Abstract:
An external suspension system for supporting an inflatable air duct includes a series of external hangers that help hold the duct open while the duct is deflated. In some embodiments, the suspension system supports the duct at a series of points that are broadly distributed in a staggered pattern across the duct, yet the entire duct can be suspended from a single overhead cable, even if the duct is a stepped tube with multiple diameters. The system includes novel ways of locking the hangers to the duct and to the overhead cable.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure generally pertains to inflatable air ducts and more specifically to a support system for such a duct. 
       BACKGROUND OF RELATED ART 
       [0002]    Ductwork is often used for conveying conditioned air (e.g., heated, cooled, filtered, etc.) discharged from a fan and distributing the air to a room or other areas within a building. Ducts are typically formed of rigid metal, such as steel, aluminum, or stainless steel. In many installations, ducts are hidden above suspended ceilings for convenience and aesthetics. But in warehouses, manufacturing plants and many other buildings, the ducts are suspended from the roof of the building and are thus exposed. In those warehouse or manufacturing environments where prevention of air-borne contamination of the inventory is critical, metal ducts can create problems. 
         [0003]    For instance, temperature variations in the building or temperature differentials between the ducts and the air being conveyed can create condensation on both the interior and exterior of the ducts. The presence of condensed moisture on the interior of the duct may form mold or bacteria that the duct then passes onto the room or other areas being supplied with the conditioned air. In the case of exposed ducts, condensation on the exterior of the duct can drip onto the inventory or personnel below. The consequences of the dripping can range anywhere from a minor irritation to a dangerously slippery floor or complete destruction of products underneath the duct (particularly in food-processing facilities). 
         [0004]    Further, metal ducts with localized discharge registers have been known to create uncomfortable drafts and unbalanced localized heating or cooling within the building. In many food-processing facilities where the target temperature is 42 degrees Fahrenheit, a cold draft can be especially uncomfortable and perhaps unhealthy. 
         [0005]    Many of the above problems associated with metal ducts are overcome by the use of flexible fabric ducts, such as a Frommelt DUCTSOX. Such ducts typically have a flexible fabric wall (often porous) that inflates to a generally cylindrical shape by the pressure of the air being conveyed by the duct. Fabric ducts seem to inhibit the formation of condensation on its exterior wall, possibly due to the fabric having a lower thermal conductivity than that of metal ducts. In addition, the fabric&#39;s porosity and/or additional holes distributed along the length of the fabric duct broadly and evenly disperse the air into the room being conditioned or ventilated. The even distribution of airflow also effectively ventilates the walls of the duct itself, thereby further inhibiting the formation of mold and bacteria. 
         [0006]    In many cases, however, once the room&#39;s conditioning demand has been met, the air supply fan is turned off or down until needed again. When the fan is off, the resulting loss of air pressure in the duct deflates the fabric tube, causing it to sag. Depending on the application and material of the fabric, in some cases, the sagging creates a poor appearance or may interfere with whatever might be directly beneath the duct. Moreover, when the duct is re-inflated, the duct can produce a loud popping sound as the duct&#39;s fabric becomes taut. 
         [0007]    To eliminate or reduce the sagging and popping noise, some inflatable ducts include structure that helps hold a deflated duct in a generally expanded shape. Examples of ducts supported in such a manner are disclosed in U.S. Pat. Nos. 6,280,320 and 3,357,088. A significant drawback of the patented systems is the amount of supporting hardware necessary to keep the duct expanded. For the air duct of the &#39;320 patent, various embodiments include two parallel support channels ( FIGS. 1-9 ), an assembly comprising numerous components (items  80 ,  94 ,  74 ,  82 , and  84  of  FIG. 12 ), or large cumbersome hoops ( FIGS. 13 and 14 ). 
         [0008]    For the air duct of the &#39;088 patent, the support structure is similar to a triangular coat hanger comprising three structural bars (items  19 ,  20  and  21 ). Bar ( 21 ) of the &#39;088 patent extends through the interior of the duct, which can disrupt the airflow. The &#39;088 device also includes grommets  23  through which the structural bars extend. If the holes in the grommets are too big, the grommets may slide around the structural bars, which would allow the duct to sag. If the holes in the grommets are too small, the resulting tight fit between the grommets and the structural bars would make it more difficult to remove the bars for periodic laundering of the fabric duct. 
