Abstract:
Disclosed is a turbofan which includes a hub coupled with a rotational shaft of a driving device, a plurality of blades installed at a circumference of the hub radially, and a shroud at an opposite side to the hub so as to be coupled with a plurality of the blades wherein the blades are placed between the shroud and the hub, and wherein the hub, blades, and shroud are formed in one body and wherein the shroud comprises a first extension protruding to extend from a coupling part with a leading edge of each of the blades in an inward radial direction of the rotational shaft and a second extension extending straightly from the first extension in a direction of the rotational axis toward a side opposite to the hub.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a turbofan, and more particularly, to a turbofan and a mold manufacturing the same.  
           [0003]    2. Background of the Related Art  
           [0004]    Generally, a turbofan is a kind of centrifugal fan sending air forcibly by a centrifugal force of air generated from revolution of an impeller thereof. The turbofan produces massive airflow so as to be suitable for a refrigerator of heavy capacity.  
           [0005]    [0005]FIG. 1 illustrates a layout of a turbofan according to a related art, and FIG. 2 illustrates a vertical cross-sectional view of the general turbofan in FIG. 1.  
           [0006]    Referring to FIG. 1 and FIG. 2, a turbofan  1  according to a related art includes a hub  10  having a boss  11  at a central part so as to be coupled with a rotational shaft  40  of a driving device (not shown in the drawings), a plurality of blades  20  at a circumferential part  10   a  of the hub  10 , and a shroud  30  arranged at a opposite face to the hub  10  so as to be coupled with the blades in one body wherein the blades  20  are inserted between the shroud  30  and the hub  10 .  
           [0007]    An internal diameter increases toward the hub  10  in a direction of the rotational shaft  40 , and has a concave shape. A cross-section of each blade  20 , as shown in FIG. 1, has an airfoil figure.  
           [0008]    The above-constructed turbofan  1  according to the related art is mainly manufacture by injection molding of synthetic resin. The blades  20  and hub  10  are formed in one body, but the shroud  30  is molded separately. Theses parts are assembled reciprocally so as to complete the turbofan  1 .  
           [0009]    When the turbofan is manufactured by the above process, the number of molding patterns increases, whereby consumes time and expense excessively. Besides, the above process needs a step of assembling separate parts, thereby extending a manufacturing time to increase overall cost of product.  
           [0010]    In order to overcome the above disadvantages or defects, a process of manufacturing a turbofan is lately used so as to reduce the number of molding patterns and skip an auxiliary assembling step. Namely, in the latest process, a maximum outer diameter dl of the hub  10  is reduced to a size less than a minimum inner diameter d 2 . And, longitudinal boundary surfaces (BSL) of upper and lower molding patterns are formed to have an inner diameter equal to the maximum outer diameter dl so as to assemble the hub  10 , blades  20 , and shroud  30  in one body reciprocally.  
           [0011]    [0011]FIG. 3 illustrates longitudinal cross-sectional views of a turbofan and a molding pattern to manufacture a turbofan, and FIG.  4  illustrates a magnified cross-sectional view of the assembly of the molding pattern in FIG. 3.  
           [0012]    Referring to FIG. 3 and FIG. 4, a molding pattern for forming a turbofan according to a related art includes a lower molding pattern part  50  arranged to be fixed to a lower part in a direction of a rotational shaft  40  and having a molding surface inside to form a partial area of a hub  10  and blades  20  and an upper molding part  60  having a molding surface inside to form the rest area of the shroud  30  and blades  20  and providing a space to form the turbofan  1  by being assembled with the lower molding part  50 .  
           [0013]    A hub molding part  61  recessed in a direction of the rotational shaft  40  is formed at a central part of the molding surface of the upper molding pattern part  60  so as to form the hub  10 . And, a boss molding part  62  is formed at a central part of the hub molding part  61  so as to mold the boss  11 . Along a radial direction of the rotational shaft  40 , a blade molding part  63  is formed at an external side of the boss molding part  62  so as to form the blade  20  in part. Along a direction of the rotational shaft  40 , a shroud molding part  64  is formed over the blade molding part  63  so as to form an upper surface of the shroud  30 .  
           [0014]    Meanwhile, a hub molding part  51  protrudes out of the central part of the upper surface of the lower molding pattern part  50 , and a boss molding part  52  is formed at a central part of the hub molding part  51 . Along a radial direction of the rotational shaft  40 , a blade molding part  53  is formed at an external side of the hub molding part  51  so as to mold the rest part of the blades  20 . And, a concave shroud molding part  54  is formed at an upper part of the blade molding part  53  so as to form a lower surface of the shroud  30 .  
