Abstract:
A method of retaining a longitudinally compressed flexible duct, the method includes disposing a strap about a closed flexible container enclosing a longitudinally compressed duct to circumferentially restrict a circumferential dimension of the flexible container and a corresponding circumferential dimension of the longitudinally compressed duct intermediate a first end of the longitudinally compressed duct and a second end of the longitudinally compressed duct. The method further includes opening an end of the flexible container to allow expansion of the longitudinally compressed duct intermediate the opened end of the flexible container and the strap.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 11/204,403, filed Aug. 16, 2005, the entire disclosure of which is hereby expressly incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO A “SEQUENCE LISTING” 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to metering a length of duct from a flexible container retaining the duct in a longitudinally compressed state, and more particularly to a choker for configuring the longitudinally compressed duct and the flexible container to generate tension in a portion of the container corresponding to a longitudinal expansion force of the duct, wherein the tension resists longitudinal expansion of a portion of the longitudinally compressed duct in the flexible container. 
     2. Description of Related Art 
     Flexible duct is used for the transfer of air, heated air or cooled air or other gases. Typically the flexible duct is designed for low-pressure usage, for example about 3 to 5 inches of water pressure. 
     The flexible duct is normally composed of an inner liner or core reinforced by a helical strand such as metal or plastic, a thick layer of flexible insulation such as fibrous glass around the liner, and a flexible plastic, i.e. polymeric, jacket surrounding the insulation. 
     Shipping, handling and storage costs, as well as installer convenience are substantially improved by longitudinally compressing the flexible duct into a container, typically an elongated box, having a length only a fraction of the initial (free) length of the duct. 
     However, upon opening the box to access the longitudinally compressed duct, the entire length of the compressed duct expands, thereby rendering it difficult to retain the unused length of duct within the box. For example, if a 10 foot length of duct were needed, the box is opened and the duct is extended to the full 25 foot length, wherein it the desired 10 foot section is then cut. Recapturing the remaining 15 feet of duct into the box is a difficult and time-consuming operation for the individual installer. Further, for longitudinally compressed duct shipped in a flexible container, such as a bag, reinsertion of the longitudinally expanded (relaxed) duct is particularly cumbersome. 
     Therefore, the need exists for a method of selectively metering a desired length of extended duct, without requiring or allowing the entire length of longitudinally compressed duct to expand. The need also exists for a metering system that can be employed without requiring significant additional material costs. In addition, the need exists for a metering system that can be readily utilized at job sites without requiring additional tools. A further need exists for a metering system that can effectively retain an unused length of the longitudinally compressed duct in the original container, wherein such retained duct remains substantially in the compressed state. 
     BRIEF SUMMARY OF THE INVENTION 
     The present metering system provides for the longitudinal expansion of a selected portion of a longitudinally compressed duct from a flexible container, wherein a remaining portion of the longitudinally compressed duct remains substantially in the longitudinally compressed state and within the container. 
     The present invention allows for the selective removal of a length of duct, including a generally predetermined length of duct, from a flexible container, wherein only the predetermined length of duct is allowed to change from a longitudinally compressed state to an extended or relaxed (free) state. Therefore, in one configuration the present invention removes the prior requirement of having to recompress any unused length of duct into the container. 
     In one configuration, the metering system includes a flexible container having a closeable first end and a longitudinally spaced closed second end; a longitudinally compressed flexible duct within the flexible container, the duct exerting a longitudinal expansion force; and a choker extending about the flexible container at a position spaced from the closed second end to locate a section of the longitudinally compressed duct intermediate the closed second end and the spaced position, the choker substantially precluding passage of the longitudinally compressed duct past the choker to the first end of the container, generating a tension in the flexible container between the closed end and the spaced position in response to the longitudinal expansion force of the retained duct. 
     In is further contemplated the method of metering can include closing a flexible container about a longitudinally compressed flexible duct; and disposing a strap about the flexible container to restrict a radial dimension of the container and resist longitudinal expansion of the duct, wherein a portion of the longitudinally compressed duct is extended. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a perspective view of a given length of flexible duct in a free, extended or relaxed state. 
         FIG. 2  is a perspective view of the given length of duct of  FIG. 1  in a longitudinally compressed state. 
         FIG. 3  is a perspective view of a flexible container and retaining straps retaining the given length of flexible duct in a longitudinally compressed state. 
         FIG. 4  is a side elevational schematic of the container and the duct of  FIG. 3 , with a choker engaged with the container. 
