Patent Publication Number: US-2022235782-A1

Title: Airflow device

Description:
BACKGROUND OF IRE INVENTION 
     This invention relates to an airflow device and, more specifically, to a ceiling-mountable fan. 
     Conventional ceiling fans are mounted in a suspended manner to a ceiling and typically have a set of motorised blades rotatable about a vertical axis to provide downward airflow. Such ceiling fans are structurally bulky and occupy a significant portion of an interior with elongated fan blades, which can be unsightly and difficult to clean. Furthermore, the exposed moving fan blades may pose a risk of injury. Movement of the fan blades during use can be noisy and disturbing in home and office environments, and do not typically produce airflow that is felt uniformly around a room. 
     The applicant has determined that it would be advantageous to provide a ceiling-mountable fan with improved aesthetic and functional performances. The present invention, in its preferred embodiments, seeks to at least in part alleviate one or more of the above-identified problems. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is provided an airflow device including:
         (i) airflow generating means for generating first and second streams of air;   (ii) first and second Coanda surfaces;   (iii) means for directing the first and second streams of air over first and second Coanda surfaces respectively; and wherein   (iv) the first stream of air leaving the first Coanda surface is directed so as to pass over the second Coanda surface.       

     Preferably the airflow generating means generates three or more streams of air and each stream of air is directed over respective Coanda surfaces, the arrangement being such that streams of air leaving upstream Coanda surfaces are directed over adjacent downstream Coanda surfaces. 
     It has been found that increased airflow can be achieved by using multiple Coanda surfaces effectively operating in series. 
     Preferably, the first Coanda surface is positioned above the second Coanda surface so as to define an outlet therebetween, and wherein a stream of air is directed by said directing means so as to pass through the outlet and over the second Coanda surface. 
     Preferably, an opening of the outlet has a height of about 20 mm or less. 
     Preferably, the first and second Coanda surfaces are positioned relatively offset to the second Coanda surface. 
     Preferably, the first and second Coanda surfaces partially overlap when seen from a plan view. 
     Preferably, at least one of the first and second. Coanda surfaces is convex in shape. Preferably, all Coanda surfaces are convex in shape. Preferably, a radius of the convex curvature is about 380 mm. 
     Alternatively, at least one of the first and second Coanda surfaces is flat. Alternatively, all Coanda surfaces are flat. 
     Preferably, the first and second Coanda surfaces extend downwardly with an angle of less than 90° relative to a vertical axis. Preferably, the downward extending angle of the first Coanda surface is between about 20° and 25° relative to a vertical axis. Preferably, the downward extending angle of the second Coanda surface is between about 30° and 35° relative to a vertical axis. 
     Preferably, the Coanda surfaces are provided on respective vanes configured in the form of annular frames. Preferably, the respective vanes are coaxially mounted relative to each other. 
     Preferably, the vane of the first Coanda surface has a smaller diameter than that of the vane of the second Coanda surface. 
     Preferably, the Coanda surfaces of the vanes have a minimum width in the radial direction of about 390 mm. 
     Preferably, one or more guide(s) are arranged in the outlet between the first and second Coanda surfaces so as to direct a stream of air passing over the second Coanda surface in an outward direction. Preferably, the outward direction is a radial angle of 90° with respect to a tangent of an outer edge of the second Coanda surface. 
     Preferably, the airflow generating means is an impeller driven by an electric motor. Preferably, the air inlet is positioned above the impeller for entraining airflow located above the impeller. 
     Preferably, the airflow generating means is configured to generate an initial stream of airflow which is divided into the first and second streams of air by a dividing portion located in a path of the initial stream of airflow. 
     Preferably, the device is substantially enclosed in a housing having an air inlet upstream of the Coanda surfaces and an air outlet downstream of the Coanda surfaces. 
     According to another aspect of the present invention, there is provided a ceiling-mountable fan comprising an airflow device as described above and means for mounting the airflow device to a ceiling. 
     According to second aspect of the invention there is provided a ceiling fan including: a housing having an outlet; an impeller located within the housing for producing a stream of air passing through the outlet; a first Coanda surface positioned in or adjacent to the outlet and arranged such that said stream of air passes over the Coanda surface and wherein ambient air is, in use, entrained into said stream of air; a second Coanda surface positioned adjacent to the first Coanda surface so that said stream of air leaving the first Coanda surface is directed to pass over the second Coanda surface. 
     Preferably, the fan further comprises a first vane and a second vane mounted such that they are located, in use, in said stream of air, and wherein the first and second Coanda surfaces are respectively located on the first and second vanes. Preferably, the fan comprises additional one or more vanes mounted such that they are located, in use, in said stream of air. Preferably, each of the additional one or more vanes includes a Coanda surface, each of which operates to direct air towards a successive one of said Coanda surfaces. Preferably; the or each vane is coaxially mounted to the housing. 
     Preferably, the impeller is substantially concealed by the housing and the vane(s), in use. 
     Preferably, the or each vane is configured in the form of an annular frame. 
     Preferably, each of the vanes includes a Coanda surface, each of which operates to direct air towards a successive one of said Coanda surfaces. Alternatively, the fan comprises two or more said vanes having respective Coanda surfaces. Alternatively, the fan comprises three or more said vanes having respective Coanda surfaces. 
     Preferably, the Coanda surfaces are vertically arranged relative to each other. Preferably, the downward extending angle of a higher Coanda surface is between about 20° and 25° relative to a vertical axis. Preferably, the downward extending angle of a lower Coanda surface is between about 30° and 35° relative to a vertical axis. 
     Preferably, the Coanda surfaces are offset in a radial direction relative to each other. Preferably, the Coanda surfaces are disposed parallel with respect to each other. Preferably, the Coanda surfaces partially overlap when seen from a plan view. 
     Preferably, each successive vane has a larger diameter than that of the housing or a preceding vane. 
     Preferably, one or more guide(s) are arranged in the outlet between adjacent Coanda surfaces so as to direct a stream of air to pass over a downstream Coanda surface in an outward direction. Preferably, the outward direction is at a radial angle of 90° with respect to a tangent of an outer edge of the second Coanda surface. 
     Preferably, the respective Coanda surface of the or each vane has a minimum width in the radial direction of about 390 mm. 
     Preferably, at least one of the Coanda surfaces is convex in shape. Preferably, all Coanda surfaces are convex in shape. Preferably, a radius of the convex curvature is about 380 mm. 
     Alternatively, at least one of the Coanda surfaces is flat. Alternatively, all Coanda surfaces are flat. 
     Preferably, the Coanda surfaces extend downwardly with an angle of less than 90° relative to a vertical axis. Preferably, the or each Coanda surface forms part of an outer surface of the housing or the vanes. 
     Preferably, an opening of the outlet has a height of about 20 mm or less. 
     Preferably, the fan includes mounting means for mounting the fan to a ceiling and an inlet which is, in use, located adjacent to the ceiling. Preferably, the inlet is located above an impeller for drawing ambient air in an downward direction toward the impeller. 
     Preferably, the housing includes a base wall and wherein a light fitting is located adjacent to the base wall. 
     According to another aspect of the present invention, there is provided a ceiling fan including: a housing having an outlet; an impeller located within the housing for producing a stream of air passing through the outlet; two or more vanes configured in the form of annular frames mounted coaxially to the housing such that they are located, in use, in said stream of air, each vane comprising a flat surface positioned in or adjacent to the outlet and arranged such that said stream of air passes over the flat surface and directed towards a successive one of said flat surfaces. 
     Preferably, each flat surface extends downwardly with an angle of less than 90° relative to a vertical axis. 
     Preferably, the flat surfaces are offset in a radial direction relative to each other. Preferably, the flat surfaces partially overlap when seen from a plan view. 
     Preferably, the impeller is substantially concealed by the housing and the vanes, in use. 
     Preferably, the fan includes mounting means for mounting the fan to a ceiling and an inlet which is, in use, located adjacent to the ceiling. 
     Preferably, the housing includes a base wall and wherein a light fitting is located adjacent to the base wall. 
     According to yet another embodiment of the present invention, there is provided a ceiling fan including: a housing having an outlet; an impeller located within the housing for producing a stream of air passing through the outlet; two or more vanes configured in the form of annular frames mounted coaxially to the housing such that they are located, in use, in said stream of air, each vane comprising a deflecting surface positioned in or adjacent to the outlet and arranged such that said stream of air passes over the deflecting surface and directed towards a successive one of said deflecting surfaces. 
     Preferably, each deflecting surface extends downwardly with an angle of less than 90° relative to a vertical axis. 
     Preferably, the deflecting surfaces are offset in a radial direction relative to each other. Preferably, the deflecting surfaces partially overlap when seen from a plan view. 
     Preferably, the impeller is substantially concealed by the housing and the vanes, in use. 
     Preferably, the fan includes mounting means for mounting the fan to a ceiling and an inlet which is, in use, located adjacent to the ceiling. 
     Preferably, the housing includes a base wall and wherein a light fitting is located adjacent to the base wall. Preferably, the inlet is located above an impeller for drawing ambient air in an downward direction toward the impeller. 
     According to another aspect of the present invention, there is provided a ceiling fan including a housing having an outlet; an impeller located within the housing for producing a stream of air passing through the outlet; and a plurality of Coanda surfaces positioned in or adjacent to the outlet and arranged such that said stream of air passes over the Coanda surface and wherein ambient air is, in use, entrained into said stream of air. Wherein each of the Coanda surfaces operates to direct air towards a successive one of said Coanda surfaces. 
     According to another aspect of the present invention, there is provided an impeller for an airflow device, comprising: a plurality of longitudinally extending blades evenly disposed on a hub member, the blades being configured to radiate outwardly, from a raised centre of hub member, along an continuous arcuate path, wherein the arcuate path follows a chord angle of between 30° and 40°. 
     Preferably, each of the plurality of blades comprises a root portion, which is located at or proximate a root end portion of the blade, a body portion and a tip end portion, and wherein the blade is configured so that its height remains constant for a root end portion of the blade and gradually reduces along the length of the blade from the body portion toward the tip end portion of the blade. 
