Abstract: A sucker rod string using composite rods is provided with socket units. The socket units are all box end units and are connected together with couplers having pin ends. Each of the socket units has a small angle tapered bore. Wedges between the rods and the tapered bore of the socket unit are prestressed by a threaded plug within the box end to a load equal to or greater than the design working load of the string.

Abstract: A composite sucker rod to be formed into a rod string for an oil well is made by placing a coupler unit having a box end on each end of the rod. The coupler unit has a bore extending the full length of the coupler unit. For fabrication, the coupling unit is telescoped over the rod and a conic expansion portion formed on the end of the rod so that the conic expansion portion may be jammed into a tapered bore on the rod. The conic expansion portion is formed when the end is clear of the coupling unit so that it may be well bonded to the rod by precise application of adhesive, heat, and pressure. By using box end couplings on the rod and pin end couplings on coupling units between the rod it is possible to have a smaller overall outside diameter for any given strength of coupling unit.

Abstract: A flexible coupler is provided for the sinker bars of the sucker rod string of a deep oil well. The coupling unit has a flexible section so that the coupling will flex to a greater extent than the sinker bars. The coupling also has a cylindrical bearing surface which is as large as will slide through the eduction tube freely. The bearing surface has longitudinal grooves for the passage of fluid. The coupling itself has a cylindrical friction fit between the pin and the box to help prevent unscrewing of the unit as well as the radial faces which are torqued to API specifications against one another.

Abstract: Operation of a downhole reciprocating oil well pump is controlled by displacement of the fluids discharged from the pump into a displacement cell closed at its upper end. Gas is trapped in the upper end of the displacement cell. Fluids flow from the lower end of the displacement cell through a dump valve into a flow line. The dump valve opens when the pressure in the displacement cell rises to a predetermined high pressure and remains open until the pressure drops to a predetermined lower pressure which may be the flowline pressure. Operation of the dump valve resets a timer that actuates a switch controlling a pumping unit that drives the downhole pump. Thus, control of the pumping unit is based on the volume of fluids displaced from the well by the pump.