Patent Publication Number: US-2012028562-A1

Title: Flexible air ducts with gradual inflation

Description:
FIELD OF THE DISCLOSURE 
     This patent generally pertains to flexible air ducts and, more specifically, to flexible air ducts that are inflatable. 
     BACKGROUND 
     Sheet metal ductwork is often used for conveying conditioned air to a comfort zone, such as a room or other areas of a building. Metal ducts, however, can be expensive, unsightly, and susceptible to condensation. Moreover, such ducts usually require supply air registers that discharge air into the comfort zone at localized areas rather than evenly distributing the air. Consequently, inflatable air ducts, such as those made of pliable fabric, are often preferred over conventional sheet metal ones. 
     Inflatable air ducts typically comprise an inflatable tube made of fabric or otherwise pliable material and are also used for conveying conditioned air to comfort zones. A blower at the inlet of the duct is selectively activated to supply conditioned air as needed. The air discharged from the blower inflates the duct to create a radially expanded tubular conduit that conveys the air along the length of the inflated tube. The pliable wall of the tube can be porous and/or be perforated along its length for evenly or strategically dispersing air from within the duct into the areas being conditioned or ventilated. 
     Inflatable air ducts are often suspended from a horizontal cable or track mounted just below the ceiling of a building. In other cases, inflatable ducts are installed beneath a floor and supply conditioned air to a comfort zone by releasing the air up through one or more openings in the floor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an example air duct system with a schematically illustrated example damper in an initial configuration. 
         FIG. 2  is a side view of the air duct system of  FIG. 2  but showing the damper in an operating configuration. 
         FIG. 3  is a side view of another example air duct system with a schematically illustrated example damper in an initial configuration and with an example inflatable tube in a deflated state. 
         FIG. 4  is a side view of the air duct system of  FIG. 3  but showing the damper in an operating configuration and showing the tube in an inflated state. 
         FIG. 5  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 6  is a cross-sectional side view of the air duct system of  FIG. 5  but showing the damper in an operating configuration. 
         FIG. 7  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 8  is a cross-sectional side view of the air duct system of  FIG. 7  but showing the damper in an operating configuration. 
         FIG. 9  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 10  is a cross-sectional side view of the air duct system of  FIG. 9  but showing the damper moving to an operating configuration. 
         FIG. 11  is a cross-sectional side view of the air duct system of  FIG. 9  but showing the damper in its operating configuration. 
         FIG. 12  is a cross-sectional side view similar to  FIG. 11  but showing an example actuator in a relaxed state. 
         FIG. 13  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 14  is a cross-sectional side view of the air duct system of  FIG. 13  but showing the damper in its operating configuration. 
         FIG. 15  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 16  is a cross-sectional side view of the air duct system of  FIG. 15  but showing the damper in its operating configuration. 
         FIG. 17  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 18  is a cross-sectional side view of the air duct system of  FIG. 17  but showing the damper in its operating configuration. 
         FIG. 19  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 20  is a cross-sectional side view of the air duct system of  FIG. 19  but showing the damper in its operating configuration. 
         FIG. 21  is a cross-sectional side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 22  is a cross-sectional side view of the air duct system of  FIG. 21  but showing the damper in its operating configuration. 
         FIG. 23  is a side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 24  is a side view of the air duct system of  FIG. 23  but with the damper in the operating configuration. 
         FIG. 25  is a cross-sectional view taken along line  25 - 25  of  FIG. 23 . 
         FIG. 26  is a cross-sectional view taken along line  26 - 26  of  FIG. 24 . 
         FIG. 27  is a side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 28  is a side view of the air duct system of  FIG. 27  but with the damper in the operating configuration. 
         FIG. 29  is a side view of another example air duct system with an example damper in an initial configuration. 
         FIG. 30  is a side view of the air duct system of  FIG. 29  but with the damper in the operating configuration. 
     
    
    
     DETAILED DESCRIPTION 
     Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify the same or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and/or conciseness. Additionally, several examples have been described throughout this specification. 
       FIGS. 1 and 2  show an example air duct system  10  comprising an inflatable tube  12  connected to a source of air (e.g., a blower  14 ). In this example, blower  14  draws in air from an inlet  16  and discharges a current of air  18  through tube  12 . As air  18  flows from an upstream end  20  of tube  12  to a downstream end  22 , pores and/or other openings along the tube&#39;s length distribute air  18  to a comfort zone, such as a room or other areas in a building. 