           [0015]    In order to manufacture the above-constructed turbofan, when the upper molding pattern part  60  is tightly coupled with the lower molding pattern part  50 , a molding space to form the turbofan constructed with the hub  10 , blades  20 , and shroud  30 , which are built in one body, is provided inside the lower and upper molding pattern parts  50  and  60 . A molten synthetic resin is then injected in the molding space for the turbofan. After the injected synthetic resin has been hardened, the upper and lower molding pattern parts  60  and  50  are separated from each other as well as the turbofan  1  is separated, the turbofan having the hub, blades  20  and shroud  30  formed in one body is manufactured.  
           [0016]    In the turbofan according to the related art, the inner diameter of the shroud  10  increases when getting closer to the hub  10  along a direction of the rotational shaft  40  so as to guide airflow with the hub  10 . Thus, a cross-section of the shroud  10  is concave. In the molding pattern for form the shape of the shroud  30 , the longitudinal boundary surface BSL, at which the lower and upper molding pattern parts  50  and  60  meet each other, is formed along the direction of the rotational shaft  40 , and an edge  55  is formed at a contact between the longitudinal boundary surface BSL and the shroud molding part  54  of the lower molding pattern part  50 . Such a sharp edge  55 , when being contacted with the upper molding pattern part  60 , is damaged or distorted by a relatively small external force with ease. Hence, durability of the molding pattern is shortened so as to need a replacement frequently. Thus, the turbofan according to the related art increases cost of product.  
         SUMMARY OF THE INVENTION  
         [0017]    Accordingly, the present invention is directed to a turbofan and mold manufacturing the same that substantially obviates one or more problems due to limitations and disadvantages of the related art.  
           [0018]    An object of the present invention is to provide a turbofan and mold manufacturing the same enabling to increase durability of the mold for manufacturing a turbofan by improving the structure of the turbofan.  
           [0019]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0020]    To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a turbofan according to the present invention includes a hub coupled with a rotational shaft of a driving device, a plurality of blades installed at a circumference of the hub radially, and a shroud at an opposite side to the hub so as to be coupled with a plurality of the blades wherein the blades are placed between the shroud and the hub, and wherein the hub, blades, and shroud are formed in one body and wherein the shroud comprises a first extension protruding to extend from a coupling part with a leading edge of each of the blades in an inward radial direction of the rotational shaft and a second extension extending straightly from the first extension in a direction of the rotational axis toward a side opposite to the hub.  
           [0021]    In another aspect of the present invention, for fabricating a turbofan including a hub coupled with a rotational shaft of a driving device, a plurality of blades installed at a circumference of the hub radially, and a shroud at an opposite side to the hub so as to be coupled with a plurality of the blades wherein the blades are placed between the shroud and the hub, and wherein the hub, blades, and shroud are formed in one body and wherein the shroud comprises a first extension protruding to extend from a coupling part with a leading edge of each of the blades in an inward radial direction of the rotational shaft and a second extension extending straightly from the first extension in a direction of the rotational axis toward a side opposite to the hub, assuming that a surface where the blades are formed is an upper surface by taking the hub as a reference, a mold for fabricating the turbofan includes lower and upper mold patterns. The lower mold pattern includes a hub molding part for molding a lower surface of the hub, a blade molding part protruding upward from a circumferential end of the hub molding part in a direction of the rotational shaft so as to mold a portion of each of the blades, and a shroud molding part for molding a lower surface of the shroud having the first extension at an upper area of the blade molding part. And, the upper molding pattern includes a hub molding part detachable from the upper mold pattern for molding an upper surface of the hub, a blade molding part having a boundary surface forming a boundary with an inner side of the blade molding part of the upper mold pattern for molding a rest portion of each of the blades, and a shroud molding part for molding an upper surface of the shroud having the second extension.  
           [0022]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention.  
