Molding apparatus for articles having internal undercuts

An injection molding apparatus for forming a molded article, the molded article having internal walls with undercuts, said injection molding apparatus comprising:

• a male mold having a plurality of outwardly directed, spaced projections and voids disposed between the projections for the formation of the internal walls of the molded article, said projections and said voids cooperatively defining an outward direction in which a molded article is removed from said male mold, at least some of said projections each having an outwardly and transversely opening lifter head recess formed therein;
• ejector means for moving the molded article outwardly from said male mold;
• a plurality of lifter heads each disposed in correspondence with a said lifter head recess, each of said lifter heads being movable between a first position in which said lifter head is received in a said lifter head recess and a second position in which said lifter head is disposed outwardly of the projection in which the lifter head is received, each of said lifter head having a first protrusion extending transversely to said outward direction beyond the projection in which the lifter head is received and into a void, each of said first protrusions having an inwardly directed first ramping surface;
• whereby the molded article is molded on said male mold with said lifter heads in said first position and said first protrusions forming first undercuts in the internal walls of the molded article, whereby the molded article is moved outwardly from said projections by said lifter heads moving from said first position to said second position, and whereby the molded article is removed from said lifter heads by said ejector means, said removal being facilitated by sliding contact between said undercuts and said ramping surfaces.

An injection molding apparatus for forming a molded article, the molded article having a plurality of internal walls disposed in intersecting relationship and forming corners therebetween, at least some of said internal walls being formed with undercuts, said injection molding apparatus comprising:

• a mold base;
• a plurality of spaced projections extending outwardly from said mold base, said projections defining voids therebetween in which the internal walls of the molded article are formed, said projections and internal walls cooperatively defining an outward direction in which the molded article is removed from said male mold, a plurality of said projections each formed with an outwardly and transversely opening lifter head recess;
• ejector means for moving the molded article outwardly from said male mold;
• a plurality of lifter heads each disposed in correspondence with a said lifter head recess, each of said lifter heads being movable between a retracted position in which said lifter head is received in a said lifter head recess and an extended position in which said lifter head is disposed outwardly of the projection in which the lifter head is received, at least some of said lifter heads comprising corner lifter heads disposed adjacent corners formed between intersecting pairs of internal walls, each of said lifter heads having a first protrusion extending transversely to said outward direction beyond the projection in which the lifter head is received and into a void, said corner lifter heads further having a second protrusion extending transversely into a void and in angularly offset relation to the first protrusion of the corner lifter head, each of said first and second protrusions having an inwardly directed ramping surface;
• whereby the molded article is molded on said projections with said lifter heads in said retracted position and said protrusions forming undercuts in the internal walls of the molded article, the protrusions of a corner lifter head forming undercuts in each of intersecting pairs of internal walls, whereby the molded article is moved outwardly from said projections by said lifter heads moving to said extended position, and whereby the molded article is removed from said lifter heads by said ejector means, the removal being facilitated by sliding contact between said undercuts and said ramping surfaces.