Impeller for a propeller pump

An impeller for a propeller pump for pumping waste water containing pollutants, comprising in combination:

• a hub having a cone angle of twenty degrees of arc, and a straight impeller shaft joined to said hub;
• a plurality of vanes attachable at arbitrary pitch angle to said hub;
• said vanes of said plurality thereof have backwards-swept leading edges;
• said hub has a cross-section which conically increases in the flow direction of said impeller;
• said vanes have tips which define a rotary circumference of said impeller;
• said vanes have chords of a given length which does not decrease towards said circumference;
• each said vane having a center of gravity and a turning axis perpendicular to said shaft said turning axis substantially bisects the center of its chord at said center of gravity;
• the distance between each leading edge of said vanes and the turning axis, at said circumference, encompasses a given distance;
• the distance between each trailing edge of said vanes and the turning axis, at said circumference, encompasses another given distance which is not more than eleven percent greater than said given distance;
• and
• at said center of gravity, the lengths between said turning axis of each said vane and its leading and trailing edge are equal.