Abstract:
A series fan frame body structure made of different materials includes at least two fans, which are serially connected with each other. The fan frames of the two fans are made of different plastic materials. Accordingly, the excited frequency of the fan is prevented from being close to the natural frequency of the fan frames. Therefore, the vibration frequencies of the fan frames are different from each other so that the co-vibration is reduced to lower the noise. By means of the series fan frame body structure made of different materials, the problem of vibration of the fan is effectively improved.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a fan frame body structure, and more particularly to a series fan frame body structure made of different materials. The vibration frequencies of the fan frames of the series fan are different from each other so that the co-vibration of the fan is reduced to lower the noise. 
         [0003]    2. Description of the Related Art 
         [0004]    The materials of the existent fan frames can be generally classified into two types, that is, metal frame body made by means of casting and plastic frame body made by means of injection molding. The cast metal frame body such as aluminum-made frame body has a higher price due to higher material cost. The plastic frame body made by means of injection molding, such as PBT, PA66 and PPE frame body has a much cheaper price than the metal frame body due to lower material cost so that the plastic frame body is popularly used in this field. 
         [0005]    The forms of the current fans include one-fan form and series fan form. The fan in the one-fan form has a frame body simply made of plastic material such as PBT, PA66 or PPE. The series fan has two frame bodies serially connected with each other. The frame bodies are made of the same material of the same composition. For example, both frame bodies are made of PBT, PA66 or PPE. 
         [0006]    No matter which form the fan has, the material and composition of the frame bodies are the same. Therefore, in the case that in operation of the fan, the excited frequency of the fan is close to the natural frequency of the fan frame, the fan will severely co-vibrate to make noise. This will ill affect the components of the fan to deteriorate the reading efficiency of hard disc of the system. Moreover, the lifetime of the system and the fan will be shortened. 
         [0007]    It is therefore tried by the applicant to provide a series fan frame body structure made of different materials to solve the problem of co-vibration of the fan. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore a primary object of the present invention to provide a series fan frame body structure made of different materials. Due to the different materials, the vibration frequencies of the fan frames of the series fan are different from each other so that the co-vibration of the fan is reduced to lower the noise. 
         [0009]    To achieve the above and other objects, the series fan frame body structure made of different materials of the present invention includes: a first fan including a first fan frame made of a first kind of plastic material; and a second fan including a second fan frame made of a second kind of plastic material. The second fan frame made of the second kind of plastic material is serially connected with the first fan frame made of the first kind of plastic material. The first kind of plastic material is different from the second kind of plastic material in composition. The first kind of plastic material is one of PBT, PA66, PPE, PA, PC, ABS and PPS, while the second kind of plastic material is another of PBT, PA66, PPE, PA, PC, ABS and PPS. The first fan frame vibrates at a first vibration frequency, while the second fan frame vibrates at a second vibration frequency. The first vibration frequency is different from the second vibration frequency. 
         [0010]    In the above series fan frame body structure, the first fan frame has a first opening and a second opening. The first and second openings are respectively formed on two opposite sides of the first fan frame. A first flow passage communicates the first opening and the second opening with each other. A first base seat is positioned in the first flow passage. A first fan impeller is disposed on the first base seat. 
         [0011]    In the above series fan frame body structure, the second fan frame has a third opening and a fourth opening. The third and fourth openings are respectively formed on two opposite sides of the second fan frame. A second flow passage communicates the third opening and the fourth opening with each other. A second base seat is positioned in the second flow passage. A second fan impeller is disposed on the second base seat. 
         [0012]    According to the above arrangement, the co-vibration of the series fan can be effectively reduced to remove the vibration frequency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein: 
           [0014]      FIG. 1A  is a perspective exploded view of the series fan structure of the present invention; 
           [0015]      FIG. 1B  is a perspective assembled view of the series fan structure of the present invention; 
           [0016]      FIG. 1C  is a top view of the series fan structure of the present invention; 
           [0017]      FIG. 2  is a sectional view taken along line X-X of  FIG. 1C ; 
           [0018]      FIG. 3  is a sectional view taken along line Y-Y of  FIG. 1C ; 
           [0019]      FIG. 4A  is a diagram showing the comparison between the operational vibration of the fan frame of the series fan of the present invention and the fan frame of the conventional fan; and 
           [0020]      FIG. 4B  is an enlarged diagram of a range of  FIG. 4A . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    The embodiments of the present invention will be described hereinafter with reference to the drawings, wherein the same components are denoted with the same reference numerals. 
         [0022]    Please refer to  FIGS. 1A ,  1 B,  1 C,  2  and  3 .  FIG. 1A  is a perspective exploded view of the series fan structure of the present invention.  FIG. 1B  is a perspective assembled view of the series fan structure of the present invention.  FIG. 1C  is a top view of the series fan structure of the present invention.  FIG. 2  is a sectional view taken along line X-X of  FIG. 1C .  FIG. 3  is a sectional view taken along line Y-Y of  FIG. 1C . 