         [0009]    Consequently, a need exists for a simple, lightweight structure that can support a deflated duct in a generally expanded shape. 
       SUMMARY 
       [0010]    In some embodiments, an air duct assembly includes an inflatable tube supported at a plurality of points that are distributed along the tube in a staggered, alternating pattern. 
         [0011]    In some embodiments, an inflatable air duct is supported by a series of hangers that do not extend into the duct. 
         [0012]    In some embodiments, an inflatable air duct is supported by a series of hangers, wherein each hanger has two ends that connect to a pair of radially displaced points on the duct. The two ends are separated by the interior of the duct so as not to interfere with airflow through the duct. 
         [0013]    In some embodiments, an inflatable air duct is externally supported such that its deflated volume is at least 70% fits inflated volume. In some embodiments, an inflatable air duct with stepped diameters is supported by a single suspension line. 
         [0014]    In some embodiments, spaced lateral supports are suspended from a support structure above the inflatable tube and are each connected to laterally spaced points on the tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a side view of an inflated air duct assembly that includes a novel suspension system. 
           [0016]      FIG. 2  is a top view of  FIG. 1  but with the suspension system&#39;s hangers, connectors, and suspension line omitted to more clearly show other features. 
           [0017]      FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 1 . 
           [0018]      FIG. 4  is a cross-sectional view similar to  FIG. 3  but showing the tube deflated. 
           [0019]      FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 1 . 
           [0020]      FIG. 6  is a cross-sectional view taken along line  6 - 6  of  FIG. 1 . 
           [0021]      FIG. 7  is an exploded perspective view of a hanger and related hardware. 
           [0022]      FIG. 8  is a front view of a D-ring. 
           [0023]      FIG. 9  is a perspective view showing a hanger assembly. 
           [0024]      FIG. 10  is front view of a hanger showing a D-ring about to be inserted into a slot of a hanger. 
           [0025]      FIG. 11  is a front view similar to  FIG. 10  but showing the D-ring being inserted into the hanger&#39;s slot. 
           [0026]      FIG. 12  is a front view similar to  FIGS. 10 and 11  but showing the D-ring being rotated into position. 
           [0027]      FIG. 13  is a front view similar to  FIGS. 10-12  but showing the D-ring in its final position within the hanger&#39;s slot. 
           [0028]      FIG. 14  is a top view showing a series of hangers that connect to an inflatable air duct at points that are slightly misaligned. 
           [0029]      FIG. 15  is a view similar to  FIG. 5  but showing a hanger that connects to the air duct at three points. 
           [0030]      FIG. 16  is a view similar to  FIG. 15  but showing an alternate hanger. 
           [0031]      FIG. 17  is a view similar to  FIG. 5  but showing an alternate suspension system. 
           [0032]      FIG. 18  is a perspective view showing another inflated air duct assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Referring to  FIGS. 1-6 , an HVAC system for heating, ventilating or air conditioning includes an air duct assembly  10  with an inflatable tube  12  made of a pliable material that encloses an air passageway  14 . Tube  12  is connected to receive pressurized air from a blower  16  or some other source and distribute that air within a building or wherever the air may be needed. To disperse the air from within the tube&#39;s air passageway  14 , tube  12  can be made of an air permeable material and/or tube  12  may be provided with a series of holes or air registers. 
         [0034]    For the HVAC system to meet the demand for air, blower  16  can be periodically energized and de-energized as needed. When energized, blower  16  inflates tube  12  to a generally cylindrical shape (or some other closed shape) as shown in  FIGS. 1 ,  3 ,  5  and  6 . Once the need for air has been satisfied, de-energizing blower  16  causes tube  12  to deflate to the shape shown in  FIG. 4 . 
