Method of making an injection molding cylindrical manifold...

Details Method of making an injection molding cylindrical manifold... Method of making an injection molding cylindrical manifold...

1999-12-06

2001-05-15

Rosenbaum, I. Cuda (Department: 3726)

Metal working

Method of mechanical manufacture

Assembling or joining

C029S464000

Reexamination Certificate

active

06230384

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to injection molding apparatus and a method of making it and more particularly to such apparatus and method wherein a number of cylindrical inserts each having a curved melt duct extending therethrough are each securely seated in a predetermined position in one of a plurality of spaced transverse openings extending through a melt distribution manifold.
Injection molding apparatus having a heated melt distribution manifold and a plurality of spaced heated nozzles each conveying melt to a different gate are well known. The melt distribution manifold has a melt passage with a number of branches extending outwardly from a common inlet portion to convey the melt to the spaced heated nozzles. Each nozzle has a central melt bore extending at 90° to the branches of the melt passage in the melt distribution manifold. It is also known to seat inserts or plugs in transverse openings extending through the melt distribution manifold in alignment with the nozzles. Each insert has a melt duct with a smoothly curved bend extending through 90° from an inlet in alignment with a respective branch of the melt passage in the melt distribution manifold to an outlet in alignment with the melt bore through an aligned nozzle.
In order to avoid colour change problems and stress in the melt it is critical that the melt duct through each insert be very accurately aligned with the respective branch of the melt passage and the central melt bore through the respective nozzle. It is also important that the insert be secured in place to withstand rearward forces from the pressurized melt flowing through the bend in the melt duct. Mold-Masters Limited, Canadian Patent Application Serial Number 2,047,461 laid open Jan. 20, 1993 entitled “Injection Molding Manifold with Removable Inserts” shows inserts which are aligned by alignment pins and are tapered to withstand the force of the melt flowing through the curved melt ducts. U.S. Pat. No. 5,366,369 to Gellert which issued Nov. 22, 1994 shows inserts having outer flange portions to securely retain them in place against these same forces. However, these previous inserts have the disadvantages that they are relatively costly to make and slight misalignment remains a problem, particularly when molding some modern materials which are very shear sensitive.
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 injection molding apparatus which is easier to make and an improved method of accurately mounting the inserts and securely retaining them in place.
To this end, in one of its aspects, the invention provides an injection molding apparatus having a heated melt distribution manifold and a plurality of spaced heated nozzles seated in a mold. Each of the heated nozzles have a melt bore extending therethrough to convey melt to a gate leading to a cavity. The melt distribution manifold has a melt passage and a plurality of spaced transverse openings extending therethrough with each transverse opening aligned with one of the nozzles. The melt passage has a plurality of branches extending outwardly from a common inlet portion towards each of the nozzles. A plurality of inserts or plugs each have a rear face, a front face, an outer surface, and a melt duct extending therethrough. Each insert is received in one of the transverse openings in the melt distribution manifold with its face abutting against the rear end of a respective nozzle. The melt duct has a smoothly curved bend extending through substantially 90° from an inlet on the outer surface in matching alignment with one of the branches of the melt passage in the melt distribution manifold to an outlet on the front face in matching alignment with the melt bore through the respective nozzle. Each transverse opening in the melt distribution manifold is cylindrical. The outer surface of each insert is cylindrical and fits tightly in said one of the transverse openings in the melt distribution manifold. Each insert has an alignment and retaining pin or plug fitting tightly in a retaining pin bore in the melt distribution manifold and an aligned alignment and retaining pin bore in the insert.
In another of its aspects, the invention further provides a method of making injection molding apparatus having a melt distribution manifold with a plurality of spaced transverse openings therethrough and a melt passage having a plurality of branches extending outwardly from a common inlet portion to the plurality of spaced transverse openings. A number of inserts each have an outer surface and a melt duct with a smoothly curved bend extending therethrough from an inlet on the outer surface. Each insert is seated in one of the transverse openings in the melt distribution manifold with the inlet to the melt duct in alignment with one of the branches of the melt passage in the melt distribution manifold. The melt distribution manifold is made with the transverse openings and the melt passage, and the inserts are made with the melt ducts. Each insert is inserted into one of the transverse openings with the inlet to the melt duct in each insert in alignment with one of the branches of the melt passage in the melt distribution manifold. The spaced transverse openings through the melt distribution manifold are made cylindrical. The inserts with their outer surfaces cylindrical to fit tightly in the transverse openings through the melt distribution manifold when the inserts and the melt distribution manifold are at the same temperature. An alignment and retaining pin bore is machined extending through the melt distribution manifold to each transverse opening. A matching alignment and retaining pin bore is machined in each insert extending radially inward from the outer surface of the insert opposite from and in alignment with the inlet to the melt duct. Alignment and retaining pins are made to fit tightly in the alignment and retaining pin bores in the melt distribution manifold and each insert when the inserts and the melt distribution manifold are at the same temperature. The melt distribution manifold is heated to a predetermined temperature. The inserts and alignment and retaining pins are cooled to a predetermined temperature. Each cooled insert is then inserted into one of the transverse openings in the heated melt distribution manifold with the alignment and retaining pin bore in the cooled insert aligned with the alignment and retaining pin bore in the heated melt distribution manifold. One of the cooled alignment and retaining pins is then inserted to extend through the alignment and retaining pin bore in the heated melt distribution manifold into the aligned alignment and retaining pin bore in each cooled insert. Thus, when the inserts and the melt distribution manifold are at the same temperature, the tight fits of the inserts in the transverse openings and the alignment and retaining pins in the alignment and retaining bores in the inserts and the melt distribution manifold both accurately align and securely retain the inserts in place.
Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings.


REFERENCES:
patent: 3724095 (1973-04-01), Laue et al.
patent: 5150636 (1992-09-01), Hill
patent: 5267384 (1993-12-01), Teeslink
patent: 5366369 (1994-11-01), Gellert

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