     Preferably, at least one of the blades comprises a step along a spine of the blade at or proximate a tip end portion of the blade. 
     Preferably, at least one of the blades is configured with a forward leaning edge at or proximate a root end portion of the blade and a backward leaning edge; at or proximate a tip end of the blade. 
     Preferably, the plurality of blades follow an anti-clockwise arcuate path with respect to the centre of the hub member when viewed from above. 
     Preferably, a tip end of each of the plurality of blades extends beyond a peripheral edge of the hub member. 
     Preferably, the impeller hub member is configured with a diameter of about 400 mm. 
     Preferably, the centre of the hub member is configured with a dome having a diameter of 90 mm. 
     Preferably, the hub member is configured with a cavity for housing a motor unit. 
     In a preferred embodiment of the invention, the airflow device is formed as a ceiling fan/light which has a curved cylindrical housing which can be made to have an attractive appearance. Part of the curved cylindrical surface functions as a Coanda surface and one or more vanes can be included so as to produce enhanced airflow because of the compound effect of the coanda surfaces. The compound Coanda surfaces also function to entrain more ambient air into the stream of air which leaves the outlet of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be further described with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view of a ceiling fan/light constructed in accordance with the invention, 
         FIG. 2  is a perspective view of the fan/light shown in  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view through the fan/light; 
         FIG. 4  is a cross-sectional view showing streams of entrained ambient air; 
         FIG. 5  is a schematic view of a fanlight housing which includes multiple Coanda surfaces; 
         FIG. 6  is a side view of the housing shown in  FIG. 5 ; 
         FIG. 7  is an enlarged fragmentary view of part of the housing shown in  FIG. 6 ; 
         FIG. 8  is a schematic diagram showing enhanced airflows produced by the compound Coanda surfaces; 
         FIG. 9  is a schematic view of a further embodiment of the fan/light; 
         FIG. 10  is a fragmentary cross-sectional view through the fan/light shown in  FIG. 9 ; 
         FIG. 11  is a perspective view showing a ceiling fan assembly in accordance with a further embodiment of the present invention; 
         FIG. 12  is a perspective view showing the ceiling fan assembly of  FIG. 11  from above; 
         FIG. 13  is a side view of the ceiling fan assembly of  FIG. 11 ; 
         FIG. 14  is a plan view of the ceiling fan assembly of  FIG. 11 ; 
         FIG. 15  is a bottom view of the ceiling fan assembly of  FIG. 11 ; 
         FIG. 16  is a sectional view of the ceiling fan assembly shown in  FIG. 13 ; 
         FIG. 17  is a partial close up sectional schematic side view of the fan assembly of  FIG. 13  showing the streams of airflow relative to surfaces of the fan assembly; 
         FIG. 18  is an exploded view from above showing the ceiling fan assembly of  FIG. 11 : 
         FIG. 19  is an exploded view from below showing the ceiling fan assembly of  FIG. 11 ; 
         FIG. 20  is a plan view of an impeller for use with the ceiling fan in accordance with a preferred embodiment of the invention; 
         FIG. 21  is a side view of the impeller of  FIG. 20 ; 
         FIG. 22  is a perspective view of the impeller of  FIG. 20  when mounted within a fan assembly embodying the present invention; 
         FIG. 23  is a perspective close up side view of the impeller of  FIG. 22 ; 
         FIG. 24  is a partial sectional schematic plan view of a fan assembly according to another embodiment of the present invention; 
         FIG. 25A  is a schematic showing CFD flows in an initial air flow phase for fan assemblies embodying the present invention having one, two and three Coanda vanes; 
         FIG. 25B  is a schematic showing CFD flows of the fan assemblies of  FIG. 25A  in a secondary air flow phase; 
         FIG. 25C  is a schematic showing CFD flows of the fan assemblies of  FIG. 25A  in a tertiary air flow phase; 
         FIG. 26  is a perspective view showing an impeller and vane housing assembly according to another embodiment of the present invention; 
         FIG. 27  is a plan view of the impeller and housing assembly of  FIG. 26 ; 
         FIG. 28  is a side view of the impeller and housing assembly of  FIG. 26 ; 
         FIG. 29  is a sectional view of the impeller and housing assembly of  FIG. 28 ; 
         FIG. 30  is a plan view of an impeller in accordance with another embodiment of the present invention; 
         FIG. 31  is a side view of the impeller as shown in  FIG. 30 ; 
         FIG. 32  is a perspective view of the impeller of  FIG. 30 ; 
         FIGS. 33 to 39  show a plan view of the impeller of  FIG. 30  and six sectional views of the impeller as indicated in  FIG. 33 ; 
         FIG. 40  is a perspective view showing an impeller and vane housing assembly according to another embodiment of the present invention; 
         FIG. 41  is a plan view of the impeller and housing assembly of  FIG. 40 ; 
         FIG. 42  is a side view of the impeller and housing assembly of  FIG. 40 ; 
         FIG. 43  is a sectional view of the impeller and housing assembly of  FIG. 40 ; 
         FIG. 44  is a plan view of an impeller in accordance with another embodiment of the present invention; 
         FIG. 45  is a side view of the impeller as shown in  FIG. 44 ; 
         FIG. 46  is a perspective view of the impeller of  FIG. 44 ; 
         FIGS. 47 to 53  show a plan view of the impeller of  FIG. 44  and six sectional views of the impeller as indicated in  FIG. 47 ; 
         FIGS. 54 to 57  show various schematic views of an impeller with an isolated continuous blade in accordance with another embodiment of the present invention; 
         FIGS. 58 to 62  show CFD simulation outputs comparing different impeller configurations in relation to overall airflow velocity and noise pressure performances; 
         FIG. 63  shows various impeller blade configuration with different chord angles; 
         FIGS. 64 to 66  show CFD simulation outputs comparing impellers having different chord angles of  FIG. 63  in relation to overall airflow velocity and noise pressure performances; 
         FIGS. 67 to 74  show CFD simulation outputs comparing different impeller and fan housing configurations in relation to airflow velocity and noise pressure performances; 
         FIGS. 75 to 77  show CFD simulation outputs comparing yet further impeller and fan housing configurations in relation to airflow velocity and noise pressure performances; 
         FIG. 78  is a perspective view showing an impeller and vane housing assembly according to another embodiment of the present invention; 
         FIG. 79  is a plan view of the impeller and housing assembly of  FIG. 78 ; 
         FIG. 80  is a sectional view of the impeller and housing assembly of  FIG. 78 ; 
         FIG. 81  is a plan view of an impeller in accordance with another embodiment of the present invention; 
         FIG. 82  is a side view of the impeller as shown in  FIG. 81 ; 
         FIG. 83  is a perspective view of the impeller of  FIG. 81 ; and 
         FIGS. 84 to 90  show a plan view of the impeller of  FIG. 81  and six sectional views of the impeller as indicated in  FIG. 84 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 4  schematically illustrate a fan/light  2  constructed in accordance with the invention. In the illustrated arrangement, the fan/light  2  is adapted for mounting on a ceiling  4 , as shown in  FIGS. 3 and 4 . The fan/light  2  includes a housing  6  which includes an upper housing portion  8  and a domed base wall  12 . The domed base wall  12  has a lower rim  11  which extends beyond a lower rim  15  of the upper housing portion  8  and defines a Coanda surface  10  in the region which is laterally beyond the rim  15 . 
     The fan/light  2  is provided with a light fitting  13  which is shown in broken lines in  FIG. 3 . The light fitting  13  can include an array of LED&#39;s with associated driving circuitry, fluorescent lamps or other light emitting elements. The light fitting  13  would typically include a translucent diffuser (not shown) so as to give the fan/light  2  an attractive appearance. Details of the light fitting  13  do not need to be described in detail as they can be the same as those commonly used in the art. It is preferred that the outer periphery of the light fitting  13  does not extend beyond the rim  11  so as to not have any influence on air flowing over the Coanda surface  10 , as will be explained in more detail below. 
     The upper housing portion  8 . Coanda surface  10  and domed base wall  12  form an internal chamber  14  within which is located an impeller  16 . The impeller  16  is mounted on an impeller shaft  18  which is driven by an electric motor  20 . It is preferred that the impeller shaft  18  is hollow so that it can carry electrical conductors (not shown) for the light fitting  13  in the usual way. The fan/light  2  includes a motor mounting bracket  22  which in use can be securely connected to the ceiling  4 . In the illustrated arrangement, the bracket  22  includes a curved skirt  23  which in use extends from the ceiling  4  and inwardly towards the interior of the chamber  14 . The lower end of the shaft  18  is connected to the base wall  12  by means of a bearing  24  which in the illustrated arrangement is connected to the upper surface  25  of the domed base wall  12 . 
     In the illustrated arrangement, the upper rim  26  of the upper housing portion  8  is spaced from the ceiling  4  so as to define an inlet  28  to the chamber. The chamber  14  has an outlet  30  which is defined by a gap between the lower rim  15  of the upper housing portion  8  and the upper surface  25  of the base wall  12 . The base wall  12  can be supported by means of ribs or brackets (not shown) connected between the upper housing portion  8  and the base wall  12  and within the chamber  14 . 
     The basic operation of the fan/light  2  is such that the motor  20  drives the impeller  16  so that it rotates about impeller axis  32 . This causes air to be drawn into the inlet  28  and pass out of the outlet  30 . The internal surfaces of the chamber  14  and the shape of the gap between the upper housing portion  8  and the upper surface  25  of the base wall  12  is such that the stream of air  34  passing through the outlet  30  has laminar flow or substantially laminar flow. The stream of air  34  passing over the Coanda surface  10  experiences the Coanda effect so that it moves adjacent to the Coanda surface and is discharged into the room below in a generally downward and outward direction. 
     Because of the curved shape of the upper housing portion  8  and the Coanda surface  10 , streams of entrained air  36  will be entrained into or adjacent to the stream of air  34  issuing from the outlet  30 . This significantly increases airflow volumes so making the fan/light of the invention efficient. In the illustrated arrangement, the upper housing portion  8  is formed as a surface of revolution about the axis  32 , although this is not essential. It is preferred, however, that the inner and outer surfaces of the housing  6  are aerodynamically shaped so as to enhance production of generally laminar flow from the outlet  30 . The domed shape of the base wall  12  also enhances laminar flow from the outlet  30 . The curved skirt  23  is preferably generally parallel to and spaced from the adjacent region of the upper housing portion  8  so as to define an inlet passage  38  and forms a generally smooth path for air entering the housing  6 . It will also be appreciated from  FIGS. 3 and 4  that the outlet passage  39  downstream of the impeller  16  is defined between the inner surface of the upper housing portion  8  and the upper surface  25  of the base wall  12  and tapers gradually towards the opening  30 . This increases air speed and again promotes laminar flow. 
     The parts which form the housing  6  could be moulded from plastics material such as polystyrene or ABS. Alternatively, they could be formed from spun or pressed metal such as aluminium. 
