Patent ID: 8348606

Claim:
A pump assembly configured to pressurize a fluid comprising: a volute defining a fluid inlet for receiving the fluid; a casing configured with the volute to define a pumping chamber that is in fluid communication with said inlet; a rotatably supported impeller configured operate within said pumping chamber, a volute fluid passage communicating the pump chamber and the fluid outlet for discharging fluid medium under pressure during a rotation of the impeller; 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; 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; 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.