Patent Application
20240053050
Heating, ventilation, and air conditioning (“HVAC”) systems often utilize flexible duct to carry treated air throughout a structure. For example, flexible duct can be used to carry heated or cooled air to various locations within a residential home or a commercial building. However, if a fire occurs within the residential home or commercial building, the flexible duct can potentially provide a passage for flames to travel. Accordingly, flexible duct is often subjected to various fire safety-related tests to ensure that flames cannot enter the flexible duct and accelerate the spread of the fire across the various locations of a home or commercial building.
One type of fire safety-related test that flexible duct may be subjected to is a flame penetration test. Generally, flame penetration tests are designed to measure a flexible duct's ability to resist being penetrated when exposed to a flame. This is typically performed by obtaining a rectangular-shaped sample of the tubular body of the flexible duct, pacing a weight on a top surface of sample, and directing a flame towards a bottom surface of sample. In order to pass the flame penetration test, neither the weight nor the flame can penetrate the top and bottom surfaces of the sample over a predetermined period of time. Thus, designing a flexible duct to withstand a flame penetration test may ensure that the flexible duct will not accelerate the spread of fire throughout a structure. Accordingly, there is a need for flexible duct and flexible duct components that are able to resist flame penetration.
Embodiments of flexible duct, scrim-bonded insulation, and related methods are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components. The features depicted in the figures are not necessarily shown to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness.
The body 20 includes a vapor barrier 40, an insulation layer 60, and a tubular core 50. The vapor barrier 40 is the radially outer layer and may be a tubular sheet that fluidly isolates the other layers from the surrounding environment. The tubular core 50 is the radially inner layer and includes a structural support 70 within a tubular sheet. The tubular core 50 fluidly isolates the other layers from the central cavity 30. The insulation layer 60 is disposed between the vapor barrier 40 and the tubular core 50 and reduces thermal interaction, and thus a rate of heat transfer, between air in the central cavity 30 and the surrounding environment.
Moisture may collect on the outer surface of the flexible duct 10 due to condensation caused by the temperature difference between the central cavity 30 and the surrounding environment. The insulation layer 60 also includes a fibrous material, such as glass fibers, which may absorb and trap moisture. In some cases, the insulation layer 60 may be constructed from a fiberglass insulation material, such as various fiberglass insulation materials known in the art. Moisture absorbed by the insulation layer 60 reduces the insulating effects of the insulation layer 60, thereby allowing more heat transfer between the central cavity 30 and the surrounding environment. Further, moisture may decrease the lifespan of the insulation layer 60. Therefore, the fluid barrier provided by the vapor barrier 40 and the tubular core 50 blocks fluids, particularly the moisture from condensation, from contacting and damaging the insulation layer 60.
When placed within an HVAC system, the flexible duct 10 may be positioned to change directions along its axial length. For example, the flexible duct 10 may be bent to carry air around corners and/or obstacles. The structural support 70 of the tubular core 50 may provide structural rigidity to the flexible duct 10 to maintain the cross-sectional area of the central cavity while also maintaining the flexibility of the flexible duct 10. The structural support 70, for example, may be a solid, such as a metal, wound into an elongated spring within the tubular sheet. Maintaining a cross-sectional area of the central cavity 30 may provide a more consistent flow path with fewer pressure variations along the length of the flexible duct 10.
To perform the flame penetration test using the testing arrangement 100, a portion of the body 20 of the flexible duct 10 is spread as a sheet across and secured to a testing frame 110 with the vapor barrier 40 facing toward a flame 130 and the tubular core 50 facing away from the flame 130. A weight 120 may be applied to the tubular core 50 while the flame 130 is applied to the vapor barrier 40. To successfully pass the flame penetration test, neither the weight 120 nor the flame 130 can penetrate through the body 20 for a predetermined period of time.
In some aspects of the present disclosure, the testing arrangement 100 can be configured according to the UL 181 flame penetration test standard. The UL 181 standard was developed by Underwriter's Laboratories, Inc. for testing the ability of air ducts to resist flame penetration. According to the UL 181 standard, the weight 120 is a 3.6 kg weight that covers an area of 2.5 cm×10.2 cm of the tubular core 50. Further, the flame 130 is applied to the vapor barrier 40 at a temperature of about 774° C. According to the UL 181 standard, the flame penetration test is failed if either the weight 120 falls through the body 20 or the flame 130 passes through the body 20 within 30 minutes. In other aspects, the testing arrangement 100 can be configured to perform a flame penetration test according to parameters that are different from the UL 181 standard.
The scrim layer 42 may be integrated into the vapor barrier 40A by being laminated between two layers of polymer film. For example, the vapor barrier 40A may include the scrim layer 42 positioned between a radially inward layer of polyester film and a radially outward layer of metallized polyester film. The metallized polyester film may provide the flexible duct 200 with a metallic appearance. Further, in some aspects, the vapor barrier 40A may be helically wound into a tubular shape using a layered sheet of scrim and laminated film components. That is, the layered sheet may be helically wound into a tubular shape with a desired circumference (e.g., greater than 6 inches) to form the vapor barrier 40A. Thus, the assembled vapor barrier 40A may have continuous, helical seam(s) where the layered sheet(s) are joined together. Accordingly, there may be interruptions in the scrim layer 42 around the circumference of the vapor barrier 40A where the seam(s) are located. In some cases, the layered sheet may have a width shorter than the outer circumference of the assembled vapor barrier 40A. The radially inward layer of polyester film, the scrim layer 42, and the radially outward layer of metallized polyester film described above may be laminated into a layered sheet having a width of about 6 inches (15.24 cm).
In some aspects of the present disclosure, the wire structure 52 may provide enough structural support to the flexible duct 300 that a scrim layer (e.g., the scrim layer 42 described above) need not be included in the vapor barrier 40 for the flexible duct 300 to adequately resist flame penetration. For example, the vapor barrier 40 may be constructed from a blown polyethylene film that does not include a scrim layer.
The scrim layer 80 may be constructed using a variety of yarn and coating materials, strand configurations, and mesh patterns. For example, the scrim layer 80 may be constructed from glass fiber textile yarn. The glass fiber textile yarn may be formed by drawing molten glass through small holes to form hair-like filaments. After the filaments cool and harden, the filaments may be gathered into strands, plied together, and/or twisted to form the glass fiber textile yarn. In some aspects, the filaments may be bound together and/or coated with various resinous and/or elastomeric binder materials such as, for example, polyvinyl alcohol, polyvinyl acetate, and/or acrylic binders to form the glass fiber textile yarn. The glass fiber textile yarn may be laid or woven into various mesh patterns. Advantageously, the yarn and binder materials, strand configurations, and/or mesh patterns of the scrim layers described herein may be configured to improve resistance to flame penetration and/or satisfaction of a flame penetration test of a corresponding flexible duct, while minimizing material and/or manufacturing costs.
The glass textile fiber yarn of the scrim layer 80 may include glass compositions known to those skilled in the art. For example, the glass textile fiber yarn may include A-glass fibers, C-glass fibers, D-glass fibers, E-glass fibers, Advantex® fibers (manufactured by Owens Corning®), ECR glass fibers, AR-glass fibers, R-glass fibers, S-glass fibers, T-glass fibers, S2-glss fibers, M-glass fibers, Z-glass fibers, or a combination thereof.
The filaments used in the glass textile fiber yarn of the scrim layer 80 may be continuous, stapled, texturized, or a combination thereof. The filaments used in the glass textile fiber yarn of the scrim layer 80 may have an average filament diameter in a range of 3 microns to 25 microns, such as, for example, about 4 microns, 4.5 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, or about 24 microns. The filaments used in the glass textile fiber yarn of the scrim layer 80 may be twisted to form a strand. Further, one or more than one strand (e.g., 1 strand, 2 strands, 3 strands, 4 strands, etc.) may be twisted together to form the glass textile fiber yarn.
The glass textile fiber yarn may be configured into various mesh patterns to form the scrim layer 80. For example,
The columns 82 referenced above with respect to
The insulation assembly 90 may be constructed by bonding the scrim layer 80 to the insulation layer 60. For example,
Various techniques may be used to bond the scrim layer 80 to the insulation layer 60 to form the insulation assembly 90. For example, the scrim layer 80 can be bonded to fiberglass insulation material of the insulation layer 60 by applying an adhesive to a surface of the scrim layer 80 and/or a surface of the fiberglass insulation material and positioning the scrim layer 80 against the fiberglass insulation material. The adhesive used to bond the fiberglass insulation material and the scrim layer 80 may include various resinous and/or elastomeric binder materials such as, for example, acrylic binders, polyvinyl alcohol binders, polyvinyl acetate binders, phenol-formaldehyde binders, polycarboxy binders, polyurea binders and/or bio-based binders.
In another aspect of the present disclosure, the scrim layer 80 may be bonded to the insulation layer 60 during the manufacturing of the fiberglass insulation material. For example, fiberglass insulation material is typically manufactured by spinning molten glass through small holes to create glass fibers. Adhesive is applied (e.g., sprayed via spray nozzles) to the glass fibers to form a mass of adhesive-coated glass fibers. The mass of adhesive coated glass fibers are cured in a curing oven to form the fiberglass insulation material. The scrim layer 80 may be applied to the adhesive-coated mass of glass fibers prior to curing. Thus, the adhesive used to form the fiberglass insulation material may also be used to bond the scrim layer 80 to the fiberglass insulation material. The fibrous strands of the scrim layer 80 of
The insulation assembly 90 can provide numerous benefits related to the manufacturing and performance of the flexible ducts described herein. In one aspect, the scrim layer 80 of the insulation assembly 90 may improve the resistance of the flexible duct 400, 500 to flame penetration by providing structural support to the flexible duct 400, 500. For example, the rate at which flame penetrates the flexible duct 400, 500 may depend on the structural properties of the flexible duct 400, 500. This may be because placing the various layers of the flexible duct 400, 500 under tension (e.g., by placing a weight on the body of the flexible duct 400, 500) may cause the layers to be more susceptible to flame penetration. The structural support provided by the scrim layer 80 may resist this tension force and therefore resist flame penetration of the flexible duct 400, 500.
As another example, as explained in more detail below related to
As also explained above with respect to
The third collar 1040 can be configured to position and/or wrap the vapor barrier 40 at least partially around the insulation assembly 90. For example, as the insulation assembly 90 and the tubular core 50 are pulled across the platform 1010, the third collar 1040 can be used direct the vapor barrier 40 around the insulation assembly 90. Heat may be applied to the vapor barrier 40 to seal any seam that results from positioning the vapor barrier 40 around the insulation assembly 90. As can be appreciated from
Further examples of the present disclosure may include:
Example 1 is flexible duct. The flexible duct includes a tubular core, a vapor barrier, and an insulation assembly. The tubular core is configured to convey a fluid. The vapor barrier surrounds the tubular core. The insulation assembly is positioned between the tubular core and the vapor barrier. Further, the insulation assembly includes an insulation layer and a scrim layer bonded to the insulation layer. The scrim layer is configured to resist flame penetration of the flexible duct.
In Example 2, the subject matter of Example 1 can further include wherein the scrim layer is bonded to a radially inward surface of the insulation layer.
In Example 3, the subject matter of Example 1 can further wherein the scrim layer is bonded to a radially outward surface of the insulation layer.
In Example 4, the subject matter of Examples 1-3 can further include wherein the scrim layer comprises a glass fiber textile yarn.
In Example 5, the subject matter of Examples 1˜4 can further include wherein the glass fiber textile yarn comprises E-glass fibers.
