Abstract:
A serial fan of the present invention includes a first fan and a second fan, each of which includes a housing and an impeller disposed in the housing. The housings respectively include a plurality of connecting elements, and there are several air-guiding recesses defined on the connecting elements of the first fan or the second fan, which can guide air to smoothly flow out from the housing so as to increase airflow and air pressure and reduce noise.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a serial fan, and in particular to a serial fan providing at least one connecting element formed with a plurality of air-guiding recesses. 
         [0003]    2. Description of the Related Art 
         [0004]      FIG. 1  is an exploded view of two serial fans R assembled in series. The assembled fans R comprise a first fan  1  and a second fan  3  which have the same structure. The first fan  1  comprises a housing  10  and an impeller  11  disposed in the housing  10 , and the second fan  3  comprises a housing  30  and an impeller  31  disposed in the housing  30 . The housing  10  of the first fan  1  comprises a frame  101 , a seat  102  disposed in the frame  101 , and a plurality of ribs  103  disposed between the frame  101  and the seat  102 . The housing  30  of the second fan  3  comprises a frame  301 , a seat  302  disposed in the frame  301 , and a plurality of ribs  303  disposed between the frame  301  to the seat  302 . The configuration of the assembled fans R can increase airflow efficiency. 
         [0005]    When the air sequentially travels through the impeller  11  and the ribs  103  of the first fan  1  and the ribs  303  and the impeller  31  of the second fan  3 , however, the wind shear and noise are relatively increased. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The invention provides a serial fan with a plurality of connecting elements. At least one connecting element is formed with a plurality of air-guiding recesses to efficiently guide air out of the fan and reduce air stagnation. 
         [0007]    A serial fan of one embodiment comprises a first fan and a second fan. The first and second fans are assembled in series. The first fan comprises a first frame, a first seat disposed in the first frame, a plurality of first connecting elements disposed between the first frame and the first seat, and a first impeller disposed on the first seat. The second fan comprises a second frame, a second seat disposed in the second frame, a plurality of second connecting elements disposed between the second frame and the second seat, and a second impeller disposed on the second seat. A plurality of air-guiding recesses are defined on at least one of the edges of the first or second connecting elements to efficiently guide air so as to increase wind pressure and wind capacity and to reduce rotational noise. Furthermore, the air-guiding recesses can be defined on both edges of the first and second connecting elements. 
         [0008]    The first and second connecting elements are ribs or static blades. The first connecting element of the first fan comprises a first edge facing the first impeller and a second edge opposite to the first edge, and the air-guiding recesses are defined on the first and second edges of the first connecting element of the first fan. The air-guiding recesses have toothed, arc, or acuminate cross-sectional profile. 
         [0009]    The first impeller of the first fan, the first housing of the first fan, the second housing of the second fan, and the second impeller of the second fan are sequentially arranged, or the first impeller of the first fan, the first housing of the first fan, the second impeller of the second fan, and the second housing of the second fan are sequentially arranged. 
         [0010]    Except for the first frame of the first fan and the second frame of the second fan assembled in series, the first and second frames can be integrally formed as a third frame so that the first and second impellers are disposed in the third frame. 
         [0011]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0013]      FIG. 1  is an exploded view of two fans assembled in series; 
           [0014]      FIG. 2  is an exploded view of a serial fan (F 1 ) of a first embodiment of the invention; 
           [0015]      FIG. 3  is a perspective view of the assembled serial fan (F 1 ) of  FIG. 2 ; 
           [0016]      FIG. 4  shows two sets of diagrams showing noise values of the conventional serial fan (R) shown in  FIG. 1  and the serial fan (F 1 ) shown in  FIG. 2  at the speed of 3,800 rpm; 
           [0017]      FIG. 5  is a characteristic diagram of the conventional serial fan (R) in  FIG. 1  and the serial fan (F 1 ) in  FIG. 2 , expressing air pressure and air volume under a noise of 39.4 dB; 
           [0018]      FIG. 6  is a characteristic diagram of the conventional serial fan (R) in  FIG. 1  and the serial fan (F 1 ) in  FIG. 2 , expressing air pressure and air volume under a noise of 38.7 dB; 
           [0019]      FIG. 7  is a perspective view of a serial fan (F 2 ) of a second embodiment of the invention; and 
           [0020]      FIG. 8  is a perspective view of a serial fan (F 3 ) of a third embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
         [0022]    In  FIGS. 2 and 3 , a serial fan F 1  of a first embodiment comprises a first fan  5  and a second fan  6   a  arranged in series. 
