| 摘要 |
A 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 includes a first layer having metallic properties and at least one of them further includes a second, plastic layer bonded to the first layer. 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. All of the layers of both the inner sleeve and the outer sleeve are of a thickness predetermined to together render the duct substantially rigid when in an extended configuration and predetermined to together enable the duct to maintain its substantial rigidity upon extension from a compacted configuration.
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