TECHNICAL FIELD

[0001] The present invention relates generally to fire resistant conduits or ductwork.

BACKGROUND

[0002] The heating and cooling systems (also referred to as HVAC) for a residential or commercial building typically have furnaces and air conditioners located in non-temperature controlled areas (such as basements, crawl spaces, attics, and roofs) and then the heated or cooled air distributed through the building using large metal ductwork that may or may not be insulated (typically with a fiberglass blanket) or larger flexible air ducts (typically between 6 and 14 inches in diameter). There is a move towards smaller ductwork that can be placed, for example, in interior residential walls.

[0003] There is a need to create ductwork that are small enough to fit into the space between walls and floor, have some insultation, and pass fire resistant tests.

BRIEF SUMMARY OF THE INVENTION

[0004] The application is directed towards an air distribution component which contains an air distribution duct and a fire resistant (FR) fleece. The air distribution duct has a duct circumference, an outer duct surface and an inner duct surface. The air distribution duct contains a polymer tube having an inner tube surface, an outer tube surface, a tube wall, and a length and a metal wire in a spirally wound along the inner or outer tube surface or within the tube wall along the length of the polymer tube. The FR fleece has a first side, a second side, a first edge, and a second edge. The FR fleece extends around the circumference of the air distribution duct and along the length of the air distribution duct. The first edge and the second edge of the FR fleece are sewn together using an FR thread and the FR fleece contains a plurality of FR staple fibers and a plurality of first char scaffold fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present invention is best understood with reference to the following detailed description of embodiments of the invention when read in conjunction with the attached drawings, in which like numerals refer to like elements, and in which:

[0006] FIG. 1 shows prospective view showing one embodiment of the air distribution component.

DETAILED DESCRIPTION

[0007] Referring now to Figure 1 , there is shown a cross-sectional, prospective illustration of one embodiment of the air distribution component 10. The air distribution component 10 contains an air distribution duct 200 having a duct circumference, an outer duct surface 200b and an inner duct surface 200a. The air distribution duct 200 contains a polymer tube 210 having an inner tube surface, an outer tube surface, a tube wall, and a length and a metal wire 220 spirally wound around the polymer tube along the length of the polymer tube (while the metal wire 220 is shown as spirally wound around the polymer tube, it can also be spirally wound within the polymer tube or be integral to the tube wall). The air distribution component 10 also contains a FR fleece 100 having a first side 100a, a second side 100b, a first edge region 101 , and a second edge region 103, where the FR fleece extends around the circumference of the air distribution duct 200 and along the length of the air distribution duct 200. The first edge region 101 and the second edge region 103 of the FR fleece are sewn together (shown as stitching 110) using an FR thread. The FR fleece 100 contains a plurality of FR staple fibers and a plurality of first char scaffold fibers. Figure 1 shows the air distribution duct 200 extending outward past the FR fleece 200, but this was only done to better show the two elements. [0008] The air distribution duct 200 can be any suitable duct. Sometimes the duct is also referred to as a liner, core, conduit, pipe, ducting, or tube. The air distribution duct 200 contains a polymer tube 210 and a metal wire 220 spirally wound metal wire along the inner or outer tube surface or within the tube wall along the length of the polymer tube 210.

[0009] Preferably, the polymer tube 210 is flexible and has a thin wall thickness. The wall thickness of the polymer tube 21 Ois preferably between about 25 and 75 micrometers. Preferably, the polymer tube 210 is made out of a thermoplastic polymer. In another embodiment, the polymer does not release toxic gas or materials when exposed to fire and/or flame. In one embodiment, the polymer tube comprises polyester, polyolefin, polyvinyl chloride, and mixtures thereof. Preferably, the polymer is polyester, more preferably polyester terephthalate. The polymer tube may be a unitary structure having a single layer or may contain multiple layers. In one embodiment, the polymer tube is co-extruded and contains two or more polymer layers. In another embodiment, the polymer tube is laminated and contains two or more polymer layers. These layers may contain the same or different polymers. The air distribution duct 200 may further contain additional layers such as aluminum foil adhered to the polymer tube.

