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United States Patent 4112519
Douris , ê et al. September 5, 1978

Vented injection molding machine and method

Kruder September 5, 1978

Abstract

Injection molding apparatus is disclosed for molding degradable synthetic resinous materials such as nylons. A vented injection molding machine includes a barrel, a rotatable reciprocable screw and means for preventing ingestion of a deleterious atmospheric gas such as oxygen. The particular apparatus whereby exclusion of the atmospheric gas may be effected includes a conduit having a terminal end thereof positioned at the vent opening of the injection molding machine barrel. The conduit communicates with a source of inert gas and directs a pressurized current of inert gas into the vent opening during the transient time interval between the end of the injection portion of the molding machine cycle and the plasticization portion of the machine cycle. If desired, the inert gas may flood the vent opening continuously. Both nitrogen and carbon dioxide are suitable inert gases for use with nylon materials.