     Various enhancements could be included in the fan/light, such as the addition of a heater, ioniser, air purifier and/or humidifier. Known techniques could also be adopted for reducing noise caused by the impeller and airflows to and from the housing  6 . The techniques for incorporating these features in fans or fan/lights is known in the art and need not be described in detail. 
     In the fan/light  2  shown in  FIGS. 1 to 4 , there is a single Coanda surface  10 . It has been found that significant improvement in performance can be obtained by providing one or more Coanda surfaces which effectively operate in series so as to lead to significantly higher volumes of ambient air which is entrained into the air flowing from the housing. 
       FIGS. 5 to 8  show a modified housing  50  which can be used to replace the housing  6  in the embodiment shown in  FIGS. 1 to 4 . In this embodiment, the same reference numerals will be used to denote parts which are the same as or correspond to those of the embodiment shown in  FIGS. 1 to 4 . The housing  50  includes an upper housing portion  8  which is somewhat truncated compared to the arrangement of the embodiment shown in  FIGS. 1 to 4 . Its upper rim  26  is circular as best seen in  FIG. 5 . In this embodiment, the base wall  12  is again domed and extends across the lower rim  15  of the upper housing portion  8  and its outer peripheral region forms the Coanda surface  10 , as in the previous embodiment. The housing includes an inwardly directed flange  52  which defines an annular outlet passageway  54  leading to the outlet  30  of the chamber  14 . The housing  50  includes first and second annular vane elements  56  and  58  which are located adjacent to the Coanda surface  10 , as best seen in  FIGS. 5 and 8 . The vane element  56  has a leading edge  60  which is located in or adjacent to the outlet  30  of the housing  50 . As best seen in  FIG. 8 , the leading edge  60  of the vane element  56  is located radially inwardly of the lower rim  15  of the housing portion  8  by a distance of about 3 to 20 mm and preferably about 10 mm (as measured tangentially relative to the outer surfaces of the vane element  56 ). Air from the chamber  14  passes through the outlet  30  and passes above and below the vane element  56  and its upper convex surface constitutes a second Coanda surface  64 . The second vane element  58  includes a leading edge  70  and trailing edge  73 . The leading edge  70  is located upstream of the trailing edge  72  of the vane element  56  and approximately midway between the trailing edge  72  and the Coanda surface  10 , as shown in  FIG. 8  (as measured in a perpendicular direction relative to the vane elements  56  and  58  and adjacent to the leading edge  70 ). The upper convex surface of the vane element  58  constitutes a third Coanda surface  74 . 
     The leading edge  70  of the second vane element  58  is located upstream of the trailing edge  72  of the first vane element  56  by a distance of about 3 to 20 mm and preferably about 10 mm (as measured tangentially relative to the outer surface of the vane element  58 ). 
     The housing  50  shown in  FIGS. 5 to 8  includes mounting elements or posts, ribs or the like (not shown) which interconnect the various parts. Typically, the upper housing portion  8  would be supported by the bracket  22  and the base wall  12  and vane elements  56  and  58  are supported from it. It will be appreciated that the upper housing portion  8 , vane elements  56 ,  58  and base wall  12  are all stationary. The vane elements  56  and  58  can be considered to have leading and trailing edges relative to the air streams which flow about the vane elements. 
     It has been found from computer simulations of the housing  50  shown in  FIGS. 5 to 8  that substantially increased airflows can be achieved by the use of multiple Coanda surfaces. For instance, with an airflow of about 4 msec in the outlet  30  an airflow of about 7.5 m/sec is predicted between the rim  15  and the leading edge  60  of the vane element  56 . A similar airflow velocity is predicted above the leading edge  70  of the second vane element  58 . The airflow decreases to about 7 m/sec at the lower rim  11  of the Coanda surface  10 . The simulations also predict increased airflows caused by the compound Coanda surfaces because of increased volumes of air entrained over the outer surface of the upper housing portion  8 , the vane elements  56  and  58  and Coanda surface  10  and entrained into the streams of air passing through the outlet  30 . This substantially improves the overall efficiency of the fan. 
     The dimensions of the vane elements  56  and  58  can be chosen so as to optimise airflow. In one embodiment, the leading edge  60  of the vane element  56  is located approximately 5 mm upstream of the rim  15 . The gap between the rim  15  and the leading edge  60  of the vane element  56  is about 2 to 20 mm and preferably about 10 mm (as measured perpendicularly relative to the outer surface of the vane element  56 ). Similarly, the gap between the leading edge  70  of the second vane element  58  is located beneath the trailing edge  72  of the first vane element by a distance of about 2 to 20 mm and preferably about 10 mm (as measured perpendicularly relative to the upper surface of the second vane element, adjacent to its leading edge  70 ). The length of the vane elements  56  and  58  (as measured in tangentially) can be varied in accordance with the overall size of the fanlight. 
     In the arrangement illustrated in  FIGS. 5 to 8  there are two additional vane elements effectively producing three Coanda surfaces. It is thought that additional vane elements could be incorporated into the fan/light in order to further increase volumes of entrained air. However, additional vane elements could lead to manufacturing complexities and also have undesirable aesthetic effects on the overall appearance of the fan/light. 
       FIGS. 9 and 10  schematically show a modified fan/light  78 . The same reference numerals have been used to denote parts which are the same as or correspond to those of the earlier embodiment. In this arrangement, a plurality of adjustable vanes  80  are mounted on or adjacent to the lower rim  11  of the Coanda surface  10 . The vanes  80  overlap one another so that they can be adjusted in orientation whilst still maintaining a generally continuous surface; that is to say without substantial gaps. It would, of course, be possible to provide the vanes in a multiple Coanda surface arrangement similar to that shown in  FIGS. 5 to 8 . In use, the vanes  80  are adjustable in orientation relative to the Coanda surface  10  so as to vary the angle of the air stream which leaves the Coanda surface  10 . The vanes  80  are connected by means of pivotal connections  82  which enable the adjustable vanes to pivot about axes  84  which are all perpendicular to the impeller axis  32  and generally tangential to the lower rim  11  of the Coanda surface  10 . Only one of the axes  84  is shown in  FIG. 9  for clarity of illustration. The vanes can be coupled to a linkage system (not shown) which can be operated by a servo-motor (not shown) in order to adjust their orientation. It is envisaged that this would be an option available to a user from a control unit (not shown) or a remote controller in order to vary the airflow distribution in a room. 
     Additional Embodiments 
       FIGS. 11 to 26  schematically illustrate a fan assembly  100  constructed in accordance with further embodiments of the invention. The fan assembly  100  is suitable for use with decorative light mountings and/or an airflow device. In the illustrated arrangement, the fan assembly  100  is adapted for mounting on a ceiling for projecting airflow in generally downward and outward directions. In one configuration, the fan assembly  100  is suitable as a speed-adjustable ceiling fan for generating high air volume flow at high blade rotation speeds. The fan assembly  100  comprises an outer housing  200 , which includes an annular upper housing portion  210  and the outer housing  200  being louvred with a plurality of annular airflow-directing frames in the form of concentric vanes  300  mounted to the housing  200 . Each vane  300  is configured with a lower rim  310  and an upper rim  320  of different diameters so that a sloped blade-like annular frame  330  is defined therebetween. In one configuration, the vanes  300  are coaxially mounted relative to each other and to the upper housing portion  210  in a vertically overlapping manner so as to define airflow passageways  168  and outlets  170 . In the preferred embodiment, the outer housing  200  is louvred with three such vanes  300  vertically connected relative to each other in an overlapped manner. In an alternative embodiment, the outer housing  200  is louvred with two such vanes  300  vertically connected relative to each other in an overlapped manner. In yet another alternative embodiment, only one vane  300  is provided and mounted to the outer housing  200 . While the outer housing  200 , upper housing  210  and vane(s)  300  of the fan assembly  100  have been described to be provided with annular configurations, it is to be understood that these features of the present invention are not limited to such circular shapes and that rectangular, ovular, square, pentagonal, hexagonal, octagonal and other non-circular shapes may also be used for the fan assembly  100 , the outer housing  200 , the vane(s)  300 , impeller  400  and any other parts of the fan assembly  100 . In the preferred embodiment, a rotating impeller  400 , in the form of a centrifugal impeller, is mounted internally within the outer housing  200  for generating streams of outflow air between the vanes  300  and an electric motor  120  is compactly seated within the impeller  400 , which acts as a housing for the motor  120 . It is intended that streams of outflow air through the louvred sections (vanes  300 ) of the outer housing  200  are a combination of internal and external air flows, wherein the latter involves entraining surrounding air along the outer housing  200  together with serial Coanda air flow effects to improve airflow volume and velocity, as will be explained in detail below. 
     Light cover and fitting(s)  240 ,  242  of any suitable shape and configuration may be installed on a lower portion  230  of the fan assembly  100 . In one example, a mounting plate  110  is affixed to the lowest-positioned vane  300  for mounting, for example, motor mounting bracket  112 , LED light fittings  242  and light fitting cover  240 . In some embodiments, the light fitting cover  240  is in the form of a dome which generally encloses the lower portion  230  of the fan assembly  100  so as to conceal components of the fan from view when in use and to provide a visually attractive appearance. The light fittings  242  can include an array of LED&#39;s with associated driving circuitry, fluorescent lamps or other light emitting elements, and would typically include a translucent diffuser (not shown) so as to give the fan assembly  100  an attractive appearance. Details of the light fitting do not need to be described in detail as they can be the same as those commonly used in the art. It is preferred that the outer periphery of the light cover and/or fitting(s)  240 ,  242  does/do not extend beyond a lower rim  310  of the lowest-positioned vane  300  so as to not have any influence on air flowing over the vanes  300 , as will be explained in more detail below. 
