| 摘要 |
An elongated drive string assembly comprising a plurality of hollow sucker rods and a connecting elements with an axis, connected together and between a drive head located at the surface of an oil well and a rotary pump located deep down hole in an oil well. Each hollow sucker rod has at least a first end comprising an internal female threaded surface engaging an external male threaded surface on a connecting element, such as a nipple. In order to further optimize the stres s distribution between the elements, frustro-conical, non-symmetrical threads with a differential diametral taper are used. The torque shoulders have a maximized mean diamete r and cross-sectional area to resist storing reactive torque in the drive string. A modified nipple preferably has a small seal at its free end to decrease corrosion erosion problems. A modified rod may have a series of holes at each extreme end, to substantially increase the flow of fluid extracted. This overall configuration ensures hig h shear strength, lowered stress concentration and a surprising resistance to storin g reactive torque, which minimizes dangerous backspin when power to the sucker rod stri ng is interrupted.
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