Patent Publication Number: US-2007116557-A1

Title: Low noise blower fan

Description:
1. FIELD OF THE INVENTION  
      The present invention relates to a blower fan, and particularly to a blower fan which has low noise.  
     2. DESCRIPTION OF RELATED ART  
      Vibration of blower fans due to rotor imbalance is noisy. If the vibrations are of a high frequency and have a large amplitude, a fairly loud noise can be produced. This noise may become annoying to users of a device with such a blower fan.  
      Referring to  FIG. 5 , a conventional blower fan is shown. A case of the blower fan includes a base plate  20 , and a bearing set  40  extends upwardly from the base plate  20 . A pair of ball bearings  10  is supported by the bearing set  40 . A shaft  50  is supported by the ball bearing  10 . A sealing plate  30  is mounted on the base plate  20 . Vibration of the shaft  50  is transmitted to the base plate  20  via the ball bearings  10 , then to the sealing plate  30 . If the sealing plate  30  and the base plate  20  have large amplitude vibrations, noise is produced.  FIG. 6  is a graph showing noise characteristics of the conventional blower fan shown in  FIG. 5 . A peak noise level is nearly 40 dB.  
      What is needed is a blower fan that produces less noise.  
     SUMMARY OF THE INVENTION  
      An exemplary low noise blower fan includes a base plate for supporting a rotating shaft and a bearing. The shaft is rotated in the bearing. A pad made of damping material is attached to the base plate to dampen vibrations.  
      It is simple and economical to employ a damping pad to dampen vibrations thereby suppressing noise of the blower fan.  
      Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded isometric view of a blower fan in accordance with a preferred embodiment of the present invention, the blower fan including a pad;  
       FIG. 2  is an assembled cutaway view of the blower fan of  FIG. 1 ;  
       FIG. 3  is a graph showing noise characteristics of the blower fan when the pad of  FIG. 1  is made of bitumen;  
       FIG. 4  is a graph showing noise characteristics of the blower fan when the pad of  FIG. 1  is made of composite materials;  
       FIG. 5  is a cutaway view of a conventional blower fan; and  
       FIG. 6  is a graph showing noise characteristics of the conventional blower fan of  FIG. 5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 1 and 2 , a case of a blower fan in accordance with a preferred embodiment of the present invention includes a base plate  100 , and a sleeve  300  extending up from the base plate  100 . A pair of ball bearings  400  is supported by the sleeve  300 . A shaft  500  is supported by the ball bearings  400 . The base plate  100  defines a recess in a surface, a sealing plate is received in the recess. The sealing plate  100  encloses one end of the sleeve adjacent the base plate  100 . A pad  600  which is made of damping material is attached to the base plate  100  and covers the sealing plate  200 . The pad  600  is pasted on the base plate  100  using glue. The sealing plate  200  is sandwiched between the base plate  100  and the pad  600 . Vibration of the shaft  500  is transmitted to the base plate  100  via the ball bearings  400 , then to the sealing plate  200 , noise is generated mostly due to the vibration of the base plate  100  and the sealing plate  200 . The pad  600  is capable of absorbing vibrations because of the energy-absorbing capacity of the elements constituting the pad  600 . It is preferred that the pad  600  should cover most of the surface area of the base plate  100  of the case of the blower.  
       FIG. 3  is a graph showing noise characteristics of the blower fan when the pad  600  is made of bitumen. It can be seen that peak noise level is no higher than 20 dB. In  FIG. 6 , which depicts noise characteristics of a conventional blower fan, peak noise levels exceed 35 dB.  
       FIG. 4  is a graph showing noise characteristics of the blower fan when the pad is made of composite materials. It can be seen that peak noise level is less than 30 dB. Employing the pad  600  made of damping materials reduces noise of the blower fan.  
      The material of the pad  600  is not limited.  
      It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.