     The upper housing portion  210  and the one or more vane(s)  300  of the outer housing  200  define an internal chamber  220  within which is located the impeller  400  and the electric motor  120 . The impeller  400  is mounted on an impeller shaft  122 , which is coaxially mounted to and driven by the electric motor  120 . In one embodiment, the impeller  400  is a centrifugal impeller. In other embodiments, the impeller  400  may be of any suitable impeller with impeller blades  420  configured to draw ambient air and generate air streams in a generally outward direction. In the preferred embodiment, the impeller  400  is configured to generate air streams in a radially outward direction that is generally, perpendicular to a vertical axis, in use. In one embodiment, the impeller  400  is axially mounted to the impeller shaft  122  and the motor  120  by way of an impeller mount  402  located between the impeller  400  and the motor  120 . In some configurations, the impeller  400  is mounted above the motor  120  with the motor  120  nestled within a hub of the impeller  400  (which will be discussed in detail in a later section), while in other configurations, the impeller  400  is mounted below the motor  120 . It is preferred that the impeller shaft  122  is hollow so that it can carry electrical conductors (not shown) for the light fitting(s)  242 . The fan assembly  100  includes a down rod  140 , which is fastened to a ceiling bracket (not shown) at one end and coupled to the impeller shaft  122  at the other end. The fan assembly  100  is also provided with motor mounting brackets  112  which in use secure the motor  120  to the outer housing  200  and/or vanes  300 . Details of the preferred impeller design will be described in a separate section below. Mounting the motor  120 , impeller  400  and the housing  200  along the same vertical impeller shaft  122  improves the ease of assembly during manufacturing and improves stability of the fan during operation. 
     In the illustrated arrangement, an upper rim  214  of the upper housing portion  210  has an opening  222  defining an airflow inlet  224  to the internal chamber  220 . The opening  222  is configured to receive a vent  130  in the form of a shroud shaped with sweeping curved airflow passageways to direct and/or draw inlet airflow  170  to an inlet of the impeller  400  which is located beneath the vent  130  when in use so as to reduce turbulent airflow at the inlet  224 , which in turn improves volume of inlet airflow and performance of the impeller  400 . Moreover, the vent  130  can be configured so as to minimise any gaps between the vent  130  and blades of the impeller for the purpose of reducing pressure loss (air leakage) around entrance to the impeller  400  as well as any noise caused by the leakage while improving performance and efficiency of the impeller  400  at lower RPM ranges. In one configuration, the vent  130  is adapted to direct air to flow through openings located closer to an outer edge of the vent  130 . It is to be understood that while inlet  224  is the primary airflow inlet for the fan assembly  100 , it is possible that air will also be drawn from other openings that are exposed to an airflow path to the impeller  400 . In some configurations, the vent  130  is not provided at the opening  222  for drawing inlet airflow  170 . 
     The louvred vanes  300  of the outer housing  200  define one or more annular outlet passageway(s)  168  leading to airflow outlet  170  from the internal chamber  220 . The outlet passageway  168  is defined by an annular gap  172  formed between adjacent vanes  300  or between the upper housing portion  210  and an adjacently mounted vane  300 . For example, the annular gap can be defined between a lower rim  212  of the upper housing portion  210  and an upper surface  340  of the sloped blade  330  of a vane  300  that is mounted immediately adjacent the upper housing portion  210 . In the preferred embodiment, additional annular outlet passageways  168  and outlets  171 ) are provided by annular gaps  172  formed between a lower rim  310  of the adjacently-mounted vane  300  and an upper surface  330  of a successive vane  300  and so on. Each annular gap  172  formed between successive sets of adjacent vanes  300  provides an additional airflow outlet  170 . The upper housing portion  210  can be spaced apart and coupled to the sloped blade  330  of the adjacent vane  300  by means of fixed-length spacer projections or sleeves  302  so as to maintain a constant outlet gap  172  therebetween. Similar spacer projections or sleeves  302  can be used to maintain a constant outlet gap  172  between adjacent vanes  300 . In some configurations, the sleeves  302  are formed on the underside of the housing  200  and/or vanes  300 . 
     It is preferable that the gap  172  between the upper housing portion  210  and the sloped blade  330  of the vanes is evenly spaced and has a uniform height of about 20 mm or less. In the preferred embodiment, the height of the gap  172  is about 15 mm, and more preferably about 10 mm. In other embodiments, the height of the gap  172  is about 5 mm. In some configurations, the positioning of the vanes  300  and/or the upper housing portion  210  and its adjacent vane  300  is configured such that annular gaps  172  of different heights are used. For example, the fan assembly  100  may have an outer housing  200  configured with three sets of annular gaps  172  having gap heights of about 11 mm, 9 mm and 7 mm, respectively. In other configurations, the fan assembly  100  may have an outer housing  200  that is configured with two sets of annular gaps  172  having gap heights of about 15 mm and 10 mm, respectively. It is to be understood that while the airflow outlet(s)  170  have been described to be annular in the preferred embodiment, non-annular and linear outlets may also be used if desired. 
     In the preferred embodiment, the fan assembly  100  is provided with a plurality of vanes  300  of increasing diameters and each vane  300  being coupled in a vertically overlapping manner to an upper surface  340  of the sloped blade  330  of a lower, successive, vane  300 . In one embodiment, the fan assembly  100  is provided with two vanes  300 , while in other embodiments the fan assembly  100  is provided with three or more vanes  300 . In some configurations, the outlet gap  172  between vanes  300  differs in height when compared with the outlet gap  172  defined between the upper housing portion  210  and the adjacently mounted vane  300 . In the preferred embodiment, the upper rim  320  of each vane  300  has a smaller diameter than the lower rim  310  of each vane, which allows the sloped blade  330  to have a generally upward-facing upper surface  340  and a generally downward-facing lower surface  350 , when mounted to a ceiling in use. The upper surface  340  forms part of an outer surface of the vanes  330 . In some configurations, the sloped blades  330  may have a width in the radial direction of about 40 mm, and preferably a minimum width of about 40 mm, though the sloped blade  330  may have any desired width. The vanes  300  are configured to be about 2 mm thick or of any suitable thickness so as to allow the vanes  300  to be readily mounted to the upper housing portion  210  and mounted to successive vanes  300  of greater diameters in a vertically overlapping manner while allowing for the formation of outlet gaps  172 . 
     In one embodiment, as shown in  FIGS. 17 and 18 , the overlapping portions between adjacent louvred vanes  300  (and/or an overlapping portion between the upper housing portion  210  and its adjacent louvred vane  300 ), which define the outlet passageway  168  are substantially parallel relative to each other. In another embodiment, the overlapping portions, and hence the outlet passageway  168 , are divergent from an inlet end to an outlet end, which means that the gap height at the outlet end is larger than the gap height at the inlet end, so as to provide favourable airflow pressure and velocity profiles at the outlet  170 . 
     Each sloped blade  330  has a leading edge  360  which is located in or adjacent to an entrance of the annular outlet passageway  168  and a trailing edge  370  which is located at an end of the vane  300  opposing the leading edge  360 . As best seen in  FIG. 17 , the leading edge  360  of each vane  300  is located radially inwardly of a lower rim  212  of the housing portion  210  or the lower rim  310  of the vane  300  by a distance of about 2 to 20 mm and preferably about 10 mm (as measured tangentially relative to the outer surfaces of the vane  300 ). Air stream from the chamber  220  flows through the annular outlet passageway  168 , through the outlet  170  and passes over the upper surface  340  of the sloped blade  330  from the leading edge  360  to the trailing edge  370 . 
     The outlet gap  172  defined between the upper housing portion  210  and the adjacent vane  300  as well as any outlet gap(s)  172  defined between said adjacent vane and any successive vanes  300  direct exit airflow from within the internal chamber  220  to the air outlet(s)  170 . In an arrangement with a plurality of vanes  300  having comparable sized outlet gaps  172 , the upper surface  340  of the lowest-mounted vane  300  of the fan assembly  100  will have the greatest airflow and therefore serve as a primary air outlet  174  of the fan assembly  100  in use. As will be described in detail below, the upper surface  340  and lower surface  350  of each vane  300  serve important functions in dictating the flow characteristics of air streams from the impeller  400  to the ambient. In the preferred embodiment, the upper surface  340  of each vane  300  is configured with a Coanda surface  342  so as to create a low pressure area at an air inlet immediately preceding the upper surface  340  during use to entrain ambient air into a stream of outlet air, thereby amplifying the magnitude of airflow at the outlet  170  (the Coanda effect). 
     Each Coanda surface  342  of the vanes  300  is configured so as to operate to direct air towards a successive one of said Coanda surfaces  342  of respective vanes  300 . For example, with reference to  FIG. 18 , airflow leaving the Coanda surface  342 A of a first vane  300 A is drawn to the Coanda surface  342 B of a second vane  300 B and additional ambient air  192  is entrained into the subsequent output airflow  190 . It has thus been found that increased airflow can be achieved by using multiple Coanda surfaces effectively operating in series. In the preferred embodiment, the output airflow  190  leaving the second vane  300 B is drawn to a further Coanda surface  342 C of a third vane  300 C which further increases the volume of ambient air  192  entrained by the exit airflow and velocity of the resultant airflow  190 . Each gap  172  formed between the respective vanes  300 A,  300 B,  300 C further increases the pressure drop of the exit airflow and enhances the drawing of ambient air into the resultant airflow. The use of multiple Coanda surfaces in this way significantly increases airflow volumes at the primary air outlet  174  (the primary outflow air  194 ), thereby improving the airflow volume and velocity profiles of the fan assembly  100 . 
     In one embodiment, the entire upper surface  340  of the sloped blade  330  constitutes the Coanda surface  342 . The Coanda surface  342  is convex and configured with a radius of the convex curvature of between about 300 mm and 400 mm. The convex curvature of the Coanda surface  342  helps guide airflow moving over the Coanda surface  342  towards a subsequent, lower, Coanda surface  342  in a series. Coanda surfaces  342  in the preferred embodiment are vertically arranged relative to each other and extend downwardly with an angle of less than 90° relative to a vertical axis. Preferably, the downward extending angle of the Coanda surface  342  is between about 20° and about 40°, more preferably between about 24° and 38°, including about 31° and 36°. In some configurations, the downward extending angle of a subsequent downstream Coanda surface  342  has a different downward extend angle than that of the preceding (upstream) Coanda surface  342 . In the preferred embodiment, all the Coanda surfaces  342  in the series of vertically arranged vanes  300  have a convex curvature. In some configurations, the vanes, and hence Coanda surfaces  342 , are positioned relatively offset to each other and arranged to be partially overlap when seen from a plan view. This arrangement improves the flow of the air stream from one Coanda surface  342  to the next in series. In one configuration, the upper surface  340  of the sloped blade  330  and hence the Coanda surface  342  of one or more vanes  300  is shaped with aerofoil contours to enhance the Coanda effect by reducing air resistance and increasing the entrainment of ambient air  192  into the outlet airflow  190 . The Coanda surface  342  may also be said to be cambered about its mid-axis. In some configurations, the vanes  300  are provided with rounded leading edges  360  and tapering trailing edges  370  to enhance aerodynamic flow characteristics. 
