Cooling fan

Abstract

A cooling fan for cooling a heat source includes a frame ( 10 ), a stator ( 20 ) mounted in the frame, a rotor ( 30 ) rotatably attached in the frame, a cover ( 40 ) fixed on the frame, and a pair of bearings ( 50, 60 ) received in the cover and the frame respectively. The rotor includes an impeller and a shaft ( 36 ) inserted through the impeller, wherein the shaft has an upper portion being received in one of the pair of bearings in the cover, and a lower portion being received in another one of the pair of bearing in the frame; thus, a vibration of the shaft can be prevented by supports of the pair of bearings, and the rotor is able to maintain a stable rotation, as the cooling fan is in a high speed operation.

1 . A cooling fan adapted for cooling a heat source, comprising:
 a frame;   a lower bearing received in the frame;   a stator attached in the frame and surrounding the lower bearing;   a rotor installed in the frame, the rotor comprising:
 a hub enclosing the stator; 
 a plurality of blades extending outwardly and radially from the hub; and 
 a shaft extending through the hub with a lower portion of the shaft being inserted into the lower bearing; 
   a cover fixed on the frame to cover the rotor; and   an upper bearing received in the cover to accommodate an upper portion of the shaft therein, wherein when the cooling fan is in operation, supports respectively provided by the lower bearing to the lower portion of the shaft, and the upper portion to the upper portion of the shaft cooperatively prevent the shaft from vibration.   
   
   
       2 . The cooling fan as claimed in  claim 1 , wherein the cover comprises a plurality of beams connecting with each other to define an opening, a plate surrounded by the plurality of beams, and a plurality of additional beams interconnecting the plate and the plurality of beams, the plurality of beams being secured on the frame to fix the cover on the frame. 
   
   
       3 . The cooling fan as claimed in  claim 2 , wherein cover comprises four beams and four additional beams, the four additional beams dividing the opening into four identical areas each having a shape similar to a square. 
   
   
       4 . The cooling fan as claimed in  claim 2 , wherein the cover further comprises a tubular body extending downwardly from the plate, the upper bearing being received in the tubular body. 
   
   
       5 . The cooling fan as claimed in  claim 4 , wherein the hub of the rotor comprises a disk having a central area concaved downwardly to form a cavity therein, and an annular flange extending downwardly from a periphery of the disk, the disk of the hub being in alignment with the plate of the cover. 
   
   
       6 . The cooling as claimed in  claim 5 , wherein the tubular body of the cover has an exterior diameter less than a diameter of the cavity of the hub, and a height larger than that of the cavity, the tubular body being partly received in the cavity of the hub. 
   
   
       7 . The cooling fan as claimed in  claim 5 , wherein the upper portion of the shaft is located above the disk and partly exposed within the cavity of the hub, and the lower portion of the shaft is located below the disk. 
   
   
       8 . The cooling fan as claimed in  claim 5 , wherein the frame comprises a lower plate, an upper plate connecting the plurality of beams of the cover thereon, and an annular sidewall interconnecting the lower plate and the upper plate, a through hole being defined through the lower plate and the upper plate for receiving the stator and the rotor therein. 
   
   
       9 . The cooling fan as claimed in  claim 8 , wherein the frame further comprises a collar formed in a center of the through hole with a plurality of ribs connecting the collar to the annular sidewall of the frame, the collar being alignment with the disk of the hub. 
   
   
       10 . The cooling fan as claimed in  claim 9 , wherein a hollow tube extends upwardly from the collar of the frame with the stator disposed therearound, the lower bearing being received in the hollow tube for accommodating the lower portion of the lower bearing therein. 
   
   
       11 . A cooling fan adapted for dissipating heat from a heat source, comprising:
 a frame;   a stator mounted in the frame, the stator having a plurality of coils for performing a magnet field when given an alternating current;   an impeller disposed in the frame, the impeller having a magnetic sleeve for being repulsed or attracted by the magnet field to rotate;   a cover secured on the frame to sandwich the stator and the impeller between the cover and the frame;   a first bearing being received in the cover;   a second bearing being received in the frame; and   a shaft extending through the impeller, the shaft having an upper portion being inserted into the first bearing, and a lower portion being inserted into the second bearing, thus the shaft can be supported at two ends thereof by the first bearing and the second bearing respectively.   
   
   
       12 . The cooling fan as described in  claim 11 , wherein the impeller has a central area concaved downwardly to form a cavity, the upper portion of the shaft being exposed within the central area of the impeller to be received in the first bearing. 
   
   
       13 . The cooling fan as described in  claim 12 , wherein the cover comprises a rectangular, annular bracket, a circular plate in a center of the cover, a plurality of beams connecting the circular plate with the rectangular, annular bracket to define four openings in the cover, and a tubular body extending downwardly from the circular plate and having a lower portion partly received in the cavity of the impeller. 
   
   
       14 . The cooling fan as described in  claim 13 , wherein the first bearing is received in the tubular body of the cover to support the upper portion of the shaft, which is spaced a distance from the circular plate of the cover for preventing an interference between the shaft and the cover. 
   
   
       15 . The cooling fan as described in  claim 14 , wherein the frame has a hollow tube formed at a lower portion thereof with the second bearing received therein, the hollow tube being surrounded by the stator that is surrounded by the magnetic sleeve of the impeller. 
   
   
       16 . The cooling fan as described in  claim 15 , wherein the first bearing, the second bearing, the circular plate of the cover, the impeller, and the hollow tube of the frame are coaxial with each other.