Patent Publication Number: US-2003223865-A1

Title: Casing for a heat-dissipating fan

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a casing for a heat-dissipating fan. In particular, the present invention relates to a casing for a heat-dissipating fan with improved air output and without turbulence.  
       [0003] 2. Description of the Related Art  
       [0004]FIG. 1 of the drawings illustrates a conventional heat-dissipating fan comprising a casing  90  having a bottom plate  91 . An axle tube  93  is engaged with an axle seat  92  formed on the bottom plate  91 . A stator bobbin  94  is mounted around the axle tube  93 . A bearing  95  is mounted in the axle tube  95  for rotatably holding a shaft  100  of a fan wheel  96 . When the fan wheel  96  turns, an air stream is driven to flow from an air inlet  98  toward an air outlet  99 . The air stream driven by the blades on the fan wheel  96  exits the air outlet  99 , as illustrated by the longer arrows in FIG. 2. However, a portion of the air stream enters a gap between the bottom wall  91  and the stator bobbin  94 , as indicated by the shorter arrows in FIG. 2. As a result, turbulence is generated and the amount of air output is decreased in addition to noise generated as a result of tangential wind.  
       [0005]FIG. 3 illustrates another conventional heat-dissipating fan, in which an annular wall  910  extends upward from the bottom plate  91  to prevent entrance of the air stream into the gap between the bottom plate  91  and the stator bobbin  94 . However, since the annular wall  910  is perpendicular to the bottom plate  91 , a portion of the air stream driven by the blades as a result of rotation of the fan wheel  96  impedes and is thus reflected by the annular wall  910 . As a result, the problems of turbulence and noise remain unsolved.  
       SUMMARY OF THE INVENTION  
       [0006] It is the primary object of the present invention to provide a casing for a heat-dissipating fan, wherein the air stream driven by the blades as a result of rotation of the fan wheel may smoothly exit the air outlet. Thus, the turbulence generated as a result of impingement of the air stream on the bottom plate or annular wall is reduced, thereby increasing the amount of air output.  
       [0007] A casing for a heat-dissipating fan in accordance with the present invention defines a space having an air inlet and an air outlet. A bottom plate is provided in the air outlet. The bottom plate rotatably supports a fan wheel having a hub and a plurality of blades extending outward from the hub. An annular wall is formed on the bottom plate and has an outer wall face that tapers gradually toward the bottom plate to form a conic shape.  
       [0008] Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 is a sectional view of a conventional heat-dissipating fan.  
     [0010]FIG. 2 is an enlarged view of a circled portion of FIG. 1.  
     [0011]FIG. 3 is a view similar to FIG. 2, illustrating another conventional heat-dissipating fan.  
     [0012]FIG. 4 is a sectional view of a first embodiment of a casing of a heat-dissipating fan in accordance with the present invention.  
     [0013]FIG. 5 is an enlarged view of a circled portion in FIG. 4.  
     [0014]FIG. 6 is a view similar to FIG. 5, illustrating a second embodiment of the casing in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0015] Preferred embodiments in accordance with the present invention will now be described with reference to the accompanying drawings.  
     [0016] Referring to FIGS. 4 and 5, a first embodiment of a casing for a heat-dissipating fan in accordance with the present invention generally includes a casing  1  defining a space  11  having an air inlet  12  and an air outlet  13 . A bottom plate  14  is provided in a central portion of the air outlet  13 . An axle seat or axle hole (not labeled) is provided on the bottom plate  14  for rotatably receiving a shaft (not shown) of a fan wheel  2 . The fan wheel  2  includes a plurality of blades  22  extending radially outward from a hub  21  thereof.  
     [0017] An annular wall  15  extends upward and outward from the bottom plate  14 , forming a conic shape. Namely, the annular wall  15  formed on the bottom plate  14  has an outer wall face that tapers gradually toward the bottom plate  14 . Preferably, the annular wall  15  includes a top that is adjacent to but not in contact with a bottom of the hub  21 , leaving a minimized gap between the hub  21  and the annular wall  15 . The annular wall  15  includes an outer wall face  16  that is at an acute angle θ with a plane on which the bottom plate  14  lies. Preferably, the outer wall face  16  is inclined and the angle θ is 60°-80°. FIG. 6 illustrates a second embodiment of the invention, wherein the outer wall face  16  of the annular wall  15  includes an arcuate portion adjacent to the bottom plate  14 . Thus, the air stream driven by the blades  22  as a result of rotation of the fan wheel  2  is smoothly outputted via the air outlet  13  in a maximum amount while avoiding generation of turbulence and noise.  
     [0018] Preferably, the annular wall  15  has a maximum outer diameter not greater than a diameter of the hub  21 .  
     [0019] Although the invention has been explained in relation to its preferred embodiments as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention. It is, therefore, contemplated that the appended claims will cover such modifications and variations that fall within the true scope of the invention.