Abstract:
A portable evaporative cooling apparatus includes a primary passage for delivering a primary air stream to an induction nozzle. A secondary passage that is substantially unobstructed extends from an ambient air inlet to the induction nozzle. A secondary air stream is induced through the secondary passage by the primary air stream and the primary and secondary air streams are ejected from the induction nozzle into the ambient air. An atomiser in the secondary passage, proximate the ambient air inlet, emits a fine spray of water into the secondary air stream. The mixing of the water spray and induced air flow is performed inside the induction nozzle, which also provides a physical and thermal barrier, and makes a completely cooled air stream available immediately outside the user, so the apparatuses may be placed close to the user&#39;s face, for example.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to personal cooling apparatuses employing the evaporative cooling principle. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is known in the art to provide a self-contained evaporative personal cooling apparatus that can be hand-held or, for instance, hung about a user&#39;s waist or neck. Such apparatuses comprise a water mister and a blower and often provide a two-stage cooling effect. In the first stage, flash evaporation of a finely divided water mist cools that air before it is blown over the skin, while in the second the air flow that carries moisture to the skin also increases the rate of evaporation of this moisture from the skin, for a wind chill effect. 
         [0003]    U.S. Pat. No. 6,371,388 describes a misting blower, secured about the waist of the user, in which a fine spray of water is provided adjacent to the blower&#39;s exhaust nozzle, such that the air and water spray mixing and cooling primarily takes place outside the nozzle outlet. However, where the outlet of such apparatuses may be placed closer to the user&#39;s face, for example, it would be advantageous that doing so would not compromise the cooling performance or create discomfort for the user. 
         [0004]    Moreover, in compact self-contained devices such as these, the fan is typically mounted directly on the output shaft of an electric motor, or gear motor, resulting in heat lost by the motor causing sensible heating of the air stream, before the air stream is subsequently humidified and cooled. 
         [0005]    It is an object of the present invention to overcome or substantially ameliorate the above disadvantages or, more generally, to provide an improved personal evaporative cooling apparatus. 
       DISCLOSURE OF THE INVENTION 
       [0006]    According to one aspect of the present invention there is provided a portable evaporative cooling apparatus comprising: 
         [0007]    an induction nozzle; 
         [0008]    a primary passage for delivering a primary air stream to the induction nozzle; 
         [0009]    an secondary passage that is substantially unobstructed and extends from an ambient air inlet to the induction nozzle, whereby a secondary air stream is induced through the secondary passage by the primary air stream and the primary and secondary air streams are ejected from the induction nozzle into the ambient air; and 
         [0010]    an atomiser in the secondary passage proximate the ambient air inlet for emitting a fine spray of water into the secondary air stream. 
         [0011]    Preferably the primary and secondary passages are bounded by substantially impermeable walls of a first housing. The walls may be rigid and formed of polymeric material, as by moulding. 
         [0012]    Preferably at least a first portion of the primary passage extends from the induction nozzle lengthwise adjacent to the secondary passage, and is separated from the secondary passage by a shared wall separating the primary and secondary passages. 
         [0013]    Preferably the first portion converges toward the induction nozzle. Preferably a second portion of the primary passage joins the first portion, the first portion is curved and the second portion is linear and extends adjacent to the tank. 
         [0014]    Preferably the induction nozzle and the atomiser are disposed at longitudinally opposing ends of the secondary passage, and the inlet is disposed generally transversely of a centreline of the secondary passage between the induction nozzle and the atomiser. 
         [0015]    Preferably the secondary passage is curved in its longitudinal direction, and the portion of the secondary passage adjacent the induction nozzle has a generally constant cross section throughout its length. 
         [0016]    The secondary passage may be bounded in part by the shared wall and in part by an external wall, the outer surface of which is exposed to ambient air. Alternatively, the secondary passage is bounded completely by the shared wall, the shared wall being tubular and disposed within an external wall, such that the primary passage surrounds the shared wall. 
         [0017]    Preferably the apparatus further comprises a water tank demountable from the apparatus, wherein the atomiser is mounted at a lower end of the tank, and a vented lid disposed in an upper end of the tank. The tank may be received in a recess in the housing disposed adjacent the second portion of the primary passage. The tank may be substantially surrounded by an insulator for reducing heat transfer through the walls of the tank. For instance, the tank may comprise a vacuum flask for holding chilled water. 
         [0018]    Preferably the atomiser is an ultrasonic atomiser. Alternatively, other types of atomiser, such as pump-actuated spray atomisers may be employed. 
         [0019]    A motor-driven oscillatory vane may be mounted to the first housing for projecting into the outlet stream from the nozzle so as to sweep the outlet stream back and forth. 
         [0020]    A second housing assembly may be demountably coupled to the first housing assembly, the second housing assembly comprising a fan for impelling the primary air stream and means for supplying power to the ultrasonic atomiser. 