         [0024]    In the drawings:  
         [0025]    [0025]FIG. 1 illustrates a layout of a turbofan according to a related art;  
         [0026]    [0026]FIG. 2 illustrates a vertical cross-sectional view of the general turbofan in FIG. 1;  
         [0027]    [0027]FIG. 3 illustrates longitudinal cross-sectional views of a turbofan and a molding pattern to manufacture the turbofan;  
         [0028]    [0028]FIG. 4 illustrates a magnified cross-sectional view of the assembly of the molding pattern in FIG. 3;  
         [0029]    [0029]FIG. 5 illustrates a bird&#39;s-eye view of a turbofan according to a first embodiment of the present invention;  
         [0030]    [0030]FIG. 6 illustrates a longitudinal cross-sectional view of the turbofan in FIG. 5;  
         [0031]    [0031]FIG. 7 illustrates a longitudinal cross-sectional view of a turbofan according to a second embodiment of the present invention;  
         [0032]    [0032]FIG. 8 illustrates longitudinal cross-sectional views of a turbofan and a mold to manufacture the turbofan according to a first embodiment of the present invention;  
         [0033]    [0033]FIG. 9 illustrates a magnified cross-sectional view of the assembly of mold patterns in FIG. 8;  
         [0034]    [0034]FIG. 10 illustrates longitudinal cross-sectional views of a turbofan and a mold to manufacture the turbofan according to a second embodiment of the present invention; and  
         [0035]    [0035]FIG. 11 illustrates a magnified cross-sectional view of the assembly of mold patterns in FIG. 10. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0037]    [0037]FIG. 5 illustrates a bird&#39;s-eye view of a turbofan according to a first embodiment of the present invention, and FIG. 6 illustrates a longitudinal cross-sectional view of the turbofan in FIG. 5.  
         [0038]    Referring to FIG. 5 and FIG. 6, a turbofan according to a first embodiment of the present invention includes a hub  110  having a boss  111  at a central part so as to receive to be coupled with a rotational shaft  140  of a driving device (not shown in the drawings), a shroud  130  guiding a flow of air with the hub  110 , and a plurality of blades  120  arranged radially at a circumferential part of the hub  110  centering around the rotational shaft  140  so as to be coupled with the shroud  130 . And, the hub  110 , shroud  130 , and blades  120  are built in one body.  
         [0039]    The hub  110  includes a boss  111  protruding along a direction of the rotational shaft  140  so as to receive to be coupled with the rotational shaft  140  of the driving device (not shown in the drawings) and a circumferential part  112  extending along a radial direction of the rotational shaft  140  so as to guide the flow of air inflow with the shroud  130 .  
         [0040]    Each of the blades  120  is arranged on the circumferential part  112  of the hub  110 , and a cross-section of each blade  120  has am airfoil figure.  
         [0041]    A cross-sectional figure of the shroud  130 , as shown in FIG. 6, includes a first extension  132  extending in a internal radial direction of the rotational shaft from a part connected to an inner side  121  of the blade  120 , a second extension  131  of which inner diameter D 1  is equal to or longer than a maximum outer diameter D 2  of the hub  110  and of which inner diameter surface protrudes from the first extension  132  in parallel with the rotational shaft, and a shroud body  133  of which inner diameter increases gradually toward the hub  110  along the direction of the rotational shaft  140  from the first extension  132 .  
         [0042]    The second extension  131 , as shown in FIG. 6, extends from an inner end  132   a  of the first extension  132  so as to form an ‘L’ figure with the first extension  132 .  
         [0043]    And, the part at which the first extension  132 , as shown in the magnified portion in FIG. 6, is connected to the shroud body  133  is preferably curved concavely when being looked at from the blade  120  so as to smooth the inflow of air.  
         [0044]    Besides, the second extension  131  of the shroud  130  may extend from an outer end of the second extension  132 .  
         [0045]    [0045]FIG. 7 illustrates a longitudinal cross-sectional view of a turbofan according to a second embodiment of the present invention.  
         [0046]    Referring to FIG. 7, a second extension  231  of a shroud  230  extends from an outer end  232   b  of a first extension  232  so as to form an ‘L’ figure, and is connected to the shroud body  233  by the same continuous surface.  
         [0047]    Moreover, the part at which the first extension  232 , as shown in the magnified portion in FIG. 7, is connected to the shroud body  233  is preferably curved concavely when being looked at from the blade  220  so as to smooth the inflow of air.  
         [0048]    Meanwhile, the turbofan according to the first or second embodiment of the present invention may be manufactured by injection molding. A mold is required for molding injection of the turbofan, which is explained in the following description in detail.  
         [0049]    [0049]FIG. 8 illustrates longitudinal cross-sectional views of a turbofan and a mold to manufacture the turbofan according to a first embodiment of the present invention, and FIG. 9 illustrates a magnified cross-sectional view of the assembly of mold patterns in FIG. 8.  
         [0050]    [0050]FIG. 10 illustrates longitudinal cross-sectional views of a turbofan and a mold to manufacture the turbofan according to a second embodiment of the present invention, and FIG. 11 illustrates a magnified cross-sectional view of the assembly of mold patterns in FIG. 10.  
         [0051]    Referring to FIGS.  8  to FIGS. 11, a mold to manufacture the turbofan according to the first or second embodiment of the present invention, when being divided into an upper part having the blades  120  and a lower part by taking the hub  110  as a reference, includes an upper mold pattern  160  or  260  and a lower mold pattern  150  or  250  which form a molding space for manufacturing the turbofan by assembly.  