[0010] Preferably, the outer diameter of the polymer tube 210 (the inner diameter plus the wall thicknesses of the polymer tube) is less than about 8”, more preferably less than about 6”, more preferably less than about 4.5”. Preferably, the outer diameter of the air distribution duct 200 (the inner diameter plus the wall thicknesses of the air distribution duct 200) is less than about 8”, more preferably less than about 6”, more preferably less than about 4.5”. The length of the air distribution duct 200 is much larger than the diameter or circumference of the duct, most times being 100, 1000, or more times larger.

[0011] The metal wire 220 is spirally wound metal wire in a spirally wound along the inner or outer tube surface or within the tube wall along the length of the polymer tube to give the tube (and duct) flexibility along the length of the duct and rigidity across the diameter of the duct. This allows the duct to be bent to go through and around structures within a house but prevents the duct from collapsing onto itself and limiting air flow through the duct. This metal wrapped duct is very similar to a dryer vent used in most residential homes. The metal wire can be any suitable type of metal and any suitable thickness. In one embodiment, the metal is steel. In another embodiment, the metal is stainless steel, copper, aluminum, or mixtures thereof. Steel and stainless steel are preferred due to their low cost and easy formation. The thickness of the wire is desired to be as low as possible while still giving the necessary strength and collapseprevention to the duct so as to save money. In one embodiment, the metal wire 220 is spirally wound around the polymer tube with between about 6 to 12 revolutions per foot. Preferably, the metal wire is adhered to the outer surface 200b of the polymer tube. More preferably, the metal wire is at least partially embedded into the polymer tube wall. One way of manufacturing the duct is to extrude the polymer tube and wrap the metal wire around the tube as it is still at least partially molten from the extruder. In another embodiment, the wire may be added while laminating the polymer films and encapsulating the wire between the layers of film. Yet another way is to coat the wire with polymer and weld it to the tube wall thermally or chemically.

[0012] Referring back to Figure 1 , there is a FR fleece 100 that wraps around the air distribution duct 200. The FR fleece extends around the circumference of the air distribution duct and along the length of the air distribution duct. Preferably, the FR fleece covers essentially all (defined as at least 95% by surface area) of the outer duct surface 200b of the air distribution duct 200. The fleece 200 serves to provide insulation and fire resistance to the duct 200.

[0013] The fire resistant (FR) fleece 100 has a first side 100a and a second side 100b. The first side 100a of the FR fleece 100 preferably faces the outer surface 200b of the duct 200. The FR fleece 100 contains a plurality of FR staple fibers and a plurality of first char scaffold fibers. Specifically, the FR fleece is designed to create a structurally stable char barrier which once formed will protect the duct 200. [0014] The FR fleece preferably contains a plurality of a plurality of FR fibers and a plurality of first char scaffold fibers. In one embodiment, the FR fleece 100 comprises between about 30 and 70% by weight FR staple fibers, between about 20 and 50% by weight FR first char scaffold fibers. Preferably, the FR staple fibers are FR rayon staple fibers. In another preferred embodiment, the FR fleece 100 also contains non-FR fibers. In one embodiment, the FR fleece 100 contains between about 0 and 30% by weight non-FR (typically polyester with no FR additives) fibers. In another embodiment, the FR fleece 100 contains less than about 25% wt non-FR fibers, preferably less than about 15% wt. In another embodiment, the FR fleece 100 contains at least 1 % wt non- FR fibers, preferably greater than about 5% wt.

[0015] The non-FR fibers may be any suitable fiber and are included for loft and bulking of the fleece. Non-FR fibers tend to be less expensive than FR fibers so it is advantageous from a cost standpoint to be able to include a percentage of non-FR fibers in the FR fleece 100. These non-FR fibers provide volume in the z direction (perpendicular to the plane of the fleece) of the nonwoven material. Types of bulking fibers would include fibers with high denier per filament (5 denier per filament or larger), high crimp fibers, hollow-fill fibers, and the like. These fibers provide mass and volume to the material. Examples of fibers used as bulking fibers include polyester, and polypropylene, as well as other low cost fibers. In one embodiment, the non-FR fibers are thermoplastic fibers, preferably polyester fibers. Preferably, the polyester fibers are crimped to maximize the amount of loft from the fibers. Additionally, these non-FR fibers help to carry the FR fibers which typically have little to no crimp and can be quite brittle. In one embodiment, the percentage by weight of non-FR fibers in the FR fleece is between about 0 and 80% wt, more preferably between about 0 and 35% wt, more preferably between about 0 and 20% wt.

