Screw injection moulding machine with final injection device - which accurately maintains press. during injection and comprises a screw and two hollow pistons

摘要

A screw injection moulding machine has an axially movable and rotatable scew in a barrel and, downstream of this screw, a storage chamber for the material propelled by the screw. Filler equipment conveys the material collected downstream of the screw into the mould and comprises an axially slidable hollow piston, the central boe of which forms a communicating passage between the storage chamber and the nozzle. A non-return valve closes the passage from the storage chamber towards the nozzle and thus maintains the final injection pressure. Hydraulic or similar drive equipment provides the advancing movement for the axially slidable hollow piston during the final injection stroke. Filler equipment assembly comprises screw, slidable, hollow non-return valve as an annular piston outside the screw having its closure position in the rearward direction; and also a hollow piston sliding in a bore downstream of the non-return valve and smaller than the bore of the barrel.