Patent ID: 6274075
Filing Date: 2001-08-14
Classification: B29C,B29K

Abstract:
A method of continuously injection molding five layer products of two different materials in a multi-cavity injection molding apparatus having at least one melt distribution manifold with a front face and a plurality of heated nozzles mounted in a mold, each heated nozzle having a rear end abutting against the at least one melt distribution manifold and a front end adjacent a gate leading to a cavity in the mold, each heated nozzle having a first central melt channel and second and third melt channels extending therethrough from the rear end to the front end, an elongated valve member having a rear end and a front end extending through the at least one melt distribution manifold into the central melt channel in each heated nozzle, the rear end of each elongated valve member being operatively connected to valve member actuating mechanism mounted in the mold, a first melt passage for conveying melt from a first melt source branching in the at least one melt distribution manifold dividing to extend both around the elongated valve member in the first central melt channel and through the third melt channel in each heated nozzle to the gate, and a second melt passage for conveying melt from a second melt source branching in the at least one melt distribution manifold and extending through the second melt channel in each heated nozzle to the gate, comprising the steps of;(a) retracting the elongated valve member from a first closed position to a second position wherein the front end of the elongated valve member is retracted sufficiently to allow melt from the first melt source flow through the third melt channel in the heated nozzle and the gate into the cavity for a predetermined period of time,(b) further retracting the elongated valve member to a third position wherein the front end of the elongated valve member is retracted sufficiently to allow simultaneous flow of melt from the second melt source through the second melt channel in the heated nozzle and from the first melt source through the third melt channel in the heated nozzle and the gate into the cavity for a predetermined period of time,(c) further retracting the elongated valve member to a fourth fully retracted open position wherein the front end of the elongated valve member is retracted sufficiently to allow simultaneous flow of melt from the first melt source to the central melt channel in the heated nozzle, melt from the second melt source through the second melt channel in the heated nozzle and melt from the first melt source through the third melt channel in the heated nozzle and the gate until the cavity is almost filled,(d) then returning the elongated valve member to the second position until the cavity is filled, and(e) driving the elongated valve member forwardly to the first closed position wherein the front end of the elongated valve member is seated in the gate to allow for ejection.