Patent ID: 7305905

Claim:
A rotatable member adapted for dynamic balancing by the addition of balancing weights in the form of projectiles fired at the member during rotation in timed relationship with the rotation of the member so as to impact the member at specific circumaxial locations for balancing of the member, said member taking the form of a centrifugal air impeller having a backplate residing in a radial plane, a circumaxially spaced series of longitudinal air moving blades extending axially therefrom and a radial end ring supporting blade end portions opposite the backplate, one of the backplate and end ring having an annular groove for receiving projectiles and securing the same at the desired locations for balancing the ring, a wall of the groove having a cross-sectional configuration approximating that of the projectile but slightly smaller than that of the projectile at least after impact in at least one direction of measurement so as to engage and capture the projectile for retention in the groove.