Abstract:
An air diffuser includes a porous fabric panel having areas of different flow coefficients. The areas&#39; positions and their relative flow coefficients provide a means for not only diffusing the air but also for strategically directing the airflow in a deliberate pattern that promotes intermixing of the air while avoiding adverse air currents. Consequently, the porous fabric itself provides air dispersion and airflow direction without the need for louvers or guide vanes. In some embodiments, the fabric&#39;s porosity is programmed by laser cutting small slits into the fabric.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The patent disclosure generally pertains to discharge air diffusers and more specifically to a fabric diffuser with programmed airflow. 
       BACKGROUND OF RELATED ART 
       [0002]    There are a wide variety of air diffusers for directing and dispersing filtered air into a room. A diffuser&#39;s ability to properly direct and thoroughly disperse the air is particularly important when the diffuser serves a room that contains a fume hood. A fume hood is an exhaust air register typically used for drawing toxic air from a controlled workstation so that the toxic air does not escape into the rest of the room. Air diffusers replenish the volume of air that the fume hood draws from the room; however, if the diffuser produces adverse air currents, the currents of air might blow or draw the toxic air out from under the fume hood, thereby allowing the toxic air to escape and circulate throughout the room. 
         [0003]    To address this problem, air diffusers often include louvers or guide vanes to direct the airflow in certain directions. In addition to guide vanes, porous materials have been used to evenly disperse the air. Although the combination of guide vanes and porous materials can provide an effective air diffuser, such a combination of elements can add unnecessary cost to the diffuser. Moreover, exposed guide vanes installed downstream of the porous material can be unsightly. Alternatively, guide vanes can be internally installed and hidden by the porous material, but then the guide vanes can be generally inaccessible, which can make it difficult to aim the airflow in a desired direction. 
         [0004]    Consequently, a need exists for a simple yet effective air diffuser that is particularly suited for critical applications. 
       SUMMARY 
       [0005]    In some examples, an air diffuser includes a porous fabric panel with areas of different porosities. 
         [0006]    In some examples, the fabric panel has some regions with a flow coefficient of between 80 and 320 cubic feet per minute through an area of one square foot at a pressure drop of 0.5 inches of water, and the panel has other regions that have a flow coefficient of between 130 and 500. 
         [0007]    In some examples, the regions of different flow coefficients are adjacent each other to promote intermixing of air therebetween. 
         [0008]    In some examples, a ratio of the first region&#39;s average flow coefficient to the second region&#39;s average flow coefficient is between 0.3 and 0.9. 
         [0009]    In some examples, a ratio of the first region&#39;s area to the second region&#39;s area is between one and ten. 
         [0010]    In some examples, the fabric panel covers an area of 3 to 20 square feet such as, for example, about 8 square feet. 
         [0011]    In some examples, the second region includes a plurality of slits each of which has a length and a width, wherein the length is at least three times greater than the width. 
         [0012]    In some examples, the slits are laser cut into the fabric material by feeding the material underneath a pulsating laser. 
         [0013]    In some examples, the slits are substantially parallel to each other. 
         [0014]    In some examples, the diffuser includes a screen that helps break the velocity pressure within the diffuser. 
         [0015]    In some examples, areas of relatively high flow coefficient are biased toward the ceiling to encourage airflow in that area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a bottom view of one example of an air diffuser. 
           [0017]      FIG. 2  is a side view of the air diffuser of  FIG. 1 . 
           [0018]      FIG. 3  is cross-sectional end view taken along line  3 - 3  of  FIG. 1 . 
           [0019]      FIG. 4  is an exploded view of  FIG. 3 . 
           [0020]      FIG. 5  is a perspective view of a screen used in the diffuser of  FIG. 1 . 
           [0021]      FIG. 6  is a perspective view illustrating a method of creating an air diffuser. 
       
    
    
     DETAILED DESCRIPTION  
       [0022]      FIGS. 1-3  show an air diffuser  10  that gently ventilates a room  12  by discharging air  14  in a strategic flow pattern. The flow pattern promotes thorough intermixing of the air yet avoids creating deleterious air currents within the room. Air diffuser  10  includes a fabric panel  16  with programmed porosity and other integral features that enable panel  16  to both disperse and direct the air without having to rely on mechanical louvers or guide vanes to do so. 
         [0023]    Basically, fabric panel  16  is attached to and suspended from a back pan  18  to create a plenum  20  between the two. A blower, or some other equivalent air mover, forces air  14  into plenum  20  via an air inlet  22  of back pan  18 . The air pressure within plenum  20  may be, for example, between 0.1 and 0.25 inches of water higher than that within room  12  so that the air in plenum  20  forces panel  16  to bulge outward as shown in  FIG. 3 . To control the shape of the diffuser  10  under pressure, diffuser  10  may include two appropriately shaped end panels  24  that connect to fabric panel  16 . Although end panels  24  may be made of porous fabric and may be disposed at an incline (relative to ceiling  26 ) as shown in  FIG. 2 , end panels  24  could alternatively be disposed perpendicular to ceiling  26 , be impervious to air, and/or be made of a rigid, non-fabric material. To evenly distribute the air pressure across suspended panel  16 , a relatively coarse screen  28  ( FIG. 5 ) may be added to help break the velocity pressure of the air traveling from inlet  22  toward panel  16 . 