         [0021]    This invention provides a personal evaporative cooling apparatus which is effective and efficient in operational use. The apparatus may be economically constructed due to an overall simple form which minimizes manufacturing costs and by offering an essentially modular design. The lengthwise mixing zone of the present invention has distinct advantages over the prior art, in which the air and water spray mixing and cooling takes place outside the nozzle outlet, well beyond the protected environment of the nozzle itself. The principal advantages of internal mixing, as opposed to external mixing, are (1) physical isolation of the mixing zone from disruption by ambient winds (2) a degree of thermal isolation of the mixing zone from the ambient air and, (3) more uniform mixing of the ambient air and water spray across the secondary passage. As the flash evaporation starts near the inlet to the secondary passage and is largely complete by the time it reaches the induction nozzle, the cooling effect at short range from the nozzle allows it to be placed closer to the user&#39;s face, for example, without depositing excessive moisture on the skin. Furthermore, the substantially unobstructed secondary passage contains no motor, or other heat source, that can compromise the cooling performance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: 
           [0023]      FIG. 1  is a schematic sectional view of a first embodiment of a cooling apparatus of the invention; 
           [0024]      FIG. 2  is a schematic section along plane  2 - 2  in  FIG. 1 ; 
           [0025]      FIG. 3  is a perspective view of the cooling apparatus of  FIG. 1 ; 
           [0026]      FIG. 4  is a schematic sectional view through a second embodiment of a cooling apparatus of the invention; 
           [0027]      FIG. 5  is a schematic section along plane  5 - 5  in  FIG. 4 ; 
           [0028]      FIG. 6  is a schematic section through a variant of second housing module of the invention; 
           [0029]      FIGS. 7 and 8  are schematic sectional views of third and fourth embodiments, respectively, of a cooling apparatus of the invention; and 
           [0030]      FIG. 9  is a perspective view of a fifth embodiment of a cooling apparatus of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Referring to  FIGS. 1 and 2 , a first embodiment of an evaporative cooler may be a hand-held cooling apparatus that, when upright (as shown) outputs a generally horizontal outlet stream of cool air and entrained water droplets for personal cooling. The apparatus comprises a first housing  10  having an upper portion  11  ergonomically designed to be conveniently cupped in the palm of a hand, allowing the user to then move the entire apparatus so as to direct the stream from the induction nozzle  12  back toward the user to a point of use. 
         [0032]    The housing  10  may be an assembly of rigid substantially impermeable walls of polymeric material, formed as by moulding, so as to define a primary passage  13  and an adjacent secondary passage  14 . The primary passage  13  extends from a supply port  15  to the induction nozzle  12  for delivering a primary air stream  16  to the induction nozzle  12 . The secondary passage  14  extends from an ambient air inlet  17  to the induction nozzle  12 . 
         [0033]    An atomiser  18  is disposed in the secondary passage  14  proximate the ambient air inlet  17  near the bottom of a water tank  19 . The atomiser may be an ultrasonic atomiser for emitting a fine spray of water into the secondary air stream. The primary air stream  16  induces a relatively smaller secondary air stream through the secondary passage  14 . Near the inlet  17  the induced secondary air flow is mixed with the fine spray of water droplets, and the flash evaporation and associated cooling of the secondary air stream that starts near the inlet  17  is largely complete by the time the air reaches the induction nozzle  12 . The primary air stream and the secondary air stream are ejected together via the induction nozzle  12  into the ambient air and directed to the point of use. 
         [0034]    The cooling apparatus may be a modular device, adapted for connection to different modules. The first housing  10  may be demountably coupled to a second housing module  20 , and by way of examples only, such a second housing  20  is shown in  FIG. 3 . The second housing module  20  may be releasably coupled to a fan  35  for impelling the primary air stream. A battery pack  36  in the second housing module  20  may be provided for supplying power to the ultrasonic atomiser  18  via the electrical contacts  21 , and to the fan  35 , thus when these three modules  10 ,  20 ,  35  are connected a self-contained, portable cooling apparatus is provided. 
         [0035]    As best seen in  FIGS. 1 and 2 , a shared wall  23  may separate the primary and secondary passages  13 ,  14 . The primary passage  13  includes a first portion  24  that extends from the induction nozzle  12  lengthwise adjacent to the secondary passage  14 , and which converges toward the induction nozzle  12  to accelerate the primary air flow into the nozzle. The second portion  25  that extends between the first portion  24  and the supply port  15  has a generally constant cross section throughout its length. The first portion  24  may be curved, while the second portion  25  may be linear and disposed adjacent the tank  19 . The primary air stream  16  thus initially follows a linear path through the second portion  25 , before curving through the first portion  24 . 
         [0036]    The secondary passage  14  may also be curved in its longitudinal direction, however the secondary passage  14  is not tapered toward its intersection with the induction nozzle  12 . The portion of the secondary passage  14  adjacent the induction nozzle  12  has a generally constant cross section throughout its length. The secondary passage  14  preferably has smooth internal surfaces and is substantially unobstructed by internal components or projections from the wall. Without a motor located in the secondary passage  14 , or upstream thereof, no sensible heating of the secondary stream occurs in the apparatus. This promotes a substantially laminar flow through the secondary passage  14 . A curved centreline  27  of the secondary passage  14  extends longitudinally between the induction nozzle  12  and the atomiser  18 . The inlet  17  is disposed generally transversely of this centreline  27  and may comprise a single aperture in the external wall  29 . In this first embodiment of the cooler, the secondary passage  14  is bounded on only one side by the shared wall  23 , and on the other sides by external walls  29  around the passage  14  are exposed to ambient air. 
         [0037]    The induction nozzle  12  may be formed integrally with the walls of the primary and secondary passages  13 ,  14 , and shaped so that the air flows are smoothly transferred from those passages into the nozzle  12 . The induction nozzle  12  converges toward its single outlet, inside which the shared wall  23  terminates. The primary and secondary streams are mixed to form a single stream that passes from the outlet, which may have a rim  28  generally disposed in a plane. Thus, while a feature of the invention is the single nozzle  12  producing a single air stream, it will be understood that the inlet  17  and the supply port  15  may comprise multiple adjacent openings in the wall of the housing. 
         [0038]    The tank  19  may be slidingly received in a recess in the housing  10  bounded by the shared wall  23  and extensions of the external walls  29 , allowing for ready removal when the housings  10 ,  20  are separated. The tank  19  is also a modular assembly comprising the atomiser  18 , and with the electrical contacts  21  for powering the atomiser  18  being fixed to the tank  19 . A vented lid  30  is disposed in an upper end of the tank  19 . With the tank  19  received in the recess in the housing  10  a lower end  31  of the tank  19  may bound the secondary passage  14 , the lower end  31  being disposed above the secondary passage  14  when the apparatus is upright. 
         [0039]    The atomiser  18  is fixed to the lower end  31  of the tank  19 , so as to be gravity fed. It may comprise a piezoelectric actuation element to cause vibration of an atomising mesh, plate or membrane. The axis of vibration may be generally aligned with the centreline  27  so that the water is generally thrown longitudinally, and downward, in the form of a fine mist. Suitable atomisers produce an average droplet size in the range of about 20 microns, or smaller. Multiple atomisers  18  may be disposed in the secondary passage  14  adjacent the inlet  17 . 
         [0040]    For use, the modules comprising the cooling apparatus are stacked upon one another, with the first housing  10  lowermost. The tank  19  may be filled with water while in place, or optionally removed, filled then dropped into the top of the first housing  10 . The first housing  10  can be held in one hand, while the second housing  20  is stacked on it and coupled thereto. This assembly of housings  10 ,  20  can then be connected to suitable air supply, or device for impelling an air flow, such as the fan  35  which is advantageously stacked upon the assembly. The modules thus connect to provide a self-contained, portable cooling apparatus which is lightweight, compact and ergonomically arranged for directing a cooling air flow in close proximity to the user. 
         [0041]    A second embodiment of the cooling apparatus is shown in  FIGS. 4 and 5 , and although it may be alike externally, it differs from the first embodiment primarily in the shape of the primary and secondary passages  113 ,  114  and the induction nozzle  112 . Whereas the output immediately outside the induction nozzle  112  may include a degree of stratification, due to the limited mixing between the primary and secondary streams that occurs within the nozzle, a greater degree of internal mixing is achieved within this induction nozzle  112 . Mixing is promoted in the induction nozzle  112  by surrounding the laminar inner secondary air stream by the semi-turbulent outer primary air stream. The shared wall  123  that separates the primary and secondary passages  113 ,  114  has a tubular form, inside which the secondary passage  114  extends, while the primary passage  113  is external to the shared wall  123 , inside the external wall  129 . The primary air stream  16   a  thus initially follows a linear path through the second portion  25 , before it is divided to flow around the shared wall  123 . Parts of this divided primary flow are represented by arrows  16   b  and  16   c  in  FIG. 4 . The first flow portion  16   b  is turned sharply and is the only part of the primary passage  113  that converges toward the induction nozzle  112 . The remaining portion of the primary flow  16   c  passes transverse to the centreline  27  and turns more gradually toward the nozzle  112 . 
         [0042]      FIG. 4  also schematically illustrates an exemplary arrangement of the second housing module  20 , and the fan  35  for impelling the primary air stream. The fan  35  may be an axial flow fan comprising a rotary electric motor  40  that turns blade  41  housed inside a cage  42 . 
