INSPRUTNINGSDON FOR TERMOPLASTER, ELASTOMERER OCH HERDPLASTER INNEFATTANDE EN ROTERBAR SAMT AXIELLT FORSKJUTBAR SKRUV OCH EN AXIELLT RORLIG SLIDVENTIL

摘要

An injection moulding machine of the type incorporating a rotatable and reciprocable screw has on the forward end of the barrel a nozzle portion providing within it a valve cylinder larger than the bore of the barrel. A differential valve plunger having an axial passage extending through it has larger and smaller diameter portions slidably and sealingly engaged in the valve cylinder and the bore of the barrel respectively. The smaller diameter end of the valve plunger can be abutted by the nose of the screw to form a seal preventing flow through the axial passage in the valve plunger and to enable the valve plunger to be driven along the valve cylinder to eject the softened material forwardly from the valve cylinder. A plug is provided which can be operated to open or close off the injection aperture in the valve cylinder. During rotation of the screw softened material passes forwardly through the passage in the valve plunger and by reason of the differential area urges the plunger rearwards towards the screw.