Patent ID: 8439085

Claim:
A 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; and a resilient wound element disposed between said inner sleeve and said outer sleeve, wherein each of said inner sleeve and said outer sleeve constitutes an aluminum foil ribbon layer, a second, plastic layer bonded to said first foil layer of at least one of said inner sleeve and said outer sleeve, wherein said second plastic layer of said two-layer laminate is bonded to said first layer thereof with a fire-retardant adhesive, wherein each of said sleeves has metallic properties, wherein said wound element imparts corrugations to said inner sleeve and said outer sleeve, 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; and 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 inner sleeve having an inward-facing surface being substantially smooth and featureless except for said wound corrugations so that there is a reduction in the tendency to accumulate lint, thereby improving airflow and reducing fire hazards.