Patent Publication Number: US-8985970-B2

Title: Axial ventilator

Description:
This application is the National Phase of International Application PCT/IB2010/054836 filed Oct. 26, 2010 which designated the U.S. and that International Application was published under PCT Article 21(2) in English. 
     This application claims priority to Italian Patent Application No. BO2009A000694 filed Oct. 26, 2009 and PCT Application No. PCT/IB2010/054836 filed Oct. 26, 2010, which applications are incorporated by reference herein. 
     TECHNICAL FIELD 
     This invention relates to an axial ventilator and, in particular, to an axial electric ventilator for automotive applications. 
     BACKGROUND ART 
     Prior art ventilators of reference in this specification, such as, for example, the one illustrated in  FIG. 8  and labelled  100 , comprise an axial fan  101  and an electric motor  102  for driving the fan. 
     The electric motor has a substantially cylindrical casing, a stator unit and a rotor unit, both housed in the casing, and a shaft protruding from the casing and rotationally driven by the rotor unit. 
     The fan has a connecting hub  103  coaxial with the shaft of the motor and a plurality of blades extending radially from the hub. 
     Usually, the fan hub is cup shaped, that is to say, it has a bottom wall  104  for connecting to the motor shaft and a substantially cylindrical lateral wall  105  from which the blades extend. 
     In order to limit the axial dimensions of the ventilator, the motor is at least partly housed inside the hub, surrounded by the lateral wall of the hub itself which extends from the bottom wall towards the motor. 
     A tubular gap  106  is defined between the motor casing and the fan hub, that is, between the casing and the lateral wall of the hub to allow the fan to rotate freely. 
     This type of ventilator has some disadvantages in heavy-duty applications such as agricultural machines or earthmoving machines. 
     In effect, in these applications, the performance of the ventilator may be seriously diminished by extraneous material such as straw, dust, soil, mud and so on, which finds its way into the gap  106  and prevents the fan from turning smoothly relative to the motor casing. 
     Under these circumstances, friction between the fan and the casing is increased, aeraulic performance is reduced and the motor may work with the rotor seized up and eventually break down. 
     To overcome these disadvantages, fans like the one described in patent EP1718872, to the same Applicant as this invention, have been developed. That patent relates to an axial fan where the bottom wall of the hub has openings in it from which the dirt that accumulates between the fan and the motor may be expelled during use. 
     In the event of prolonged use under heavy-duty conditions, however, the holes tend to become clogged, eventually bringing the fan to a stop. 
     In other prior art solutions, the fan hub is sealed and is defined by a box-shaped body. 
     Examples of hubs of this kind are described and illustrated in documents U.S. Pat. Nos. 2,664,961, 3,006,417, 3,904,314, 4,610,600, 3,231,022, 2,495,433, GB-A-630773 and GB-A-716389. 
     A detail of another prior art fan  101  is illustrated in  FIG. 8   a . In that fan, the hub  103  is defined by revolving a substantially T-shaped section  107 . 
     In practice, the hub  103  is defined by a rigid disc  108  and an annular wall  109  connected at a middle portion of it to the disc  108 . 
     The wall  109  forms a single part with the disc  108  and allows the blades  110  to be connected to the disc  108 . 
     In this solution, too, however, as illustrated, gaps  111  are formed which are eventually filled by material such as mud, soil, sand and so on, leading to imbalance of the fan  101 ; the fan  101  illustrated in  FIG. 8   a  also features reinforcement ribs  112 . 
     DISCLOSURE OF THE INVENTION 
     In this context, the main technical purpose of this invention is to propose an axial ventilator which is free of the above mentioned disadvantages. 
     It is an aim of this invention to propose an axial ventilator which limits the risk of accumulated dirt bringing the fan to a stop. 
     Another aim of the invention is to propose an axial ventilator which limits the risk of accumulated dirt increasing friction and imbalance and leading to vibrations and/or noise. 
     A yet further aim of the invention is to propose an axial ventilator that can be used continuously for heavy-duty applications in the presence of mud, dust, soil and the like. 
