Abstract:
A fan blade assembly includes a fan blade body, which has an axle housing downwardly suspending in a center accommodation open chamber thereof at the center and defining therein an axle hole and an inside annular flange in the axle hole, and a core shaft, which is inserted into the axle hole of the axle housing to support magnetic levitation rotation of the fan blade body and has a coupling groove extending around the periphery thereof and coupled to the inside annular flange of the axle housing with a gap left therebetween.

Description:
[0001]    This application claims the priority benefit of Taiwan patent application number 096217239 filed on Oct. 15, 2007. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an electric fan and more specifically, to fan blade assembly, which facilitates accurate installation of the core shaft in the fan blade body for enabling the core shaft to support magnetic levitation rotation of the fan blade body stably. 
         [0004]    2. Description of the Related Art 
         [0005]    Cooling fans are intensively used in different electronic apparatus for quick dissipation of heat energy. When the mechanical operation speed of a cooling fan is increased, the noise level resulted from friction between the core shaft and the axle bearing is relatively increased. Excessive high temperature during operation of a cooling fan may cause burnout of the component parts. 
         [0006]      FIG. 1  illustrates a conventional magnetic levitation motor fan. According to this design, a fan blade assembly, referenced by  1 , of the magnetic levitation motor fan comprises a fan blade body  11 , a core shaft  12 , and magnetic devices  13 . The fan blade body  11  comprises an accommodation chamber  112 , a metal guide plate  113  mounted on the inner surface of the peripheral wall of the accommodation chamber  112 , and a plurality of radial blades  111  equiangularly spaced around the periphery. The magnetic devices  13  are mounted on the magnetic guide plate  113 . The core shaft  12  is vertically downwardly suspending in the accommodation chamber  112 . When the core shaft  12  is coupled to the magnetic levitation motor (not shown), the magnetic devices  13  act with the magnetic levitation motor, causing magnetic levitation rotation of the fan blade assembly  1 . This design of magnetic levitation motor fan still has drawbacks. According to this design, the core shaft  12  is made by means of injection molding and fixedly mounted inside the fan blade body  11 . During installation of the core shaft  12  in the fan blade body  11 , the perpendicularity of the core shaft  12  must be accurately checked. A small deviation of the core shaft  12  will cause unstable rotation of the fan blade assembly  1 . The complicated installation procedure of the core shaft  12  greatly increases the consumption of labor and time during fabrication of the magnetic levitation motor fan. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a fan blade assembly, which facilitates accurate installation of the core shaft in the fan blade body for enabling the core shaft to support magnetic levitation rotation of the fan blade body stably. 
         [0008]    To achieve this and other objects of the present invention, the fan blade assembly comprises a fan blade body and a core shaft. The fan blade body comprises a center accommodation open chamber and an axle housing downwardly suspending in the center accommodation open chamber at the center. The axle housing has an axle hole axially and downwardly extending to its bottom side, and an inside annular flange transversely extending around the inside wall and suspending in the axle hole. The core shaft is inserted into the axle hole of the axle housing to support rotation of the fan blade body on the core shaft, having a coupling groove extending around the periphery and coupled to the inside annular flange of the axle housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a sectional view of a conventional magnetic levitation motor fan. 
           [0010]      FIG. 2  is a cutaway of a fan blade assembly in accordance with a first embodiment of the present invention. 
           [0011]      FIG. 3  is an exploded view of  FIG. 2 . 
           [0012]      FIG. 4  is an enlarged view of a part A of  FIG. 2 . 
           [0013]      FIG. 5  is a schematic sectional side view of the fan blade assembly in accordance with the first embodiment of the present invention. 
           [0014]      FIG. 6  corresponds to  FIG. 5 , showing a magnetic member fastened to the locating hole of the fan blade body. 
           [0015]      FIG. 7  is a schematic sectional side view of the fan blade assembly in accordance with a second embodiment of the present invention. 
           [0016]      FIG. 8  is a schematic sectional side view of the fan blade assembly in accordance with a third embodiment of the present invention. 
           [0017]      FIG. 9  is a schematic sectional side view of the fan blade assembly in accordance with a fourth embodiment of the present invention. 
           [0018]      FIG. 10  is a schematic sectional side view of the fan blade assembly in accordance with fifth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Referring to  FIGS. 2˜4 , a fan blade assembly in accordance with a first embodiment of the present invention is shown comprised of a fan blade body  2  and a core shaft  3 . 