[0016] The FR fleece also contains an FR fiber, which is defined to be fibers having a Limiting Oxygen Index (LOI) value of 20.95 or greater, as determined by ISO 4589-1 . The FR fiber may be, for example, FR chemically treated fibers and/or inherently FR fibers. Preferably, the FR fibers are FR rayon staple fibers. In one embodiment, the percentage by weight of FR fibers in the FR fleece is between about 20 and 80%, more preferably between about 25 and 65, more preferably between about

25 and 45%.

[0017] The FR fleece also preferably includes a plurality of first char scaffold fibers. Char scaffold fibers are defined to be fibers that once burned, retain a portion (at least about 80%) of their original strength. These fibers give strength to the fleece after other FR fibers such as the FR rayon fibers are oxidized into a char barrier. The char scaffold fibers may be mineral fibers such as silica and basalt, aramids, carbon fibers including partially oxidized polyacrylonitrile (PAN) and fully carbonized carbon, ceramic fibers. Preferably, the char scaffold fibers are partially oxidized acrylonitrile (also sometimes referred to as PANOX) staple fibers or silica staple fibers. In one embodiment, the char scaffold fibers are partially oxidized acrylonitrile staple fibers. In another embodiment, the char scaffold fibers are silica staple fibers. Preferably, the FR fibers and char scaffold fibers are different fibers (made from different materials). In one embodiment, the percentage by weight of first char scaffold fibers in the FR fleece is between about 20 and 80%, more preferably between about 25 and 65, more preferably between about 25 and 45%.

[0018] In a further preferred embodiment, a 50/50 mixture by weight of partially oxidized acrylonitrile fabrics and mineral fibers provided a surprising FR improvement in performance due to increased char strength.

[0019] Often the char scaffold fibers employed are more brittle and contain significantly less crimp than more traditional fibers used in these applications. For these reasons, numerous enhancements are encouraged including elliptical needling, and proper blending of the fibers in terms of both type and denier to allow proper web formation and carriage through the carding process. Additionally, appropriate web weight and number of crosslaps becomes extremely important when dispersing fibers such as silica and basalt to impart a scaffolding to the char barrier formation.

[0020] The fibers in the FR fleece are typically blended to create a uniform fiber blend but when certain performance characteristics are desired can be stratified and or layered. Additionally, the FR fleece may have additional treatments added to it after batt formation including intumescent chemistries, elliptical needle entanglement, calendering, and the like.

[0021] In one embodiment, the fleece has a tensile strength of between 100 and 1000 Ib/f and a tear strength of between 50 and 500 Ib/f. Tensile strength is measured according to ASTM D4632 and tear strength is measured according to ASTM D4533.

[0022] In one embodiment, the FR fleece 100 may have a reinforcing scrim located within the fleece. The reinforcing scrim is embedded into the fleece and the fleece (including the scrim) preferably has a tensile strength of between 100 and 1000 Ibf and a tear strength of between 50 and 500 Ibt Tensile strength is measured according to ASTM D4632 and tear strength is measured according to ASTM D4533. This reinforcing scrim may contain the first char scaffold fibers (therefore contributing the first scaffold fibers to the FR fleece 100 when the scrim is located in the fleece) or alternatively, may contain second char scaffold fibers. In this embodiment, the FR fleece would contain first char scaffold fibers (preferably as loose fibers) and second char scaffold fibers in the form of a reinforcing scrim. The second char scaffold fibers may be selected from the same group of materials as the first char scaffold fibers. In one embodiment, the second char scaffold fibers are a different fiber than the first char scaffold fibers. In one embodiment, the reinforcing scrim contains fiberglass fibers. Preferably, the FR fleece has a tensile strength strong enough to allow the component 10 to be pulled on or through standard construction materials.

