Patent ID: 7121805

Claim:
An electric fan comprising: a rotary hub comprising a central sleeve and a hollow two-layer cylinder including a plurality of blade mounts each including a gap between the layers, an axial 5 first coupling edge abutted on an adjacent blade mount, an arcuate second coupling edge joined with the first coupling edge at an inner end thereof, two axial, spaced, internal ridges, and a rib interconnected the cylinder and the sleeve, the rib having a threaded aperture; and a plurality of detachable revolving blades comprising a base, a blade 10 section supported on the base, a raised member on the base, a connecting edge in a joining portion of the blade section and the raised member, two side shoulders on the base, and a radially inward projection having a hole; wherein the base of each blade is inserted into the gap with the shoulders matingly engaged with the ridges, the connecting edge matingly engaged with 15 the second coupling edge, and one side of the raised member matingly engaged with the first coupling edge respectively, and a fastener is adapted to drive through the hole into the threaded aperture for securing each blade to each blade mount.