Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Flash or sprue removal type
Reexamination Certificate
1998-11-13
2001-05-08
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
Flash or sprue removal type
C264S328700, C264S328900, C264S328120
Reexamination Certificate
active
06228303
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of Invention The invention relates to plastic molding equipment and more particularly to injection port shutoff devices and methods.
2. Related Art
The conventional way of shutting off injection molding gates is by a gate that moves transversely across the gate opening. In some injection molding devices the shutoff is at the sprue end and in others there is a cold runner which runs from the end of the sprue to the mold gate and the shutoff is transverse to that cold runner. A few of the molding devices which have the shutoff at the end of the sprue use an oblique shutoff than goes into the gate to end up substantially flush with the inner surface of the mold wall, thus minimizing the amount of extra material left on the molded part. However, since the sprue is typically heated, this is hot molten plastic and will thus leave a mold flashing in the region of the clearance between the gate and the gate port. With the cold runner shutoffs, there is typically a tab left. These tabs and flashings are ubiquitous in molded plastic parts despite their recognized undesirability.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an injection molding apparatus which has no flashing or gate tab on the finished part.
It is further an object of the present invention to provide a method and apparatus capable of eliminating the tab on molded parts which have use a cold runner.
It is also an object of the present invention to provide a new approach to shut off of injection molding plastic in which the partially cross-linked partially hardened tab is forced into the molded part, to make it disappear.
These and other objects are surprisingly all achieved by the present invention which provides a shutoff assembly for a plastic injection molding mold cavity port in which a shutoff gate is oriented at an angle relative to a cold runner and is sized and shaped so as to fully displace an intersected portion of the cold runner Into the molded part and end such displacement at a position flush with an interior wall of the mold cavity so as to produce a flush molded part surface.
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Ortiz Angela
Semco Plastics Company, Inc.
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