     The Coanda effect may also be achieved with one or more upper surfaces of each vane  300  being configured with flat Coanda surfaces  342 , though the angle of the exit airflow from each flat Coanda surface  342  may differ from vanes in which the Coanda surfaces  342  are convex to assist with entrainment of ambient air  192  and with directing the flow of air stream from one Coanda surface  342  to another in the series. In an alternative embodiment, all the Coanda surfaces  342  are flat. This configuration reduces manufacturing complexity and cost. 
     The vanes  300  are arranged so that they are located, in use, in the path of the exit stream of air from the impeller  400 . The lower surfaces  350  of each vane  300  function as deflectors positioned downstream of the impeller  400  to divide the exit air stream into one or more separate streams of air, each routed through a respective outlet passageway  168  and gap  172  formed between adjacent vanes  300  or the upper housing portion  210  and its adjacent vane  300 . With reference to  FIG. 18 , the separated streams of air  180  are then directed by the lower surface  350  to pass through gaps  172  and over the respective Coanda surface  342 . The separated streams of air  180  augment the serial Coanda airflow stream  190  (as described above) to further enhance the flow rate and volume characteristics of the resultant airflow output  194  through the primary air outlet  174  from the fan assembly  100 . 
     The dimensions of the vanes  300  can be chosen so as to optimise airflow. The length of the vanes  300  (as measured in tangentially) can be varied in accordance with the overall size of the fan assembly  100 . In the embodiment as shown in  FIGS. 11 to 20 , three additional vanes  300  are mounted to the upper housing portion  210  to effectively produce three Coanda surfaces  342 . It is thought that additional vanes  300  could be incorporated into the fan assembly  100  in order to further increase volumes of entrained air. However, additional vanes  300  could lead to manufacturing complexities and also have undesirable aesthetic effects on the overall appearance of the fan assembly  100 . 
     The synergistic effect of 1) multiple Coanda surfaces  342  of the upper surfaces  340  working in a series to entrain ambient air  192 , and 2) supplementing said Coanda airflows  190  with additional streams of airflow  180  from the impeller  400  substantially improves the overall performance of the fan assembly  100 . With reference to  FIG. 17  for instance, resultant airflow velocity of about 6.4 m/sec has been achieved at the primary air outlet  174  of a third vane  300 C with an impeller of 400 mm in diameter operating at about 620 revolutions per minute. This airflow velocity is significantly higher than that of a stream of air leaving an outlet  170  of the first vane  300 A. Referring to  FIGS. 25A to 25C , which relates to time-based sectional flow profile comparisons of initial to tertiary air flow phases of fan assemblies embodying the invention having one, two and three Coanda surfaces, it can be seen that having multiple Coanda surfaces working in series improved the volume of surrounding air entrained by the fan assembly as well as airflow velocity of the fan assembly at the primary outlet airflow. The Coanda surfaces also serve to direct the exit airflow in a substantially downward and outward direction to a user below. 
     In the illustrated arrangement, the upper housing portion  210  is formed as a surface of revolution about the axis Y, although this is not essential. It is also preferred, that the inner and outer surfaces of the housing  200  are aerodynamically shaped so as to enhance production of generally laminar flow to the outlets  170  and the primary air outlet  174 . The curved configuration of the upper and lower surfaces  340 ,  350  of the sloped blades  330  of the vanes  300  provide smooth airflow pathways and also enhances laminar flow to the outlets  170 ,  174 . In one configuration, an internal leading edge of the sloped blades  330  is configured with an annular shape and centred so that the impeller  400  can rotate within its required tolerances. In one embodiment, the housing  200  and the vanes  300  are configured such that an outlet passage downstream of the impeller  400 , defined between the inner surface of the upper housing portion  210  and the upper surface  340  of the respective vane  300 , tapers gradually towards the opening  170 . This increases airflow velocity and again promotes laminar flow. 
     In some embodiments, the housing  200  may include mounting elements or posts, ribs or the like (not shown) which interconnect the various parts. Typically the upper housing portion  210  would be supported by the stationary down rod  140  and ceiling mounting brackets, and the one or more vanes  300  are supported from it. It will be appreciated that the upper housing portion  210 , the one or more vanes  300  and any light fitting are all stationary. 
     In a further embodiment, a plurality of adjustable vanes  300  are instead mounted on or adjacent to the lower rim  212  of upper housing portion  210 . The adjustable vanes  300  overlap one another so that they can be adjusted in orientation whilst still maintaining sufficient outlet gaps  172  allowing outflow of air. It would, of course, be possible to provide the vanes in a multiple Coanda surface arrangement similar to that shown in  FIGS. 11 to 20 . In use, the vanes  300  are adjustable in orientation relative to the Coanda surface(s)  342  so as to vary the angle of the air stream which leaves the Coanda surface  342 . In one configuration, the adjustable vanes  300  are connected by means of pivotal connections which enable the adjustable vanes  300  to pivot about axes perpendicular to the impeller axis Y and generally tangential to the lower rim  310  of the vanes  300 . The vanes  300  can be coupled to a linkage system (not shown) which can be operated by a servo-motor (not shown) in order to adjust their orientation. It is envisaged that this would be an option available to a user from a control unit (not shown) or a remote controller in order to vary the airflow distribution in a room. 
     With reference to  FIG. 24 , in an alternative embodiment, guides in the form of arcuate deflectors  390  which are provided circumferentially between the annular outlet passageways  168  and/or outlet gaps  172  on the sloped blade  330  of the vanes  300  to direct and guide the outlet airflow  180 ,  190  to flow in an outward direction. In one configuration, the outward direction is at a radial angle of 90° with respect to a tangent of an outer edge of the sloped surface  340  or the Coanda surface  342 . In the illustrated embodiment, the arcuate deflectors  390  span across two adjacent vanes  300 . It is to be understood that the deflectors  390  may occupy one vane  300  or spread across a plurality of vanes  300 . The deflectors  390  as shown in  FIG. 25  are arcuate as seen from a plan view, however linearly configured deflectors  390  may also be used if desired. The arcuate deflectors are attached to the underside of the vanes and span from leading edge to trailing edge of the same vane. 
     In  FIG. 16 , the basic operation of the fan assembly  100  is such that the motor  120  drives the impeller  400  so that it rotates about impeller axis Y. This causes air to be drawn into the inlet  130  and flow through outlets  170 ,  174 . The internal surfaces of the internal chamber  220  and the shape of the gap  172  between the upper housing portion  210  and the upper surface  340  of the vanes  300  are such that the stream of air  180  passing through the outlets  170 ,  174  has laminar flow or substantially laminar flow. The stream of air  180  passing over the Coanda surface  342  experiences the Coanda effect so that it moves adjacent to the Coanda surface  342  and is discharged into the room below in a generally downward and outward direction or to a Coanda surface of a subsequent vane mounted in series. As described above, it has been found that significant improvement in performance can be obtained by providing multiple Coanda surfaces  342  which effectively operate in series so as to lead to significantly higher flow velocity and volume of ambient air Which is entrained into the air flowing from the housing  200 . The parts which form the housing  200  and vanes  300  could be moulded from plastics material such as polystyrene or ABS. Alternatively, they could be formed from spun or pressed metal such as aluminium. 
     Impeller Design 
     Impeller for use with a preferred embodiment of the invention will now be described with reference to  FIGS. 20 to 23 . While any suitable impeller which draws ambient air from an axial direction and generates air streams in an outward direction that is generally orthogonal to the axial direction may be used with the fan assembly  100  of the present invention, a centrifugal type impeller is used in the preferred embodiment. A centrifugal impeller can be defined as an impeller configured with an annular flow path that is substantially parallel to the axis of rotation at an inlet and substantially perpendicular to the axis of rotation at an outlet. 
     In the preferred embodiment, the impeller  400  comprises a rotatable impeller hub  410 , which is mountable to the motor  120  by way of an impeller mount  402 , to which the impeller hub  410  is fastened. The impeller hub  410  is of a general dome shape having a raised centre in the form of a hub dome  412  and the height of hub  410  transitions smoothly from its highest point at or about the hub dome  412  to its lowest point which is at the peripheral (circumferential) edge of the hub  410 . In one configuration, the hub  410  is seated above the motor  120  when assembled and also acts as a housing for concealing the motor  120  however, it is also possible for the motor  120  to be mounted above the impeller  400  closer to a ceiling. The hub  410  is provided with a central opening  414  for receiving the down rob  140  or impeller shaft  122 . In one configuration, the impeller hub has a diameter of about 400 mm, though it is to be appreciated that the impeller embodying the present invention can be configured according to any suitable dimension. 
     As can be seen in  FIGS. 20 to 23 , the impeller  400  comprises two sets of blades positioned upon the hub  410 . A set of arcuate continuous blades  420  is evenly spaced on the hub  410 , each continuous blade is positioned at a root end  434 , which is located proximate the centre of the hub  410 , and extends to a peripheral edge  416  of the hub  410 . A set of arcuate splitter blades  422  is positioned between adjacent continuous blades  420 ; splitter blades  422  have shorter blade lengths and serve to reduce the gap (air channel) between adjacent continuous blades  420  so as to prevent excessive diffusion of air flow as the air channels increase in size with the increasing impeller hub circumference from the hub dome  412  to the periphery edge  416 . In the preferred embodiment, the impeller blades  420 ,  422  are curved along their lengths (towards the left when viewed from the perspective of the blade root end  434 ) so as to be optimised for clockwise rotation. In other embodiments, the curvature of the impeller blades  420 ,  422  is optimised for anti-clockwise rotation. The height of the continuous blades  420  vary along the blade length starting with maximum blade height at the blade root end  434  and slopes to a lowest blade height at the blade tip end  432 . The variance of blade height along its length allows the impeller blades  420 ,  422  to fit within the outer housing  200  and louvred vanes  300  of the fan assembly  100 . A blade step  430  in the form of a kink in an upper portion of each blade  420 ,  422  is provided to accommodate the position of an adjacent louvred vane  300 . This reduces any air channel gap formed between the blades  420 ,  422  and corresponding undersides of the upper housing  210  and/or louvred vanes  300  to improve air flow through outlet passageways  168  formed by the outer housing  200  and reduce turbulence. In one configuration, the blade step  430  has a forward leaning edge, in which the top edge of the step  430  has a greater radius than an inside edge the step  430 . The angle of the top edge of the blade step can be configured to suit an angle of the outlet passageways  168  formed by the outer housing  200 . 