     In some examples, tube  12  includes a pliable fabric or other pliable sheet of material. In the illustrated example, a series of hangers  24  suspends tube  12  from an overhead supporting structure  26  (e.g., a ceiling or beam). In other examples, tube  12  is installed in other locations such as, along a wall, just above a floor, or even below a floor. When blower  14  is inactive, the resulting relatively low static air pressure within tube  12  allows tube  12  to become generally limp in a deflated state, as shown in  FIG. 1 . When blower  14  is active and pressurizes tube  12  with relatively high static air pressure, tube  12  inflates to an inflated state with the tube&#39;s sidewalls becoming taut, as shown in  FIG. 2 . In this example, an end cap  28  is attached to the tube&#39;s downstream end  22  to help ensure that tube  12  can fully inflate. 
     To prevent tube  12  from suddenly inflating immediately upon energizing blower  14 , air duct system  10  includes a damper  30 . Upon energizing blower  14 , damper  30  moves relatively slowly from an initial configuration ( FIG. 1 ) to an operating configuration ( FIG. 2 ). In the example where damper  30  is at the tube&#39;s upstream end  20 , damper  30  provides a greater obstruction to airflow when damper  30  is in the initial configuration than in the operating configuration. The flow obstruction provided by damper  30  being in the initial configuration controls (e.g., limits) the flow of air  18  from blower  14  to tube  12  and, thus, causes tube  12  to inflate relatively slowly or controllably. When tube  12  is fully inflated, or nearly so, damper  30  will have moved to its operating configuration to minimize the damper&#39;s obstruction to airflow through tube  12 . 
     Additionally or alternatively to installing damper  30  at the tube&#39;s upstream end  20 ,  FIGS. 3 and 4  show an example air duct system  32  wherein a damper  40  is installed at downstream end  22  to prevent tube  12  from suddenly inflating immediately upon energizing blower  14 . Upon energizing blower  14 , damper  40  moves relatively slowly from an initial configuration ( FIG. 3 ) to an operating configuration ( FIG. 4 ). In this example, damper  40  provides a greater obstruction to airflow when damper  40  is in the operating configuration than in the initial configuration. 
     While blower  14  is energized, the flow obstruction provided by damper  40  being generally closed in the operating configuration blocks off an otherwise open downstream end of tube  12  (end cap  28  is eliminated in this example). Blocking off the tube&#39;s downstream end  22  allows blower  14  to create a relatively high static air pressure that is sufficient to fully inflate tube  12  during the air duct system&#39;s normal steady-state operation. When blower  14  is first energized, damper  40  being in a generally open initial configuration releases air  18  out through the open downstream end  22  of tube  12 . Air escaping out through the tube&#39;s open downstream end  22  keeps air  18  at a relatively low static air pressure that slowly or controllably inflates tube  12 . 
     Dampers  30  and  40  are schematically illustrated in  FIGS. 1-4  to represent any structure or flow regulating means that can provide a variable obstruction to airflow. Examples of dampers  30  and  40  include, but are not limited to, a single butterfly damper blade (e.g., generally round or generally rectangular), a series of generally parallel damper blades (moving independently or in unison), a fabric or otherwise flexible sheet of material (e.g., deformable parachute, movable curtain, inflatable funnel, inflatable bladder, etc.). Control of a damper&#39;s movement between its initial and operating configurations can be achieved by various actuators, examples of which include, but are not limited to, an air-powered device, an electric motorized device, a spring, a weight, an inflatable bladder, a turbine, a motion-dampening device, a flywheel with rotational inertia, a piston/cylinder, a pliable elongate member (e.g., string, chain, wire, cable, strap, etc.), and/or various combinations thereof. 
     In some examples, the structure of damper  30  is as shown in  FIGS. 5 and 6 , wherein a damper  30   a  corresponds to damper  30 . In this example, damper  30   a  is installed within a damper housing  34  disposed at an upstream end  20 ′ of an inflatable tube  12 . Damper  30   a  is shown in a generally closed initial configuration in  FIG. 5  and is shown in a more open operating configuration in  FIG. 6 . Damper  30   a , in this example, includes a series of damper blades  42  pinned to a connecting bar  44  so that damper blades  42  pivot in unison. In some examples, ends of blades  42  may be pivotably coupled to damper housing  34 . 
