METHOD FOR PREVENTING BACKFLOW IN PREPLASTICATING TYPE INJECTION MOLDING MACHINE

摘要

PROBLEM TO BE SOLVED: To prevent a looseness of a valve disc tending to occur in the case of shutting OFF a resin channel due to a contact of the disc with a valve seat by forcibly retreating a screw by a way of retreating operation of the screw. ;SOLUTION: An injection cylinder 12 in which a plunger 10 is internally mounted communicates with a plasticizing cylinder 22 in which a plasticizing screw 20 is internally rotatably and telescopically mounted via a resin passage 3 provided over an end and the cylinders 12 and 22 are juxtaposed. A screw moving hydraulic cylinder 24 and a rotating motor 25 are provided at a rear part of the cylinder 22. When the plunger 10 is retracted by charging a material by a rotation of the screw 20 and its retracted position arrives at a position immediately before a metering ending position, a rotating speed of the screw 20 is switched to a low speed. Thereafter, the screw 20 is retracted to be moved by a lower pressure than that at the time of opening a valve, and then the valve is closed. After the valve is closed, the screw is stopped, and a backflow of the resin to the plasticizing cylinder side is prevented after the metering is finished.;COPYRIGHT: (C)1999,JPO