     The impeller blades  420 ,  422  can be said to have a twisted profile along the blade length. The continuous blade  420  can be divided into three distinct sections, namely (1) a blade root portion  424 , which refers generally to a portion of the blade  420  that is closest to the blade root end  434  (2) a blade mid portion, which refers generally to a mid-portion of the blade  420 , and (3) a blade end portion, which refers generally to the portion of the blade that is close to the blade tip end  432 . In one embodiment, as can be clearly seen in  FIG. 22 , the blade root portion  424  is configured with the greatest blade height and comprises a blade wall having a forward lean (leaning forward in the direction of clockwise rotation). The blade mid portion  426  extends continuously from the root portion  424  with reduced blade height and the blade wall transitions to a generally neutral lean (no leaning). The last third of the blade length, the blade end portion  428  extends continuously from the blade mid portion  426 , with its blade height reducing, with increasing radial distance from the centre of the hub  410 . In one configuration, the blade wall of the blade end portion  428  transitions from the neural lean of the blade mid portion  426  back to a forward lean. 
     The height and leaning characteristics of the mid portions  426  and end portions  428  of the splitter blades  422  are generally consistent with corresponding portions of the continuous blades  420 , though the root portion  423  of the splitter blades are positioned further away from the impeller hub centre and configured with a blade wall that is lower than the walls of adjacent continuous blades  420  and substantially parallel relative to a horizontal plane. In one configuration, the tip end  432  of the impeller blades  420 ,  422  overhang (protrudes) from the periphery edge  416  of the impeller hub  410  for the purpose of improved fit with the housing  200 . It is to be understood that profiles of the impeller blades  420 ,  422  are not limited to the examples described as the blade profiles should be configured to correspond with the shape and configurations of the annular outlet passageways  168  defined by the outer housing  200  and louvred vanes  300  so as to reduce any gaps formed therebetween, thereby reducing undesired turbulence effects. 
     In use, the impeller is configured to rotate in a clockwise manner and ambient air is drawn into an upper portion (centre) of the dome shaped impeller hub  410  from the airflow inlet  224 . Air at the inlet is travelling in a direction parallel to the axis of the impeller rotation (vertically, when the impeller is mounted in a ceiling fan) and enters the impeller hub  410  closest to its centre and the root portions of the continuous blades  420 . Air is subsequently driven forward by the impeller blades  420 ,  422  from the blade root end  434  to the blade tip end  432 . As air travels through the impeller  400 , the flow direction changes by centripetal acceleration and by following the profile of the blades  420 ,  422  so that the flow direction changes from being parallel to the axis of rotation to being perpendicular to it in all directions. The outflow air stream  180  leaving the tip end  432  of the blades travels through the outlet passageway  168  defined between outlet gap  172 . 
     While the centrifugal impeller  400  of the preferred embodiment has been described to operate in a clockwise rotation, it is to be understood that the impeller  400  is not limited to this orientation and may also be operated in an anti-clockwise rotation. In some experiments, it has been observed that operating the impeller  400  in the anti-clockwise rotation provided higher airflow volume and velocity at the primary airflow outlet. 
     Additional embodiments of a centrifugal impeller  400  are shown in  FIGS. 26 to 39 ,  FIGS. 40 to 53  and  FIGS. 54 to 57 , experimental data supporting the efficacy of the additional embodiments are shown in  FIGS. 58 to 66 . More specifically,  FIGS. 26 to 39  show a centrifugal impeller  400 , labelled in the Figures as the R7 variant, for use with a housing  200  and three layers of vanes  300  as described earlier, and  FIGS. 40 to 53  show an impeller  400 , labelled in the Figures as the R8 variant, for use with a housing  200  and, two layers of vanes  300 .  FIGS. 54 to 57  show various views illustrating a single continuous blade  420  of the R7 variant impeller  400 .  FIGS. 58 to 62  show fluid modelling data comparing the performance of the R7 and R8 variants with earlier impeller designs in relation to relative velocity, absolute velocity of airflow leaving the fan assembly  100  and noise measurements, while  FIGS. 63 to 66  show a comparison of key measurement parameters for an R7 variant impeller  400  having chord angles of 30°, 35°, and 40°. Referring to  FIG. 54 , the chord angle refers to the angle formed between a first chord extending from the root end  434  of the blade  420  with respect to an arcuate path followed by the blade  420  and a second chord extending from the centre of the hub  410  and the tip end  432  of the blade  420 . 
     Returning to  FIGS. 26 and 39 , the R7 variant impeller  400  comprises a rotatable impeller hub  410 , which is mountable to the motor  120  by way of an impeller mount  402 , to which the impeller hub  410  is fastened. The impeller hub  410  is of a general dome shape having a raised centre in the form of a hub dome  412  and the height of hub  410  transitions smoothly from its highest point at or about the hub dome  412  to its lowest point which is at the peripheral (circumferential) edge of the hub  410  (see  FIG. 34 ). The impeller  400  comprises a single set of continuous blades  420  positioned on the hub  410 . Each continuous blade  420  extends from a blade root end  434 , which is located closer to a central hub dome  412 , radially outwards towards the hub peripheral edge  416 , during which the blade  420  transitions between three distinctive geometry stages—a blade root portion  424 , a blade mid portion  426  and a blade end portion  428 . 
     At the blade root portion  424 , the blade  420  is configured with a “positive lean”, that is a top portion of the blade root portion  424  is curved toward the direction of a clockwise rotation of the impeller  400  so as to be substantially flattened at an end closer to the hub dome  412 . This initial curvature and configuration of the blade  420  helps draw airflow from the vent  130  or an air inlet downwardly into the impeller  400  and disperse the airflow through channels formed between adjacent blades  420 . The top portion of the blade root portion  424  and its positive lean configuration results in the airflow channels formed between adjacent blades  420  being at least partially covered by the blade root portion  424 , which reduces the occurrence of air flowing between the channels and therefore reduces turbulence. The positive lean of the configuration of the blade root portion  424  progressively adjusts back to a neutral position  450  along the length of the continuous blade  420 , in which the blade  420  is substantially upright as opposed to lean any one side to the other. It is at or about this neutral position  450  of the blade  420  that the blade  420  then turns into a “negative lean” configuration. Negative lean can be understood as the blade  420  body curving away from the direction of a clockwise rotation of the impeller  400 . The transition between the positive and negative lean geometries of the blade  420  along its longitudinal length provides the appearance that the blade  420  twists along its length between the blade root end  434  and the blade tip end  432 . It has been found that the negative lean configuration of the mid portion  426  and end portion  428  of the blade  420  advantageously reduces noise pressure generated by the impeller  400  during use. 
     Referring to  FIGS. 54 to 57 , the positive lean of the blade root portion  424  is be greater than the negative lean of the blade mid portion  426  and the blade end portion  428 . In one embodiment, the blade  420  transitions from the position lean configuration to the negative lean configurations at or about a neutral position  450 , though it is to be understood that the blade  420  may also be configured so as to continue in a neutral upright position for some distance before transitioning to a negative lean configuration at the blade mid portion  426  and/or the blade end portion  428 . It is to be understood that the described impeller blade  420  configuration has been designed for a clockwise rotating impeller and the geometries and configurations may be inversed for an anti-clockwise rotating impeller. 
     The continuous blade  420  also comprises spine portions  442 ,  440 ,  444  which follow the contours of the blade body along the length of the blade  420 , though in general the spine of the blade  420  reduces in height along the length of the blade from the blade root end  434  to the blade tip end  432 . Specifically, the root portion spine  442  maintains a substantially equal height along the root portion  424  of the blade before the transition to neutral point  450  and/or negative leaning mid portion  426  of the blade so that the root portion  424  of the blade covers a substantial portion of the vent inlet  130 . It is noted that the root portion spine  442  maintains the height of the blade  420  across the vent inlet  130  even though the impeller hub  410  is sloping towards its periphery edge  416 . The mid portion spine  440  of the blade mid portion  426  then progressively reduces in height from or about the neutral point  450  toward the blade end portion  428  and the blade tip end  432 . In the R7 impeller variant, as shown in  FIGS. 30 to 39 , a blade step  430  as described previously is similarly provided between the blade mid portion  426  and the blade end portion  428  so as to accommodate an adjacent louvered vane  300  and provide improved airflow through the adjacent louvered vane  300 . 
     The R7 variant impeller  400  comprises a plurality of like continuous blades  420  described above evenly positioned on the impeller hub  410  about the hub dome  412 . In one configuration, the impeller comprises 16 like blades  420 .  FIGS. 33 to 39  show sectional views of the blades  420  as assembled on the impeller hub  410 . Referring now to  FIGS. 63 to 66 , it has been found that the chord angles of the blades  420  influence the output velocity of the impeller  400  at the blade tip end  432 . The chord angle as used in the context of the impeller blades  420  of the present invention refers to the angle which governs how far the blade tip end  432  curves backwards from the blade root end  434  and/or the blade root portion  424  as shown in  FIGS. 54 and 63 . More specifically, the chord angle measures an angle between a linear part of the blade root portion  424  and a radial line drawn between the blade tip end  432  and the centre of the impeller hub  410  (the centre of rotation). It has been found, as seen in  FIGS. 64 to 66 , that a chord angle of 40° resulted in significant attenuation of noise pressure. Between the chord angles of 30° to 40°, it has been found that 40° provided an overall reduced in noise while retaining satisfactory absolute and relative airflow velocity profiles. 
     Referring now to  FIGS. 40 to 53 , another embodiment of the impeller  400  known as the R8 variant is illustrated. The R8 variant of the impeller  400  has been designed to work with a fan assembly  100  having only two layers of louvred vanes  300 . In this configuration, it has been found that the blade step  430  is no longer necessary to ensure sufficient airflow through the outlet gap  172  between the vane blades  330 , and the air outlets  170 . Therefore the R8 variant of the impeller  400  is similar to that of the R7 variant impeller  400  with the primary difference being that the continuous blades  420  of the R8 variant impeller  400  has a smooth transition of the blade body and blade spine between the blade mid portion  426  and the blade end portion  428 , as seen in  FIGS. 44 to 46 , without requiring a blade step  430 . 
       FIGS. 58 to 62  show simulation outcomes based on computational fluid dynamics (CFD) modelling, which were conducted to test a number of impeller designs, including those of the R7 and R8 impeller variants, in relation to airflow velocity and noise performance parameters of the fan assembly  100  in accordance with the present invention. In comparison with the benchmark performance of an earlier described impeller, seven additional impeller configurations were tested. According to the performance output, the R7 and R8 impeller variants as described advantageously produces a most desirable balance of airflow velocity output at the impeller blade tip end  432  and the level of noise produced. 
     Extensive CFD simulations and testing indicate that there are balancing and trade-off considerations between power efficiency and overall airflow throughput between various configurations of ceiling fan assemblies embodying the present invention. Referring now to  FIGS. 67 to 74 , further CH) simulations have been conducted with respect to the R7 variant impeller  400  as described above with a housing having annular louvred vanes  300  with three sloped blades  330 , and the R8 variant impeller  400  as described above with a housing having annular louvred vanes  300  with two sloped blades  330 . Overall, it has been found that increasing the outlet gap size generally resulted in a decrease in desired performance as in all cases, a smaller outlet gap results in lower power consumption but still produced the highest flow ratio and lowest peak noise pressure. All else being equal; the combination of impeller design and louvred vane configurations of the R8 fan assembly variant as described earlier utilised up to 25% less power while achieving between 6% to 10% better flow ratio results when compared with the impeller design and louvred vane configurations of the R7 fan assembly variant as described earlier. However, reducing the number of sloped blades  330  in the louvred vanes  300  further, as seen in  FIGS. 75 to 77  clearly resulted in reduced airflow performances while improving overall power usage and peak noise performance. 
       FIGS. 78 to 90  show another variant of the impeller  400  that is suitable as a standalone impeller  400  or for generating airflow for a ceiling fan assembly  100 . The impeller  400  is similar in configuration with the R7 and R8 variants previously described, and comprises a rotatable impeller hub  410 , which is mountable to the motor  120  by way of an impeller mount  402 , to which the impeller hub  410  is fastened. The impeller hub  410  is of a general dome shape having a raised centre in the form of a hub dome  412  and the height of hub  410  transitions from its highest point at or about the hub dome  412  to its lowest point which is at the peripheral (circumferential) edge of the hub  410  (see  FIG. 83 ). 
     The impeller  400  comprises a single set of continuous blades  420  positioned on the hub  410 . Each continuous blade  420  extends from a blade root end  434 , which is located closer to a central hub dome  412 , radially outwards towards the hub peripheral edge  416  in an arcuate path. In the configuration as shown, each continuous blade  420  comprises three blade sections that follows an arcuate path; a first section that extends linearly towards the left side of the hub centre, a second section that curves substantially in an anti-clockwise direction when the impeller is viewed from above and a third section that extends substantially linearly towards the tip end  432  of the blade. It is to be appreciated that the reverse configuration would also be possible in other embodiments. Each blade is configured with a chord angle of between 30° and 40°. Each blade has, as measured at a top portion of its spine, a height that reduces along the length of the blade from the root end  434  to the blade&#39;s tip end  432 . In some configurations, the height of the spine of each blade maintains a uniform height in a section that overlaps with the opening  222  or inlet vent  130  of the housing  200 , when in use. Unlike the R7 and R8 impeller variants, the impeller  400  as shown in  FIGS. 78 to 90  do not have a geometrical twist or “lean” along the length of each blade. Rather, each blade is configured to rise substantially vertically from the hub  410  as seen in sectional views shown in  FIGS. 80, and 85 to 90 . It has been determined that this design improves ease of manufacturing as no undercut moulding is required and the resulting impeller provides acceptable performances in comparison with the earlier described impeller variants. 
     Further Embodiments 
     In one embodiment, the fan assembly  100  is advantageously provided with an integrated heater configured to heat the air streams inside the internal chamber  220 . The heater may be in the form of a heating element or of any other suitable heater and provided with sensors and control circuitry for temperature control by a user. The heater unit is configured to be mountable to the fan assembly  100 , preferably within the internal chamber  220 , and connected to the same electrical system which powers the motor  120  and/or light fittings  242 . In other configurations, heating elements may be located below the outer housing  200  or mounted to a bracket under the motor  120 . The integrated heater works synergistically with the bladeless fan assembly  100  of the present invention as heated air streams in the internal chamber  220  and/or heated ambient air  190  around/under the outer housing  200  can be effectively circulated (and drawn, in the case of warm ambient air) by the high-volume and high-velocity laminar exit airflow resulting from the Coanda vanes working in series in the present invention. The incorporation of a heater in the fan assembly  100  advantageously allows the ceiling fan assembly  100  to be used in response to either warm or cool seasonal conditions—thereby extending the usefulness of the ceiling fan throughout the year. 
     Devices for filtering air can also be incorporated into the fan assembly  100 . Membrane-based filters such as High Efficiency Particulate Air (HEPA) filters can be installed at the airflow inlet  224  and/or proximate the outlet passageway  168  to filter pollutant particles from air streams drawn into the internal chamber  220  or airflow downstream of the impeller  400 , prior to the air being circulated external of the fan assembly  100 . In one embodiment, filter members may be installed relative to the vent  130  of the airflow inlet  224  so that air can be filter upstream of the vent  130  or downstream of the vent  130  but before entering an inlet of the impeller  400 . In some configurations, an air ioniser, which uses electrical charge to filter pollutant particles in the ambient air, can be incorporated into the fan assembly  100 . In this regard, the air ioniser can be installed at the airflow inlet  224  and/or proximate the outlet passageway  168 . An air filter and/or air ioniser will work synergistically with fan assemblies  100  embodying the present invention to improve air quality of the room in which the fan is located as the fan assembly  100  actively draws and entrains ambient air into the output airflow for filtration purposes. Details of the air filter and ioniser do not need to be described in detail as they can be the same as those commonly used in the art. The ioniser power and control units are configured to be mountable to the fan assembly  100 , preferably within the internal chamber  220 , and connected to the same electrical system which powers the motor  120  and/or light fittings  242 . 
     Internet router and wireless connectivity capabilities can also be integrated into the fan assembly  100 . In one embodiment, a suitable on-board wireless network (Wi-Fi) chipset and/or circuit board can be mounted below the motor  120  and connected to the same electrical system which powers the motor  120  and/or light fittings  242 . It is to be understood that the wireless network chipset can be mounted internally or externally to the fan assembly  100  and located at any suitable mounting location so as to not have significant adverse influence on airflow characteristics of the fan assembly  100 . Wireless network chipsets may include any suitable chipsets that are compatible with standard Wi-Fi signal relay and transmission, as well as features such as the ability to establish local connectivity networks (wireless hot spots) and/or signal repeaters. Details of the wireless chipset do not need to be described in detail as they can be the same as those commonly used in the art. Ceiling fans are ideal carriers for the location of Wi-Fi routers for the transmission and relay of wireless network data due to their typically elevated positions in a room (which enhances network coverage and reach through a property). The combination of wireless network capabilities and ceiling fans work synergistically as it makes improved use of ceiling mounting spaces and reduces the need for separate network devices/repeaters throughout a property, reduce clutter and provide an aesthetically attractive and multi-functional device. In another embodiment, a Bluetooth and/or Wi-Fi enabled speaker is installed under fan assembly  100  so that devices can connect via Bluetooth and/or Wi-Fi to emit surround sound to the occupants, as the centre of a room environment is an ideal location for occupants to listen to a speaker. 
     Power saving features may also be incorporated into a ceiling fan embodying the present invention. In particular, motion sensors in the form of infra-red, sonar or image sensors, or any other suitable sensors, can be mounted to a lower surface of the fan assembly  100  so as to detect movement or human activity within the room in which the fan assembly  100  is mounted or a target area. The fan assembly  100  can be programmed to be powered on automatically and provide airflow in accordance with predetermined settings when human activity/movement is detected in the room or the target area. In one configuration, the fan assembly  100  is programmed to be powered down or turned off when no activity has been detected for a predetermined period of time. In one embodiment, the motion sensor(s) for detecting movement and occupancy can be mounted to or incorporated within the light cover  240  and connected to the same electrical system which powers the motor  120  and/or light fittings  242 . 
     Although the fan assembly  100  has been described to be applicable for use as a ceiling fan, it is to be understood that the fan assembly  100  can be equally suitable for use as a standing fan. In one embodiment, the fan assembly  100  is configured with reduced dimensions so as to be suitable for a table fan. In such embodiments, the down rod  140  can be coupled to a table mount having one or more arcuate arms which reach/contour(s) over the annular louvred vanes  300 . The table mount comprises a base for seating the fan assembly  100  on a table. In an alternative embodiment, the down rod  140  is removed and the fan assembly  100  is provided with a vertical member that is configured to be coupled, integrally or otherwise, to the lower portion  230  of the fan assembly  100  or to the light fitting cover (if light fittings are provided). The vertical member is connected at an opposing end to a base, which seats the fan assembly  100  on a table. In an alternative embodiment, the fan assembly  100  can also be configured as a pedestal fan (free standing). In this embodiment, mounting mechanisms similar to that described in relation to the table fan can be applied to the fan assembly  100  when used as pedestal fan, except dimensions of the fan assembly  100 , mounting mechanisms and pedestal bases will be adjusted accordingly. The fan assembly  100  can be rotated so that the airflow is directed to the direction that the occupant desires by means of a pivoting device connected to the vertical member. The techniques for incorporating a pivoting device in fan assembly or light fitting is known in the art and need not be described in detail. 
     Known techniques could also be adopted for reducing noise caused by the impeller  400  and airflows to and from the housing  200 . The techniques for incorporating these features in fan assembly or light fitting is known in the art and need not be described in detail. 
     While aspects of the fan assembly have been described for use in combination with each other in the preferred embodiments of the present invention, it is to be understood by a skilled person that some aspects of the present invention are equally suitable for use between different fan embodiments and/or as standalone inventions that can be individually incorporated into fan assemblies, ceiling fans or standing fans not described herein. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments. 
     Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. 
     
