Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1999-06-03
2001-06-12
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C264S328120, C264S328140, C425S549000, C425S568000
Reexamination Certificate
active
06245278
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an injection nozzle and a method for injection molding, particularly hot runner nozzles and nozzle tips.
Hot runner nozzles, especially nozzle tips, typically contain hang up areas in their flow channels that make color or material changing of the resin problematic. Purging the new color material through the nozzle tip can be time consuming and wasteful of the resin. Heretofore, the only completely effective way to make a clean color change is to dismantle and clean the nozzle assembly to remove all traces of the previous color resin. Clearly, this can be very time consuming and expensive and risks damaging the equipment if the color changes are frequently made.
U.S. Pat. Nos. 5,513,976 and 5,716,651 to McGrevy and 5,545,028 to Hume et al. show a nozzle tip with an element that induces a spiral flow pattern in order to promote improved color changing. U.S. Pat. No. 4,965,028 to Maus et al. and U.S. Pat. No. 4,711,602 to Baker show nozzle tips with mixing elements to improve the homogeneity of the resin flowing through the nozzle tips. However, these references are not entirely effective in overcoming the foregoing problem and promoting rapid color changing.
European Patent Application 0 546 554 to Gellert, published Jun. 16, 1993 shows a nozzle tip containing a central element with spiral vanes that promote a swirling motion to the flow of infeeding resin; however, this also is not entirely effective.
U.S. Pat. No. 4,501,550 to Nikkuni shows a nozzle tip having a central infeed channel which diverges into multiple channels to feed past a central tip in order to improve inconveniences of color or material exchange. However, this does not promote flushing of the melt bubble in the narrow annular space underneath the nozzle support flange.
It would be desirable to provide a simple and effective nozzle tip design that conveniently promotes flushing out of the previous material to make efficient material and color changes possible.
Accordingly, it is a principal object of the present invention to provide an improved injection molding nozzle and method for injection molding.
It is a further object of the present invention to provide an improved nozzle and method as aforesaid including a simple and effective nozzle tip design that simply and effectively promotes flushing out of the previous material to make efficient material and color changes possible.
Further objects and advantages of the present invention will appear hereinbelow.
SUMMARY OF THE INVENTION
In accordance with the present invention, the foregoing objects and advantages are readily obtained.
The injection nozzle of the present invention comprises: a nozzle including a nozzle body portion communicating with a source of molten resin and a tip portion, including an injection orifice, for transferring molten resin to a mold cavity; wherein said nozzle has a longitudinal axis and at least one internal flow channel for transferring molten resin from said source of molten resin to said mold cavity; said internal flow channel including a longitudinal flow channel, at least one angular channel, and preferably a plurality of angular channels, extending from the longitudinal channel (1) in a first direction at an acute angle with respect to the longitudinal axis, and (2) in a second direction at an acute angle with respect to said first direction, an annular channel extending from the angular channel, and a passageway extending from the annular channel to the injection orifice; wherein said angular channel causes a swirling action in the annular channel to flush out resin from the annular channel.
The method of the present invention comprises: providing an injection nozzle including a nozzle body portion communicating with a source of molten resin and a tip portion, and including an injection orifice, for transferring molten resin to a mold cavity, wherein said nozzle has a longitudinal axis; transferring molten resin from said source of molten resin to said mold cavity via at least one internal flow channel in said injection nozzle, including the steps of transferring said molten resin via a longitudinal flow channel of said internal flow channel, at least one angular channel, and preferably a plurality of angular channels, of said internal flow channel extending from the longitudinal flow channel (1) in a first direction at an acute angle with respect to the longitudinal axis, and (2) in a second direction at an acute angle with respect to said first direction, an annular channel of said internal flow channel extending from the angular channel, and a passageway of said internal flow channel extending from the annular channel to the injection orifice; wherein the angular channel causes a swirling action in the annular channel to flush out resin from the annular channel.
Further features of the present invention will appear hereinbelow.
REFERENCES:
patent: 2817115 (1957-12-01), Freifeld et al.
patent: 4303382 (1981-12-01), Gellert
patent: 4501550 (1985-02-01), Nikkuni
patent: 4711602 (1987-12-01), Baker
patent: 4965028 (1990-10-01), Maus et al.
patent: 5324191 (1994-06-01), Schmidt
patent: 5513976 (1996-05-01), McGrevy
patent: 5545028 (1996-08-01), Hume et al.
patent: 5716651 (1998-02-01), McGrevy
patent: 5840231 (1998-11-01), Teng
patent: 5871786 (1999-02-01), Hume et al.
patent: 0546554 (1993-06-01), None
Gauss Ralph
Lausenhammer Manfred
Mai Arnold
Schwarzkopf Udo
Bachman & LaPointe P.C.
Heitbrink Jill L.
Husky Injection Molding Systems Ltd.
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