Abstract:
The present invention relates to a compact fan, comprising a fan wheel, in particular a radial fan wheel ( 1 ), which is fastened on a rotor of an external rotor motor ( 82 ). The fan wheel ( 1 ) is supported between a front plate ( 8 ) having an air inlet opening ( 9 ), which is central, and a motor mount ( 11 ). The front plate ( 8 ) and the motor mount ( 11 ) are connected to one another via multiple spacers ( 12 ), which are disposed around the circumference. The front plate ( 8 ) and the motor mount ( 11 ) are formed as plastic or metal spray parts. The spacers ( 12 ) are formed as plastic or metal parts entirely or partially in one piece to the front plate ( 8 ) and/or the motor mount ( 11 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to PCT/EP2009/051069 filed Jan. 30, 2009 and DE 20 2008 002 356.4 filed Feb. 19, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a compact fan of a type having a centrifugal impeller fixed to a rotor of an external rotor motor. 
       BACKGROUND OF THE INVENTION 
       [0003]    A compact fan of the above general type is disclosed by DE-G 90 17 873.4, for example. 
         [0004]    Proceeding from such a compact fan, the object of the present invention is to achieve a compact construction that is technically easy to assemble, having improved flow characteristics. 
         [0005]    According to the invention the front plate and the motor mount of the fan are formed as injection molded plastic or metal parts and the spacers, as injection molded plastic or metal parts, are wholly or in part integrally connected to the front plate and/or the motor mount. It is advantageous here if the front plate, the motor mount and the spacers form one integral injection molded part. It may also be advantageous if the front plate, the motor mount and the spacers are formed from two injection molded plastic or metal parts that can be connected together in the area of the spacers. 
         [0006]    According to the invention, a simple construction that is technically easy to manufacture is therefore created, since the housing formed from the front plate and the motor mount is either integrally formed or may consist of just two separate parts. Moreover, all major functions can be incorporated into the housing. Advantageous embodiments of the invention will be explained in more detail on the basis of the exemplary embodiments represented in the drawings attached. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    In the figures below the same parts are in each case identified by the same reference numerals. 
           [0008]      FIG. 1  shows an exploded view of a first embodiment of a compact fan according to the invention, 
           [0009]      FIG. 2  shows a view of the compact fan according to  FIG. 1  viewed in the direction II in  FIG. 1 , 
           [0010]      FIG. 3  shows a view of the compact fan according to  FIG. 2  in the finally assembled state, 
           [0011]      FIG. 4  shows a section along the line of section IV-IV in  FIG. 3 , 
           [0012]      FIG. 5  shows a view of a further embodiment of a compact fan according to the invention, 
           [0013]      FIG. 6  shows an exploded view of a further embodiment of a compact fan according to the invention, 
           [0014]      FIG. 7  shows a view of the compact fan according to  FIG. 6  in a pre-assembly position, 
           [0015]      FIG. 8  shows a view of the finally assembled compact fan according to  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    A compact fan according to the invention comprises a fan impeller, in particular a centrifugal fan impeller  1 , which is fixed, in particular pressed onto a rotor of an external rotor motor  2 . The fan impeller  1  comprises a front cover plate  3  and a rear cover plate  4 . 
         [0017]    Backwardly curved blades  6  are arranged between these two cover plates  3  and  4 . The front cover plate  3  has a circular air inlet opening  7 , see  FIG. 2 . In the exemplary embodiment shown the external rotor motor  2  with the centrifugal fan impeller  1  is supported between a front plate  8  having an air inlet opening  9  and a motor mount  11 , as shown in  FIG. 3 . The front plate  8  and the motor mount  11  are connected together by multiple spacers  12  arranged circumferentially on the circumference of the two parts  8  and  11 . At the same time spacers  12  define the width of an air outlet gap  13  circumferentially formed around the centrifugal fan impeller  1 . The front plate  8  and the motor mount  11  together with the spacers  12  are here embodied as an integral injection molded part composed of plastic or metal. The circular air inlet opening  9  has an inner rim area  14  formed as inlet flow orifice. In the assembled state this inlet flow orifice-like inner rim area  14  (inlet flow orifice) extends into the air inlet opening  7  of the front cover plate  3 , so that its inside diameter is somewhat larger than the outside diameter of the inlet flow orifice  14 . 