         [0023]    As shown in  FIGS. 1A to 1C ,  2  and  3 , the series fan frame body structure made of different materials of the present invention includes a first fan  10  and a second fan  20 , which are serially connected with each other. The first fan  10  includes a first fan frame  11  made of a first kind of plastic material. A first opening  12  and a second opening  13  are respectively formed on two opposite sides of the first fan frame  11 . A first flow passage  16  communicates the first opening  12  and the second opening  13  with each other. A first base seat  15  is positioned in the first flow passage  16  in adjacency to the second opening  13 . Multiple radial support ribs are disposed on an outer circumference of the first base seat  15  to connect with an inner wall of the first fan frame  11 . A first fan impeller  14  is rotatably disposed on the first base seat  15 . 
         [0024]    The second fan  20  includes a second fan frame  21  made of a second kind of plastic material. A third opening  22  and a fourth opening  23  are respectively formed on two opposite sides of the second fan frame  21 . A second flow passage  26  communicates the third opening  22  and the fourth opening  23  with each other. A second base seat  25  is positioned in the second flow passage  26  in adjacency to the third opening  22 . Multiple radial support ribs are disposed on an outer circumference of the second base seat  25  to connect with an inner wall of the second fan frame  21 . A second fan impeller  24  is rotatably disposed on the second base seat  25 . 
         [0025]    The second opening  13  of the first fan  10  is correspondingly adjacent to the third opening  22  of the second fan  20 . The first flow passage  16  communicates with the second flow passage  26 . When the first and second fan impellers  14 ,  24  rotate, the fluid flows through the first, second, third and fourth openings  12 ,  13 ,  22 ,  23 . The first and second fans  10 ,  20  can be serially connected by any conventional measure. For example, the opposite sides of the first and second fans  10 ,  20  can be provided with mating members. Alternatively, the four corners of the two fans  10 ,  20  can be formed with perforations and four securing members can be correspondingly passed through the perforations to lock the two fans with each other. Still alternatively, the two fans can be connected with each other by means of adhesion. 
         [0026]    It should be noted that the first plastic material and the second plastic material are different from each other in composition. The first plastic material is one of PBT (Polybutylene Terephthalate), PA66 (Polyamide 66 Resin), PPE, PA, PC, ABS and PPS. The second plastic material is another of PBT, PA66, PPE, PA, PC, ABS and PPS. In order to specifically distinguish the different materials from each other, the different materials are shown by different sectional lines in the drawings. As shown in the drawings, the first fan frame is made of PA66, while the second fan frame is made of PBT in adaptation to the first fan frame. In another embodiment, the first fan frame is made of PBT, while the second fan frame is made of PA66 in adaptation to the first fan frame. 
         [0027]    The plastic material of the first fan frame  11  is different from the plastic material of the second fan frame  21  in composition. Therefore, when the first and second fan impellers  14 ,  24  operate, the first fan frame  14  vibrates at a first vibration frequency, while the second fan frame  24  vibrates at a second vibration frequency. The first vibration frequency is different from the second vibration frequency. 
         [0028]    Moreover, the first and second base seats  15 ,  25  not only serve to support the first and second fan impellers  14 ,  24 , but also serve to dissipate the heat. Accordingly, the first base seat  15  can be made of the same plastic material as the first plastic material of the first fan frame  11  or made of a metal material such as aluminum or copper. Similarly, the second base seat  25  can be made of the same plastic material as the second plastic material of the second fan frame  21  or made of a metal material such as aluminum or copper. 
         [0029]    Please now refer to  FIGS. 4A and 4B .  FIG. 4A  is a diagram showing the comparison between the operational vibration of the fan frame of the series fan of the present invention and the fan frame of the conventional fan.  FIG. 4B  is an enlarged diagram of a range of  FIG. 4A . In the diagrams, the curve Fl indicates the fan frame of the conventional series fan is made of single material of PBT. The curve F 2  indicates the fan frame of the conventional series fan is made of single material of PA66. The curve F 3  indicates the first fan frame  11  of the first fan  10  of the present invention is made of PA66, while the second fan frame  21  of the second fan  20  is made of PBT. The curve F 4  indicates the first fan frame  11  of the first fan  10  of the present invention is made of PBT, while the second fan frame  21  of the second fan  20  is made of PA66. In  FIG. 4A , the horizontal data mean the frequency up to 5000 Hz, while the vertical data mean the vibration g value.  FIG. 4B  is an enlarged diagram of a range of  FIG. 4A  from 0 to 1600 Hz. It can be seen from  FIGS. 4A and 4B  that as a whole, the vibration g value presentation of curve F 3  of the present invention versus the respective frequencies is lower than the curves F 1  and F 2  of the conventional fans. However, as shown by the curve F 4 , it is also possible that the vibration of the conventional fan is not greatly improved as expected. 
         [0030]    In conclusion, the first and second fan frames of the series fan of the present invention are made of different materials. The different materials have different vibration frequencies so that the co-vibration is reduced to remove the vibration frequency. 
         [0031]    The present invention has been described with the above embodiments thereof and it is understood that many changes and modifications in the above embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.