METHOD AND APPARATUS FOR CONTINUOUSLY MANUFACTURING ARTICLES FROM FOAMED THERMOPLASTIC MATERIAL

1,270,581. Moulding foamed thermoplastic articles. T. W. WINSTEAD. 28 April, 1969 No. 21589/69. Addition to 1,159,562. Heading B5A. Continuously extruded foamed thermoplastic sheet or tubing has one or both surfaces or portions thereof chilled to produce continuous or discontinuous unexpanded skins on the sheet or tubing, and such material is passed directly to moulding apparatus which utilizes the residual heat of extrusion in the formation of articles. Such an apparatus is described in the parent Specification and shown in Fig. 2 (not reproduced) where trays are formed from sheeting utilizing a rotating vacuum-forming wheel. It is stated that by suitable cooling a surface may have portions with and without skins producing a checkerboard effect. Extrusion dies.-In the embodiment of Fig. 1 extrudate leaves die head 7 via a fan-shaped reservoir 12a and arcuate extrusion orifice as described in Specification 1,159,561. Cooling is effected by air or gas emanating from an arcuate orifice 18 of a housing 16. In a second embodiment, Fig. 3 (not shown), cooling is by conduction, cooling fluid flowing in passageways (33) of die head 7. Also provided are heat insulating blocks (31) and a diverging die mouth (34) preferably provided with a PTFE coating. In modifications, mouth (34) may be partially divergent or parallel sided.