Patent Publication Number: US-8113766-B2

Title: Fan and fan frame thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fan and a fan frame thereof, and in particular to a noiseless fan with disposition of sound absorbers requiring limited space, successfully reducing noises during operation. 
     2. Description of the Related Art 
     Within the field of heat dissipation of electronic devices, fans are commonly used in computer systems and many electronic products mainly because fans are cheap, reliable and efficient. In early years, fans were valued based upon heat dissipating efficiency, but noise produced by the fans were ignored. However, in an electronic device, most noise is originated from fans. As shown in  FIG. 1 , a standard fan  1  has a frame  101  covering an impeller  102 , and impeller  102  rotates to produce air flows for heat dissipation. However, the wall of the frame  101  is made of rigid materials. When the impeller  102  rotates, the pressure at the wall changes periodically, and then produces steady sounds (or call noises). Further, the higher the frame  101 , the louder the noises produced by the fan because the sound wave reflects, diffracts and resonates between the walls of the frame  101 . 
     An improved conventional fan is disclosed in  FIG. 2 . A conventional computer fan is disposed within the chamber  13  of the housing  10 , and a sound-absorbing cotton  23  is disposed in the housing  10  for surrounding the fan. The periphery of the frame  20  of the fan has several holes  24 , so that noise produced during operation of the impeller  40  can be absorbed by the sound-absorbing cotton  23  in the chamber  13 . 
     Nevertheless, fans used in electronic production have standard sizes. For example, a fan labeled 80*30 means the length and width are both 80 mm, and the height is 38 mm. If the above method is applied to a standard-sized fan to reduce noises, the size of the fan and the manufacturing cost would increase accordingly. The increase of size makes the fan to be a non-standard sized fan. For users, fans with non-standardized sizes may cause problems when fitted to modulated heat dissipating systems. In other words, the fans applications are limited when applying to standardized computer and electronic systems. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a fan and fan frame thereof. At least one sound absorber is disposed using a limited space in a fan without increasing fan volume, such that the sound is absorbed during the operation, thereby decreasing or even eliminating noises produced by the fan. 
     Accordingly, the present invention provides a fan including an impeller and a fan frame. The fan frame has a main body having a passage for receiving the impeller. A plurality of flanges are disposed on the periphery of the main body. A recess is defined between the two adjacent flanges. An aperture is disposed on a wall of the main body corresponding to the recess so as to allow the recess to communicate with the passage. The fan frame further has at least one sound absorber, the shape of the sound absorber corresponds to the shape of the recess, and the size of the sound absorber is slightly less than the size of the recess, such that the sound absorber can be disposed in the recess. The sound absorber is made of a porous material, and a plurality of holes with different diameters is formed on the porous material. 
     The fan frame further includes a cover, wherein the shape of the cover corresponds to the shape of the recess, and the size of the cover is less than the size of the recess, such that the cover can be disposed in the recess and covers the sound absorber. A gap is formed between the cover and the sound absorber. Additionally, when the cover covers the recess, an exterior surface of the cover is flush with the lateral surface of the main body, and does not protrude from the main body. 
     A first through hole is formed on each of the flanges, and a second through hole is correspondingly formed on the sound absorber so as to allow an additional fixing member to pass through and then to secure the fan in a computer or an external system. Furthermore, a supporting member is disposed in the aperture for securing the sound absorber within the recess and ensuring a regular operation of the impeller. 
     The present invention provides a fan frame including a main body and at least one sound absorber. The main body has a passage, and a plurality of flanges are disposed on the periphery of the main body. A recess is defined between the two adjacent flanges. An aperture is disposed on a wall of the main body corresponding to the recess so as to allow the recess to communicate with the passage. The shape of the sound absorber corresponds to the shape of the recess, and the size of the sound absorber is slightly less than the size of the recess, such that the sound absorber can be disposed in the recess. The sound absorber is made of a porous material, and a plurality of holes with different diameters is formed on the porous material. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic view of a conventional fan; 
         FIG. 2  is an exploded view shows a conventional fan disposed in a conventional housing with a sound-absorbing cotton; 
         FIG. 3  is an exploded view of a fan having a sound absorber according to the preferred embodiment of the present invention; 
         FIG. 4  is an exploded view of the fan shown in  FIG. 3  with a cover; 
         FIG. 5  is a schematic view of the fan with the cover in  FIG. 4 ; 
         FIG. 6  is a schematic view showing the relative position of the sound absorber and the cover of the fan in  FIG. 5 ; 
         FIG. 7  is a curvature diagram showing the noise characteristics of the conventional fan; and 
         FIG. 8  is a curvature diagram showing the noise characteristics of the fan of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  is an exploded view of a fan with a sound absorber according to the preferred embodiment of the present invention, and  FIG. 4  is an exploded view of the fan shown in  FIG. 3  with a cover. Referring to  FIGS. 3 and 4 , the fan  3  can be used in a computer as a heat dissipating fan, but the example is not limited thereto. In other embodiments, the fan  3  can be applied to servers or telecommunication products. The fan  3  includes a fan frame  5  and an impeller  52  disposed within the fan frame  5 . The fan frame  5  has a rectangular main body  51 , at least one sound absorber  6  and at least one cover  7  disposed close to the main body  51 . In  FIGS. 3 and 4 , there are four sound absorbers  6  and four covers  7  corresponding to these sound absorbers  6 . The main body  51  has a passage  511  formed in the main body  51  for receiving the impeller  52  and the motor (not shown). There are two flanges  512 ,  513 , which are relative to the inlet and the outlet of the fan frame  5  respectively, formed on each of the corners of the main body  51 , and a recess  514  is defined between the adjacent flanges  512 ,  513 . 
