Duct configuration for a through-air drying apparatus in a papermaking

Abstract

A through-air drying apparatus for drying a traveling wet paper web supported on a continuous fabric comprises a dryer roll about which the fabric and web are partially wrapped and which has a foraminous roll face, a supply hood which surrounds the portion of the roll about which the fabric and web are wrapped and which supplies heated air through the fabric and web and through the roll face into the interior of the roll, and an exhaust system for exhausting air from the roll. An axial exhaust passage is formed through at least one head of the roll. An exhaust manifold is connected to the exhaust passage and defines two outlets on opposite sides of the manifold. A pair of movable ducts are sealingly and releasably engaged with the outlets in the opposite sides of the manifold, the ducts being spaced apart on opposite sides of the roll so that an access space is defined between the two ducts for access to the roll and supply hood. The movable ducts are pivotally connected to fixed ducts by bendable bellows sections of the movable ducts and by hinges. The movable ducts pivot about axes parallel to the rotation axis of the dryer roll such that the ducts extend axially beyond the roll by about the same axial extent in both the open and closed positions. The duct system is also suitable for supplying air to the interior of a roll in an outward-flow type of through-air drying apparatus.