Patent ID: 8613608

Claim:
A progressive cavity pump comprising: at least one inner rotor with Z external thread starts; and at least one outer rotor with a helical cavity with Z+1 internal thread starts, wherein the at least one outer rotor is assembled from a plurality of rotor inserts axially following closely one after another, the rotor inserts having helical cavities and Z+1 internal thread starts, wherein each rotor insert of the plurality of rotor inserts is tightly surrounded by and concentrically fixed in a common rigid rotor sleeve, wherein the rotor sleeve is detachably connected to at least one removable end piece with a principally concentric through hollow portion extending axially through the at least one removable end piece, and wherein the through hollow portion forms a gradual transition between a principally circular cross section furthest out from the plurality of rotor inserts and a cross section in the rotor insert nearest to the at least one end piece.