Improved
sucker rod joints for down hole
petroleum pumping applications are provided within the form factor of standard API sucker rods, such that existing inventory in suitable condition is fully
usable in more demanding applications. The pin ends are selected or processed such as to provide preselected
axial distance between a flat pin end and at least one
reference surface, such as a threaded region or reference shoulder or both. The coupler is dimensioned such that the pin ends are in
abutment either with each other or with opposite sides of an intervening torque
washer in the
central region, when the connection is made to a selected level of thread engagement. Furthermore, the engagement is such as to put the pin ends in compression and the coextensive length of coupler in tension. This increases frictional restraints and locks the elements together to
resist fatigue failure upon
cycling and to insure together with an anaerobic
adhesive sealant, against back threading. This arrangement enables standard quality sucker rods to be employed in a configuration which is mechanically secure and highly resistant to tensile, bending and
torsional forces, thus assuring a greater strength at the joint than in the rod itself, and resisting the effects of
material fatigue arising from long term and stressful
cycling operations.