Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-06-08
2001-08-14
Nguyen, Nam (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S328800, C425S130000
Reexamination Certificate
active
06274075
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a multi-cavity injection molding apparatus for five layer molding and more particularly to such apparatus having actuating mechanisms for reciprocating elongated valve members between four different positions.
Multi-cavity injection molding apparatus for making five layer protective containers for food or preforms or parisons for beverage bottles are known. Two layers of a barrier material such as ethylene vinyl alcohol copolymer (EVOH) or nylon are typically molded between two outer layers and a central layer of a polyethylene terephthalate (PET) type material. However, this has previously been done by sequentially injecting first the PET, then the barrier material and finally the PET again. While this is satisfactory for some applications, sequential molding has the disadvantage that it requires relatively expensive tooling.
Valve gated multi-cavity injection molding apparatus having elongated valve members which reciprocate are also known. For instance, U.S. Pat. No. 4,657,496 to Ozeki et al. which issued Apr. 14, 1987 shows an actuating mechanism having an outer piston reciprocating in an outer cylinder and a inner piston reciprocating in an inner cylinder. The inner piston drives the elongated valve member and the outer piston drives a stem surrounding the elongated valve member and they operate in a controlled injection cycle to sequentially mold three layer products. None of the prior art actuating mechanisms are capable of reciprocating the elongated valve members between four different positions according to the present invention to provide five layer molding by simultaneous injection.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to at least partially overcome the disadvantages of the prior art by providing a valve gated multi-cavity injection molding apparatus for five layer molding having fluid actuating mechanisms for reciprocating each elongated valve member between four different positions.
To this end, in one of its aspects, the invention provides a multi-cavity sprue gated injection molding apparatus for multi-layer molding having at least one melt distribution manifold with a front face and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end abutting against the melt distribution manifold and a front end adjacent a gate leading to a cavity in the mold. Each heated nozzle has 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 has a rear end and a front end extending through the melt distribution manifold into the central melt channel in each heated nozzle. The rear end of each elongated valve member is operatively connected to valve member actuating mechanism mounted in the mold. A first melt passage for conveying melt from a first melt source branches in the 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. A second melt passage for conveying melt from a second melt source branches in the melt distribution manifold and extends through the second melt channel in each heated nozzle to the gate. Each valve member actuating mechanism reciprocates the elongated valve member between a first closed position and second, third and fourth positions according to a continuous predetermined injection cycle. Each valve member actuating mechanism comprises means to retract the elongated valve member from the first closed position to the 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 nozzle and the gate into the cavity for a predetermined period of time. It also comprises means to then further retract the elongated valve member to the 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 nozzle and from the first melt source through the third melt channel in the nozzle and the gate into the cavity for a predetermined period of time. Each actuating mechanism also includes means to then further retract the elongated valve member to the 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 through the central melt channel in the nozzle, melt from the second melt source through the second melt channel in the nozzle and melt from the first melt source through the third melt channel in the nozzle and the gate until the cavity is almost filled. It also includes means to then return the elongated valve member to the second position until the cavity is filled, and means to first drive 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.
In another of its aspects, the invention provides a multi-cavity sprue gated injection molding apparatus for multi-layer molding having at least one melt distribution manifold with a front face and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end abutting against the melt distribution manifold and a front end adjacent a gate leading to a cavity in the mold. Each heated nozzle has 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 has a rear end and a front end extending through the melt distribution manifold into the central melt channel in each heated nozzle. The rear end of each elongated valve member is operatively connected to valve member actuating mechanism mounted in the mold. A first melt passage for conveying melt from a first melt source branches in the 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. A second melt passage for conveying melt from a second melt source branches in the melt distribution manifold and extends through the second melt channel in each heated nozzle to the gate. Each valve member actuating mechanism comprises a front cylinder and a rear cylinder both aligned in the mold with each elongated valve member. A first piston is seated in the front cylinder and connected to the rear end of the elongated valve member. A second piston is seated in the rear cylinder. A third piston is seated behind the second piston in the rear cylinder. The third piston has a stem portion which extends forwardly through an opening in the second piston into the first cylinder. First and second fluid lines from fluid pressure means are connected to the front cylinder on opposite sides of the first piston. A third fluid line from fluid pressure means is connected to the rear cylinder on the front side of the second piston, and a fourth fluid line from fluid pressure means is connected to the rear cylinder on the rear side of the third piston. Fluid pressure applied through the first, second, third and fourth fluid pressure lines reciprocates the elongated valve member between a first closed position and second, third and fourth positions according to a continuous predetermined injection cycle.
During this cycle, fluid pressure from the second fluid line is first released and fluid pressure is applied from the fourth fluid line to drive the second and third pistons forwardly and fluid pressure is applied from the first fluid line to drive the first piston and the elongated valve member rearwardly from the first closed position until the rear end of the first piston abuts against the front end of the third piston in the second position. In the second position, the front end of the elongated valve member is retracted sufficientl
Babin Denis L.
Gellert Jobst Ulrich
Foley & Lardner
Luk Emmanuel
Mold-Masters Limited
Nguyen Nam
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