         FIG. 5  is a side elevational schematic of the container, the duct and the choker of  FIG. 4 , showing a released portion of the duct in the free state and a retained portion of the duct in the longitudinally compressed state. 
         FIG. 6  is a side elevational schematic of the container, the duct and the choker of  FIG. 5 , showing re-closure of the flexible container after separation of the released portion of the duct while maintaining the retained portion of the duct in the longitudinally compressed state. 
         FIG. 7  is a side elevational schematic of the container and the duct of  FIG. 6 , after re-closure of the flexible container showing the retained portion of the duct in the longitudinally compressed state. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present system provides for the controlled release of a flexible duct  10  as seen in  FIG. 1 . 
     The flexible duct  10  is often used to transport fluids such as heated, cooled or exhaust air. The duct  10  can have any of a variety of configurations. Typically, the flexible duct  10  has a tubular construction formed by a resilient, such as wire, helix disposed between at least two pliable layers. The duct  10  thus provides a channel through which the fluid travels. As used in describing the duct  10 , the term longitudinal means along a length of the duct, such as extending between ends of the duct. The term radial is used to describe a direction transverse to the longitudinal direction. 
     For purposes of illustration, a representative duct  10  is described, without limiting the metering system. An industry available duct  10  included a flame penetration resistant duct  10  having a plurality of concentric components. The concentric components include a flexible core, a reinforcing layer, an insulative layer and a retaining jacket. It is understood the components employed in a given duct are dictated by design considerations, and applicable building or construction codes setting forth the minimum standards which must be satisfied. 
     The core includes a flexible inner layer and a supporting helix, such as a resilient metal or polymer. The pitch and resilience of the helix are dictated by the intended operating parameters of the duct  10 . 
     In the flame penetration resistant duct, the reinforcing layer is wrapped about the core. The reinforcing layer is typically a fiberglass netting, yarn or scrim. In the scrim configuration, the scrim is wrapped about the outside of the flexible core so as to encircle the core. 
     The insulative layer can be a fiberglass blanket wrapped about the scrim and the core. The insulative layer enhances the thermal integrity of the transported fluid. The insulative capacity of the fiberglass blanket is determined by the fluid to be transported and the permissible heat transfer rate from the fluid. 
     The retaining jacket is a plastic sheath wrapped about the insulative layer, the reinforcing layer and the core to provide an outer housing which retains the components in the proper orientation and relation. It is understood the duct  10  can be formed by the core and the relating jacket surrounding the core. 
     A further construction of the duct  10  is shown in U.S. Pat. No. 5,526,849, herein incorporated by reference. 
     Significant lengths of the duct  10  may be required in a given building. To minimize storage and shipping costs, the duct  10  is usually retained in a longitudinally compressed state within a container. Thus, the duct  10  has a relaxed, extended or free state seen in  FIG. 1  and a longitudinally compressed state shown in  FIGS. 2-7 . As seen in  FIGS. 1 and 2 , a given length of the duct  10  can be longitudinally compressed into a substantially reduced length. For example, a 25 foot length of the duct  10  can be longitudinally compressed down to a length of approximately 48 inches to 36 inches or less. 
     Due to resiliency in the components of the duct  10 , the longitudinally compressed duct  10  exerts a longitudinal expansion force tending to return the duct to the uncompressed length. This longitudinal expansion force is counteracted by the container and/or secondary retaining straps  40 . 
     Referring to  FIG. 3 , a configuration of the flexible container  20  is shown in partial cutaway with the given length of the longitudinally compressed duct  10  retained in the container. It is understood the compressed duct  10  may also have an overlying accordion or pleated configuration (taken herein to be encompassed by the description of “longitudinally compressed”). 
     The container  20  has the general shape of an elongated tube, with a first end  22  and a second end  26 . In one configuration, the first end  22  is an openable/re-closable end. The first end  22  can be re-closable by any of a variety of closure mechanisms  30  described herein. The second end  26  of the flexible container  20  can be a closed or sealed end. 
     The container  20  can be formed from any of a variety of materials including polymers such as polypropylene or polyethylene. A satisfactory material has been found to be polypropylene having a thickness of approximately 2-12 mils. It is also understood the container  20  can be formed of a laminate or a plurality of layers. The container  20  is at least locally deformable, flexible, pliable or resilient to allow the container to effect engagement of a choker  60 , the container and the longitudinally compressed duct  10 . 