     The stated technical purpose and aims of the invention are substantially achieved by a ventilator as described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention are more apparent in the detailed description below, with reference to a preferred, non-restricting, embodiment of a ventilator as illustrated in the accompanying drawings, in which: 
         FIG. 1  is a schematic perspective view of a ventilator according to this invention; 
         FIG. 2  is a different schematic perspective view, with some parts cut away in order to better illustrate others, of the ventilator of  FIG. 1 ; 
         FIG. 3  is a suitably interrupted schematic cross section of the ventilator of the preceding figures; 
         FIG. 4  illustrates a detail of a second embodiment of a ventilator according to the invention in a transversal cross section; 
         FIG. 5  illustrates a third embodiment of a ventilator according to the invention in a transversal cross section; 
         FIG. 6  illustrates a fourth embodiment of a ventilator according to the invention in a perspective view from above; 
         FIG. 7  is a perspective view from below of the fan of the ventilator of  FIG. 6 ; 
         FIG. 8  is a schematic perspective view of a prior art ventilator; 
         FIG. 8   a  is a schematic cross section of a detail of a prior art fan; 
         FIG. 9  illustrates a fifth embodiment of a ventilator according to the invention in a perspective view from above; 
         FIG. 10  is a perspective view from below of the ventilator of  FIG. 9 ; 
         FIG. 11  is a schematic side view of the ventilator of  FIGS. 9 and 10 ; 
         FIG. 11   a  is a suitably interrupted schematic cross section of the ventilator of  FIG. 11 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     With reference to the accompanying drawings, the numeral  1  denotes a ventilator according to this invention. 
     Preferably, the ventilator  1  is of the heavy-duty type, that is to say, designed for use in conditions where straw, soil, mud, dust, water and other extraneous materials might prevent the ventilator  1  from functioning properly. 
     The ventilator  1  comprises an electric motor  2  and a fan  3 , rotationally driven by the motor  2 . 
     Schematically, the motor  2  comprises a casing  4 , a stator, not illustrated, and a rotor, not illustrated, rotatable inside the casing  4  about an axis of rotation R. 
     The motor  2  is of a substantially known type and therefore described only insofar as necessary for understanding this invention. 
     The rotor of the motor  2  comprises a shaft  5  with an end portion  6  which protrudes from the casing  4  and to which the fan  3  is coupled. 
     The fan  3  comprises a plurality of blades  7  and a hub  8  for mounting the blades  7  and connecting the fan  3  to the shaft  5 . 
     As illustrated in particular in  FIGS. 3 and 4 , the hub  8  has a bottom portion or wall  9  with a hole  10  made in it to allow it to be fitted to the shaft  5 , and a perimeter portion or wall  11  which extends from the bottom portion  9 . 
     The blades  7  are connected to the bottom portion  9  by the perimeter portion  11 , which defines, in the hub  8 , a connecting base for the blades  7 . 
     As illustrated in  FIG. 1 to 5 , the perimeter portion  11  is substantially cylindrical and defines a cylindrical wall  12  for mounting the blades  7 . 
     As clearly illustrated, the wall  12  extends from the bottom wall  9  on the side opposite the casing  4  with respect to the bottom wall  9  itself. 
     In other words, the bottom wall  9  and the cylindrical wall  12  give the hub  8  a cup shape extending on the side opposite the motor  2 , which is not, therefore, housed inside the cup. 
     As illustrated, the bottom wall  9  has a smooth outside surface. 
     More precisely, the bottom wall  9  is smooth in the geometric sense, that is to say, it does not have protuberances, protrusions, recesses or the like. 
     In order to prevent extraneous materials from finding their way into the hub  8 , the ventilator  1  comprises a cover  13 , illustrated in  FIGS. 1 ,  3 ,  4  and  5 , for closing the cylindrical wall  12 . Advantageously, as will become clearer as this description continues, the outside surface of the cover  13  is smooth. 
     In practice, the cover  13  closes the perimeter portion  11  on the side opposite the bottom wall  9 . 
     The bottom wall  9 , the perimeter portion  11 , or more specifically, the cylindrical wall  12 , and the cover  13 , define a box-shaped body  14  that constitutes the hub  8  of the fan  3 . 
     It should be observed that the outside surfaces of the body  14  are substantially smooth in order to facilitate the expulsion of mud, soil and the like thanks to the centrifugal force due to the rotation of the fan  3  during use. 