         [0024]    Diffuser  10  can be assembled as shown in  FIG. 4 . End panels  24  can be sewn or otherwise joined to fabric panel  16 . To help attach and suspend panels  16  and  24  from back pan  18 , a bead  30  extends along the periphery of panels  16  and  24 . Bead  30  fits within a slot  32  in a generally rectangular frame  34 , and threaded fasteners  36  can be used to fasten frame  34  to back pan  18 , thereby clamping bead  30  between frame  34  and a rim  38  of back pan  18 . To hold screen  28  in place, additional fasteners  40  can hold four mounting ears  42  ( FIG. 5 ) of screen  28  to back pan  18 . The assembled diffuser  10  may have, for instance, nominal dimensions of two feet by four feet to conveniently fit within a rectangular opening normally meant for receiving standard size ceiling tiles. The total area of fabric panel  16  may be between three and twenty square feet. 
         [0025]    To thoroughly mix and disperse air  14 , the example fabric panel  16  includes two or more discrete regions that have different flow coefficients so that diffuser  10  releases air  14  at different flow rates through panel  16 , thereby creating an airflow with a predetermined pattern and promoting intermixing of adjacent airstreams. In this manner, the fabric of diffuser  10  can serve the function of both diffusing the air passing therethrough as well as properly separating and directing the airflow. The latter of these functions is conventionally achieved with internal guide vanes or louvers behind a diffuser panel. This conventional structure can be eliminated by giving the diffuser  10  itself areas of differing porosity to thereby separate and direct the airflow to create an airflow of desired pattern. The areas of different porosity can be referred to as having differing flow coefficients. The term, “flow coefficient” refers to a volumetric flow rate through a given area for a given pressure drop. Although the actual units for a flow coefficient may vary, the subject disclosure will be described and claimed using units of cubic feet per minute through an area of one square foot for an industry-standard pressure drop of 0.5 inches of water. The regions of different flow coefficients can be laid out in various locations across panel  16  to program a certain airflow pattern that provides a desired effect. 
         [0026]    Referring to  FIG. 1 , in some examples, panel  16  includes a first region  44  whose flow coefficient is determined by the inherent porosity of the fabric material itself. Panel  16  can be a polyester fabric with a mock leno weave that provides a flow coefficient of 80 to 320, and for example, about 160 cubic feet per minute per unit area at a pressure drop of 0.5 inches of water. A second region  46 ; comprising areas  46   a ,  46   b ,  46   c  and  46   d ; has a flow coefficient of 130 to 500, and for instance, about 260 cubic feet per minute per unit area at a pressure drop of 0.5 inches of water. To ensure thorough air dispersion, a ratio of the first region&#39;s area to the second region&#39;s area may be between one and ten, and a ratio of the first region&#39;s average flow coefficient to the second region&#39;s average flow coefficient may be between 0.3 and 0.9. 
         [0027]    Referring to  FIG. 6 , the additional porosity or increased flow coefficient of region  46  can be produced in various ways including, but not limited to, laser cutting a plurality of slits  48  into a fabric sheet  50  that can later be used for making panel  16 . To create slits  48 , a plurality of laser units  52  can be pulsed on and off as sheet  50  is fed across laser beams  54 . Good airflow characteristics have been achieved, for example, when each slit is at least three times longer than they are wide. In some cases, each slit is about ⅛ inch long, and the slits are spaced about ⅛ inch apart end-to-end. The slits can run generally parallel to each other and be spaced about 3/16 inches apart from side-to-side. The slits can be grouped to provide areas  46   a ,  46   b ,  46   c  and  46   d  of different widths. In some cases, for instance, areas  46   c  and  46   d  are about 1.5 inches wide (dimension  56 ), and areas  46   a  and  46   b  are about 1.7 inches wide (dimension  58 ). 
         [0028]    Areas  46   a ,  46   b ,  46   c  and  46   d  can be positioned on panel  16  to direct a disproportionate amount of air horizontally near ceiling  26 , thus avoiding the creation of strong downward currents of air that might disrupt the operation of a fume hood below diffuser  10 . To accomplish this, the position of areas  46   a ,  46   b ,  46   c  and  46   d  can be biased toward a first upper region  60  and a second upper region  62  of panel  16  ( FIGS. 1 and 3 ), wherein a central lower region  64  has a relatively low average flow coefficient and regions  60  and  62  have a relatively high average flow coefficient. Regions  60 ,  62  and  64  are defined as each comprising one third of panel  16 , wherein first upper region  60  lies along a first lateral edge  66  of rim  38 , second upper region  62  lies along a second lateral edge  68  of rim  38 , and central lower region  64  is interposed between and adjacent to upper regions  60  and  62 . 
         [0029]    The nearly horizontal flow at ceiling  26  may be enhanced when panel  16  droops about 6.5 inches (dimension  70 ) for a two-foot wide panel as shown in  FIG. 3 . It may also be helpful to have the wider regions  46   a  and  46   b  (which are about 1.7 inches wide) close to ceiling  26  and to have the narrower regions  46   c  and  46   d  (which are about 1.5 inches wide) a little farther away from ceiling  26 . 
         [0030]    Although the invention is described with respect to various examples, modifications thereto will be apparent to those of ordinary skill in the art. For example, the porosity of the first region need not be the same as the native porosity of the fabric—treatment such as coating and/or perforating the material can be used to set its porosity. The shape and location fo the areas of different porosity could also be different than those depicted herein—and chosen to adhieve a desired airflow patterns or characterictics. For example, while the slits  48  shown on the end panels  24  are parallel to those on the panel  16 , they could be perpendicular thereto or disposed at some other angle. Given that such modification are possible without departing from inventive concepts herein, the scope of the invention, is to be determined by reference to the following claims: