Patent ID: 8551374

Claim:
A method for producing a solid expanded polystyrene foam element having a uniform cross section, different sections of the solid expanded polystyrene foam element having differing densities, the method comprising the following steps: (i) causing pre-expansion of pearls of expandable polystyrene to various densities; (ii) resting the pre-expanded pearls in an air environment for a predetermined time period depending on the respective densities of the pre-expanded pearls at atmospheric conditions; (iii) feeding the rested pre-expanded pearls of various densities to a partial molding chamber and keeping the pre-expanded pearls separated in different zones based on their respective densities using a pusher/divider; (iv) feeding saturated steam at a first pressure for a predetermined time to the partial molding chamber to form a partial molded segment of expanded polystyrene foam; (v) transferring the partial molded segment to a final molding chamber using the pusher/divider, the final molding chamber having a separating zone and a clamping zone, the separating zone having a height that is slightly smaller than a height of the partial molding chamber and the clamping zone having a height that is slightly smaller than the height of the separating zone; and (vi) clamping the partial molded segment in the separating and clamping zones of the final molding chamber and simultaneously feeding saturated steam at a second pressure for a predetermined time to the final molding chamber to form the solid expanded polystyrene foam element, the second pressure being higher than the first pressure.