     In one configuration, the container  20  has sufficient strength (tensile strength) to substantially withstand the longitudinal expansion force of the longitudinally compressed duct  10  within the container. It is understood that cost considerations can dictate that the container  20  elongate a limited percentage when subject to the full expansion force of the longitudinally compressed duct  10 . Alternatively, the container  20  can be of such material, such as a Kevlar reinforced sheet, that can withstand the expansion force of the longitudinally compressed duct  10  without any material elongation. 
     The supplemental or secondary retaining straps  40  can be applied to the flexible duct  10  either prior to retention within the container  20 , or extending about the container (with the longitudinally compressed duct retained within the container). The retaining straps  40  can be a relatively inextensible material (with respect to the expansion forces of the duct  10 ), and can thus resist the expansion force such that the container  20  is not tensioned by the expansion force. The retaining straps  40  are well known in the packaging industry, and are commercially available. 
     Typically, the flexible duct  10  is loaded into the container  20  by inserting a length of the duct  10  through the open end  22  until a leading end of the duct abuts the closed second end  26 . The duct  10  is then compressed into the container  20  by a suitable apparatus such as a ram or plunger, until a trailing end of the duct has passed the open first end  22  of the container. 
     The open first end  22  of the container  20  is then secured by any of a variety of closure mechanisms  30  such as ties, tape, cleats, knots or adhesives. The ties can include plastic or wire ties. 
     If desired, the retaining straps  40  can then be applied to resist the longitudinal expansion force of the retained longitudinally compressed duct  10 . The retaining straps  40  can be sized to counteract all or substantially all of the longitudinal expansion force of the retained longitudinally compressed duct  10 . That is, the flexible container  20  can be substantially tension free upon engagement of the retaining straps  40 . Alternatively, the flexible container  20  can be sufficiently tensioned to balance all or substantially all of the expansion force from the longitudinally compressed duct  10 . 
     It is understood the longitudinally compressed duct  10  can be temporarily retained in the container  20 , prior to applying the retaining straps  40 . That is, the flexible container  20  can be closed by a tie or similar fastener  30  to restrain the longitudinally compressed duct  10 . Subsequently, and typically prior to significant elongation of the flexible container  20 , the retaining straps  40  are applied to restrain elongation of the longitudinally compressed duct  10 . 
     In the configuration with the retaining straps  40  disposed about the outside of the container  20 , the longitudinally compressed duct  10  exerts the longitudinally directed expansion force against the straps, and for those constructions of the straps having a smaller longitudinal dimension than the container, the container is not materially tensioned by the longitudinal expansion force of the longitudinally compressed duct. 
     Alternatively, if the retaining straps  40  are disposed about the longitudinally compressed duct  10 , within the container  20 , then upon release or removal of the retaining straps, the longitudinally compressed duct exerts the longitudinally directed expansion force against the inside of the container. 
     Although the container  20  has been described in connection with the retaining straps  40 , it is understood the present invention is not limited to such configuration, and can be employed with those containers that do not employ the longitudinal retaining straps. 
     To meter the release of the longitudinally compressed duct  10  from the container  20 , any retaining straps  40  are removed. The longitudinal expansion force of the compressed duct  10  then acts against the closed first end  22  of the container  20  and the closed second end  26  of the container. 
     The choker  60  is a device for restricting a local diameter of the container  20  by a sufficient amount to contact, engage and even partially radially compress the longitudinally compressed duct  10  within the container. Typically, the choker  60  is a strap or belt of flexible material having a circumference at least as great as the container  20 . 
     The choker  60  can cooperate with a clip or cleat  62  for maintaining a given periphery of the choker. The clip  62  can have any of the variety of configurations, such as a belt buckle, detent mechanism, a cam that rotates into and out of contact with the choker  60  or a finger. The choker  60  can include a periphery maintaining structure such as a typical clothing belt having a series of apertures and a finger moveable into and out of engagement with the apertures. 
     In one configuration, the choker  60  is formed by the retaining straps  40  (after removal from the operable position along the longitudinal dimension of the container  20 ), wherein the choker cooperates with the clip  62  to maintain the desired reduced local periphery of the container. 
     The choker  60  is disposed about a periphery of the container  20  intermediate the closed first end  22  and the closed second end  26 . The choker  60  restricts a local periphery of the container  20  by a sufficient amount such that the expansion force of the retained compressed duct  10  acts against the closed second end  26  of the container  20  and the choker, thereby creating a tension in the container between the choker and the closed second end. That is, the choker  60  radially restricts the container  20  and the corresponding local section of the retained longitudinally compressed duct  10 . It is believed the portion of the container  20  pinched between the restricted periphery of the choker  60  and the compressed duct  10  becomes sufficiently bound relative the choker and the local compressed duct, that the container does not slip or slide between the choker and the container. Thus, upon opening the first end  22  of the container  20  the choker provides for the expansion force of the longitudinally compressed duct  10  between the closed second end  26  and the choker to create a tension in the corresponding section of the container  20 . In addition, the choker  60  can define an opening (periphery) that is too small for the retained portion of the longitudinally compressed duct to pass through. 