[0023] The reinforcing scrim in the FR fleece 100 provides additional integrity to the fleece both before and after a fire event. The reinforcing scrim is preferably incorporated into the fleece, preferably needle-punched with the nonwoven fibers to create the nonwoven fleece. It has been found that the addition of the scrim within the fleece increased the strength of the fleece as compared to having the scrim on one side of the fleece. Preferably, the scrim within the FR fleece 100 comprises a plurality of yarns. These yarns are preferably formed from a plurality of fibers which have an average staple length of at least about 12 inches. More preferably, the fibers have an average staple length of at least about 20 inches, more preferably at least about 10 feet, more preferably at least about 100 feet, more preferably considered continuous yarns. In another embodiment, the fleece may contain a plurality of yams as described above not in a scrim structure. The reinforcing scrim can be any suitable fabric including knit, woven, or non-woven and has a machine and cross-machine direction. The reinforcing scrim preferably has a thickness of between about 5 and 15 mils. In one embodiment, the FR fleece contains a plurality of yarns that are not in the form of a scrim, these may be unidirectional or randomly placed yarns within the fleece. In one embodiment, the scrim is about 15-50% by weight of the FR fleece.

[0024] In one embodiment, the reinforcing scrim is a laid scrim where yarns (or fibers) are laid in the machine and cross machine direction or multi-axially and are attached together at their cross-over points. Typically, the scrim is designed in an open construction such that fibers from the nonwoven pass around and through the scrim. Preferably, tensile strength of the reinforcing scrim in the machine direction is at least about 100 Ib/f.

[0025] The FR fleece 100 is wrapped around the duct 200 such that the ends of the FR fleece come together to form a sleeve. The first edge region 101 and the second edge region 103 of the FR fleece 100 may be attached together in any suitable method including, but not limited to stitching, adhesive, grommets, snaps, and Velcro. Combinations of these methods may also be used. One embodiment includes a stitched seam and bonding of the inner surface of the fleece with the outer surface of the tube using adhesive (some adhesives may be adequate for the overall adhesion of the surfaces but lack the peel strength to be used for the seam - which would typically be an overlap when adhesive is used. The fleece could also be butted together at the edges when adhered to the tube wall either at the edges of the fleece or in its entirety. Adhering the fleece to the tube over the total area of the tube wall may provide advantages for running the duct inside building structures as the tube and fleece would act as one layer versus potential slipping of the fleece on the duct when the edges of the fleece are attached one to another.) [0026] In one preferred embodiment, the first edge region 101 and the 103 are sewn together forming stitching 110. This stitching can be right at the very edge of the fleece or can be inset a little (typically between about 0.5 and 3” from the true edge). Both of these locations of stitching are considered to be at the edge region of the FR fleece in this application. In one embodiment, there are multiple rows of stitching and they may be on top on one another for additional strength or at different locations in the edge regions.

[0027] When the stitching is done away from the very edge of the fleece but still within the edge region, the fleece forms a double layered plane parallel to the radius of the duct, forming a ridge down the length of the component such as shown in Figure 1 . The ridge may be further attached using additional stitching or adhesives to fold the two sides of the FR fleece together. The ridge may also further contain additional features advantageous to the installation or use of the component 10 such as grommets, a pull line, or metal wire. In one embodiment, in the area of the FR fleece where the FR fleece is sewn together using an FR thread, the FR fleece first edge and second edge are also adhered together with an adhesive.

[0028] The FR fleece wrapped around the air distribution duct has a circumference defined to be the length of FR fleece from the seam formed by the stitching the FR thread, around the duct, and to the seam formed by the stitching the FR thread. In one embodiment, the circumference of the FR fleece is within 10% of the length of the circumference of the air distribution duct. In another embodiment, the circumference of the FR fleece is within 5%, more preferably within 2% of the length of the circumference of the air distribution duct. Having very similar circumferences is desirable so as to minimize the sliding the of the fleece relative to the duct during formation, storage, installation, and use.

[0029] In one embodiment, the stitching is made using a chain or lock stitch such that the threads used in said stitch interlock with the scrim structure within the FR fleece. Any suitable thread may be used for the stitching, but preferably the thread is fire resistant. In one embodiment, the FR thread comprises meta-aramid. Preferably, the product is able to meet the requirements of the UL181 Factory-Made Air Duct standard - particularly the Flame Penetration test the puncture test and UL723 (tunnel test).

[0030] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0031] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e. , meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0032] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the abovedescribed elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.