     An aperture  516  is formed on a wall of the main body  51  neighboring to the recess  514 , allowing the recess  514  to communicate with the passage  511  of the main body  51 . A supporting member  515  is disposed in the aperture  516 . Further, there is one first through hole  517  formed on each of the flanges  512 ,  513 , respectively, to allow an additional fixing member, a screw for example (not shown), to pass through, in order to secure the fan  3  in a computer or a external system (not shown). It is noted that the number and the size of the aperture  516  on the wall of the main body  51  is varied according to tactual noise frequency produced by the impeller  52 , and together with the disposition of the sound absorber  6 , the appropriate number and the size of the aperture  516  is then decided to obtain the best absorption result. The number of the aperture  516  is one, but it is not limited thereto. 
     The shape of the sound absorber  6  corresponds to the shape of the recess  514  of the main body  51 , which implies that the shape of the sound absorber  6  is varied with the shape of the recess  514 . The size of the sound absorber  6  is slightly less than the size of the recess  514 , such that the sound absorber  6  is able to be received in the recess  514 . The supporting member  515  secures the sound absorber  6  within the recess  514  and ensures the regular operation of the impeller  52  due to the interruption caused by sliding of the sound absorber  6 . The sound absorber  6  is made of a porous material, and a plurality of holes (not shown) with different diameters are formed on the porous material. Moreover, in consideration of a screw (not shown) passing through the through holes  517  for securing the fan  3  in a computer or a external system, a second through hole  61  is formed in the sound absorber  6  for matching the relative through holes  517  when the sound absorber  6  is disposed in the recess  514  and between two flanges  512  and  513 . 
     The cover  7  is assembled to the corresponding recess  514  and is fixed on the main body  51  of the fan frame  5 . The shape of the cover  7  corresponds to the shape of the recess  514 . In the embodiment, the shape of the cover  7  is in L shape, but it is not limited thereto. The shape of the cover varies with the shape of the recess  514 . As shown in  FIG. 5 , when the cover  7  covers the recess  514 , the exterior surface  71  is flush with the lateral surface of the main body  51  and does not protrude from the main body  51 , thereby improving the overall appearance of the fan  3 . 
     The noiseless fan of the present invention includes the sound absorber  6  in the recess  514  of the main body  51  to absorb noises without increasing original volume. The technique of the present invention is further described as below. The cover  7  covers the recess  514  to conceal the sound absorber  6  in the recess  514 . In addition, the aperture  514  is on the wall  515  of the main body  51  so as to allow the recess  513  to communicate with the passage  511  of the main body  51 . Thereby, the sound absorber  6  successfully absorbs noises produced by the rigid material of the main body  51 . When the sound wave produced during the rotation of the impeller  52  passes the surface of the sound absorber  6  with holes, sound energy is transferred into thermal energy by friction effect, thereby reducing noises of the fan. 
     As shown in  FIG. 6 , a gap  8  is formed between the sound absorber  6  in the recess  514  of the main body  51  and the cover  7 . The gap  8  changes the acoustic resistance of the sound absorber  6  so as to allow the sound absorber  6  to absorb noises with different sound waves. As a result, the method can be used to eliminate noise with particular frequencies. On the other hand, the gap  8  is not sufficient between the sound absorber  6  and the cover  7  to sustain efficient absorption. In the present invention, the gap  8  is kept between the sound absorber  6  and the cover  7 , but it is not limited thereto. 
     Referring to  FIGS. 7 and 8 , curvature diagrams show measurement of the conventional standard 9 cm fan in  FIG. 1  and the noiseless 9 cm fan of the present invention by a precise instrument. The longitudinal axis represents noise level and the lateral axis t represents frequency. In the diagram, the noise level of 61.6 dB(A) is measured from the noiseless fan of the present invention, and the noise level of 63.6 dB(A) is measured from the conventional fan. As a result, compared to the conventional fan, the fan of the present invention successfully reduces noise level by 2 dB(A). 
     As described, the present invention discloses a noiseless fan. At least one sound absorber is disposed using a limited space in a fan, thereby absorbing noises during the operation of the impeller of the fan and decreasing the noise level produced by the fan. In other words, the volume and height of the fan are not increased in order to keep its original appearance, saving costs, conforming to standard sizes and raising noise comfort. 
     While the present invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the present invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.