         [0035]    As tube  12  changes between its inflated and deflated shapes, it is desirable to minimize the amount that tube  12  sags, minimize the duct&#39;s change in volume, and/or minimize a popping sound when tube  12  suddenly inflates. To accomplish one or more of these goals, a suspension system  18  comprising a plurality of hangers  20  and a plurality of connectors  22  may be used to help hold the deflated tube in a generally expanded shape, as shown in  FIG. 4 . 
         [0036]    Although the actual design of hangers  20  may vary, in one embodiment, each hanger  20  comprises an arcuate arm  24  made of ⅛″ thick sheet metal, which is more rigid than the material of tube  12 . In this example, each hanger  20  includes a first termination point  26 , a second termination point  28  and an intermediate termination point  30 . Termination points  26  and  28  are coupled to tube  12  at approximately 10:00 and 2:00 positions, and intermediate point  30  is at about a 12:00 position coupled to a top central portion  32  of tube  12 . 
         [0037]    Hangers  20  can be supported by any suitable support structure including, but not limited to, a ceiling; joist; beam; bracket; or in the case of one example, an overhead suspension line  34  such as a cable, cord, wire, chain, rope, strap or elongate bar. In general, hangers  20  would be suspended from the support structure along a line generally collinear with the longitudinal extent of the tube  12 , or a portion thereof. One of skill in the art will appreciate that the hangers will likely not be connected to the support structure along a strict geometric line given variation in the building, etc. Even so, the combination of the support structure and spaced hangers can be thought of as defining a longitudinal support (i.e. extending along the longitude of the tube  12 ) with space lateral (i.e. generally extending perpendicular to the longitude of the tube) supports attachable to the exterior of tube  12 . Perhaps the clearest example of this description of the depicted structure is the embodiment of  FIG. 18 , in which line  34  represents the longitudinal support and hangers  62 ,  64  represent the spaced lateral supports, In the case of the hangers being attached to other structure (ceiling joists, beams, etc.) the longitudinal support may not have a continuous longitudinal extent like line  34 . Returning to  FIGS. 7 ,  8  and  9 , to connect hanger  20  to suspension line  34 , hanger  20  can be provided with a line-receiving slot  36  near intermediate point  30 . Slot  36  can have a shape that helps prevent line  34  from readily escaping, and/or a stopper  38  can be added to help hold line in place. Stopper  38 , for example, can be a plastic plug that snaps into a mating detent  40  in slot  36 . Another way of connecting hanger  20  to line  34  includes, but is not limited to, adding a link, fastener or coupling between hanger  20  and line  34 . 
         [0038]    Termination points  26  and  28  can be coupled to tube  12  in any number of ways. In a one embodiment, a plastic D-ring  42  with a short fabric strap  44  can be used. Strap  44  can be sewn, riveted or bonded to tube  12  or attached to tube  12  in some other way. D-ring  42  can be inserted into a slot  46  in hanger  20 . To help hold D-ring  42  in place, the shape of slot  46  and the surrounding sheet metal material can be such that D-ring  42  needs to be rotated about  90  degrees in order to insert or remove D-ring  42  from within slot  46 . Each hanger  20  can be provided with two D-rings  42  so that each hanger  20  can be connected to a pair of points  48  on tube  12  ( FIG. 2 ). 
         [0039]      FIGS. 10-13  illustrate one way of inserting and holding D-ring  42  into slot  46  of hanger  20 . In this example, D-ring  42  has a bar  66  that fits into slot  46 . Bar  66  has a thickness  68  that is approximately equal to a width  70  of slot  46 , which makes is easy to insert bar  66  into slot  46  and slide the bar from the position of  FIG. 11  to that of  FIG. 12 . A width  72  of bar  66 , however, is slightly greater than the slot&#39;s width  70 , so bar  66  tightly binds within slot  46  as D-ring  42  is rotated from the position of  FIG. 12  to that of  FIG. 13 . To further ensure that D-ring  42  stays within slot  46 , hanger  20  includes a protrusion  74  that nearly fills a gap  76  between bar  66  and a second bar  78  of D-ring  42 , thus bar  66  cannot slide straight back out of slot  46  without first counter-rotating D-ring  42  back to its position of  FIG. 11 . 
