Apparatus for injection molding multi-layer articles

摘要

Apparatus for selectively controlling the flow of at least three melt material streams through the nozzle of a machine for injection molding multi-layer plastics articles. The nozzle has, for each stream, a flow passageway terminating at an exit orifice. Sleeve means having an internal axial material flow passageway, communicate with the central channel and with one of the flow passageways and are movable axially and/or rotationally to block and unblock at least two orifices. Each flow passageway can include material flow directing means for balancing stream flow around the passageway and its exit orifice, and a tapered portion adjacent its orifice. Preferably, the orifices are fixed. Means can pressurize melt material in a flow passageway between the flow directing means and the associate orifice so that the start of flow of the material through the orifice is substantially uniform thereabout. Co-injection nozzle means for multi-polymer injection molding and blow molding machines are provided having valve means and/or one or more of the afore-mentioned features.