     More specifically, the outside surfaces of the bottom wall  9  and of the cover  13 , that is to say, the outside surfaces of the walls of the body  14  transversal to the axis of rotation R are smooth in order to facilitate expulsion of dirt in a substantially radial direction by applying centrifugal force. 
     With reference to  FIGS. 3 and 5 , it should be noted that the bottom wall  9  is substantially frustoconical in shape, with vertex on the axis of rotation R and concavity facing the inside of the hub  8 , in such a way as to assist in expelling the dirt from its outside surface. 
     The further the bottom wall  9  extends away from the axis of rotation R towards the periphery of the hub  8 , the further it lies from the casing  4 . 
     With reference to  FIGS. 3 and 4  in particular, it should be noted that the ventilator  1  comprises an annular gasket  15  to better guarantee the seal between the cover  13  and the wall  12 . 
     The cover  13  has a discoidal portion  13   a , preferably suitable for insertion into the cylindrical perimeter portion  11 , while the wall  12  has an abutment  16  against which the cover  13  stops. 
     The gasket  15  is preferably interposed between the cover  13  and the abutment  16 . 
     Preferably, the cover  13  comprises a ring  13   b  which extends outwards from the discoidal portion  13   a  and is designed to be inserted into the wall  12 . 
     Preferably, the discoidal portion  13   a  of the cover  13  is frustoconical in shape, with vertex on the axis of rotation R and concavity facing the inside of the hub  8  for expelling the dirt during use of the ventilator  1 . 
     The ventilator  1  comprises a stop system  17  for keeping the cover  13  stably associated with rest of the hub  8 . 
     More in detail, the system  17  operates between the bottom portion  9  and the cover  13 . 
     The system  17  comprises a tube  18  coaxial with the bottom portion  9  and extending from the latter towards the cover  13 . 
     The system  17  also comprises a pin  19  which extends centrally along the axis of rotation R and which is designed to be engaged in the tube  18 . 
     In order to keep the pin  19  securely coupled within the tube  18 , the ventilator  1  comprises locking means  20 . 
     In the embodiment illustrated, the tube  18  has an end portion  18   a  close to the cover  13  and comprising flexible elements  21  that extend along the axis R. 
     The flexible elements  21  are movable between a close-up position, illustrated in  FIGS. 3 and 4 , and a spaced-apart position. 
     The movement between these two positions is permitted by the flexibility of the elements  21 , which can therefore be tightened around the pin  19  in the close-up position. 
     The system  17  comprises a spring  22  fitted round the tube  18  in such a way as to impinge on the flexible elements  21 . 
     The spring  22  forces the flexible elements  21  into the close-up position causing them to retain the pin  19 . 
     Preferably, the tube  18  has a base portion  18   b  which extends from the cylindrical bottom wall  9 . The flexible elements  21  extend from the base portion  18   b.    
     Between the base portion  18   b  and the flexible elements  21 , there is defined an annular abutment  18   c  against which the spring  22  stops. 
     In alternative embodiments not illustrated the cover  13  is fastened and sealed to the hub  8  by gluing the cover  13  to the hub  8 . 
     Alternatively, the cover  13  might be welded, for example by laser or ultrasound welding, to the hub  8 . 
     As illustrated in dashed line style in  FIG. 4 , the stop system  17  comprises pins  33 , which extend from the bottom wall  9  towards the cover  13 , and corresponding pins  34  which extend from the cover  13  towards the pins  33  and abut the latter end to end. The system  17  comprises screws, not illustrated, which engage in the pins  33  through the portion  13   a  of the cover  13  and the pins  34 . 
       FIG. 5  shows another embodiment of a ventilator  1  according to the invention. 
     Inside it, the hub  8  of the fan  3  comprises an axial sleeve  36  inside which the shaft  5  passes and which extends for the full axial dimension of the hub  8  itself. 
     In practice, the sleeve  36  defines the hole  10  through which the shaft  5  passes. 
     In the preferred embodiment illustrated, the sleeve  36  extends substantially for the full height of the hub  8 , that is, approximately the same height as the perimeter portion  11 . 
