Injection molding method
AssigneeKord Products Limited
InventorsRalph William Welsh, Geoffrey Walker
Life of this patent
Estimating the term…
Abstract
A molded container top 140 has engravings 145 formed by an embossing 108. The core 120 withdrawn from the cavity 102 and a retaining ring 110 holds the hot molded part 140 in the cavity 102. The molded part 140 shrinks away from the cavity 102 and is pushed out of the cavity 102 by an ejector 105. The part 140 has no witness lines on its circumferential skirt 142.
Claims14
An injection molding process for molding a plastic part comprising the steps of:
- providing a molding volume defined by space between a molding cavity and a one piece molding core, said molding volume having a one piece circumferential skirt with first and second ends, said molding volume having an outer surface defined by said molding cavity and an inner surface defined by said molding core, said molding core having an annular region partially overlapping said second end of said circumferential skirt and said molding cavity having a seamless surface in a region defining the outer surface of the circumferential skirt;
- the circumferential skirt having cylindrical surfaces in said molding cavity defining the outer and inner surfaces of the molded plastic part, said outer cylindrical surface comprising one or more designs selected from the group consisting of an embossing and an engraving;
- providing a retaining ring aligned with said molding cavity and partially enclosing said molding volume in an annular region by overlapping the remainder of the second end of the circumferential skirt;
- injecting molten plastic into the molding volume to mold a plastic part in the molding volume with a circumferential skirt having a seamless outer surface;
- withdrawing the molding core from the cavity and simultaneously removing the plastic part from said molding core and holding the plastic part in the cavity by exerting a retaining force on the second end of the molded circumferential skirt;
- cooling the molded plastic part to shrink its circumferential skirt an amount greater than the height of the inner diameter of the retaining ring.
An injection molding process for molding a plastic part into a cup shape with an end wall at one end, a circumferential skirt disposed transverse to the end wall and extending from said end wall and terminating at a rim, comprising the steps of:
- providing a cavity with an inner surface having a cup shape with an end wall surface at one end, a seamless one piece circumferential skirt surface with inner and outer cylindrical surfaces, said outer cylindrical surface comprising an engraving, an embossing, or both an engraving and an embossing, said circumferential skirt extending transverse to said wall and terminating in an annular rim;
- providing a one piece core having an outer surface corresponding to the shape of the cavity and spaced from said cavity a distance to define a cup shape molding volume with an annular end, said core having an annular surface extending outwardly from said core to partially enclose the annular end of the molding volume;
- closing the molding volume at its annular end with a retaining ring extending at least partially across the rim of the molding volume toward the annular surface of the core, whereby the outer surface of the circumferential skirt of a part molded in the molding volume is seamless;
- injecting a molding compound into the molding volume to form a molded cup;
- withdrawing the core and simultaneously retaining the rim of the molded cup in the cavity with the retaining ring.
Dependencies are inferred from the claim text.