Centrifugal pump impeller attachment

In a centrifugal pump having a casing forming an annular chamber between fluid inlet and outlet, a rotatable pump shaft coaxial with the chamber, an impeller in the chamber and mounted against a shoulder carried on the pump shaft, a nut releaseably mounted upon a threaded portion of the pump shaft for holding the impeller against the shoulder, and key means for interconnecting the impeller and pump shaft into a nonrotating assembly, the improvement comprising:

• (a) said impeller having a central hub with a central opening forming an annulus between said hub and said pump shaft, and a first face on said hub seated against said shoulder carried on said pump shaft;
• (b) said nut having a tubular body received in said annulus between said hub and said pump shaft and said nut at one end spaced apart from said shoulder on said pump shaft;
• (c) a radial flange carried on said nut and seated against a second face on said impeller;
• and,
• (d) said key means comprising at least one longitudinal key received slideably in an off-center axial opening in said flange and said second face on said impeller whereby said key means axially separates upon unthreading of said nut leaving said impeller freely rotatable on said pump shaft.