     A first annular gasket  37  is interposed between the perimeter portion  11  and the cover  13 . 
     A second annular gasket  38  is interposed between the cover  13  and the sleeve  36  and the fastening of the cover  13  to the hub  8  is described in more detail below. 
       FIGS. 3 and 5  illustrate a first system of coupling the fan  3  to the shaft  5 . 
     The shaft  5  has a hole  23  passing through it transversally of the axis of rotation R and accommodating a peg  25  whose ends protrude from the shaft  5  itself. 
     The bottom wall  9  of the hub  8  has a radial slot  24  passing through the axis R and designed to receive the peg  25  and, more specifically, the ends of the latter. 
     The slot  24  is formed on an outside face of the bottom wall  9 , that is to say, on the side of the latter opposite the cylindrical perimeter wall  11 . 
     In the embodiment of  FIG. 3 , the portion of the shaft  5  that is inside the box-shaped body has an annular groove  26  made in it for receiving a snap ring  27 . 
     In other words, the annular groove  26  is formed in the end portion  6  of the shaft  5  on the side opposite the slot  24 , or the through hole  23 , with respect to the bottom wall  9 . 
     Advantageously, the distance between the hole  23  and the annular groove  26  substantially corresponds to the thickness of the bottom wall  9 . 
     To prevent impurities and dirt from getting into the box-shaped body  14  through the hole  23  for the passage of the shaft  5 , the fan  2  comprises a sealing element  28  located between the bottom wall  9  and the shaft  5 . 
     More specifically, the sealing element  28  is forced into the tube  18 , inside the box-shaped body  14 , in coaxial manner creating a tight seal against the wall of the tube  18  itself. 
     In practice, once the fan  3  has been coupled to the shaft  5  using the peg  25  and the fan  3  has been locked to the shaft using the snap ring  26 , the seal is enhanced by inserting the element  28  into the tube  18 . 
     The lower portion  18   b  of the tube  18  thus defines a housing for the sealing element  28 . 
     In the embodiment of  FIG. 5 , the annular groove  26  is formed on the end of the shaft  5  which, in this embodiment, extends beyond the cover  13 . 
     In other words, the shaft passes right through the box-shaped body  14  and the hub  8  is locked by the snap ring  27  and held to the shaft  5  by the peg  25  which rotationally drives the fan  3 . 
     In this case, the sealing action of the seal inside the hub  8  is guaranteed by the gaskets  37 ,  38  for closing the cover  13 . 
     It should be noted that preferably it is the snap ring  27  that keeps the cover  13  locked to the hub  8  since the shaft  5  passes right through the box-shaped body  14 . 
     In practice, in this embodiment, the ring  27  locks both the hub  8  and the cover  13  to the shaft  5 , holding them together in a closed configuration. 
     As illustrated in  FIG. 4 , the fan  3  comprises a bushing  29  coaxial with the hub  8  and co-moulded in the latter&#39;s bottom wall  9 . 
     In this case, the fan  3  is coupled to the shaft  5  by an interference fit and the seal that keeps extraneous material out of the box-shaped body  14  is guaranteed by the bushing  29 . 
     More specifically, the seal is guaranteed by the tight coupling between the shaft and the bushing  29 . 
     Preferably, in both of the embodiments, as illustrated in  FIGS. 3 ,  4  and  5 , the structure of the hub  8  is stiffened by ribs  30  formed on the inside of the box-shaped body  14 . 
     As illustrated, the ribs  30  are arranged radially and their profile increases from the centre to the periphery of the hub  8  in such a way as to make the hub strong enough to support the added weight of dirt that might settle on the blades  7 . 
     When assembling the ventilator  1 , particularly the embodiments of it illustrated in  FIGS. 3 and 4 , the fan  3 , that is, the bottom wall  9  combined with the wall  11  of the hub  8 , are coupled to the shaft  5  in the above mentioned ways. 
     The spring  22  is fitted round the tube  18  in such a way as to bend the flexible elements  21  towards the axis of rotation R. 
     Next, after fitting the gasket  15 , the cover is coupled to the box-shaped body  14 , positioning it so it is coaxial with the latter and inserting the pin  19  between the flexible elements  21  which hold it in position. 
