| 摘要 |
A cooling fan includes a frame (100) and an impeller (200) with blades (240) disposed in the frame (100). The frame (100) has a base (140) and a sidewall (160) extending from a periphery of the base (140) with an air outlet (180) defined therein. The base (140) has an air inlet (142) and a vent hole (148) defined therein. The vent hole (148) is near the air outlet (180) and between tip portions of the blades (240) and the sidewall (160). In a preferred embodiment, the base (140) has a supporting portion (144) disposed in the air inlet (142). Two ribs (146) extend from a periphery of the supporting portion (144) towards the base (140). One of the ribs (146) is arranged adjacent to the air outlet (180) and has a changeable width which is gradually increased along a direction from the supporting portion (144) to the base (140).
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