to the wedge shape  114 . The wedge shape  114  has a length that increases from the closed end  104  to the open end  106  of the end fitting  100 . The wedge shaped portions  114  may have a length that decreases from the closed end  104  to the open end  106  of the end fitting  100 . 
     In yet another embodiment, a method for manufacturing a sucker rod is provided. The method comprises the steps of constructing an end fitting comprising an exterior surface, a closed end, an open end, and an interior surface. The interior surface comprises at least three wedge shaped portions defining a cavity. The wedge shaped portions have an apogee and a first and second length extending from the apogee. The apogee forms a perimeter that is the narrowest part of the cavity associated with each wedge shaped portion such that the first length is longer than the second length with the first length facing the open end and the second length facing the closed end with respect to each wedge shaped portion. The method further comprises engaging an end of a fiber composite rod into the cavity of the end fitting for creating a void between the fiber composite rod and the wedge shaped portions of the end fitting. Thereafter, injecting an epoxy into the void to bond with the fiber composite rod and to fixedly engage the wedge shaped portions of the end fitting for securing the end fitting to the fiber composite rod. This arrangement causes the stress to increase the elastic limit without permanent alteration of the fiber composite rod and epoxy combination in the cavity of the end fitting. 
     Thus, a first wedge shaped portion proximate to the closed end receives compressive forces that are greater than the compressive forces for which a second wedge shaped portion proximate to the open end receives, and an intermediate wedge shaped portion between the first and second wedge shaped portions for receiving compressive forces that are intermediate of the first and second wedge shaped portions. Such that the compressive forces create a force differential along the wedge shaped portion greater at the closed end of the fitting and decreasing toward the open end of the fitting. 
     The method for manufacturing a sucker rod may further comprise the step of creating different compressive forces on each respective surface of the wedge shaped portions with the compressive force being approximately proportional to the length of each surface. 
     Further, the method for manufacturing a sucker rod may comprise the step of the compressive force on each surface increasing toward the closed end and decreasing toward the open end. 
     Still further, the method for manufacturing a sucker rod may comprise the compressive force on each first surface being proportional to the length of each surface. 
     Yet still further, the method for manufacturing a sucker rod may comprise the compressive force on each second surface being proportional to the length of each second surface. 
     The method for manufacturing a sucker rod may comprise the plurality of wedge shaped portions being determined by the angle associated between the first surface and the second surface of each concaved surface. The method for manufacturing a sucker rod may have the angle between the first surface and the second surface of each concaved surface being obtuse. 
     The method for manufacturing a sucker rod wherein each wedge shape has a length proportional to the compressive force applied to the wedge shape. The method for manufacturing a sucker rod wherein each wedge shape has a length that increases from the closed end to the open end of the end fitting. The method for manufacturing a sucker rod wherein each wedge shape has a length that decreases from the closed end to the open end of the end fitting. 
     The relationship of the stress verses the strain with respect to the effect on the elastic limit within the scope of the present disclosure is unique. The yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically. Prior to the yield point, the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed some fraction thereof, the deformation will be permanent and non-reversible. 
     Knowledge of the yield point is vital when designing a component since it generally represents an upper limit to the load that can be applied. It is also important for the control of many materials production techniques such as forging, rolling, or pressing. In structural engineering, this is a soft failure mode that does not normally cause catastrophic failure or ultimate failure unless it accelerates buckling. It is often difficult to precisely define yielding due to the wide variety of stress-curves exhibited by real materials. In addition, there are several possible ways to define yielding. 
     True elastic limit is the lowest stress at which dislocations move. This definition is rarely used, since dislocations move at very low stresses, and detecting such movement is very difficult. The proportionality limit is an amount of stress that is proportional to strain (i.e., Hooke&#39;s law), so a stress-strain graph is a straight line, and the gradient will be equal to the elastic modulus of the material. 
     Elastic limit (yield strength) is the elastic limit, where permanent deformation will occur. The lowest stress at which permanent deformation can be measured. This requires a manual load-unload procedure, and the accuracy is critically dependent on equipment and operator skill. For elastomers, such as rubber, the elastic limit is much larger than the proportionality limit. Also, precise strain measurements have shown that plastic strain begins at low stresses. The yield point is the point in the stress-strain curve at which the curve levels off and plastic deformation begins to occur. 
     The relationship of the stress verses the strain with respect to the enhanced strain achieved with the present disclosure exceeds that of prior known devices. The structure of the present disclosure achieves the ability to receive and adapt to enhanced stress. The ability to receive and accommodate the enhanced amounts of stress provides for enhanced strain characteristics. 
     The invention has been shown in several of its embodiments. It should be apparent to those skilled in the art that the invention is not so limited, but is susceptible to various changes and modifications without departing from the spirit of the invention. 
     It is understood that the steps of the method described above or as claimed is not required to be performed in the order as disclosed. It is further understood that not all of the steps are necessary to carry out the claimed method and different embodiments of the method may not use all of the steps as disclosed above. 
     While the present disclosure has been described with emphasis on certain embodiments, it should be understood that within the scope of the appended claims, the present locating sub system and method could be practiced other than as specifically described herein. Thus, additional advantages and modification will readily occur to those skilled in the art. The disclosure in its broader aspects is therefore not limited to the specific details, representative apparatus, and the illustrative examples shown and described herein. Accordingly, the departures may be made from the details without departing from the spirit or scope of the disclosed general inventive concept.