Patent Publication Number: US-6905304-B2

Title: Heat dissipation fan

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a heat dissipation fan, and in particular to a heat dissipation fan having reduced turbulence induced in the back side of fan blades and enhancing protection of the blades. 
   2. The Related Art 
   Heat dissipation fans are commonly employed to enhance removal of heat generated in computers in order to maintain proper operation of the computers. A side-mount heat dissipation fan comprises a casing having an open top for intake of surrounding air and a side opening in communication with a heat sink to conduct air flow toward and through the heat sink. The casing has a bottom that is closed for supporting the fan blades thereon. Since the fan blades are rotated at a high speed, undesired impact of the fan blades with the bottom of the casing inevitably causes damage to the fan blades. To reduce the risk of impact, the fan blades are arranged at a sufficient distance from the bottom. This effectively overcomes the impact issue. However, a large gap is formed between the fan blades and the bottom of the casing, and air that is sucked into the fan in an axial direction may flow to the back side of the fan blades instead of being driven out of the fin along the side opening by centrifugal force. The air that flows to the back side of the fan blades induces turbulence that interferes with the air flowing toward the side opening and thus reducing the operation efficiency of the fan. 
   The present invention is thus aimed to overcome the problem caused by the back side turbulence of a side-mount heat dissipation fan. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a heat dissipation fan wherein a stuffing pad is disposed on a bottom of a casing housing a rotary fan assembly in order to substantially eliminating the distance between fan blades and the casing bottom. 
   Another object of the present invention is to provide a heat dissipation fan wherein a soft pad is arranged between a fan assembly and a casing to eliminate damage caused by undesired impact of the fan with the casing. 
   A further object of the present invention is to provide a heat dissipation fan wherein a gap between fan blades and a casing is effectively eliminated while the fan blades are maintained impact free with respect to the casing. 
   To achieve the above objects, in accordance with the present invention, there is provided a heat dissipation fan comprising a casing having a bottom wall and a side wall extending from the bottom wall and defining an open top of the casing. The side wall itself defines a side opening. A rotary fan assembly is housed in the casing and is rotatably supported on the bottom wall. The fan assembly comprises fan blades that are spaced from the bottom wall of the casing whereby a gap is formed therebetween. Air is drawn into the casing by the fan blades via the open top of the casing and driven out of the casing through the side opening. A stuffing pad is arranged in the gap and positioned on the bottom wall to reduce the gap wherein air flowing to the back side of the fan blades is limited and turbulence induced thereby is alleviated. The stuffing pad is made of a soft material whereby damage may not occur on the fan blades when the fan blades impact the stuffing pad. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment of the present invention, with reference to the attached drawings, in which: 
       FIG. 1  is a perspective view of a heat dissipation fan constructed in accordance with the present invention; 
       FIG. 2  is an exploded view of the heat dissipation fan of the present invention; 
       FIG. 3  is a cross-sectional view of the heat dissipation fan of the present invention; and 
       FIG. 4  is a schematic view showing the operation of the heat dissipation fan of the present invention for generation of air flow. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
   With reference to the drawings and in particular to  FIG. 1 , a heat dissipation fan constructed in accordance with the present invention, generally designated with reference numeral  10 , comprises a casing  12  made of a rigid material, such as metal and hard plastics. The casing  12  defines a cavity  14  in which a fan assembly  16  is received as shown in  FIG. 3 . The casing  12  has a bottom wall  18  on which the fan assembly  16  is rotatably supported. For example, a shaft  20  of the fan assembly  16  extends through a bore  21  defined in the bottom wall  18  as shown in  FIG. 2  and supported by bearing means (not shown). Alternatively, the shaft  20  is fixed to and extends from the bottom wall  18  into the cavity  14  to which the fan assembly  16  is rotatably mounted. The casing  12  comprises a side wall  22  extending from the bottom wall  18  to define an open top  24  of the casing  12 . A side opening  26  in communication with the cavity  14  is defined in the side wall  22 . 
   Also referring to  FIGS. 2 and 3 , the fan assembly  16  comprises a number of blades  28  which, when the fan assembly  16  rotates, draw air into the cavity  14  via the top opening  24  of the casing  12  and induce a radial flow through the side opening  26  as shown in  FIG. 4 . To avoid undesired impact between the fan blades  28  of the fan assembly  16  and the bottom wall  18  of the casing  12 , a gap  30  is present between the fan blades  28  and the bottom wall  18 , see  FIG. 3 . 
   In accordance with the present invention, a stuffing pad  32  or a layer of stuffing material is positioned on the bottom wall  18  of the casing  12  and between the bottom wall  18  and the fan blades  28  whereby the gap  30  is effectively reduced and even eliminated. The size of the gap  30  can thus be controlled by use of stuffing pads  32  of different thickness. The stuffing pad  32  defines a hole  34  for the extension of the fan shaft  20 . 
   Since the gap  30  is reduced, impact of the fan blades  28  with the stuffing pad  32  inevitably occurs during the rotation of the fan assembly  16 . To protect the fan blades  28 , the stuffing pad  32  is made of a soft material, such as rubber or flexible plastics that cause no damage to the fan blades  28  when the pad  32  is hit by the fan blades  28 . The stuffing pad  32  can also be in the form of a gel-like or paste-like substance supported on the bottom wall  18 . 
   By fitting the stuffing pad  32  between the fan blades  28  and the bottom wall  18  of the casing  12 , the gap  30  is substantially reduced. This in turn reduces the turbulence induced on the back side of the fan blades  28 . In addition, by means of the softness or flexible characteristics of the stuffing pad  32 , damage to the fan blades  28  caused by undesired impact with the stuffing pad  32  can be effectively eliminated. 
   Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims. For example, the stuffing pad may be replaced by paste-like or gel-like substance that maintains the shape thereof during the operation of the fan.