Sprueless moulding with foam core - sprue duct being sealed by front faces of sliding sleeve and pin closure members

摘要

A moulding having a foam plastics core and thermoplastics outer skin is injection moulded using a nozzle in which the annular die for the skin is constituted between the fixed outer nozzle head and an axially sliding tube, while the central core injection nozzle is constituted by the passage in this tube itself, in turn closed by a sliding pin. In the closed position, the front flat faces of the pin and tube are flush with the flat front face of the fixed nozzle component so that they constitute the inner wall of the moulding in the sprue region thus leaving no sprue in the moulding.