Patent ID: 6241926
Filing Date: 2001-06-05
Classification: A42C,B29C,Y10T

Abstract:
A process for molding an expanded polystyrene bead construct within a mold assembly, said mold assembly including a female half mold having a first, continuous, peripheral edge surface and an interior surface configured to impart a desired exterior surface to the construct, a male half mold having a second, peripheral edge surface in mating alignment with the first peripheral edge surface when the female half mold and the male half mold are aligned on an alignment axis, a first male mold insert mountable on the male half mold and having a third, beveled, continuous peripheral edge surface, the female half mold and the first male mold defining a first volume therebetween when the first male mold is inserted into the female half mold, and a second male mold insert mountable on the first male mold insert, the female half mold and the second male mold insert defining a second, reduced volume therebetween when the second male mold insert is inserted into the female half mold, the process comprising:(a) filling the female half mold with pre-expanded polystyrene beads of a predetermined density;(b) mounting the first male mold insert on the male half mold;(c) molding the beads under applied heat and pressure by forcing the first male mold insert against the beads to fuse the beads together to form a first intermediate product of a first volume having a continuous, beveled edge surface formed between the beveled edge surface of the first male mold insert and the peripheral edge surface of the female half mold;(d) rapidly cooling the fused first intermediate product to within a subplasticizing temperature range to cause lower than atmospheric pressure within the beads of the first intermediate product;(e) mounting the second male mold insert on the first male mold insert; and(f) compressing the cooled first intermediate product between the second male mold insert and the female half mold to a second, reduced volume before the low pressure conditions within the beads equilibrate to ambient conditions to produce a fused expanded bead body of at least 200 percent higher density than the predetermined density of the pre-expanded beads.