HVAC Duct System, Method and Machine
A method for connecting two duct sections having an outer layer of thermoplastic material and an inner layer of foam, and duct produced by the method. The method entails the use of thermoplastic material to form at least one flange in the finished duct. The thermoplastic material may be a portion of the outer thermoplastic layer of the duct section or it may be made, in-situ, from a separate strip or strips of thermoplastic material. In the latter case, a strip of thermoplastic material may be fashioned into a sleeve in which the ends of the duct sections reside or a separate strip may be securely fastened to each of the ends of each of the duct sections. In the latter case, a portion of the strip extends radially outwardly and a belly band or the like is positioned over the radially outwardly extending portion of the strip and tightened to bring them together and seal the interface between the ends of the duct sections.
1 . A method for connecting a first duct section to a second duct section where the duct sections comprise a laminate formed of an outer layer of a thermoplastic sheet and an inner layer of a foam sheet, said method comprising the steps of
providing a strip of thermoplastic material,
heating the strip of thermoplastic material to soften it,
wrapping a first portion of the heated strip around the end of the first duct section so that a second portion of the strip extends beyond the end of the first duct section,
securely fastening the first portion of the heated strip around the end of the first duct section,
inserting the end of the second duct section into the sleeve, and
securely fastening the sleeve portion of the heated strip around the end of the second duct section.
2 . The method claimed in claim 1 wherein the length of the strip, before heating, is less than the outer circumference of the first and second duct sections and wherein, when the strip is heated, it is stretched until it has a length equal to the outer circumference of the first and second duct sections and wherein the shape and length of strip is held until the thermoplastic strip cools.