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US 4,892,442 AGranted
Prelubricated innerduct
AssigneeDura-Line Corporation
InventorJohn Shoffner
Life of this patent
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AssigneeDura-Line Corporation
InventorJohn Shoffner
Estimating the term…
An innerduct is disclosed which can fit inside a preexisting conduit and extend along the length thereof or can be directly buried with a plow or in an open trench, for receiving transmission cables and, in particular, fiber optic cables. The innerduct is formed by coextruding first and second materials, the material for the inner portion of the innerduct including a lubricous material impregnated therein so that friction is reduced between the inner surface of the interduct and cables which are pulled therethrough. Ribs can be provided on the inner and outer surfaces of the innerduct of the duct can be formed with undulated walls so as to further reduce friction between same and cables slid therethrough by minimizing the surface contact between these elments. The ribs and/or undulations also faciliate the dissipation of heat due to friction of assembly, heat during the extrusion process, and from ambient sources of heat.
A relatively flexible coextruded plastic tube for slidably receiving and providing a protective housing for a cable, said tube consisting essentially of a pair of telescopically related inner and outer cylindrical portions, said inner portion being formed from a highly lubricous polymeric material to provide a permanently lubricated inner surface for the tube which has a low coefficient of friction to enable substantially low friction placement of the cable therewithin and said outer portion being formed from a high tensile strength polymeric material for maintaining the structural integrity so that a protective housing is defined for the cable by the tube.
A prelubricated innerduct for installing at least one of a cable, a rod, or a tube in a length of conduit, said prelubricated innerduct slidably receiving and providing a protective housing for said cable, rod, or tube, said prelubricated innerduct consisting essentially of:
Dependencies are inferred from the claim text.