     In this example, damper  30   a  is opened by an air-powered actuator  46  comprising a turbine wheel  48  that drives the rotation of a spool  50 . A flexible elongate member  52  threaded through a hole or aperture  54  in damper housing  34  has one end  52   a  attached to bar  44  and an opposite end  52   b  wrapped around and attached to spool  50 . 
     Operation can begin with blower  14  inactive and damper  30   a  in its initial configuration of  FIG. 5 . Blower  14 , upon being energized, discharges air  18  against the generally closed damper  30   a  (in some examples, damper  30   a  is slightly open in the initial configuration), and some air  18  blows through a nozzle  56  that directs a stream of air  18  across turbine wheel  48 . The air through nozzle  56  turns turbine wheel  48  and spool  50  to draw in elongate member  52 , which pulls on bar  44  to slowly or controllably open damper  30   a . As damper  30   a  opens, a slowly increasing volume of air  18  passes through damper  30   a  to gradually increase the static pressure in tube  12  until tube  12  is fully inflated with damper  30   a  being at its operating configuration of  FIG. 6 . 
     When blower  14  is de-energized, airflow decreases through nozzle  56  and damper  30   a  settles, by its own weight, back down to return to its initial configuration of  FIG. 5 . As damper  30   a  moves from its operating position of  FIG. 6  to its initial position of  FIG. 5 , bar  44  pulls on elongate member  52  to back spin spool  50  and turbine wheel  48 . 
     Although damper  30   a  is shown having its own damper housing  34  with a short section of tube  58  connecting damper housing  34  to a blower housing  60 , in some examples, damper  30   a  is installed within and/or supported by blower housing  60 , thereby eliminating tube section  58  and/or separate damper housing  34 . Such modifications, similar or identical thereto, may also be applied to other examples disclosed herein. 
     Referring to  FIGS. 7 and 8 , to reduce the discharge pressure of blower  14  when damper  30   a  is generally closed in its initial configuration ( FIG. 7 ), an example air duct system  62  includes an example pressure relief valve  64 . In this example, a linkage or elongate member  66  connects bar  44  to a flap  68  on valve  64  such that valve  64  opens as damper  30   a  closes and vice versa.  FIG. 8  shows damper  30   a  in its generally open operating configuration with valve  64  closed to block off an opening or aperture  70  in a damper housing  72 . In other respects, the structure and operation of the air duct systems shown in  FIGS. 5-8  are similar. 
     Some example air duct systems, such as example duct system  74  shown in  FIGS. 9-12 , include a damper  30   b  in the form of a collapsible funnel  76  made of a pliable sheet of material. Damper  30   b  may be installed at an upstream end  78  of an inflatable tube  80 .  FIG. 9  shows damper  30   b  in an initial configuration to obstruct flow through tube  80 , and  FIG. 12  shows damper  30   b  in an operating configuration to provide generally unrestricted airflow. In this example, damper  30   b  has a wide air inlet  82  at its base and a narrower air outlet  84  at its apex. An upper peripheral section  86  of the inlet&#39;s base is attached to an upper sidewall of tube  80  such that funnel-shaped damper  30   b  tends to hang in its generally expanded initial configuration ( FIG. 9 ), particularly when blower  14  is first energized because blower  14  discharging into inlet  82  tends to force damper  30   b  to billow outward. 
     To actuate damper  30   b , a flexible elongate member  88  connects to a lower end  90  of damper  30   b , feeds through a hole or aperture  92  in the sidewall of tube  80 , and connects to a damper actuator  94 . In some examples, actuator  94  is an air-powered actuator comprising an inflatable bladder  96  made of a pliable sheet of material. In the illustrated example, bladder  96  overlies an upper portion of tube  80  to create a bladder chamber  98  between the sheet material of bladder  96  and the upper surface of tube  80 . 
