Metal fusion bonding – Process – With shaping
Reexamination Certificate
2000-07-11
2001-09-11
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S144000, C228S165000
Reexamination Certificate
active
06286751
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to multi-layer injection molding apparatus and more particularly to such apparatus having integral multi-layer melt dividing bushings seated in the melt distribution manifold for dividing the melt flowing to annular melt channels in the heated nozzles.
Injection molding apparatus for making multi-layered protective containers for food or preforms or parisons for beverage bottles are well known. Often the inner and outer layers are made of a polyethylene terephthalate (PET) type material with one or more barrier layers made of a material such as ethylene vinyl alcohol copolymer (EVOH) or nylon. In some multi-cavity apparatus the two different melts are distributed through a single melt distribution manifold having different passages, but preferably for materials such as these having different injection temperatures of about 565° F. and 400° F. respectively, the two melts are distributed through two different melt distribution manifolds. In some cases, the melts are injected sequentially, while in other cases both coinjection and sequential injection are utilized. The two materials are injected through a heated nozzle having a central melt channel and one or more annular melt channels extending around the central melt channel to a gate leading to the cavity.
It is also known to divide the melt flowing to the annular melt channel to provide more uniform distribution around the annular melt channel. As seen in the applicant's U.S. Pat. No. 5,094,603 which issued Mar. 10, 1992, this has been done by providing a single layer melt distribution plate mounted between the rear end of the heated nozzles and the front face of the melt distribution manifold. While this is suitable for many situations, it has the disadvantage of requiring extensive machining of the front face of the melt distribution manifold and the rear ends of the heated nozzles. Also, it is not suitable for receiving melt from two separate manifolds and has the disadvantage of increasing the height of the mold.
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 multi-layer injection molding apparatus having the melt flowing to an annular channel in the heated nozzles divided in integral multi-layer melt dividing bushings seated in the melt distribution manifold.
To this end, in one of its aspects, the invention provides a melt dividing bushing having a side surface extending from a rear end to a front end. The melt dividing bushing is used in a multi-cavity hot runner injection molding apparatus having a plurality of heated nozzles mounted in a mold, for dividing a melt passage extending therethrough from a single inlet to four outlets at its front end. The melt dividing bushing comprises at least first, second and third layers integrally joined together. The first layer has a rear face and a front face. The third layer has a rear face, a front face and four spaced holes extending therethrough. The second layer has a rear face, a front face and two spaced holes extending therethrough. The rear face of the second layer abuts against the front face of the first layer and the front face of the second layer abuts against the rear face of the third layer. The front face of the first layer and the rear face of the second layer have matching grooves which form a first melt conduit which branches from the single inlet to the two spaced holes extending through the second layer. The front face of the second layer and the rear face of the third layer having matching grooves which form two second melt conduits. Each of the second melt conduits branches from one of the two spaced holes through the second layer to two of the four spaced holes extending through the third layer. Thus, the melt passage extends from the single inlet through the first melt conduit, the two spaced holes through the second layer, the two second melt conduits and the four spaced holes through the third layer.
In another of its aspects, the invention provides multi-cavity hot runner 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, a front end, a central melt channel extending therethrough from the rear end to the front end, an annular melt channel extending around the central melt channel to the front end and four spaced melt bores extending from the rear end to the annular melt channel. A first melt passage from a first melt source branches in the melt distribution manifold and extends through the four spaced melt bores and the annular melt channel in each heated nozzle to a gate adjacent the front end of the heated nozzle leading to a cavity in the mold. A second melt passage from a second melt source branches in the at least one melt distribution manifold and extends through the central melt channel in each heated nozzle to the gate. There are a number of integral three layer melt dividing bushings each having a rear end, a front end, and a central bore extending therethrough from the rear end to the front end. Each melt dividing bushing is seated in the front face of the melt distribution manifold with its front end abutting against the rear end of one of the heated nozzles. The second melt passage from the second melt source extends through the central bore in each melt dividing bushing to the central melt channel extending through each heated nozzle. Each melt dividing bushing has a first layer at its rear end, a third layer at its front end, and a second layer between the first and third layers. The first, second and third layers are integrally joined together to form the melt dividing bushing. The first layer has a rear face and a front face. The rear face abuts against the melt distribution manifold. The third layer having a rear face, a front face, and four holes spaced around the central bore extending therethrough from the rear face to the front face. The front face of the third layer abuts against the rear end of the heated nozzle with the central melt bore through the melt dividing bushing aligned with the central melt channel in the heated nozzle and the four spaced holes through the third layer aligned with the four spaced melt bores at the rear end of the heated nozzle. The second layer has a rear face, a front face, and two holes spaced around the central melt bore extending therethrough from the rear face to the front face. The rear face of the second layer abuts against the front face of the first layer. The front face of the second layer abuts against the rear face of the third layer. The front face of the first layer and the rear face of the second layer have matching grooves therein which form a melt conduit which branch from an inlet aligned with the first melt passage in the melt distribution manifold to the two spaced holes extending through the second layer. The front face of the second layer and the rear face of the third layer having matching grooves therein which from two melt conduits. Each of the melt conduits branches from one of the two holes through the second layer to two of the four spaced holes extending through the third layer. The first melt passage from the first melt source extends through the two spaced holes through the second layer and the four spaced holes through the third layer of each melt dividing bushing and the four spaced melt bores and the annular melt channel through each heated nozzle.
In another of its aspects, the invention provides multi-cavity hot runner injection molding apparatus for multi-layer molding having one or more melt distribution manifolds with a front face and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end, a front end, a central melt channel extending therethrough from the rear end to the front end, an inner annular melt channel extending around the central melt channel to the front end with at least one melt bore extending fro
Babin Denis L.
Gellert Jobst Ulrich
Dunn Tom
Foley & Lardner
Johnson Jonathan
Mold-Masters Limited
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