       
         
           
               
             
               
                   
               
               
                 LIST OF PARTS 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 fan/light 
                 2 
               
               
                   
                 ceiling 
                 4 
               
               
                   
                 housing 
                 6 
               
               
                   
                 upper housing portion 
                 8 
               
               
                   
                 Coanda surface 
                 10 
               
               
                   
                 lower rim 
                 11 
               
               
                   
                 base wall 
                 12 
               
               
                   
                 light fitting 
                 13 
               
               
                   
                 internal chamber 
                 14 
               
               
                   
                 lower rim 
                 15 
               
               
                   
                 impeller 
                 16 
               
               
                   
                 impeller shaft 
                 18 
               
               
                   
                 electric motor 
                 20 
               
               
                   
                 bracket 
                 22 
               
               
                   
                 curved skirt 
                 23 
               
               
                   
                 bearing 
                 24 
               
               
                   
                 upper surface 
                 25 
               
               
                   
                 upper rim 
                 26 
               
               
                   
                 inlet 
                 28 
               
               
                   
                 outlet 
                 30 
               
               
                   
                 impeller axis 
                 32 
               
               
                   
                 stream of air 
                 34 
               
               
                   
                 streams of entrained air 
                 36 
               
               
                   
                 inlet passage 
                 38 
               
               
                   
                 outlet passage 
                 39 
               
               
                   
                 housing 
                 50 
               
               
                   
                 flange 
                 52 
               
               
                   
                 annular outlet passageway 
                 54 
               
               
                   
                 first vane element 
                 56 
               
               
                   
                 second vane element 
                 58 
               
               
                   
                 leading edge 
                 60 
               
               
                   
                 second Coanda surface 
                 64 
               
               
                   
                 leading edge 
                 70 
               
               
                   
                 trailing edge 
                 72 
               
               
                   
                 trailing edge 
                 73 
               
               
                   
                 third Coanda surface 
                 74 
               
               
                   
                 modified fan/light 
                 78 
               
               
                   
                 adjustable vanes 
                 80 
               
               
                   
                 pivotal connections 
                 82 
               
               
                   
                 axes 
                 84 
               
               
                   
                 fan assembly 
                 100 
               
               
                   
                 mounting plate 
                 110 
               
               
                   
                 motor mounting bracket 
                 112 
               
               
                   
                 motor 
                 120 
               
               
                   
                 impeller shaft 
                 122 
               
               
                   
                 vent 
                 130 
               
               
                   
                 down rod 
                 140 
               
               
                   
                 inlet airflow 
                 160 
               
               
                   
                 annular outlet passageway 
                 168 
               
               
                   
                 air outlet 
                 170 
               
               
                   
                 outlet gap 
                 172 
               
               
                   
                 primary airflow outlet 
                 174 
               
               
                   
                 outflow air stream 
                 180 
               
               
                   
                 Coanda airflow 
                 190 
               
               
                   
                 entrained ambient airflow 
                 192 
               
               
                   
                 primary outlet airflow 
                 194 
               
               
                   
                 housing 
                 200 
               
               
                   
                 upper housing portion 
                 210 
               
               
                   
                 lower rim 
                 212 
               
               
                   
                 upper rim 
                 214 
               
               
                   
                 internal chamber 
                 220 
               
               
                   
                 opening 
                 222 
               
               
                   
                 airflow inlet 
                 224 
               
               
                   
                 lower portion 
                 230 
               
               
                   
                 light fitting cover 
                 240 
               
               
                   
                 LED light fittings 
                 242 
               
               
                   
                 housing collar 
                 250 
               
               
                   
                 vane 
                 300 
               
               
                   
                 sleeve 
                 302 
               
               
                   
                 lower rim 
                 310 
               
               
                   
                 upper rim 
                 320 
               
               
                   
                 sloped blade 
                 330 
               
               
                   
                 upper surface 
                 340 
               
               
                   
                 Coanda surface 
                 342 
               
               
                   
                 lower surface 
                 350 
               
               
                   
                 leading edge 
                 360 
               
               
                   
                 trailing edge 
                 370 
               
               
                   
                 deflector 
                 390 
               
               
                   
                 impeller 
                 400 
               
               
                   
                 impeller mount 
                 402 
               
               
                   
                 impeller hub 
                 410 
               
               
                   
                 impeller hub dome 
                 412 
               
               
                   
                 impeller hub opening 
                 414 
               
               
                   
                 impeller hub periphery edge 
                 416 
               
               
                   
                 impeller blade (continuous) 
                 420 
               
               
                   
                 impeller blade (splitter) 
                 422 
               
               
                   
                 split blade root portion 
                 423 
               
               
                   
                 blade root portion 
                 424 
               
               
                   
                 blade mid portion 
                 426 
               
               
                   
                 blade end portion 
                 428 
               
               
                   
                 impeller blade step 
                 430 
               
               
                   
                 impeller blade tip end 
                 432 
               
               
                   
                 blade tip projection 
                 433 
               
               
                   
                 impeller blade root end 
                 434 
               
               
                   
                 blade root portion spine 
                 442 
               
               
                   
                 blade mid portion spine 
                 440 
               
               
                   
                 blade tip portion spine 
                 444 
               
               
                   
                 blade neutral point 
                 450