In Example 6, the subject matter of Examples 1-5 can further include wherein the scrim layer comprises at least one of tri-axial pattern, a rectangular patter, or a square pattern.
In Example 7, the subject matter of Examples 1-6 can further include wherein the insulation layer comprises a fiberglass insulation material.
In Example 8, the subject matter of Examples 1-7 can further include wherein the scrim layer is a first scrim layer, and wherein the vapor barrier comprises a second scrim layer.
In Example 9, the subject matter of Example 8 can further include wherein the vapor barrier further comprises a radially inward polyester film layer and a radially outward metallized polyester film layer surrounding the second scrim layer.
In Example 10, the subject matter of Examples 1-7 can further include wherein the vapor barrier comprises a blown polyethylene film.
Example 11 is an insulation assembly for use in a flexible duct. The insulation assembly can include a fiberglass insulation layer and a scrim layer bonded to the insulation layer. The scrim layer can be configured to resist flame penetration of the flexible duct when used in the flexible duct.
In Example 12, the subject matter of Example 11 can further include wherein the scrim layer comprises a glass fiber textile yarn.
In Example 13, the subject matter of Examples 11-12 can further include wherein the glass fiber textile yarn comprises E-glass fibers.
In Example 14, the subject matter of Examples 11-13 can further include wherein the scrim layer comprises at least one of tri-axial pattern, a rectangular patter, or a square pattern.
In Example 15, the subject matter of Examples 11-14 can further include wherein the insulation assembly is formed by spinning molten glass into glass fibers, applying adhesive to the glass fibers to form an adhesive-coated mass of glass fibers, applying the scrim layer to the adhesive-coated mass of glass fibers, and curing adhesive-coated mass of glass fibers.
In Example 16, the subject matter of Examples 11-14 can further include wherein the insulation assembly is formed by applying an adhesive to at least one of the scrim layer or the fiberglass insulation layer and placing the scrim layer against the fiberglass insulation layer.
Example 17 is a method for assembling a flexible duct. The method can include positioning an insulation assembly around a tubular core. The insulation assembly can include an insulation layer and a scrim layer bonded to the insulation layer. The method can further include positioning a vapor barrier around the insulation assembly to form the flexible duct. The scrim layer can be configured to improve a flame penetration resistance of the flexible duct.
In Example 18, the subject matter of Example 17 can further include wherein positioning the insulation assembly around the tubular core comprises positioning the scrim layer adjacent to the tubular core.
In Example 19, the subject matter of Example 17 can further include wherein positioning the insulation assembly around the tubular core comprises positioning the scrim layer adjacent to the vapor barrier.
In Example 20, the subject matter of Example 17-19 can further include wherein the insulation layer is a fiberglass insulation material. The method can further include assembling the insulation assembly. Assembling the insulation assembly can include spinning molten glass into glass fibers, applying adhesive to the glass fibers to form an adhesive-coated mass of glass fibers, applying the scrim layer to the adhesive-coated mass of glass fibers, and curing the adhesive-coated mass of glass fibers.
In Example 21, the subject matter of Examples 1-10 can further include wherein the scrim layer is configured to resist flame and weight penetration of the flexible duct when subjected to a flame penetration test according to Underwriters Laboratories (UL) test standard UL 181.
In Example 22, the subject matter of Examples 11-16 can further include wherein the scrim layer is configured to resist flame and weight penetration of the flexible duct when subjected to a flame penetration test according to Underwriters Laboratories (UL) test standard UL 181.
In Example 23, the subject matter of Examples 17-20 can further include wherein the scrim layer is configured to resist flame and weight penetration of the flexible duct when subjected to a flame penetration test according to Underwriters Laboratories (UL) test standard UL 181.
One or more specific embodiments of the flexible duct, scrim-bonded insulation, and related methods have been described. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function.
Reference throughout this specification to “one embodiment,” “an embodiment,” “embodiments,” “some embodiments,” “certain embodiments,” “aspects” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, these phrases or similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.
