Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
2000-07-03
2001-11-20
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
Reexamination Certificate
active
06318990
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to injection molding and more particularly to apparatus for locating and sealing an injection molding nozzle in an opening in the mold.
Very accurate location of a heated nozzle in an opening in a cooled mold has become more and more critical for successful hot tip gating. As seen in the applicant's U.S. Pat. No. 4,557,685 which issued Dec. 10, 1985 and U.S. Pat. No. 4,768,945 to Schmidt et al. which issued Sep. 6, 1988 it is well known for heated injection molding nozzles used for hot tip gating to have a rear locating flange and a front seal extending therearound. Another example of hot tip gating is shown in U.S. Pat. No. 5,658,604 to Gellert et al. which issued Aug. 19, 1997 in which the front seal is provided by a threaded nozzle seal which is screwed into the front end of the nozzle.
U.S. Pat. No. 4,771,534 to Gellert et al. shows a nozzle with a sealing and locating flange but it does not abut against an inwardly tapered surface. U.S. Pat. No. 5,269,676 shows a seating and sealing insert, but it does not have an inwardly tapered surface against which a locating and sealing ring can seat.
However, the previous apparatus all has the disadvantage that extremely close tolerances are required to ensure the front end of the nozzle is accurately aligned and there is a good seal against melt leakage.
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 wherein each nozzle has a locating and sealing ring which abuts against an inwardly tapered shoulder or surface whereby thermal expansion improves the seal.
To this end, in one of its aspects, the invention provides injection molding apparatus having an integral heated nozzle extending into an opening in a mold. The opening has a rear end and a surface extending to a gate leading to a cavity. The integral heated nozzle has an elongated inner portion, an outer collar portion, and an electrical heating element. The elongated inner portion has a rear end, a front end, a melt bore extending therethrough from the rear end to the front end, and a generally cylindrical outer surface with a spiral groove extending therearound. The electrical heating element is wound into the spiral groove extending around the outer surface of the inner portion and the outer collar portion fits around the inner portion adjacent the rear end of the inner portion. The surface of the opening in the mold has a first locating shoulder extending inwardly near the rear end and a second locating shoulder extending inwardly near the gate. The nozzle has a rear locating flange to extend outwardly into locating contact with the first inwardly extending locating shoulder of the surface of the opening in the mold. A front locating and sealing ring is mounted around the heated nozzle near the front end of the heated nozzle to provide locating contact the with the second inwardly extending locating shoulder of the surface of the opening in the mold. The distance between the first inwardly extending locating shoulder and the second inwardly extending locating shoulder being greater than the distance between the rear locating flange and the front locating and sealing ring. Thus, during insertion of the nozzle into the opening in the mold and thermal expansion of the nozzle, the rear locating flange comes into locating contact with the first inwardly extending locating shoulder of the surface of the opening in the mold to prealign the nozzle before the front locating and sealing ring comes into locating and sealing contact with the second inwardly extending locating shoulder of the surface of the opening in the mold.
In another aspect, the invention proves an injection molding apparatus having a nozzle extending into an opening in a mold. The opening extends to a gate leading to a cavity. The opening has a surface with a tapered portion that tapers inwardly toward the gate. The nozzle has a melt bore extending therethrough. A locating and sealing ring secured to the nozzle contacts the inwardly tapered portion of the surface. Thus, thermal expansion from heating to an operating temperature drives the locating and sealing ring forwardly into greater contact against the inwardly tapered portion of the surface of the opening.
In a further aspect, the invention provides a n injection molding apparatus having a nozzle extending into an opening in an insert received in an opening in a mold. The opening in the mold extends to a gate leading to a cavity. The opening in the insert has a surface with a tapered portion that tapers inwardly toward the gate. The nozzle has a melt bore extending therethrough. A locating and sealing ring secured to the nozzle contacts the inwardly tapered portion of the surface of the opening in the insert. Thus, thermal expansion from heating to an operating temperature drives the locating and sealing ring forwardly into greater contact against the inwardly tapered portion of the surface of the opening in the insert.
Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings.
REFERENCES:
patent: 4557685 (1985-12-01), Gellert
patent: 4768945 (1988-09-01), Schmidt et al.
patent: 4771534 (1988-09-01), Gellert et al.
patent: 5032078 (1991-07-01), Benenati
patent: 5208052 (1993-05-01), Schmidt et al.
patent: 5269676 (1993-12-01), Gellert
patent: 5533882 (1996-07-01), Gessner et al.
patent: 5658604 (1997-08-01), Gellert et al.
patent: 5795599 (1998-08-01), Gellert
patent: 0 374 549 (1990-06-01), None
patent: 0 475 143 (1992-03-01), None
patent: 0 835 732 A1 (1998-04-01), None
patent: 0 885 707A1 (1998-12-01), None
Babin Denis L.
Gellert Jobst Ulrich
Olaru George T
Foley & Lardner
Heitbrink Tim
Mold-Masters Limited
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