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Improved End Fittings For Sucker Rods

Typically, the end fittings used for sucker rods are made of metal, but they may be made from a variety of materials. These fittings can be used for steering, tensioning, or motion control. However, they are often susceptible to premature failure. This is a problem that is often caused by improper materials handling. The present invention provides a better method of assembling and using end fittings for sucker rods. In addition, it provides an improved design for the wedge that makes them more reliable.

The wedge in the present invention consists of a solid adhesive that is pressed against a complementary form of end fitting. This forces the adhesive to deform into an annular wedge. The adhesive is then cured. The wedges disperse the destructive forces evenly throughout the interface, which can help to reduce the possibility of failure. The wedges can be made from carbon steel or alloy steel. They are particularly suited for bearing arrangements that are subject to heavy alternating loads. However, the wedges are also useful for transmitting pumping forces and absorbing negative load forces.

The improved design of the end fitting provides a greater surface area to fill with adhesive, increasing the amount of wedges that are formed when the adhesive is cured. This increase in surface area allows for more accurate centering between the end fitting and rod. The wedge also provides a more robust gripping surface to connect the end fitting to the rod. The wedge also prevents pullouts, which can be caused by excessive mechanical forces. This can be catastrophic in some instances.

The improved design of the end fitting also changes the sloping angle of the outer wall of the annulus. This change in angle provides a more uniform wedge during assembly. In addition, the wedge provides a more consistent surface that is more resistant to stress concentration areas. The wedge can also be made larger to better accommodate larger rods. The wedge is also able to absorb negative load forces, which can cause catastrophic shear failure.

In addition to the wedges, the end fitting also has an axial receptacle defined by a series of outwardly converging tapered surfaces. This provides a wave-shaped transition surface that helps to avoid an abrupt discontinuity in the internal surface curvature. The wedges are also able to capture the forces that are applied to the end fitting, providing a reliable cooperating grip. The wedges also have back relief to prevent them from pulling out of the end fitting.

The wedges of the present invention can be made from carbon steel or alloy steel, although the materials used may be different. The wedges can also be coated with a rust inhibitor to provide corrosion resistance in dry environments. These wedges can be used in conjunction with thread protectors or other forms of protection.

These wedges can also be made with a black oxide finish to prevent corrosion. They are also heat cured. Curing time will depend on the type of adhesive used, the type of rod bodies, and the ambient temperature and humidity.