Sucker Rod End Fittings and Method of Using Same

Abstract

An end fitting for sucker rods or continuous sucker rods defines a rod receptacle with an interior surface defining void spaces having an axial radius of curvature of at least twenty inches. In one form, the fitting receptacle defines two such void spaces and the radius of curvature differs between them.

1 . A sucker rod end fitting for receiving a sucker rod including an interior wall surface defining:
 a rod receptacle having an open axially outer end and a closed axially inner end for housing a sucker rod, said interior wall surface having a first surface proximal to said open end converging outward toward said open axially outer end, and a second surface distal to said open end and proximal to said closed end converging axially outward toward said open axially outer end, and   at least one of said first surface and second surfaces having radius of curvature of approximately twenty (20) inches;   a transition surface from said first axially outward converging surface to said second axially outward converging surface and a transition surface from said second axially outward converging surface to said distal end of said closed axially inner end,   said transition surfaces having a wave-shaped cross-section.   
     
     
         2 . A sucker rod end fitting as claimed in  claim 1  wherein said transition surfaces approach said rod asymptotically, said first surface and said second surface defining a leading edge for distributing positive forces and said transition surfaces defining a trailing edge for distributing negative forces. 
     
     
         3 . A sucker rod end fitting as claimed in  claim 1  wherein said surfaces converging axially outward each having radius of curvature of approximately twenty (20) inches. 
     
     
         4 . A sucker rod end fitting as claimed in  claim 1  wherein the radius of curvature of one of said first and second surfaces is different than the radius of curvature of the other of said surfaces. 
     
     
         5 . A method for assembling a sucker rod body and end fitting comprising the steps of:
 providing at least one end fitting having a central longitudinal axis, and an interior wall defining a receptacle for housing a sucker rod end having a closed axially inner end, an open axially outer end defining plurality of axially spaced void spaces, said interior wall having a first section adjacent said open axially outer end converging axially outward, a second section converging axially inward, a third section adjacent said closed axially inner end converging axially outward, and a fourth section converging axially inward toward said central axis and approaching said central axis asymptotically and terminating at a base, said first and third sections providing a wedge shape having a leading edge for distributing positive forces and said second and fourth sections each comprising a transition surface between said first and third sections and providing a trailing edge for distributing negative forces;   said first and third-sections converging axially inward each having a different radius of curvature each said radius of curvature being approximately twenty (20) inches;   providing a sucker rod body having a first end, and an exterior surface, wherein said first end is configured for mating with said end fitting wherein said rod has a cross section other than round;   cutting a centering hole near the closed axial inner end, wherein said cutting forms a substantially circular centering hole;   providing an adhesive to the interior of said end fitting;   inserting said rod body into said adhesive filled end fitting, and causing said adhesive to fill said void space between said interior wall surface of said fitting and said exterior surface of said rod;   centering said rod body within said end fitting; wherein said centering is guided by said centering hole; and   heat treating rod body with end fitting, wherein said heat treatment bonds adhesive to the rod body.   
     
     
         6 . The method of  claim 5 , wherein said heat treating cures said adhesive to form wedges in said void space between said interior wall surface of said fitting and said exterior surface of said rod. 
     
     
         7 . The method of  claim 5 , further comprising the step, after heat treating, of pulling said rod body in a direction away from said end fitting. 
     
     
         8 . A sucker rod body and end fitting comprising:
 at least one end fitting having a central longitudinal axis, a closed axially inner end, an open axially outer end, and an interior wall surface defining a receptacle for housing a sucker rod end, said interior wall having a first section adjacent said open axially outer end converging axially outward, a second section converging axially inward, a third section adjacent said closed axially inner end converging axially outward, and a fourth section converging axially inward and terminating at a base, said first and third-sections providing a wedge shape having a leading edge for distributing positive forces and said second and fourth sections comprising a transition surface between said first and third sections and said third section and said base approaching said rod asymptotically and providing a trailing edge for distributing negative forces;   at least one of said first and third sections having a radius of curvature of approximately twenty (20) inches;   a rod having an end with an outer surface received within said rod receptacle through said open axially outer end and cooperating with said interior wall surface to define an annular chamber between said outer surface of said end of said rod and said interior wall surface of said rod receptacle.   
     
     
         9 . A sucker rod body and end fitting as claimed in  claim 8  wherein the radius of curvature of one of said first and third sections is different than the radius of curvature of the other of said first and third sections. 
     
     
         10 . A sucker rod body and end fitting as claimed in  claim 8  wherein said first and third surfaces each have a radius of curvature of approximately twenty (20) inches. 
     
     
         11 . A sucker rod construction comprising
 an end fitting defining a rod receptacle;   said rod receptacle having an interior wall surface defining a cavity, having a closed axially inner end, an open axially outer end, a plurality of integrally formed, axially aligned, axially spaced void spaces, tapered to be of decreasing diameter towards said open axially outer end,   at least one of said void spaces defined by a wall surface having a radius of curvature approximately twenty (20) inches;   a rod having an end with an outer surface received within said rod receptacle through said open axially outer end and cooperating with said interior wall surface to define an annular chamber between said outer surface of said end of said rod and said interior wall surface of said rod receptacle;   a body of initially flowable adhesive cured to bond to said outer surface of said end of said rod and solidified to form a plurality of wedges in said tapered void spaces engaging said interior wall surface of said fitting.   
     
     
         12 . The sucker rod construction of  claim 10 , further comprising said interior wall surface defining one of said void spaces having a radius of curvature greater than the radius of curvature of another of said void spaces defined by said interior wall surface. 
     
     
         13 . The sucker rod construction of  claim 10  further comprising, a transition surface between said closed axially inner end and the surface defining said void space distal from said open axially outer end, and a transition surface between said axially aligned, axially spaced void spaces, wherein said transition surfaces have a wave-shaped cross-section. 
     
     
         14 . The sucker rod construction of  claim 10  wherein said transition surfaces approach said rod asymptotically, said wedges having a leading edge for distributing positive forces and a trailing edge for distributing negative forces. 
     
     
         15 . The sucker rod construction of  claim 10 , further comprising:
 a cylindrical rod having an end having a cylindrical outer surface received within said rod receptacle through said open axially outer end and cooperating therewith to define said annular chamber between said outer surface of said end of said rod and said interior wall surface.   
     
     
         16 . The sucker rod construction of  claim 11 , wherein the cylindrical rod comprises fiberglass.