Multi-chamber positive displacement fluid device

A multi-stage positive displacement pump comprising:

• a suction stage having one or more axially stacked positive displacement suction pump sections, each suction pump section having a rotor chamber for pumping fluid from an inlet adapted for connection to a fluid source to a discharge manifold;
• at least one pressure stage, arranged axially with the suction stage, each pressure stage having one or more stacked positive displacement pressure pump sections, each pressure pump section having a rotor chamber for pumping fluid from a suction manifold to a discharge manifold adapted for connection to a fluid destination;
• a crossover section sandwiched axially between the suction stage and the at least one pressure stage, for fluidly connecting the discharge manifold of the suction stage to the suction manifold of the pressure stage;
• and
• a drive shaft extending axially into each suction pump section and into each pressure pump section which rotates for moving fluid from the fluid source to the fluid destination.

A method of pumping fluid comprising the steps of:

• providing two or more positive displacement pump sections, each section having a pair of parallel and contra-rotating rotors operable in a rotor chamber of each section for displacing fluid from each rotor chambers' inlet to a respective discharge when rotated, the pair of rotors for each section being aligned axially with the pair of motors for each other section;
• forming a suction stage by axially stacking one or more pump sections within the suction stage so that respective axes of the rotors align and the discharges form a contiguous discharge manifold;
• forming at least one pressure stage by axially stacking one or more pump sections within the pressure stage so that the respective axes of the rotors align, the inlets forming a contiguous suction manifold and the discharges forming a contiguous discharge manifold;
• stacking the suction stage and the one or more pressure stages axially and aligning the respective axes of the rotors;
• sandwiching cross-over sections axially between the suction stage and each successive pressure stage, each cross-over section having a passage for fluid connection of each stage's discharge manifold to the suction manifold of each successive pressure stage;
• and
• driving the rotors of each pump section with a timed drive shaft and cooperating idler shaft each of which extend axially and drivably through the axis of each rotor of each pump section, the driveshaft extending axially through the suction stage and each successive pressure stage to draw fluid through the inlets and discharge the fluid through the discharge manifold.