High inertia insulating cooling fan for electric motor device

Claim 1

In a portable electric motor-driven device including a housing, an electric motor contained within said housing, a shaft driven by said motor and a cooling fan driven by said motor and serving to provide a flow of cooling air over said motor, said fan comprising a body of insulating material mounted on and extending radially from said shaft, the improvement wherein said fan body comprises a first, generally cup-shaped portion having a central aperture through which said shaft extends, said cupshaped portion including a generally planar member extending radially from said shaft and said cup-shaped portion also including an axially extending lip formed on the radial extremity of said planar membeR; said fan body further including a plurality of fan blades extending radially outwardly from said lip; and a metallic inertial member fixed to said fan body within said cup-shaped portion, said inertial member including a first, radially extending part fixed to said planar member of said cupshaped portion and said inertial member further including an axially extending lip disposed within said lip on said cup-shaped portion to provide a stabilizing inertial weight radially spaced from said shaft, said lip on said cup-shaped member partially enclosing said metallic inertial member to increase the effective tracking distance between said inertial member and electrically live portions of said electric motor.