     Operation of duct system  74  may begin with damper  30   b  in its initial configuration, as shown in  FIG. 9 . Upon energizing blower  14 , air  18  forces damper  30   b  to billow outward to create a significant airflow obstruction that slows the tube&#39;s inflation. Initial inflation is achieved by air flowing through outlet  84  and around the outer periphery of damper  30   b . Some air  18  discharged from blower  14  also flows through an air passageway  100  in tube  80  to slowly inflate bladder  96 . As bladder  96  inflates, elongate member  88  pulls the bottom edge of damper  30   b  upward, as shown in  FIG. 10 . As bladder  96  begins collapsing or flattening under the pull of elongate member  88 , a greater volume of air  18  flows past damper  30   b  to inflate tube  80  more fully or with greater pressure. 
       FIG. 11  shows bladder  96  fully expanded and damper  30   b  fully collapsed. The air pressure in tube  80  helps flatten damper  30   b  up against the inner wall of tube  80 . Damper  30   b  being collapsed not only provides generally unrestricted flow past damper  30   b  but also places damper  30   b  to where the material of damper  30   b  can block off air passageway  100 . 
     After bladder fully inflates to collapse damper  30   b , as shown in  FIG. 11 , air within chamber  98  slowly leaks out through an opening or aperture  102  in bladder  96 . Eventually, bladder  96  collapses generally flat against tube  80 , as shown in  FIG. 12 . With bladder  96  collapsed, air flowing through tube  80  can still hold damper  30   b  up against the inner wall of tube  80  to maintain generally unrestricted airflow through tube  80 . When blower  14  is turned off, bladder  96  is free to fall under its own weight back down to its initial configuration. 
     In some examples, the structure of damper  30  of  FIGS. 1 and 2  is as shown in  FIGS. 13 and 14 , wherein a damper  30   c  corresponds to damper  30 .  FIG. 13  shows damper  30   c  at upstream end  36  of tube  12  in an initial configuration, and  FIG. 14  shows damper  30   c  is an operating configuration. Damper  30   c  is similar to damper  30   a  of  FIGS. 5 and 6 ; however, damper  30   c  is blown open by air  18  discharged from blower  14 . To slow the tube&#39;s rate of inflation, a motion-dampening device  104  is connected to damper  30   c . In some examples, device  104  includes a piston  106  and a fluid-filled cylinder  108 , wherein the fluid (e.g., air) can leak past or axially through piston  106  to dampen the piston&#39;s movement within cylinder  108  and thus dampen the movement of damper  30   c.    
     In some examples, the structure of damper  30  of  FIGS. 1 and 2  is as shown in  FIGS. 15 and 16 , wherein a damper  30   d  corresponds to damper  30 .  FIG. 15  shows damper  30   d  at upstream end  20 ′ of tube  12  in an initial configuration, and  FIG. 16  shows damper  30   d  is an operating configuration. In this example, damper  30   d  includes a generally round butterfly damper blade  110  rotatable about a pivotal axis  112  that is radially offset from the damper blade&#39;s physical centerline such that air  18  discharged from blower  14  urges damper blade  110  to rotate to its open operating configuration of  FIG. 16 . 
     To slow the damper blade&#39;s pivotal movement and thus slow the tube&#39;s rate of inflation, a motion-dampening device  114  is connected to damper blade  110 . In this example, device  114  includes a gear  116  fixed to damper blade  110  such that gear  116  and damper blade  110  rotate as a unit. A series of speed-increasing gears  118  couples gear  116  to a flywheel  120  such that flywheel  120  rotates significantly faster than gear  116 , thus the flywheel&#39;s mass moment of inertia resists the damper&#39;s rotational acceleration as damper  30   d  moves between its initial and operating configurations. 
     Additionally or alternatively, to resist the movement of damper blade  110 , device  114  may include a weight  122  that slides along an arm or rod  124  rigidly extending from damper blade  110 . When damper  30   d  is in the initial configuration of  FIG. 15 , weight  122  is at a distal end  126  of arm  124  to provide a significant moment that opposes but does not completely stop the damper blade&#39;s opening movement. As damper  30   d  fully opens to the operating configuration shown in  FIG. 16 , weight  122  slides down toward a proximal end  128  of arm  124 . Weight  122  at proximal end  128  reduces the moment that weight  122  exerts against damper blade  110 , so air  18  discharged from blower  14  can readily hold damper  30   d  fully open during normal, steady-state operation. 
