Molding apparatus for articles having internal undercuts

摘要

An injection molding apparatus is disclosed for forming articles with internal undercuts by the use of lifter heads with transversely extending protrusions. The lifter heads are received in recesses in the mold projections which form the interior of the molded article. The transverse protrusions of the lifter heads extend into the voids surrounding the projections to form the undercuts. The lifter heads are extended outwardly from the projections to remove the article from the mold. Ejector pins move the molded article outwardly from the lifter heads. The lifter head protrusions have inward ramping surfaces which facilitate the removal of the molded article. A lifter head may include two, angularly offset protrusions which form two undercuts near the corner between intersecting internal walls of the molded article. The protrusions have beveled release surfaces which allow the molded article to shift transversely off the lifter heads.