Multi-element centrifugal pump impellers with protective covering against corrosion and/or abrasion

Claim 1

A pump device comprising: an impeller unit having substantially parallel front and back walls including; a first plate having a central aperture therethrough, a plurality of separator discs also each having a central aperture therethrough, and a plurality of solid vanes with assembly holes therethrough; an expeller unit having substantially parallel front and back walls with a plurality of solid vanes between said walls, a central input aperture leading to openings between said vanes and walls, and peripheral openings around the circumference of said expeller unit; aligning and fastening means for aligning and holding the solid vanes, the first plate, the separator discs and the expeller unit together; means for diverting liquid flowing inwardly through said central apertures outwardly to said vanes; non-frictional seal means at the central aperture of said first plate; said aligning and fastening means for aligning and holding the component elements together comprising a plurality of separate dowels and separate assembly screws; said separate dowels fitting through inner circumferential holes in the solid vanes, the first plate, and the separator discs; and said separate assembly screws fitting through outer circumferential holes in the solid vanes, the first plate, and the separator discs, and being screwed into tapped holes of the expeller unit.