Annular extrusion nozzle for expanded plastic - formed by centre body mounted by perforated radial plate in a chamber

摘要

An extrusion nozzle includes a chamber within a housing which pref. is formed in two parts which are bolted together with a perforated plate between them and a torpedo shaped centre-body is located concentrically in the chamber, the centre-body being supported by pref. being screwed into a central aperture in the perforated plate. The space between the centre-body and chamber wall defines an annular feed duct through which melt passes to an annular extrusion aperture defined by a pref. cylindrical portion of the body and a pref. circular mouth of the chamber and pref. a sleeve is slidable along a part of this cylindrical portion projecting through the mouth to allow adjustment of the size of the extrusion aperture. Pref. the annular feed duct narrows to a throttle immediately downstream of the perforated plate. The nozzle allows extrusion of expanded polystyrene foam to produce tubes having wall thicknesses of 0.203-0.254 mm. The tube may be subsequently split axially to produce a flat sheet.