摘要 |
<p>A FLEXIBLE DUCT COMPRISING A FIRST, INNER LAYER (15) THAT INCLUDES MULTIPLE HELICAL WINDINGS OF A STRIP OF THIN FLEXIBLE MATERIAL, A SECOND LAYER (16) OVERLAYING AND ADHERED TO SAID FIRST, INNER LAYER AND INCLUDING MULTIPLE HELICAL WINDINGS OF A TUBE (13) CONTAINING INSULATING MATERIAL (18), AND A HELICALLY WOUND REINFORCING ELEMENT (17). ALSO DISCLOSED IS A METHOD OF FORMING A FLEXIBLE DUCT INCLUDING HELICALLY WINDING A TUBE CONTAINING INSULATING MATERIAL, WHEREIN THE TUBE IS DELIVERED INTO ITS INITIAL WINDING AT A RATE OF DELIVERY SO THAT AT THE OUTER PERIPHERY OF THE WINDING THE TUBE REMAINS SUBSTANTIALLY UNSTRETCHED AND UNCOMPRESSED CIRCUMFERENTIALLY, WHILE AT THE INNER PERIPHERY THE TUBE IS ALLOWED TO PUCKER CIRCUMFERENTIALLY. STILL FURTHER DISCLOSED IS A METHOD OF FORMING AN INSULATING TUBE, INCLUDING THE STEPS OF DRAWING A STRIP OF FLEXIBLE MATERIAL RELATIVELY LATERALLY OF AND INTO A FORMING HEAD THAT DELIVERS THE STRIP FORWARDLY FROM THE FORMING HEAD AS A TUBULAR CASING IN THE DIRECTION OF THE AXIS OF THE CASING, AND DELIVERING FIBROUS INSULATING MATERIAL INTO SAID CASING AT THE FORMING HEAD AS A GAS-ENTRAINED STREAM OF THE MATERIAL.</p> |