Patent ID: 8469062

Claim:
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.