Injection molding method and apparatus

  • US 8,163,208 B2
  • Filed: 02/21/2011
  • Issued: 04/24/2012
  • Est. Priority Date: 04/23/2008
  • Status: Expired due to Fees
First Claim
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1. A machine for injection molding comprising:

  • a barrel having an interior and having a longitudinal axis;

    a screw auger positioned within the barrel interior, wherein the screw auger is substantially concentric with the barrel and is operable to rotate and transmit a material along the length of the barrel, wherein the screw auger includes a bore also substantially aligned with the longitudinal axis;

    a heating element in thermal communication with said barrel;

    an injection chamber;

    a channel, wherein the channel provides fluid communication between the injection chamber and the barrel;

    a plunger substantially aligned for movement along the longitudinal axis and with the bore and being substantially coaxial with said screw auger, wherein the plunger in a first position impedes fluid communication between the barrel and the injection chamber, wherein the plunger in a second position does not impede fluid communication between the barrel and the injection chamber;

    an injection tube wherein the injection tube is in fluid communication with the injection chamber, and wherein the injection tube is located adjacent the plunger; and

    a temperature sensor in communication with one of the barrel, the injection chamber, and the injection tube;

    wherein rotation of the screw auger is dependent of a first pressure reading obtained from a first pressure sensor and a second reading of a second pressure sensor, wherein the first reading is indicative of a force applied to the screw auger in a direction that is substantially along the longitudinal axis, and wherein the second reading is indicative of a pressure of the material when heated to at least a flowable state;

    wherein a barrier is formed by the compaction of pellets within said barrel as said pellets travel toward a melting zone, said barrier preventing melting plastic from flowing backward in said machine, said machine being devoid of a valve that prevents substantial flowback of melted plastic.

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