Nozzle apparatus for airborne paper web dryers

Claim 1

Apparatus for airborne paper web dryers of the non-impingement or underpressure type over which a web is supported in a running plane comprising: a blow box member defined by top web supporting and bottom wall portions, and back and front wall portions interconnecting said top and bottom wall portions, said blow box having an interior defined by said wall portions, said front wall portion having at least an upper portion which has a substantially planar configuration; means provided on said front wall portion for defining an upwardly directed nozzle gap having a width and an exit plane, said nozzle gap being in fluid communication with the blow box interior whereby gas flow is directed through said nozzle gap from said blow box interior along said substantially planar upper portion of said front wall portion; said front and top wall portions being interconnected by a curved guide surface having a radius of curvature, said curved guide surface and front wall portion meeting at a guide surface entry edge plane and said guide surface and top wall portion meeting at a guide surface exit edge plane, said nozzle gap exit plane being spaced a predetermined distance below said guide surface entry edge plane and located at a point from which said substantially planar upper portion of said front wall portion extends; and the relative values of the width of the nozzle gap and the curved guide surface radius of curvature are such that said gas flow follows the planar portion of said front wall and a portion of said curved guide surface and departs from the latter prior to said exit edge plane thereof.