Impeller for a cooling fan

摘要

An impeller (10) for a cooling fan includes a hub (20) having a circular wall (22) and an annular sidewall (24) extending downwardly from a rim of the circular wall, and a plurality of blades (30) extending radially from the sidewall of the hub. Each of the blades includes a first portion (32) near the hub and a second portion (34) away from the hub, wherein each of the first portions is identical to an adjacent one of the first portions, and each of the second portions is different from an adjacent one of the second portions regarding a height thereof, thereby reducing a noise level of the impeller when the it operates.