         [0043]    The second housing module  20  may be a moulded polymeric hollow body that tapers from a broad end that attaches to the fan  35  to a narrow end that attaches to the housing  10 . Internally, an air passage  43  correspondingly narrows in the axial direction between the broad end and the narrower end, which is located in registration with the supply port  15 . A flange  44  at the broad end may be provided with latches  45 , connected as by hinges  46  to the flange  44 , for engaging the periphery of the cage  42  and thereby latching the fan  35  to the second housing module  20 . Latching features, such a integrally moulded live hinged or snap type elements (not shown) may allow the second housing module  20  to readily connected to, and disconnected from, the housing  10 . The second housing module  20  also holds a battery pack  36  for supplying power to the fan  35  and ultrasonic atomiser  18 . The activation of the atomiser  18  and fan  35  may be controlled by a user-actuable on/off switch  38  and a control circuit  37 . The control circuit  37  may also include an air pressure switch  138  disposed in the air passage  43  to provide a signal indicative of operation of the fan  35 . The control circuit  37  may thus control the atomiser  18  to operate only when air flow is induced in the secondary passage  114 . The air pressure switch  138  may replace the on/off switch  38 , and this is particularly suited to embodiments in which the fan  35  is powered by a separate power source, so that the atomiser  18  is actuated by air flow. 
         [0044]    Alternatively, a psychrometric microprocessor controller (not shown) may be provided for controlling the atomiser  18  in response to user demand and ambient conditions. The controller, may be responsive to sensors for sensing the wet and dry bulb temperature of the primary and/or secondary air stream at different positions, as well as the fan speed, and the pressure differentials within the apparatus, and control the activation of the atomiser  18  and the fan speed. An advantage of providing a psychrometric microprocessor controller is that the appropriate amount of water mist can be generated according user demand and ambient conditions, so that over-wetting of the air may be avoided. 
         [0045]    A variant of the second housing  120  is illustrated in  FIG. 6 , in which the fan  135  is internally mounted, such that only two modules  10 ,  120  need be connected to provide a self-contained, portable cooling apparatus. 
         [0046]      FIGS. 7 and 8  illustrate third and fourth embodiment of the cooling apparatus and, in particular, show further preferred alternative forms of the secondary passage  214 ,  314 . In both embodiments, the ambient air inlets  117  and induction nozzles  212 ,  312  are generally disposed at longitudinally opposing ends of secondary passages  214 ,  314  that have centrelines  127 ,  227 . The atomiser  18  is disposed on a lower side of the tank  119 , above a base  80  of the tank  119 , and generally transversely of the centrelines  127 ,  227 . The ambient air inlets  117  are located below the base  80 . The secondary passages  214 ,  314  comprise, extending in their longitudinal direction from the inlet  17 , an inlet throat portion  81 ,  181  below the base  80  that joins an enlarged outlet portion  82 ,  182  that extends to the induction nozzle  212 ,  312 . In this manner, a dogleg is provided in both secondary passages  214 ,  314 , where the inlet throat portion  81  meets the outlet portion  82 ,  182 . 
         [0047]    As shown in  FIG. 7 , in the secondary passage  214  the outlet portion  82  of the secondary passage  214  adjacent the induction nozzle  212  has a generally constant cross portion throughout its length. With this arrangement, a greater air flowrate through the secondary passage  214 , and consequently from the nozzle  212 , may be obtained for a given pressure rise across the fan, due to lower pressure losses, by avoiding a sharp change in air flow direction at the inlet  117 . 
         [0048]    Referring to  FIG. 8 , the secondary passage  314  diverges in the longitudinal direction between the inlet  117  and the induction nozzle  312  and the induction nozzle  312  is likewise divergent. This divergent arrangement, may also produce a higher volumetric flowrate for a given pressure rise across the fan, because of the reduced flow restriction. This higher volumetric flowrate has been found to be advantageous in reducing condensation formed on the inner walls of the secondary passage. 
         [0049]    Referring to  FIG. 9 , an oscillatory vane  50  may be mounted to the first housing  10  for projecting into the outlet stream from the nozzles  12 ,  112  so as to sweep the outlet stream back and forth. The vane  50  may include a vane portion  53  with a surface complementary to the external surface of the nozzle, so that it may swing back and forth adjacent the nozzle outlet. Integral with the vane portion  53  and extending from opposite sides are leg portions  52 . The vane and leg portions  53 ,  52  form a generally U-shaped vane  50  that is hung by coaxial pivots  51  fixed to the first housing  10  to define a swing axis. As shown, the swing axis is generally horizontal when the apparatus is upright. The tip of one of the leg portions  52  is fixed via a link (not shown) to an eccentric  54  turned by a rotary motor  55 , and in this manner this crank and rocker mechanism, or four bar linkage, may be used to drive the oscillatory movement. 
         [0050]    Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.