         [0052]    One of the upper mold pattern  160  or  260  and the lower mold pattern  150  or  250  is arranged to be fixed to something, while the other is detachable by assembly/disassembly in a direction of the rotational shaft  140 .  
         [0053]    An upper surface of the lower mold pattern  150  or  250  has a hub molding part  151 , a blade molding part  153 , and a shroud molding part  154  or  254  so as to mold the hub  110 , blades  120 , and shroud  130  or  230  with the upper mold pattern  160  or  260 , respectively.  
         [0054]    A central part of the hub molding part  151  protrudes in the direction of the rotational shaft  140 , and a boss molding part  152  protrudes from an upper area of the hub molding part  151  so as to mold an inner diameter surface of the boss  111 .  
         [0055]    The blade molding part  153  forms a portion of each of the blades  120 . The blade molding part  153  protrudes upward in a direction of the rotational shaft  140  from one end  151   a  of the hub molding part  151  along a radial direction of the rotational shaft  140 , and has a longitudinal boundary surface BSL having an inner diameter equal to the maximum outer diameter D 2  of the hub  110 .  
         [0056]    At an upper part of the blade molding part  153 , formed are a first extension molding part  155  or  255  and a shroud body molding part  154  or  254  extending in a radial direction of the rotational shaft  140  so as to mold lower surfaces of the first extension  132  or  232  and shroud body  133  or  233 .  
         [0057]    Specifically, the lower mold pattern  150  or  250 , as shown in FIG. 9 or FIG. 11, has a corresponding convex part so as to make the concavely-curved surface of the connecting portion between the first extension  132  or  232  and the shroud body  133  or  233 .  
         [0058]    A lower surface of the upper mold pattern  160  or  260  has a hub molding part  161 , a blade molding part  163 , and a shroud molding part  164  or  264  so as to mold the hub  110 , blades  120 , and shroud  130  or  230  with the upper mold pattern  160  or  260 , respectively.  
         [0059]    The hub molding part  161  is recessed upward from a central part of the lower surface of the upper mold pattern  160  or  260  so as to mold the upper surface of the hub  110 , and a boss molding part  162  is formed at a central area of the hub molding part  161 .  
         [0060]    At an end  161   a  of the hub molding part  16 , a longitudinal boundary surface BSL having an outer diameter similar to the maximum outer diameter D 2  of the hub  110  is formed so as to make a pair with the longitudinal boundary surface BSL of the blade molding part  153  in the lower mold pattern  150  or  250 . And, a blade molding part  163  is formed inside the longitudinal boundary surface BSL so as to mold the rest of the blades  120 .  
         [0061]    At an upper part of the blade molding part  163  in a direction of the rotational shaft  140 , as shown in FIG. 10 or FIG. 11, a shroud molding part  164  or  264  is formed to correspond to the second extension  132  or  232  in the turbofan according to the first or second embodiment of the present invention so as to mold the second extension  131  or  231 , an upper surface of the first extension  132  or  232 , and an upper surface of the shroud body  133  or  233 .  
         [0062]    Namely, the mold for the turbofan according to the first embodiment of the present invention, as shown in FIG. 9, forms a molding space for the second extension  131  to extend to the longitudinal boundary surface BSL of the upper mold pattern  160 . Yet, the mold for the turbofan according to the second embodiment of the present invention, as shown in FIG. 11, forms a molding space for the second extension  231  outside the longitudinal boundary surface BSL of the upper mold pattern  260  so as to continue from the upper surface with the shroud body  233 .  
         [0063]    The above-constructed turbofan according to the first or second embodiment of the present invention is manufactured using the above mold(s) by the following process.  
         [0064]    First, the lower mold pattern  150  or  250  and the upper mold pattern  160  or  260  are assembled together. A molten synthetic resin is then injected in the molding space provided by the assembly of the lower mold pattern  150  or  250  and the upper mold pattern  160  or  260 . After the injected synthetic resin has been hardened, the upper and lower mold patterns  150 / 160  or  250 / 260  are separated from each other. The molded turbofan is then separated from the lower mold pattern  150  or  250 .  
         [0065]    As mentioned in the above description, the present invention improves the structure of the coupling part at which the shroud and blade insides are coupled so as to prevent the sharp edge from occurring in the mold for the turbofan fabrication.  
         [0066]    Accordingly, the present invention elongates durability of the mold, thereby enabling to reduce cost of product.  
         [0067]    The forgoing embodiments are merely exemplary and are not to be construed as limiting the present invention. The present teachings can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.