         [0020]    The fan blade body  2  has an accommodation open chamber  22  disposed at the center and facing one side, namely, the bottom side, a plurality of radial blades  21  equiangularly spaced around the peripheral wall of the accommodation open chamber  22 , a metal guide plate  23  mounted on the inner surface of the peripheral wall of the accommodation open chamber  22 , a plurality of permanent magnets  24  affixed to the metal guide plate  23 , a locating hole  26  located at the center of the top wall of the accommodation open chamber  22  and disposed outside the accommodation open chamber  22  for accommodating a magnetic member  27  (see  FIG. 6 ), and an axle housing  25  downwardly extending from the center of the top wall of the accommodation chamber  22  opposite to the locating hole  26  and suspending inside the accommodation open chamber  22 . According to this embodiment, the locating hole  26  is a recessed hole. The axle housing  25  has an axle hole  251  axially and downwardly extending to its bottom side, and an inside annular flange  252  transversely extending around the inside wall and suspending in the axle hole  251 . The core shaft  3  is inserted with its one end into the axle hole  251  of the axle housing  25 , having a coupling groove  31  extending around the periphery and forced into coupling with the inside annular flange  252  of the axle housing  25 . 
         [0021]    Referring to  FIG. 5 , by means of inserting one end of the core shaft  3  into the axle hole  251  of the axle housing  25  to force the coupling groove  31  into coupling with the inside annular flange  252  of the axle housing  25 , the installation of the core shaft  3  is quite easy, and a user needs not to worry about alignment between the fan blade body  2  and the core shaft  3 . After installation of the core shaft  3  in the axle housing  25 , a gap about 0.1 mm exists between the coupling groove  31  and the inside annular flange  252 , and the permanent magnets  24  are spaced around the core shaft  3  at a distance. 
         [0022]    Referring to  FIG. 5  again, when the electric fan is started, the magnetic lines of force of the permanent magnets  24  are separated, and the fan blade body  2  pulled downwards due to the effect of magnetic attraction, keeping the core shaft  3  in position. Because a gap about 0.1 mm exists between the coupling groove  31  and the inside annular flange  252 , the fan blade body  2  is supported on the top edge of the core shaft  3  and made to rotate stably in a magnetic levitation rotation manner. During magnetic levitation rotation of the fan blade body  2 , the axle housing  25  does not touch the core shaft  3 , therefore the friction coefficient between the fan blade body  2  and the core shaft  3  is minimized. 
         [0023]    Referring to  FIG. 6 , after installation of the magnetic member  27  in the locating hole  26  of the fan blade body  2 , the magnetic member  27  imparts a magnetically attractive force to the core shaft  3  to secure the core shaft  3  to the inside of the axle hole  251 . At this time, the core shaft  3  has its top edge stopped against the center of the top wall of the accommodation open chamber  22  and is kept suspending in the axle hole  251  without touching the peripheral wall of the axle housing  25 . Therefore, the fan blade body  2  can be rotated stably in a magnetic levitation rotation manner, lowering friction and noise level. 
         [0024]      FIG. 7  is a schematic sectional side view of the fan blade assembly in accordance with a second embodiment of the present invention. This second embodiment is substantially similar to the aforesaid first embodiment with the exception that the locating hole  26  of this second embodiment is a through hole disposed in axial connection with the axle hole  251 , and the top edge of the core shaft  3  is directly stopped against the magnetic member  27 , enhancing the positioning accuracy. 
         [0025]      FIG. 8  is a schematic sectional side view of the fan blade assembly in accordance with a third embodiment of the present invention. This third embodiment is substantially similar to the aforesaid first embodiment with the exception that the locating hole  26  of this third embodiment is a through hole disposed in axial connection with the axle hole  251 , and the top end of the core shaft  3  is inserted into the axle hole  251  and the locating hole  26  and secured in place by a retainer ring  28  that is mounted inside the locating hole  26 . 
         [0026]      FIG. 9  is a schematic sectional side view of the fan blade assembly in accordance with a fourth embodiment of the present invention. This fourth embodiment is substantially similar to the aforesaid first embodiment with the exception that the axle housing  25  according to this fourth embodiment comprises an axially extending axle hole  251 , an annular stop flange  29  suspending at the bottom side of the axially extending axle hole  251 , an axle bearing  32  mounted in the axle hole  251 , and a retaining ring  28  mounted in the axially extending axle hole  251  and stopped between the axle bearing  32  and the annular stop flange  29  and fastened to the coupling groove  31  of the core shaft  3  to secure the top end of the core shaft  3  to the inside of the axle bearing  32 ; the locating hole  26  according to this fourth embodiment is a through hole disposed in axial connection with the axle hole  251  and holding a magnetic member  27  in direct contact with the top edge of the core shaft  3 . According to this fourth embodiment, the axle bearing  32  is a slide bearing. 
         [0027]      FIG. 10  is a schematic sectional side view of the fan blade assembly in accordance with fifth embodiment of the present invention. This fifth embodiment is substantially similar to the aforesaid fourth embodiment with the exception that the axle bearing  32  according to this fifth embodiment is a ball bearing. 
         [0028]    Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.