     The choker  60  is thus tightened about a periphery of the container  20  intermediate the closed first end  22  and the closed second end  26 . The closed first end  22  of the container  20  is then opened and the portion of the longitudinally compressed duct  10  between the choker  60  and the open first end of the container expands as a result of the longitudinal expansion force. The retained portion of the longitudinally compressed duct  10  exerts the longitudinal expansion force against the closed second end  26  of the container  20  and the choker  60 , thereby generating tension in the container between the closed second end and the choker. This tension in the container  20  resists further longitudinal expansion of the retained longitudinally compressed duct  10 . Thus, the portion of the longitudinally compressed duct between the closed second end  26  of the container  20  and the choker  60  remains substantially in the compressed state. In one configuration, the retained longitudinal compression is sufficient to substantially preclude the admission (or introduction) of air into voided portions of the duct  10 . Specifically, for those constructions of the duct  10  having a glass fiber insulating layer, the longitudinal compression of the duct removes a substantial portion of the interstitial spaces within the insulation, thereby forcing a substantial amount of the air from the insulation. In one configuration of the system, engagement of the choker  60  with the container  20  and the corresponding local portion of the retained longitudinally compressed duct  10  is sufficient to substantially preclude expansion of compressed interstitial spaces in the retained longitudinally compressed duct. By maintaining the collapsed interstitial spacing, air is not entrained into the longitudinally compressed duct  10 , and thus the compressed state is substantially maintained (or at least sufficiently maintained so that any remaining length of the longitudinally compressed duct fits within the container  20 ). 
     As seen in  FIG. 5 , upon applying the choker  60  and opening the first end  22 , a released length of the duct  10  extends from the free end of the duct to the choker  60  and a retained compressed length extends from the choker to the closed second end  26  of the container  20 . 
     The released, and generally extended length of the duct  10 , is then cut. Typically the duct  10  is cut proximal to the choker  60  (typically within inches). This reduces the amount of duct  10  that must be re-compressed longitudinally to the disposed within the container  20 . However, it is understood the released length of duct  10  can be cut outside, or spaced from the open end  22  of the container  20 . The first end  22  of the container  20  can then be re-closed or resealed adjacent the choker  60 , the choker removed and the container (with a retained longitudinally compressed duct  10 ) transported and stored in an economical manner. 
     It is also contemplated the choker  60  can remain engaged with the container  20 , without requiring a re-closure of the first end  22  of the container. 
     It is believed the choker  60  sufficiently reduces the local diameter of the container  20  to cause a length of the container intermediate the choker and the closed second end  26  of the container to resist longitudinal expansion of the duct  10 . That is, such portion of the container  20  is put into tension by the longitudinal expansion force of the duct  10 . 
     It has been found that the amount of radial compression from the choker  60  against the longitudinally compressed duct  10  is below a deformation threshold of the duct. That is, the present metering system does not create unusable portions of the duct  10 . The amount of constriction by the choker  60  is a balance between (i) a sufficient amount of constriction to preclude significant longitudinal expansion of the duct  10  from the compressed state, intermediate the choker and the closed second end  26  of the container  20 , and (ii) a constriction which would degradingly deform a local region of the duct in the compressed state. 
     It is further contemplated the container  20  can include a scale, gradations, markings or rulings corresponding to an extended (free) length of the duct  10 . That is, if a 25 foot length of flexible duct  10  is compressed to 4 feet, the container  20  may include markings at approximately every 9.6 inches, wherein each marking represents approximately a 5 foot length of extended (free) duct. Thus, an installer can set the choker  60  at approximately 20 inches from the closed first end  22  of the container  20 , then open the first end thereby extracting approximately 10 feet of duct, while the remaining 15 feet of duct (between the choker and the closed second end  26 ) substantially remains in the longitudinally compressed state. 
     Alternatively, or in combination with the scale or gradations, the container  20  can include an equivalency or correspondence between a compressed length of duct  10  to a relaxed or nominal length of duct. For example, the container  20  may include a statement conveying the information that “1 inch of compressed duct equals approximately 1¼ feet of duct in the relaxed state.” 
     While the invention has been described in connection with a particular embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.