Patent Publication Number: US-2003228234-A1

Title: Axial flow fan structure

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to an axial flow fan structure. In particular, the present invention relates to an axial flow fan structure allowing simplified manufacture and having reduced noise resulting from tangential wind during rotation of the fan wheel.  
       [0003] 2. Description of the Related Art  
       [0004]FIG. 1 of the drawings illustrates a conventional fan structure comprising a casing  90  having a bottom plate  91  on which a stator bobbin  92  is mounted. The stator bobbin  92  comprises an axle tube  93  for rotatably receiving a shaft  95  of a fan wheel  94 . When the winding mounted around the stator bobbin  92  is energized, the fan wheel  94  is driven to turn. Thus, the blades  96  on the fan wheel  94  drive air current to exit the casing  90  via an air outlet  97  of the casing  90 .  
       [0005] In manufacture of the fan structure, the stator bobbin  92  is assembled inside the narrow space in the casing  90 . Since the casing  90  has a considerable wall thickness, assembly inside the casing  90  is difficult and the cost is increased. Further, when the fan wheel  94  turns, noise resulting from tangential wind is generated between the fan wheel  96  and the wall of the casing  90  surrounding the fan wheel  96 . Further, noise resulting from turbulence is generated on the air outlet side due to interference from the rods supporting the bottom plate  91 . And the amount of outputted air is decreased.  
       SUMMARY OF THE INVENTION  
       [0006] It is an object of the present invention to provide an axial flow fan structure that allows easy manufacture at a lost cost.  
       [0007] It is another object of the present invention to provide an axial flow fan structure having a low noise resulting from tangential wind during rotation of the fan.  
       [0008] It is a further object of the present invention to provide an axial flow fan structure that allows smoother introduction of incoming air and smoother expelling of outgoing air, providing an improved heat-dissipating effect.  
       [0009] The axial flow fan structure in accordance with the present invention includes a bottom plate having a mounting portion to which a stator is mounted. The stator includes a pivotal portion for rotatably receiving a shaft of a fan wheel. A plurality of blades extends outward from a hub of the fan wheel and each has a distal end that terminates at a cylindrical guide wall that is integral with the blades. The guide wall includes an air inlet in an end thereof and an air outlet in the other end thereof.  
       [0010] 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  
     [0011]FIG. 1 is an exploded perspective view of a conventional axial flow fan.  
     [0012]FIG. 2 is an exploded perspective view of a first embodiment of an axial flow fan structure in accordance with the present invention.  
     [0013]FIG. 3 is a top view of the axial flow fan structure in FIG. 2.  
     [0014]FIG. 4 is a sectional view taken along plane  4 - 4  in FIG. 3.  
     [0015]FIG. 5 is a sectional view similar to FIG. 4, illustrating a second embodiment of the invention.  
     [0016]FIG. 6 is a sectional view similar to FIG. 4, illustrating a third embodiment of the invention.  
     [0017]FIG. 7 is a sectional view similar to FIG. 6, illustrating a fourth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0018] Preferred embodiments in accordance with the present invention will now be described with reference to the accompanying drawings.  
     [0019] Referring to FIG. 2, a first embodiment of an axial flow fan structure in accordance with the present invention generally includes a bottom plate  1 , a stator  2 , and a fan wheel  3 .  
     [0020] The bottom plate  1  includes a mounting portion  11  to which the stator  2  is mounted. Fasteners  12  are provided to secure the bottom plate  1  to an appropriate position. If necessary, the bottom plate  1  can be a circuit board having electrical elements that are required for forming a driving circuit.  
     [0021] The stator  2  includes polar plates (not labeled) and a winding (not labeled). The winding may be a conventional radial or axial winding. The stator  2  is mounted to the mounting portion  11  of the bottom plate  1  and includes a pivotal portion  21  for rotatably receiving a shaft  32  of a fan wheel  3 .  
     [0022] The fan wheel  3  includes a hub  31  with the shaft  32 . The shaft  32  of the hub  31  is rotatably received in the pivotal portion  21  of the stator  2 . The fan wheel  3  includes a plurality of blades  33  extending outward from the hub  31 . Each blade  33  has a distal end that terminates at a cylindrical guide wall  34  that is integral with the blades  33 . The guide wall  34  includes an air inlet  35  in an end thereof for introducing air and an air outlet  36  in the other end thereof. Preferably, an axial height of the guide wall  34  is greater than that of the blades  33 .  
     [0023] Referring to FIGS. 3 and 4, in assembly, the stator  2  is mounted to the mounting portion  11  of the bottom plate  1 , and the shaft  32  of the fan wheel  3  is rotatably received in the pivotal portion  21  of the stator  2 . The bottom plate  1  can be directly mounted by fasteners  12  to any desired position. Thus, when the fan wheel  3  turns, the blades  33  drive the air current to enter via the air inlet  35  of the guide wall  34  and then exit via the air outlet  36  of the guide wall  34 . Since tangential wind only occurs in the upper end of the blades  33  during rotation of the fan wheel  3  and since the blades  33  terminate at the cylindrical guide wall  34  that rotates together with the blades  33 , a relatively small noise resulting from tangential wind is generated during rotation of the fan wheel  3 .  
     [0024]FIG. 5 illustrates a second embodiment of the invention. In this embodiment, in order to provide an improved driving effect of air when the fan wheel  3  turns, the guide wall  34  includes a trumpet mouth-like outwardly expanding conic wall portion  37  in each of an outlet side and an inlet side thereof. Since the outwardly expanding conic wall portions  37  are not directly connected to the blades  33 , the air introducing effect in the air inlet  35  of the guide wall  34  and the air output effect in the air outlet  36  of the guide wall  34  are both improved. Thus, the axial flow fan has a smoother air current-driving effect for dissipating a larger heat-generating area.  
     [0025]FIG. 6 illustrates a third embodiment of the invention. In this embodiment, the guide wall  34  includes a trumpet mouth-like outwardly expanding conic wall portion  37  in the inlet side thereof. Since the outwardly expanding conic wall portion  37  is directly connected to the blades  33  and since the top edge of the conic wall portion  37  is located at a level not higher than the blades  33 , a better air introducing effect is obtained in the air inlet  35  of the guide wall  34  when the fan wheel  3  turns.  
     [0026]FIG. 7 illustrates a fourth embodiment of the invention. In this embodiment, the guide wall  34  includes a trumpet mouth-like outwardly expanding conic wall portion  37  in the inlet side thereof that has a larger diameter. Further, the outlet  36  side of the guide wall  34  is in the form of an inverted cone having a smaller diameter. In this embodiment, several support rods  13  extend outward from the bottom plate  1 , and the outlet  36  allowing the driven air current to flow therethrough is defined between the support rods  13 . Further, a post  14  is provided on an end of each support rod  13 , and a fastener  12  is attached to an end of the respective post  14  for mounting the bottom plate  1  to any desired position. Thus, when the fan wheel  3  turns, a better air introducing effect is obtained in the air inlet  35  of the guide wall  34 . Also, a larger output air pressure is obtained in the air outlet  36 .  
     [0027] The axial flow fan structure in accordance with the present invention provides a simplified structure in which the guide wall  34  on the distal ends of the blades  33  replaces the conventional casing wall. Thus, the axial flow fan is simple in manufacture and assembly. The cost is thus reduced, and the noise resulting from tangential wind during rotation is lowered.  
     [0028] 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.