     In some examples, as shown in  FIGS. 17 and 18 , an air duct system  130  slowly inflates tube  12  using an auxiliary source of air (e.g., auxiliary blower  132 ) that provides an initial current of air  135  at a lower flow rate and/or lower static pressure than that of blower  14 . The auxiliary blower  132  may be powered by a power source  150  electrically coupled thereto. In some example, the power source  150  includes one or more batteries. The one or more batteries may be coupled to the blower housing, the damper housing or some other structure, for example. The one or more batteries may be positioned in a battery pack. 
     In other examples, the power source  150  may include one or more solar panels. The solar panel(s) may be configured to harness energy from incandescent and/or fluorescent light, for example. The solar panel(s) may be positioned adjacent to or at a distance from the auxiliary blower  132 . In some examples, the solar panel(s) may be coupled to the blower housing, the damper housing or some other structure. 
     In this example, a damper  30   e  (e.g., series of free-swinging damper blades) is disposed downstream of blower  14 , and a check valve  134  (e.g., a flap) is downstream of auxiliary blower  132 . 
     In operation, auxiliary blower  132  initially inflates tube  12  with air  135  at a relatively low flow rate, while main blower  14  is inactive with damper  30   e  closed, as shown in  FIG. 17 . When there is a greater demand for air in the comfort zone, main blower  14  is activated, and the resulting air  18  discharged from main blower  14  forces damper  30   e  open. In some examples, the activation of main blower  14  and/or the deactivation of auxiliary blower  132  closes check valve  134 , as shown in  FIG. 18 . In some examples, auxiliary blower  132  operates continuously, regardless of whether main blower  14  is operating. In other examples, auxiliary blower  132  is deactivated upon energizing main blower  14 . In still other examples, auxiliary blower  132  is only activated for a time period just prior to activating blower  14 . The time period may be related to the amount of time for auxiliary blower  132  to blow sufficient air into tube  12  to reduce or preferably minimize popping and/or shaking that may otherwise occur. Auxiliary blower  132  can be at any location along the length of tube  12 . 
     In some examples, the structure of damper  40  of  FIGS. 3 and 4  is as shown in  FIGS. 19 and 20 , wherein a damper  40   a  corresponds to damper  40 .  FIG. 19  shows damper  40   a  at downstream end  22  of tube  12  in an initial configuration, and  FIG. 20  shows damper  40   a  is an operating configuration. In this example, damper  40   a  includes a generally round butterfly damper blade  136  rotatable about a pivotal axis  138  that is radially offset from the damper blade&#39;s physical centerline such that air  18  discharged from blower  14  urges damper blade  136  to rotate to its open initial configuration of  FIG. 19 . In some examples, the damper blade&#39;s center of gravity also urges damper blade  136  to its open initial configuration. 
     In some examples, damper  40   a  is closed by a motorized actuator  140  that drives the rotation of spool  50 . The motorized actuator  140  may be powered by a power source  200  electrically coupled thereto. In some example, the power source  200  includes one or more batteries. The one or more batteries may be coupled to the blower housing, the damper housing or some other structure, for example. The one or more batteries may be positioned in a battery pack. 
     In other examples, the power source  200  may include one or more solar panels. The solar panel(s) may be configured to harness energy from incandescent and/or fluorescent light, for example. The solar panel(s) may be positioned adjacent to or at a distance from the motorized actuator  140 . In some examples, the solar panel(s) may be coupled to the blower housing, the damper housing or some other structure. 
     A flexible elongate member  142  threaded through a hole or aperture  144  in a housing  14   b  has one end  148  attached to damper  40   a  and an opposite end  150  wrapped around and attached to spool  50 . 
     Operation can begin with blower  14  inactive and damper  40   a  open in its initial configuration. Upon activating blower  14 , tube  12  starts inflating but slowly and not completely because damper  40   a  being open releases much of the air pressure within tube  12 . After tube  12  is partially inflated, motorized actuator  140  is energized to slowly pull damper  40   a  from its generally open initial configuration of  FIG. 19  to its generally closed operating configuration of  FIG. 20 . Once damper  40   a  closes to its operating configuration, air  18  discharged from blower  14  can fully inflate tube  12 , as shown in  FIG. 20 . Deactivating blower  14  and backspinning spool  50  allows damper  40   a  to return to its initial open configuration of  FIG. 19  and causes tube  12  to deflate. 
