Sequential co-injection unit adapted for structural foam molding

Abstract From the Canadian patent

A single screw injection device or extruder sequentially injects skin and foamed plastics melt into a mould to produce structural skin covered foam moulded parts free from swirl marks. A single extrusion screw or plasticator selectively feeds, compresses and meters a plastics melt to a first injector for skin melt injection or to a gas injection well where it meters gas flow into the melt mixes the gas and melt to form a foam and feeds the foam to a second injector for foam melt injection into the mould. A valve controls the flow of the plastics melt and the foamed plastics melt to a single injection nozzle for discharge into the mould. In sandwich moulding a small amount, of the unfoamed …