Process for molding a polystyrene foam structure with a bonded covering

Claim 1

A process for molding in situ in a mold with a female cavity and a male member a polystyrene foam structure with relatively rigid thermoplastic sheet bonded to at least a substantial portion of the top, edges, and sides of the structure which comprises: (a) applying a heat-activated adhesive to one surface of a relatively rigid thermoplastic sheet, cutting the sheet to desired dimensions, and folding the sheet to form a folded sheet to the desired shape of the structure; (b) inserting the folded sheet into the female cavity of a mold so that the coated surface is exposed to the male member of the mold and attaching a plurality of reinforcing ribs with a plurality of transfer holes to the male member of the mold before closing so that the ribs project perpendicular from the male member, said ribs having a depth at least equal to a major portion of the depth of the female cavity so as to reinforce the structure molded; (c) injecting heat expandable polystyrene molding material into the interior of the folded sheet; (d) heating the polystyrene sufficiently to expand it to fill the interior of the folded sheet with polystyrene being transferred through the transfer holes so the density of the structure molded is fairly uniform and to force the sheet against the interior surface of the female cavity and heating the adhesive so that the sheet is bonded to the polystyrene; and (e) removing the structure from the mold.