METHOD AND APPARATUS FOR INJECTION MOLDING Russian patent published in 1994 - IPC

FIELD: plastic material molding. SUBSTANCE: method of injection molding with use of a molding machine, having mold, comprises steps of plasticization and batching of the material, step of injection and step of pressure holding the material. After the injection step over a time period of performing the step of the pressure holding of the material a duct, having increased volume and passing from the molding machine housing up to a molding hole of a refining cavity of the mold, is being closed in its intermediate portion for interrupting its connection with an inner cavity of the machine housing. The step of the pressure holding of the material is being performed with use of at least a valve for subjecting to an inner pressure, a front part of the injected material, had been separated due to the closing of the molding duct and compacted in a constant-volume closed space, restricted by the valve and including the refining cavity of the mold. At performing this step the next step of plasticization ad batching is being begun. Before the end of the step of the inner pressure holding, upon each molding cycle a quantity of the material in the constant- volume closed space is being controlled by discharging an excess part of the material from a system, including the molding machine. EFFECT: enhanced accuracy of molded articles. 6 cl, 9 dwg