         [0040]    Hangers  20  can be distributed at spaced-apart intervals along line  34  to evenly support tube  12  along the tube&#39;s length  50  (longitudinal length or lengthwise direction). The face of hanger  20  may lie generally perpendicular to line  34  to provide hanger  20  with beam strength. D-rings  42  can couple first termination point  26  to a first lateral set of points  52  on tube  12  and couple second termination points  28  to a second lateral set of points  54 . In some cases, lateral points  52  and  54  are substantially aligned in registry with each other, as shown in  FIG. 2 . In other cases, due to manufacturing or other inaccuracies, points  52  and  54  may be weak positioned somewhat out of registry with each other, as shown in  FIG. 14 . This is not a problem, however, as hangers  20  are self-aligning in that they have the freedom to pivot about a vertical axis relative to line  34 , thereby compensating for the misalignment of points  52  and  54 . In an embodiment in which hangers  20  are suspended from other structure—such as dealings, joists, beams, etc—similar compensation can be provided for. In that instance, the hangers  20  would be suspended from such structure by a connector that would give them the necessary freedom of movement to allow such mis-registry compensation. Examples of such connectors include cables and swiveling or pivoting connectors. 
         [0041]    Although hangers  20  can be used alone, the addition of optional connectors  22  provide tube  12  with additional support. In some embodiments, connectors  22  are installed between hangers  20  in an alternating pattern along suspension line  34 . They could also be attached directly to the ceiling joists, beams or other longitudinal support as referred to above. In other embodiments, as shown in  FIG. 15 , connectors  22  can be connected to a central point  80  of a slightly modified hanger  82 . In either case, connectors  22  can be anything suitable for coupling a longitudinal support such as line  34  or hanger  82  to a central set of points  56  on the top central portion  32  of tube  12  or a tube  12 ′. Examples of connector  22  include, but are not limited to, a hook, clip, link, loop, ring, etc. The embodiment of  FIG. 15  also illustrates that strap  44  holding D-ring  42  can extend radially or at any angle relative to the exterior surface of tube  12  or  12 ′. 
         [0042]    In another embodiment, shown in  FIG. 16 , suspension line  34  can be an integral part of an inflatable tube  84  by inserting line  34  within a fabric loop  86  that extends a full or partial length of tube  84 . A slightly modified hanger  88  can be provided with a central notch  90  that snaps over or otherwise attaches to line  34  and/or loop  86 . 
         [0043]    In yet another embodiment, shown in  FIG. 17 , a wire hanger  92  includes a first termination point  94  and a second termination point  96  that hook into corresponding grommets  98  in an inflatable tube  100 . Hanger  92  includes an intermediate point  102  with a coiled loop  104  that wraps around suspension line  34 . An air passageway  106  separate points  94  and  96 . An advantageous feature of this design is that tube  100  can be removed from hanger  92  while the hangers remain attached to line  34 . Other embodiments depicted herein share the same feature. In this embodiment, connectors  22  can be added for additional support if necessary. 
         [0044]    With various embodiments of duct assembly  10 , excellent results have been achieved when the central set of points  56  are staggered out of registry with the lateral set of points  52  and  54 , as shown in  FIG. 2 . This particular arrangement of points  52 ,  54  and  56  helps maintain a deflated tube  12  in a more open shape, as shown in  FIG. 4 . In some cases, the deflated air volume in tube  12  ( FIG. 4 ) is at least 70% of the inflated volume in tube  12  ( FIG. 3 ), thus the minimal change in air volume reduces the popping sound if tube  12  is suddenly inflated. Favorable aesthetics are also provided. 
         [0045]    Air duct assembly  10  is particularly useful in situations where a large diameter tube  58  feeds a smaller diameter tube  60 , as shown in  FIG. 18 . In this case, a single suspension line  34  can be used for supporting both ducts  58  and  60 . A plurality of relatively large hangers  62  can support tube  58 , and a plurality of relatively small hangers  64  can support tube  60 . 
         [0046]    Although the invention is described with respect to various embodiments, modifications thereto will be apparent to those of ordinary skill in the art. The scope of the invention, therefore, is to be determined by reference to the following claims: