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A durable, semi-rigid, flexible duct including a pair of coaxial sleeves, namely an inner sleeve and an outer sleeve disposed parallel to and about the inner sleeve and a resilient wound element disposed between the sleeves. Each of the inner sleeve and the outer sleeve constitutes an aluminum foil

A durable, semi-rigid, flexible duct including a pair of coaxial sleeves, namely an inner sleeve and an outer sleeve disposed parallel to and about the inner sleeve and a resilient wound element disposed between the sleeves. Each of the inner sleeve and the outer sleeve constitutes an aluminum foil ribbon. The wound element imparts corrugations to the two sleeves, such that the duct is extendible between a compacted configuration suitable for storage and for shipping and an extended configuration suitable for installation in a gas transport arrangement. Closely and evenly-spaced ridges that are situated in between the corrugations, add rigidity and durability to the duct. Both the inner sleeve and the outer sleeve are of a predetermined thickness rendering the duct substantially rigid when in an extended configuration and enabling the duct to maintain its substantial rigidity upon extension from a compacted configuration.

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1. A durable semi-rigid, flexible air duct having an axis running the length of said duct and having an inner and outer surface, comprising: a pair of coaxial sleeves, including an inner sleeve and an outer sleeve disposed parallel to and about said inner sleeve;a resilient wound element disposed be

1. A durable semi-rigid, flexible air duct having an axis running the length of said duct and having an inner and outer surface, comprising: a pair of coaxial sleeves, including an inner sleeve and an outer sleeve disposed parallel to and about said inner sleeve;a resilient wound element disposed between said inner sleeve and said outer sleeve;wherein said inner sleeve is bonded to said outer sleeve with a fire-retardant adhesive;wherein each of said inner sleeve and said outer sleeve constitutes an aluminum foil ribbon layer,wherein each of said sleeves has metallic properties,wherein said wound element imparts corrugations to said inner sleeve and said outer sleeve, said inner and outer sleeves being formed with a plurality of closely and evenly-spaced ridges embossed in-between a pair of said corrugations,thereby adding strength and resilience to said duct and such that said duct is axially extendible between a compacted configuration suitable for storage and for shipping and an extended configuration suitable for installation in an air transport arrangement,such that there is no loss of the inner diameter of said duct when re-extended so there is a reduction in the tendency to accumulate lint, thereby improving airflow and reducing fire hazards;wherein said layers of both said inner sleeve and said outer sleeve are of a predetermined thickness rendering said duct substantially rigid when in said extended configuration and enabling said duct to maintain its substantial rigidity upon extension from said compacted configuration; and wherein said closely and evenly-spaced ridges impart additional rigidity to said duct, causing said duct to be resilient and withstand heavy impact forces, which might crush the duct and reduce its diameter. 2. The duct of claim 1, wherein said duct is in said extended configuration after having been compressed to said compacted configuration, said inner sleeve having an inward-facing surface being substantially smooth and featureless except for said wound corrugations and said closely and evenly-spaced ridges. 3. The duct of claim 1, wherein both said aluminum foil ribbon layer of said inner sleeve and said aluminum foil ribbon layer of said outer sleeve are of a thickness in a range of 24 to 35 microns. 4. The duct of claim 1, wherein said duct has a cross-sectional configuration selected from the group which consists of: a circular configuration, a polygonal configuration and a compound configuration wherein said duct is partially circular and partially polygonal. 5. The duct of claim 1, wherein, when a predetermined length L of said duct, of diameter d, is in the extended configuration and is disposed horizontally and supported at a first end thereof, said duct is operative to bend under the influence of gravitational force such that a second unsupported end thereof is lower than said first supported end by no more than y, such that (y/L)×100≦p, wherein p is a predetermined percentage of L. 6. The duct of claim 1, wherein, when a predetermined length L of said duct, of diameter d, is in the extended configuration and is disposed horizontally and supported at both ends thereof, said duct is operative to bend under the influence of gravitational force such that the central portion thereof is lower than the level of said supported ends by no more than c, such that (c/L)×100≦q, wherein q is a predetermined percentage of L. 7. The duct of claim 3, wherein, when L=2 meters and d=10 centimeters, c≦0.001M, and wherein, when said duct is in said extended configuration upon extension from said compacted configuration, c≦0.003M. 8. The duct of claim 1, wherein each of said inner sleeve and said outer sleeve are fabricated of aluminum ribbon of predetermined thicknesses, and wherein said inner sleeve is an inner wound wrapping with a predetermined overlap of said inner sleeve and said outer sleeve is an outer wound wrapping with a predetermined overlap of said outer sleeve. 9. The duct of claim 1, wherein said resilient wound element is fabricated of a metal having spring-like resilience. 10. The duct of claim 9, wherein said resilient wound element is a wound galvanized wire having a diameter in the range of 0.9 to 1.3 millimeters. 11. The duct of claim 1, wherein said duct is selected from the group which consists of: a gas transport duct; and a duct for enclosing utility supply lines. 12. The duct of claim 1, wherein said duct has a cross-sectional configuration selected from a group which consists of: circular, polygonal, square; and rectangular configuration. 13. The duct of claim 1, wherein said closely and evenly-spaced ridges of said duct serve as threads that enable a screw-type connection. 14. The duct of claim 13, wherein said screw-type connection is provided by a duct connector ring comprising tooth-like projections matching said closely and evenly-spaced ridges of said duct, said projections provided on one side thereof, the other side thereof comprising means for connection to additional accessories. 15. The duct of claim 14, wherein said means for connection comprises an annular ridge, for connection to an adaptor ring formed with an annular groove on one side thereof, said groove matching said annular ridge of said duct connector ring, so that when said adaptor ring and said duct connector ring are brought together they connect via a snap-on connection between said annular ridge and said annular groove, and wherein the other side of said adaptor ring is the appliance connection side for connecting to at least one of a dryer and pipe. 16. The duct of claim 14, wherein said duct connector ring is connected to a lint trap, for the purpose of collecting lint that is released from said duct, so as not to allow said lint to scatter around the vicinity of the dryer, said lint trap comprising a top part having an integrally formed said adaptor ring, including said annular groove for connecting to said connector ring. 17. The duct of claim 16, wherein said duct connector ring is connected to a draft blocker which is utilized for the exhaust on the end of said duct, connecting it through a wall, said draft blocker comprising, an inlet section functioning as said adaptor ring for connecting to said connector ring threaded onto said duct. 18. A method for manufacturing a semi-rigid, flexible duct, comprising the steps of: a) providing a mandrel of preselected diameter for fabricating a duct therearound;b) providing a first continuous aluminum ribbon of predetermined thickness;c) providing a second continuous aluminum ribbon of predetermined thickness;d) wrapping said first continuous ribbon with a predetermined overlap around said mandrel to form an inner sleeve;e) winding a wire around said inner sleeve;f) wrapping said second continuous ribbon with a predetermined overlap around said inner sleeve and the wire winding to form an outer sleeve disposed parallel to and about said inner sleeve, wherein said outer sleeve is bonded to said inner sleeve using a fire-retardant adhesive, thereby to form a duct; andg) forming ridges on said aluminum ribbon by causing engagement of a ridged break-down wheel with a modified roller, while said aluminum ribbon is in between them, wherein said ridged break-down wheel is supported by a mounting arm external to said mandrel. 19. The method of claim 18, wherein in said step f) of wrapping said second ribbon, the wire is wound around said outer sleeve and said inner sleeve. 20. The method of claim 18, wherein said step e) of winding a wire includes the sub-step of aligning said wire with the overlap of said first ribbon so that the wire is approximately centered over the overlap of said first ribbon, and wherein said step f) of wrapping said second ribbon includes the sub-step of aligning said second ribbon so that the overlap thereof is approximately centered over the spaces between the wire windings. 21. The method of claim 18, wherein said step d) of winding said first aluminum ribbon, said step e) of winding the wire, and said step f) of winding said second aluminum ribbon, are performed by rotating said mandrel as said first aluminum ribbon, the wire, and said second aluminum ribbon are respectively taken up by said mandrel, continuously and with predetermined phase differences therebetween, with respect to the rotation of said mandrel. 22. The method of claim 18, wherein said step d) of winding said first aluminum ribbon and said step e) of winding the wire are performed continuously and with a first preselected phase difference therebetween, with respect to the rotation of said mandrel; and wherein said step e) of winding the wire and said step f) of winding said second aluminum ribbon are performed continuously and with a second preselected phase difference therebetween, with respect to the rotation of said mandrel. 23. The method of claim 18, wherein said modified roller of said step g) of forming ridges on said aluminum ribbon, is modified by adding circumferential grooves to the distal end of said roller, and wherein said grooves match said ridges on said break-down wheel, and wherein said grooves and said ridges mesh with each other by engagement, while said aluminum ribbon is in between them, thus forming said closely and evenly-spaced ridges on said aluminum ribbon. 24. The method of claim 18, wherein said arm supporting said break-down wheel is adjustably moved into position during the setup of said manufacturing process, and once established is maintained during production. 25. The method of claim 18, and further including, after said step f) of wrapping, the additional step of imparting to at least a portion of said duct, a polygonal cross-sectional configuration. 26. The method of claim 25, and wherein said additional step of imparting a polygonal cross-sectional configuration to at least a portion of said duct comprises imparting thereto a square or rectangular cross-sectional configuration. 27. The method of claim 18, wherein said first continuous aluminum ribbon and said second continuous aluminum ribbon maintain a substantially constant and identical tension, while being wrapped around said mandrel, in the range of 65-70 kgf, and wherein said wire is also maintained in the same said tension of both said aluminum ribbons. 28. The method of claim 18, wherein said mandrel comprises a plurality of rollers each mounted so as to be individually rotatable on a fixed plate at a predetermined angle, each comprising a set of precision-shaped grooves for accepting said wire, and wherein said grooves are precision-spaced apart in order to accept a predetermined flow of said wire, established by said predetermined angle of said rollers, onto said mandrel, such that said wire becomes a spiral form within said duct being drawn off said mandrel in an automatic fashion. 29. The method of claim 28 wherein each of said rollers is mounted on said plate so as to provide a flexible spring-like action which absorbs any irregularities in said tension and irregularities associated with said wire and said ribbons.