Patent ID: 8163208

Claim:
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.