# US 2023/0054867 A1 · Double-Walled Round and Oval HVAC Ductwork Systems Using Phenolic Insulation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0054867 A1 - Document ID: US20230054867A1 - Status: Published application - Kind: A1 - Application number: 18/045,305 - Filed: 2022-10-10 - Published: 2023-02-23 - Earliest claimed: 2019-05-08 - Assignees: Spiral Pipe of Texas - Applicants: Spiral Pipe of Texas, Inc. - Inventors: Robert Stephen Reid; Reid Boydstun - Web page: https://patentgrep.com/patent/US20230054867A1 ## CPC - F24F 13/0263: {Insulation for air ducts} - F24F 13/0245: {Manufacturing or assembly of air ducts; Methods therefor} - F24F 13/0281: {Multilayer duct} - F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02) ## Abstract The present invention involves the preparation and manufacture of phenolic insulation boards for use in double-walled ductwork systems. The preparation of the phenolic insulation board, having a first and second surface each having a foil coating, includes the cutting or grooving of V-grooves into the first surface of the phenolic insulation and first foil coating. This grooving process creates a continuous piece of phenolic insulation having trapezoidal shapes along the second surface and second foil coating. The prepared phenolic insulation board can then be wrapped around an inner sheet metal duct and then covered with an outer shell. Alternatively, the prepared phenolic insulation board can be inserted between an inner duct and outer shell. Both result in a double-walled phenolic insulation ductwork systems. ## Claims ### Claim 1 A double-walled ductwork segment comprising: a first cylindrical sleeve comprising an interior diameter; a second cylindrical sleeve comprising an outer diameter smaller than the interior diameter of the first cylindrical sleeve; and an insulation layer situated between the first cylindrical sleeve and the second cylindrical sleeve, the insulation layer comprising a first surface, a second surface, and a closed-cell membrane, wherein the insulation layer further comprises a plurality of trapezoidal segments comprising channels formed on the first surface and in the closed-cell membrane, wherein each trapezoidal segment comprises a first surface and a second surface, wherein when the insulation layer is situated between the first cylindrical sleeve and second cylindrical sleeve the first surface of a first trapezoidal segment abuts the second surface of an adjoining trapezoidal segment. ### Claim 2 (depends on 1) The double-walled ductwork segment of claim 1, wherein the first cylindrical sleeve is circular. ### Claim 3 (depends on 2) The double-walled ductwork segment of claim 2, wherein the second cylindrical sleeve is circular. ### Claim 4 (depends on 1) The double-walled ductwork segment of claim 1, wherein the first cylindrical sleeve is oval. ### Claim 5 (depends on 4) The double-walled ductwork segment of claim 4, wherein the second cylindrical sleeve is oval. ### Claim 6 (depends on 1) The double-walled ductwork segment of claim 1, wherein the insulation layer comprises phenolic insulation board. ### Claim 7 (depends on 6) The double-walled ductwork segment of claim 6, wherein the first surface of the insulation layer comprises a first foil coating. ### Claim 8 (depends on 7) The double-walled ductwork segment of claim 7, wherein the first surface of the insulation layer comprises a second foil coating. ### Claim 9 (depends on 8) The double-walled ductwork segment of claim 8, wherein the trapezoidal segments are shaped and angled to minimize voids between the first and second surfaces of the plurality of trapezoidal segments in the insulation layer when the insulation layer is wrapped around an exterior surface of the second cylindrical sleeve. ### Claim 10 An apparatus comprising: a first circular tube comprising an interior diameter; a second circular tube comprising an outer diameter smaller than the interior diameter of the first circular tube; an insulation layer situated between the first circular tube and second circular tube, wherein the insulation layer comprises a first surface, a second surface, and a phenolic insulation board. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the insulation layer further comprises a plurality of v-shaped grooves formed on the first surface and in the phenolic insulation board, wherein each v-shaped groove comprises a first surface and a second surface. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein when the insulation layer is situated between the first circular tube and the second circular tube the first surface of a first v-shaped groove of the plurality of v-shaped grooves abuts a second surface of an adjacent second v-shaped groove. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the first surface of the insulation layer is a first foil coating. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the second surface of the insulation layer is a second foil coating. ### Claim 15 (depends on 12) The apparatus of claim 12, wherein the first circular tube and second circular tube comprise sheet metal. ### Claim 16 (depends on 14) The apparatus of claim 14, wherein the first circular tube and second circular tube comprise sheet metal. ### Claim 17 (depends on 16) The apparatus of claim 16 wherein the v-shaped grooves are shaped and angled to minimize voids between the first and second surfaces of the plurality of v-shaped grooves in the insulation material when the insulation material is wrapped around the exterior surface of the second circular tube. ### Claim 18 A method of preparing a double-walled ductwork segment comprising: routing a plurality of v-shaped grooves into an insulation material, wherein each v-shaped groove has a first surface and a second surface; wherein the plurality of v-shaped grooves are spaced and angled to allow the first surface of a first v-shaped groove to abut the second surface of an adjacent v-shaped groove when the insulation material is wrapped around an exterior surface of an interior duct; and insertion of the insulation material wrapped interior duct into an annular space of an exterior duct. ### Claim 19 (depends on 18) The method of claim 18 wherein the insulation material comprises phenolic insulation board further comprising a first surface, a second surface, and a close-cell membrane situated between the first and second surfaces. ### Claim 20 (depends on 19) The method of claim 19 wherein the v-shaped grooves are shaped and angled to minimize voids between the first and second surfaces of the plurality of v-shaped grooves in the insulation material.