Cooling fan with tapered hub

Abstract

A cooling fan includes a fan housing and a rotor received in the fan housing. The fan housing has an air inlet and an outlet opposite to the air inlet. The rotor includes a shaft, a hub engaged with the shaft, and a plurality of rotary blades extending outwardly from the hub. The hub has an outer surface expanding along a direction parallel to a central axis of the shaft from the air inlet to the air outlet.

1 . A cooling fan comprising:
 a fan housing having an air inlet and an outlet opposite to the air inlet;   a rotor received in the fan housing, the rotor comprising a shaft, a hub engaged with the shaft, and a plurality of rotary blades extending outwardly from the hub, the hub having an outer surface expanding outwards along a direction parallel to a central axis of the shaft from the air inlet to the air outlet.   
     
     
         2 . The cooling fan of  claim 1 , wherein a distance between the outer surface of the hub and the shaft gradually increases from the air inlet to the air outlet. 
     
     
         3 . The cooling fan of  claim 1 , wherein the fan housing has a lateral wall with an inner surface facing the hub, the inner surface being parallel to the central axis of the shaft. 
     
     
         4 . The cooling fan of  claim 1 , wherein the hub comprises a circular top wall and an annular wall extending from the top wall towards the air outlet, an outer surface of the circular top wall of the hub facing the air inlet being flat, an outer surface of the annular wall of the hub expanding from the air inlet to the air outlet. 
     
     
         5 . The cooling fan of  claim 4 , wherein the annular wall of the hub has an inner surface facing the shaft, the inner surface defining a cylinder having a constant diameter. 
     
     
         6 . The cooling fan of  claim 5 , wherein the hub receives a stator therein, and a magnet is attached on the inner surface of the annular wall and surrounding the stator. 
     
     
         7 . A cooling fan comprising:
 a fan housing having an air inlet and an outlet opposite to the air inlet;   a rotor received in the fan housing, the rotor comprising a shaft, a hub engaged with the shaft, and a plurality of rotary blades extending outwardly from the hub, the hub having an outer surface tapered from the air outlet to the air inlet.   
     
     
         8 . The cooling fan of  claim 7 , wherein a distance between the outer surface of the hub and the shaft gradually increases from the air inlet to the air outlet. 
     
     
         9 . The cooling fan of  claim 7 , wherein the fan housing has a lateral wall with an inner surface confronting the hub, the inner surface being parallel to a central axis of the shaft. 
     
     
         10 . The cooling fan of  claim 7 , wherein the hub comprises a circular top wall and an annular wall extending from the top wall towards the air outlet, an outer surface of the circular top wall of the hub facing the air inlet being flat, an outer surface of the annular wall of the hub expanding from the air inlet to the air outlet. 
     
     
         11 . The cooling fan of  claim 10 , wherein the annular wall of the hub has an inner surface facing the shaft, and the inner surface has a constant diameter. 
     
     
         12 . The cooling fan of  claim 11 , wherein the hub receives a stator therein, and a magnet is attached on the inner surface of the annular wall and surrounding the stator.