| 摘要 |
An injection molding apparatus having a non-return valve assembly mounted on the front end of an extruder screw within a heated barrel for accummulating a charge of thermoplastic material in the forepart of the barrel by the retrograde and rotary movement of the screw when the valve is in open position, and by ejecting the charge through a nozzle mounted at the front of the barrel by the reverse reciprocating movement of the feedscrew, which simultaneously forces the valve to close and prevents escape of the material backward into the barrel along the screw. The valve is formed of two components, one of which is shaped with a convexly contoured annular protuberance which is alternately spaced from the other one, and in close abutment therewith, in the alternate movements of the feedscrew, with only screws or bolts connecting the two, to permit freedom of movement therebetween.
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