         [0023]    The first fan  5  comprises a first housing  50  and a first impeller  51  disposed in the first housing  50 . The first housing  50  comprises a rectangular first frame  501 , a first seat  502  disposed in the first frame  501 , a plurality of first connecting elements  503  disposed between the first frame  501  and the first seat  502 , and a plurality of first air-guiding recesses  504  defined on each of the first connecting element  503 . In this embodiment, the first connecting elements  503  are formed in the shape of ribs. The first connecting elements  503  comprise a first edge  5031  and a second edge  5032 . The first edge  5031  is a front edge facing the first impeller  51 , and the second edge  5032  is a rear edge opposite to the first edge  5031 . The air-guiding recesses  504  are inwardly square indentations defined on the first edge  5031  of the first connecting element  503  so as to form a rough profile thereon. Note that the depth and width of the side view of the air-guiding recesses  504  depend on the size of the fan and the actual requirements. Except for the square profile, the air-guiding recesses  504  substantially have toothed, arc, peak, or acuminate cross-sectional profile. The first impeller  51  comprises a first hub  510  supported by the first seat  502  of the first housing  50  and a plurality of first blades  511  outwardly disposed on the first hub  510 . 
         [0024]    The second fan  6   a  comprises a second housing  60   a  and a second impeller  61  disposed in the second housing  60   a . The second housing  60   a  comprises a rectangular second frame  601   a , a second seat  602   a  disposed in the second frame  601   a , a plurality of second connecting elements  603   a  disposed between the second frame  601   a  and the second seat  602   a . The first frame  501  and the second frame  601   a  form a main frame W 1 , and the first seat  502  and the second seat  602   a  form a seat structure T 1 . In this embodiment, the second connecting elements  603   a  are formed in the shape of ribs or static blades. The second connecting element  603   a  comprises a first edge  6031  and a second edge  6032 . The first edge  6031  is a front edge facing the second impeller  61 , and the second edge  6032  is a rear edge opposite to the first edge  6031 . The second impeller  61  comprises a second hub  610  supported by the second seat  602   a  of the second housing  60   a  and a plurality of second blades  611  outwardly disposed on the second hub  610 . 
         [0025]    In the serial fan F 1 , the first impeller  51  of the first fan  5 , the first housing  50  of the first fan  5 , the second housing  60   a  of the second fan  6   a , and the second impeller  61  of the second fan  6   a  are sequentially arranged along an axis a-a shown in  FIG. 2 . In this embodiment shown in  FIG. 3 , the first fan  5  and the second fan  6   a  can be assembled by screwing, engaging, riveting, adhering or other equivalent methods. 
         [0026]    When the serial fan F 1  is started, air is efficiently guided by the first air-guiding recesses  504  defined on the first connecting elements  503  of the first housing  50  so as to increase wind pressure and wind capacity. Furthermore, rotational noise can be decreased by the first connecting elements  503  because that the first connecting elements  503  are different in height and wind pressure differences are formed therebetween. 
         [0027]    In  FIG. 4 , two sets of diagrams respectively shows the noise values of the conventional serial fan R shown in  FIG. 1  and the serial fan F 1  of the present invention shown in  FIG. 2  at the speed of 3,800 rpm. With respect to the conventional serial fan R providing 52.3 dB of averaged noise value, the serial fan F 1  of one embodiment provides 45.9 dB of averaged noise value, accordingly decreasing rotational noise. 
         [0028]    In  FIG. 5 , a characteristic diagram shows air pressure and air volume under a noise of 39.4 dB of the conventional serial fan R shown in  FIG. 1  and the serial fan F 1  shown in  FIG. 2 . The serial fan F 1  of the first embodiment provides a maximum increased air pressure of 17% and a maximum increased air volume of 8.5%. In  FIG. 6 , a characteristic diagram shows air pressure and air volume under a noise of 38.7 dB of the conventional serial fan R shown in  FIG. 1  and the serial fan F 1  shown in  FIG. 2 . The serial fan F 1  of the first embodiment provides a maximum increased air pressure of 62% and a maximum increased air volume of 21%. At the same decibel level, the serial fan F 1  of the invention provides a higher air pressure and air volume than the conventional serial fan R at high or low rotational speeds. 
         [0029]    Except for the described first air-guiding recesses  504  defined on the first edge  5031 , the first air-guiding recesses  504  can also be defined on the second edge  5032  of the first connecting element  503 , or defined on both the first and second edges  5031 ,  5032  of the first connecting element  503 . 