     The hub  8  made in the above manner, whether with or without the reinforcement ribs  30 , is sufficiently stiff to guarantee the correct operation of the ventilator  1 . 
     Placing the motor entirely on the outside of the fan also makes the ventilator particularly efficient for heavy-duty applications because there are no interstices where dirt can accumulate. 
     Alternatively, in the embodiment of  FIG. 5 , the hub  8  is locked to the shaft  5  by the peg  25 , and the cover  13  is also placed on the shaft  5  after interposing the gaskets  37  and  38 , and pressed against the hub  8 . 
     The box-shaped body  14  is then securely locked axially by the snap ring  27 . 
       FIGS. 6 and 7  show a third embodiment of a fan according to this invention. 
     In the case of low-power ventilators, for example, less than 100 watts, the fan  3  comprises the hub  8 , whose bottom wall  9  allows the fan  3  to be coupled to the shaft  5 , and the perimeter portion  11  for mounting the blades  7 . 
     In practice, in the case of low-power units, the box-shaped hub  8  of the embodiments described above, is merely a rigid disc. 
     In this embodiment, too, the hub  8  does not surround the motor but, to limit axial dimensions and optimize mouldability in connection with the reduced dimensions and power, is in the form of a disc. 
     Preferably co-moulded in the bottom wall  9 , there is a bushing  31  which guarantees the coupling of the fan  3  to the shaft  5  by an interference fit. 
     Alternatively, in another embodiment that is not illustrated, the hub  8  is made entirely of a plastic material and the end portion  6  of the shaft  5  is machined in such a way as to present longitudinal protrusions. 
     By way of an example, these protrusions are obtained by “pinching” the cylindrical outside surface of the shaft. 
     The term “pinching” is used to mean squeezing the cylindrical surface of the shaft according to a direction transversal, in particular perpendicular, to the directrices of the surface itself. 
     In the hub  8  of  FIGS. 6 and 7  the perimeter portion or wall  11  extends from the bottom portion  9  on the side opposite the motor  2 . 
     The wall  11  has a substantially cylindrical outside face  32  and an inside face  35  facing the axis of rotation R and connected to the bottom wall  9 . 
     In this embodiment, the hub  8  is defined by a rigid disc  39  comprising the portion  9  and the portion  11  which the blades  7  are associated with. 
     The wall  11  forms a sort of circular crown  11  which extends on the periphery of the wall  9 . 
     Advantageously, at least the inside face  35  diverges from the bottom wall  9  outwards and away from the axis of rotation R. 
     That way, any dirt that settles on the hub  8 , in particular on the bottom wall  9  may be expelled by centrifugal force without encountering obstacles. 
     The crown  11  contributes to conferring on the fan  3  the rigidity necessary for its correct operation. 
     As illustrated in particular in  FIG. 7 , on the side opposite the crown  11  there extend from the bottom wall  9  a plurality of bases  11   a  substantially at each blade  7 . 
     The surface connecting each blade  7  to the base wall  9  is therefore defined by a portion of the perimeter wall  11  and by the corresponding base  11   a.    
     This configuration, too, is particularly suitable for heavy-duty applications because it does not have interstices where extraneous material can accumulate. 
     More specifically, none of the surfaces of the bases  11   a  extends in a direction at right angles to the centrifugal (radial) direction. 
       FIGS. 9 to 11   a  show a yet further preferred embodiment of the ventilator according to the invention. 
     As illustrated, the hub  8  is defined by the rigid disc  39  comprising the bottom wall  9  which allows the fan  3  to be coupled to the shaft  5 . 
     Preferably, the hub  8  has walls which are smooth in the geometrical sense and still more preferably, it is made by revolving a substantially triangular section to form a frustoconical body which confers strength and rigidity on the hub  8  itself. 
     More in detail, as illustrated in  FIG. 11   a , the bottom wall  9  has the form of a frustoconical surface. 
     Advantageously, the concavity of the bottom wall  9  faces the motor  2 . 
     In other words, the frustoconical hub  8  formed substantially by the bottom wall  9 , is defined as a portion of a conical surface whose vertex is on the axis of rotation R and whose concavity faces the motor  2 . 
