Patent ID: 8388327

Claim:
A progressing cavity pump comprising: a pump casing; and at least first and second pump sections, wherein the first pump section comprises a first outer pump rotor and a first inner pump rotor, and the second pump section comprises a second outer pump rotor and a second inner pump rotor, wherein the first and second inner pump rotors are enclosed by the first and second outer pump rotors, respectively, such that one or more separate pump cavities are collectively formed which are configured to move axially through the pump upon bringing the first and second outer pump rotors in coordinated rotation with respect to their respective first and second inner pump rotor, wherein the first and second outer pump rotors are axially fixedly supported and arranged along a same rotary axis, and the first and second inner pump rotors are supported in axially fixed positions relative to the pump casing, and at least one differential arranged to allow each of the first and second outer pump rotors of the first and second pump sections to rotate at mutually different rotational speeds when driven by a same motor.