         [0018]    The external rotor motor  2  with its stator flange  16  is fixed by means of an intermediate mount  17  to the motor mount  11 , that is to say to a circumferentially closed rim web  18  of the motor mount  11 . The intermediate mount  17  has a central retaining plate  19 , to which the motor flange  16  is fixed by means of screws, for example. Extending approximately radially outwards from the central retaining plate  19  are multiple spoke webs  21 , which in the area of their free ends are connected by a circumferential annular web  22 . The spoke webs  21  continue radially outwards with web extensions  23  beyond the annular web  22 . In cross section the spoke webs  21  are formed as unilaterally open channels, that is to say they are of U-shaped cross section, which is useful for strength reasons and for saving material. At the same time one of the spoke webs  21  can thereby serve to accommodate a motor connection cable. The intermediate mount  17  can be manufactured as a plastic injection molded part or as a molded metal part, in particular as a metal casting. When formed as a molded metal part the intermediate mount  17  simultaneously serves as a heat conducting element. On its side  24  remote from the front plate  8  the motor mount  11  has mounting sockets  26 , which with the intermediate mount  7  in the assembled state serve for mounting the web extensions  23  on the motor mount  11 . In the exemplary embodiment shown four spoke webs  21  are formed on the central retaining plate  19 , these spoke webs  21  each enclosing a right angle with their respective extensions. Here the spoke webs  21  do not run precisely radially, but are arranged so that in each case they run radially offset in relation to the central axis. Like the spoke webs  21  the annular web  22  of U-shaped cross section is also designed as a unilaterally open channel, again in order to save material and to increase the rigidity. The central retaining plate  19  also has a design accordingly adapted to the spoke webs  21 . On their upper side the web extensions  23  have lugs  27 , which with the intermediate mount  7  in the assembled state engage in matching depressions  28  ( FIG. 1 ) in the mounting sockets  26  for positioning the parts in relation to one another. The intermediate mount  17  connected to the external rotor motor  2  is connected by screwed connections to the motor mount  11 . For this purpose the external rotor motor  2  pre-assembled on the intermediate mount  17  with the centrifugal fan impeller  1  fastened to it is introduced into the intermediate space between the front plate  8  and the motor mount  11  through a circular mounting aperture  29  in the motor mount  11 . For this purpose the diameter of the mounting aperture  29  is somewhat larger than the outside diameter of the centrifugal fan impeller  1 . As shown in  FIGS. 1 and 2 , the spacers  12  are embodied as struts of approximately rectangular cross section having tapered corners, which run perpendicularly to the front plate  8  and to the rim web  18 . 
         [0019]    As emerges from  FIG. 4 , in particular, it is advantageous according to the invention if the web-shaped spacers  12  have the shape of streamlined profiles. These suitably take the form of vane profiles, which are aerodynamically and aero-acoustically optimized. Avoiding air flow separations or eddying on the spacer profiles consequently serves to preclude any negative effects on the air output and the noise caused by the spacers  12  themselves. As can be seen from  FIG. 4 , the streamlined spacers  12  have a longitudinal axis X and a transverse axis Y, the longitudinal axis X being longer than the transverse axis Y. The streamlined spacers  12  are at the same time arranged in such a way that they are oriented with their rounded front side opposed to the direction of rotation Z. For optimizing the flow properties of the spacers  12  it may be advisable for their longitudinal axis X to run at an acute angle of incidence α of preferably −10°≦α≦60° to a tangent T, which is applied to the circular circumference of the centrifugal fan impeller  1 , or to the straight line P running parallel to the tangent T. Another refinement according to the invention is to optimize the strut interval A of the struts from the center point or the central axis M of the centrifugal fan impeller  1 , the strut interval A preferably being designed in such a way that: 1.05×R≦A≦1.5 R, where R is the radius of the centrifugal fan impeller  1 . 