     Preferably, the conicity is such as to guarantee that dirt of any kind and nature can be expelled by the centrifugal force generated during rotation of the fan  3 . 
     More in detail, in the solution illustrated, the motor  2  has facing it the inside surface of the hub  2  which is substantially conical and which facilitates the expulsion of dirt. 
     It should be noted that, as already mentioned, dirt may give rise to static and/or dynamic imbalance which may lead to vibrations and noise and reduce the working life of the ventilator itself. 
     This shape is optimal also for moulding the fan. 
     Preferably, as illustrated, and unlike the prior art solution shown in  FIGS. 8 and 8   a , the section of revolution of the hub  8  has no surfaces extending at right angles to the direction of the centrifugal force (the radial direction) since such surfaces would acts as traps for the dirt. 
     The absence of such surfaces guarantee that not only dirt but any kind of material, whether solid, such as dust, sand, fine particles of straw or hay, or liquid, mainly rainwater or condensate, may be trapped inside the hub, whatever the assembly position. 
     The solution described is particularly advantageous for use in roof-mounted applications such as in buses and vans, since any condensate and rainwater that may collect can be immediately expelled by centrifugal force as soon as the ventilator is switched on, thus preventing noise, imbalances and oxidization and/or corrosion of metallic parts, if any. 
     In order to allow the blades  7  to be connected to the hub  8 , a plurality of bases  11   a  extend from the bottom wall  9  on the opposite side with respect to the motor  2  substantially at each blade  7 . 
     The surface connecting each blade  7  to the base wall  9  is therefore defined by the corresponding base  11   a.    
     In other words, the hub  8  is provided with a plurality of undercuts  40 , between each blade  7  and the blade  7  adjacent to it. 
     The undercuts  40  are defined between adjacent bases  11   a.    
     This configuration is particularly suitable for heavy-duty applications because it does not have interstices where extraneous material can accumulate. Any extraneous material can be expelled through the undercuts  40  as soon as the fan  3  starts turning. 
     Advantageously, also, as mentioned above, the face of the hub  8  facing the motor  2  is completely smooth and defined by the base wall  9  so as to facilitate expulsion of any dirt that may have accumulated between the fan and the motor. 
     With reference in particular to  FIG. 11 , it may be observed that, preferably, in order to confer suitable stiffness on the fan  3 , the blades  7  extend from the hub  8  towards the motor  2  to form a substantially frustoconical surface. 
     The axial dimensions of the ventilator are thus reduced. 
     Preferably, each undercut  40  is located at the trailing edge of the respective blade  7 . 
     Preferably, in order to make the air moved by the fan  3  strike the motor  2  directly to guarantee cooling, the diameter of the rigid disc  39  is approximately equal to the outside diameter of the motor  2 . 
     In other words, the hub  8  is substantially equal in diameter to the motor  2 . 
     Preferably, the largest diameter of the bottom wall  9  in the frustoconical configuration is substantially equal to the diameter of the motor  2 . 
     In the embodiments illustrated in  FIGS. 9 to 11 , the bases  11   a  themselves define the perimeter portion  11  for connection to the blades  7 . 
     It should be observed that the embodiment illustrated in  FIGS. 6 and 7  is preferably used when the available axial dimensions are not large enough to fit a frustoconical hub  8 . In this case, therefore, the bases  11   a  protrude at least partly towards the motor  2 . 
     This is the case mainly when the diameter of the hub  8  is almost equal to the diameter of the motor  2 . 
     Generally speaking, the frustoconical shape of the hub is created preferably when the disc  39  is larger enough in diameter than the motor  2  and, still more preferably, when the bases  11   a  protrude from the wall  9  on the side opposite the motor. 
     In other words, the frustoconical shape of the bottom wall  9  is preferable when the axial dimensions of the bases  11   a , extending on the side opposite the motor  2  are smaller than the axial dimensions of the wall  9  itself. 
     The invention brings important advantages. The hubs described have smooth surfaces which facilitate expulsion of dirt by centrifugal force in such a way as to protect the fan for example from imbalances. 
     The hub is well clear of the motor, with enough space between them to avoid creating gaps and interstices where dirt can accumulate and lead to ventilator malfunctioning.