Washer pump

A centrifugal pump assembly having a casing including a volute which defines a pumping chamber configured to operably contain a rotatable impeller which, when driven, draws fluid into a fluid inlet and pumps the fluid to and through a fluid outlet, wherein said volute has an exterior sidewall that has a constant internal first radius over a first sidewall portion and transitions to a second sidewall portion of increasing radius;

• and wherein said second sidewall portion defines a first end at a sidewall transition point which is tangent to said constant radius sidewall segment, and defines a second end which is tangent to said volute's fluid outlet and has a second radius that is greater than said first radius;
• said pump volute's sidewall defining a spiral deviation wherein the pump chamber's radial sidewall flares away from the swept area of the impeller's vanes and defines a fluid outlet that contributes to higher P-Q performance, especially when pumping colder fluids;
• and
• wherein said impeller has a central axis of rotation and a central shaft aligned along said impeller's axis of rotation and carrying a plurality of radially projecting curved primary vanes;
• wherein each primary vane has a twist in the radial direction so that each vane has provides an angled, convex leading surface;
• wherein said impeller also has a plurality of radially projecting secondary vanes affixed to said central shaft such that each secondary vane is also aligned with and affixed to said radially projecting curved primary vanes.