         [0020]    As can further be seen from  FIG. 1 , the air inlet opening  9  in the front plate  8  may be closed by a protective grille  32 . For this purpose the protective grille  32 , which in particular is embodied as a plastic injection molded part, is latched to the front plate  8  by means of a clip connection. An integral formation with the front plate  8  is also possible, however. The front plate  8  is preferably dimensioned in such a way that it projects circumferentially beyond the motor mount  11  at its outer rim. The compact fan according to the invention can thereby be inserted so far through an insertion opening in a wall or a housing accommodating the compact fan until the front plate  8  bears against the wall accommodating the compact fan, thereby covering the insertion opening. The front plate  8  may serve for screw fastening of the compact fan according to the invention. The front plate  8  and the motor mount  11  are preferably square-shaped with each of the corners  30  and  35  being tapered. 
         [0021]      FIG. 5  represents a compact fan according to the invention in an alternative embodiment to that shown in  FIGS. 1 to 4 . Here the intermediate mount comprises the central retaining plate  19  and spoke webs  21  formed on this. There are four spoke webs  21 , which in this exemplary embodiment are of curved shape, uniformly distributed around the circumference. The spoke webs  21  can be connected directly to the rim web  18  of the motor mount  11 , so that in this embodiment there is no annular web. In the exemplary embodiment shown the spacers  12  are embodied as streamlined struts of curved cross section. Here the curved shape is selected in such a way that the resulting curved struts have a convex contour facing towards the interior of the compact fan. The spacers  12  run obliquely to the front plate  8  and to the rim web  18  and they each originate and terminate in the corners  30  and  35 . It can further be seen that a terminal box  40  is provided, partially in the intermediate space between the centrifugal fan impeller  1  and the front plate  8 . Instead of a terminal box  40  for the electrical connection, just a single cable connection may also be provided. 
         [0022]      FIGS. 6 to 8  represent a further alternative embodiment of a compact fan according to the invention. In this embodiment the front plate  8 , the motor mount  11  and the spacers  12  are formed from two injection molded plastic or metal parts that can be connected to one another in the area of the spacers  12 . An intermediate mount as provided in the embodiments according to  FIGS. 1 to 5  is therefore absent in this embodiment. The motor mount  11  comprises a central retaining plate  19  for fixing the stator flange  16  of an external rotor motor  2 . Running outwards from this central retaining plate  19  are approximately radial spoke webs  21 , which terminate in a circumferentially closed rim web  37 . The rim web  37 , the spoke webs  21  and the central retaining plate  19  consequently form the motor mount  11 . In the exemplary embodiment shown both the front plate  8  and the motor mount  11  each comprise segments  38  and  39  of the spacers  12  on their mutually opposing sides. These segments  38  and  39  may be of equal or different length and without departing from the scope of the invention it is also possible for the spacers  12  to be formed in their entire length either on the front plate or on the motor mount  11 . The compact fan according to the invention is here assembled in such a way that the centrifugal fan impeller  1  with the external rotor motor  2  is first screw-fastened on the motor mount  11 , that is to say on the side of the motor mount  11  facing the front plate  8 . The motor mount  11  is then connected to the front plate in the area of the abutting segments  38  and  39  of the spacers  12 , for example by screwing fastening screws through the segments  39  and  39 . This is preferably done from the rear side of the motor mount  11 . The intermediate assembly position, in which the centrifugal fan impeller  1  is connected to the motor mount  11 , is shown in  FIG. 7 .  FIG. 8  shows the compact fan according to the invention in the completed state. In order to achieve a secure connection of the segments  38  and  39 , it is advisable for these to be formed in such a way that they interlock at their butt joints. In the embodiment represented in  FIGS. 6 to 8  the front plate  8  and the motor mount  11  are, in particular, produced as injection molded plastic parts. The protective grille  32  may be designed to clip on or it may also be integrally formed with the front plate  8 . In this exemplary embodiment shown the front plate  8  and the motor mount  11 , in particular its rim web  18 , also have an approximately square peripheral contour, the corners of the square each being tapered. However, the invention is not limited to such a design of the front plate  8  and the motor mount  11 . Both the front plate  8  and the motor mount  11  may be reinforced by rib structures  33  and  34 , respectively. 
         [0023]    The invention is not limited to the exemplary embodiments shown, but also encompasses all means exercising essentially similar effects within the scope of the invention 
         [0024]    While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope and fair meaning of the accompanying claims.