     In some examples, the structure of damper  40  of  FIGS. 3 and 4  is as shown in  FIGS. 21 and 22 , wherein a damper  40   b  corresponds to damper  40 .  FIG. 21  shows damper  40   b  at downstream end  22  of tube  12  in an initial configuration, and  FIG. 22  shows damper  40   b  is an operating configuration. In this example, damper  40   b  includes the material of tube  12  itself, wherein the material can be pulled back into tube  12  to create parachute-like flaps  152  that can obstruct airflow. 
     In this example, damper  40   b  is pulled closed by air-powered actuator  46  comprising turbine wheel  48  that drives the rotation of spool  50 . A flexible elongate member  153  threaded through a hole or aperture  154  in a housing  156  has one end  158  coupled to each flap  152  of damper  40   b  and an opposite end  160  wrapped around and attached to spool  50 . 
     Operation can begin with blower  14  inactive and damper  40   b  open in its initial configuration of  FIG. 21 . Upon activating blower  14 , tube  12  starts inflating but slowly and not completely because damper  40   b  being open releases much of the air pressure within tube  12 . While blower  14  is operating, some air  18  blows through nozzle  56  that directs a stream of air across turbine wheel  48 . This turns turbine wheel  48  and spool  50  to draw in elongate member  153 , which pulls on flaps  152  to move damper  40   b  to its more closed operating configuration of  FIG. 22 . Once damper  40   b  moves to its operating configuration, air  18  discharged from blower  14  can fully inflate tube  12 , as shown in  FIG. 22 . 
     In some examples, returning to the initial state shown in  FIG. 21  involves deactivating blower  14  and backspinning spool  50  to release the tension in elongate member  153 . This allows blower  14 , the next time it is activated, to blow damper  40 B back out to its initial configuration of  FIG. 21 . The backspinning of spool  50  can be achieved by various devices such as, for example, a torsion spring that urges spool  50  to its position of  FIG. 21 . In some examples, motorized actuator  140  ( FIGS. 19 and 20 ) is used instead of air-powered actuator  46 . 
       FIGS. 23-26  show an example air duct system  162  comprising an example damper  164  at upstream end  20  of inflatable tube  12 . To slowly and controllably inflate tube  12  at startup, damper  164  in an initial configuration ( FIGS. 23 and 25 ) allows limited airflow to pass when blower  14  is first energized. The limited airflow through and/or past damper  164  can be achieved by a porous area  160  (e.g., a screen, an opening, or a series of holes) and/or by a radial clearance  168  between an outer periphery of damper  164  and an inner periphery of tube  12 . After tube  12  is partially inflated at the reduced flow rate, damper  164  opens fully to an operating configuration ( FIGS. 24 and 26 ) to complete the tube&#39;s inflation at a greater flow rate. In this example, an axle  170  allows damper  164  to pivot between its initial configuration and its operating configuration. 
     In this example, air discharged from blower  14  urges damper  164  to its operating configuration. At blower startup, however, a trigger or arm  172  engages and holds damper  164  at its initial configuration until tube  12  is partially inflated to a predetermined amount, at which time trigger  172  releases damper  164  so that blower  14  can blow damper  164  fully open to its operating configuration. Later, when blower  14  is de-energized while damper  164  is in its operating configuration, damper  164  swings under its own weight back down to its initial configuration to become reengaged with trigger  172 .  FIGS. 23 and 25  show trigger  172  in a hold position engaging damper  164 , and  FIGS. 24 and 26  show trigger  172  in a release position disengaged from damper  164 . 
     The design and actuation of trigger  172  may vary. In some examples, trigger  172  includes an arm  174  that pivots about an axle  176 . The arm&#39;s center of gravity relative to the position of axle  176  urges trigger  172  to pivot to its hold position, wherein a first edge  178  of trigger  172  engages damper  164 . In this example, a flexible elongate member  180  (e.g., string, cord, strap, rope, chain, wire, cable, etc.) connects a second end  182  of trigger  172  to sidewalls  12   a  of tube  12 . 