         [0030]    Additionally, the air-guiding recesses defined on the first edge  5031  of the first connecting element  503  can symmetrically correspond to the air-guiding recesses defined on the second edge  5032  of the first connecting element  503 , or the air-guiding recesses defined on the first edge  5031  of the first connecting element  503  and the air-guiding recesses defined on the second edge  5032  of the first connecting element  503  can be asymmetrically or alternatively arranged. In other embodiments, the first connecting elements  503  can be ribs or static blades. 
         [0031]    In  FIG. 7 , a serial fan F 2  of a second embodiment comprises the first fan  5  and a second fan  6   b . The serial fan F 2  differs from the serial fan F 1  in that the second fan  6   b  has the same structure as the first fan  5 . 
         [0032]    The serial fan F 2  comprises the first fan  5  and a second fan  6   b . The second fan  6   b  comprises a second housing  60   b  and a second impeller  61  disposed in the second housing  60   b . The second housing  60   b  comprises a second frame  601   b , a second seat  602   b  disposed in the second frame  601   b , a plurality of second connecting element  603   b  disposed between the second frame  601   b  and the second seat  602   b , and a plurality of first air-guiding recesses  604   b  defined on the first edge  6031  of each second connecting elements  603   b . The first frame  501  of the first housing  5  and the second frame  601   b  of the second housing  60   b  form a main frame W 2 , and the first seat  502  of the first housing  50  and the second seat  602   a  of the second housing  60   b  form a seat structure T 2 . In this embodiment, the air-guiding recesses  504  and  604  have the same shape and size. 
         [0033]    The first and second fans  5 ,  6   b  are isotropic with respect to an axis b-b shown in  FIG. 7 , i.e., the first air-guiding recesses  504  defined on the first connecting elements  503  of the first frame  501  and the air-guiding recesses  604   b  defined on the second connecting elements  603   b  of the second housing  60   b  are directed to the same direction. Further, the first impeller  51  of the first fan  5  and the second impeller  61  of the second fan  6   a  are isotropic with respect to the axis b-b. 
         [0034]    Except for the described arrangement of the elements of the first and second fans  5 ,  6   a  in the first embodiment, the elements of the first and second fans  5 ,  6   b  of the second embodiment can have another arrangement as shown in  FIG. 7 . In the serial fan F 2 , the first impeller  51  of the first fan  5 , the first housing  50  of the first fan  5 , the second impeller  61 , and the second housing  60   b  of the second fan  6   a  are sequentially arranged along the axis b-b. 
         [0035]    Except for the arrangements shown in  FIGS. 2 and 7 , the frames  101  and  301  can also be integrally formed in other embodiments for receiving the first and second impellers  51  and  61 . 
         [0036]    In  FIG. 8 , a serial fan F 3  of a third embodiment comprises a first impeller  71 , a second impeller  72  and a housing  73 . The housing  73  comprises an frame  731 , a seat structure  732  disposed in the frame  731 , and a plurality of connecting elements  733  disposed between the frame  731  and the seat structure  732 . The seat structure  732  has two opposite sides t 1  and t 2 . The first and second impellers  71 ,  72  disposed in the housing  73  are supported by the sides t 1  and t 2  of the seat structure  732 , respectively. The first and second impellers  71 ,  72  have the same structure as the first and second impellers  51 ,  61  of the first embodiment. 
         [0037]    The connecting element  733  comprises a first edge  7331  and a second edge  7332 . The first edge  7331  is a front edge facing the first impeller  71 . The second edge  7332  is a rear edge opposite to the first edge  7331 . The air-guiding recesses  734  are defined on the first edge  7331  of each of the connecting elements  733  so as to form a rough profile thereon. Note that the depth and width of the air-guiding recesses  734  depend on the size of the fan structure and the actual requirements. Except for the square profile, the air-guiding recesses  734  substantially have toothed, arc, peak, or acuminate cross-sectional profile. Except for the described air-guiding recesses  734  defined on the first edge  7331  of the connecting element  733 , the air-guiding recesses  734  can also be defined on the second edge  7332  of the connecting element  733 , or the air-guiding recesses  704  can be defined on both the first and second edges  7331 ,  7332  of the connecting element  733 . Additionally, the air-guiding recesses defined on the first edge  7331  of the connecting element  733  can symmetrically correspond to the air-guiding recesses defined on the second edge  7332  of the connecting element  733 , or the air-guiding recesses defined on the first edge  7331  of the connecting element  733  and the air-guiding recesses defined on the second edge  7332  of the connecting element  733  can be symmetrically, asymmetrically or alternatively arranged. The described connecting elements  733  can be formed in the shape of rib or static blade. 
         [0038]    While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. 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.