Injection molding method and system with expandable cavity element

An expandable cavity core element adapted for use in an injection molding system to form a molded article having external surface projections or openings, which expandable core cavity element is integrally formed of a spring steel metal and comprises:

• a) a base having a first upper end and a second lower end, said base having a base opening therethrough and having a plurality of upwardly, generally vertically extending, tapered arms extending from said second lower end of said base about a longitudinal axis of said opening, to a first open end, said arms of said first open end adapted to extend into a mold cavity during an injection molding method;
• b) said arms of said first upper end characterized by having a tapered exterior surface and an interior surface having an opening or projection thereon to form openings or projections on the exterior surface of the injected, molded article;
• c) said arms having a generally arcuate band element having an exterior surface generally parallel to the longitudinal axis of said base opening and extending downwardly from said tapered exterior surface a selected distance to provide an exterior arcuate surface wherein the band elements form a generally cylindrical peripheral exterior surface in a closed molding position;
• and
• d) said arms of said expandable cavity element arranged and constructed to move between;
• i) an open, relaxed, biased, non-molding use position in a molding system, and
• ii) a closed, force-retained molding position in a molding system, wherein said arms of said first upper end are held in the molding position by a mechanical force against said exterior tapered surface and said band element.

An injection molding system to provide an injection-molded article having external surface projections or openings;

• and which injection molding system comprises in combination:
• a) an injection mold having a first mold part and a second mold part, said mold parts adapted to move between a closed molding position and an open, article recovering position, and which mold defines a mold cavity for an article to be molded;
• b) an expandable cavity element of a spring steel metal and having a base with an opening therethrough with a longitudinal axis, and a plurality of generally vertical arms extending from said base and about said opening to a first upper open end, said arms at said first upper end extending into said mold cavity and having at said first upper end an exterior tapered surface and having an interior surface to form a projection or opening on said exterior surface of the article to be molded, and having a generally cylindrical band element having an exterior surface generally parallel to the longitudinal axis and extending downwardly from said tapered surface, said arms of said expandable cavity element adapted to move at said first upper end between an open unbiased position with said ends of said arms in an open, non-side-contacting position, and a closed, biased molding position with said ends of said arms in a closed-end, side-contacting position;
• c) said second mold part having a sleeve means having a surface portion tapered, so that in said closed, molding position of said mold said tapered surface mechanically forces said one end of said arms of said expandable cavity element into the closed, biased position on movement of said second mold part;
• d) means to inject a molded plastic material into the mold cavity to form a molded article;
• and
• e) means to move said first and second mold parts between a closed and open mold position whereby said second mold part is moved to a closed, molding position forcing said first upper open end of said arms of said expandable cavity element in the mold cavity into a closed, biased, molding position during the molding process and said second mold part moving to the article recovery position, permitting said arms of said expandable cavity element to spring without mechanical means into the open unbiased position.