Flexible shaft assembly for progressing cavity pump

Abstract

A progressing cavity, positive displacement rotary pump for liquid or semiliquid material, having a specially designed flexible coupling shaft for connecting a drive shaft to an orbital rotor. The pump components include a tubular stator with an interior helical surface and a hollow tubular orbital rotor within the stator operably connected to the shaft and having an exterior helical surface. The rotor and stator define therebetween sealed pumping cavities that advance axially as the rotor rotates and orbits within the stator. The rotor has a tapered socket with a polygonal transverse cross-section (e.g., pyramid-shaped) at its outer end. The rotor is coupled to the rotor drive shaft by the flexible coupling shaft that extends through the hollow rotor and that has an enlarged tapered head formed to fit tightly in the socket and be retained therein by a threaded fastener. The opposite end of the coupling shaft is connected to the drive shaft outside of the rotor. The coupling shaft flexes to accommodate orbital movement of the rotor during operation of the pump. Also, a unique seal retainer is used to locate a packing-gland-type shaft seal for the drive shaft. The retainer facilitates removal and replacement of the seal components.