     When tube  12  is deflated, as shown in  FIG. 25 , elongate member  180  is slack. Elongate member  180  being slack allows trigger  172  to tip to its hold position of  FIGS. 23 and 25 . When blower  14  is energized while trigger  172  is in its hold position and damper  164  is in its initial configuration, blower  14  inflates tube  12  slowly due to the significant flow resistance of damper  164 . As tube  12  inflates to the shape shown in  FIG. 26 , the tube&#39;s sidewalls  12   a  pull elongate member  180  taut, which pulls trigger  172  to its release position of  FIG. 24 . Trigger  172  releasing damper  164  allows blower  14  to blow damper  164  fully open to its operative configuration of  FIG. 24  and complete the tube&#39;s inflation. In this example design, sidewall  12   a  of tube  12  serves as an air-powered actuator that is operatively coupled to damper  164 . 
       FIGS. 27 and 28  show another example air-powered actuator. In this example, the air-powered actuator includes a collapsible bladder  184  disposed within tube  12 . In some examples, bladder  184  is made of a pliable fabric; however, other examples of bladder  184  are comprised of other materials including, but not limited to, a flexible plastic sheet. To trip trigger  172 , a flexible elongate member  186  (e.g., string, cord, strap, rope, chain, wire, cable, etc.) connects bladder  184  to end  182  of trigger  172 . 
       FIG. 27  shows damper  164  generally closed in its initial configuration, shows trigger  172  in its hold position engaging damper  164 , and shows bladder  184  in a relaxed expanded state. Upon energizing blower  14  under such conditions, limited airflow through and/or past damper  164  slowly inflates tube  12 . As tube  12  inflates, the static air pressure within tube  12  increases, which tends to compress bladder  184 . Sidewall  12   a  of tube  12  includes a restricted air passageway  188  (e.g., hole, opening, screen, porous fabric, etc.) that places the air within bladder  184  in restricted fluid communication with atmospheric pressure. Consequently, as the elevated static pressure in tube  12  applies compressive pressure against the bladder&#39;s exterior, bladder  184  slowly collapses as air within bladder  184  leaks out to atmosphere through passageway  188 . As bladder  184  compresses, bladder  184  pulls elongate member  186  taut, which pulls trigger  172  from its hold position ( FIG. 27 ) to its release position ( FIG. 28 ). Trigger  172  releasing damper  164  allows blower  14  to blow damper  164  fully open to its operative configuration of  FIG. 28  and complete the tube&#39;s inflation. 
     In another example, shown in  FIGS. 29 and 30 , damper  164  is held to its initial configuration ( FIG. 29 ) by a trigger  190  that is responsive to pressure in tube  12 . In some examples, for instance, trigger  190  is a solenoid responsive to a signal  192  from a pressure sensor  194  such that in response to the pressure in tube  12  reaching a predetermined limit sufficient to partially inflate tube  12 , sensor  194  provides signal  192  to command solenoid  191  to retract from its hold position of  FIG. 29  to its release position  FIG. 30 . Trigger  190  releasing damper  164  allows blower  14  to blow damper  164  fully open to its operative configuration of  FIG. 30  and complete the tube&#39;s inflation. Trigger  190  and sensor  194  can be separate items, as shown, or the two can be incorporated into a single assembly. 
     In the example shown in  FIGS. 29 and 30 , damper  164  may still include a porous area  160  (e.g., a screen, an opening, or a series of holes) to allow a small percentage of airflow to pass through the damper when blower  14  is first energized. Furthermore, an actuation mechanism other than pressure sensor  194  (e.g., airflow sensor, optical eye, etc.) and trigger  190  could be used to release damper  164  to its fully open position. For example, an actuator could be coupled to axle  170 , wherein the actuator includes a timer that begins when the blower  14  is first energized. After a preset amount of time has passed after energizing blower  14 , the timer and associated actuator may rotate axle  170 , causing damper  164  to open. Alternatively, an actuator could be equipped with a variable speed motor, in which the motor rotates axle  170  very slowly when blower  14  is first energized and then more quickly as time passes, until damper  164  reaches is fully-open position. 
     Some of the aforementioned examples may include one or more features and/or benefits including, but not limited to, the following: 
     In some examples, an inflatable air duct is inflated slowly without the need for a damper controlled by an electrically powered actuator. 
     In some examples, an inflatable air duct is inflated slowly without having to regulate the speed of a supply air blower. 
     In some examples, an inflatable air duct is sometimes lightly inflated by a relatively small auxiliary blower and at other times is more forcibly inflated by a larger blower. 
     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of the coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.