This invention relates to a mold design, injection molding machine and amethod for forming a multi-layer plastic article by over molding where thesecond layer ofthe article includes a portion having a different geometrical profile than thefirst one. Thenovel injection mold and injection molding machine for producing over-moldedarticlescomprises an array of one or more cores which engage arrays of one or morefirst cavity andarrays of one or more composite cavities. Each composite cavity is formed fromthecombination of a second cavity and a cavity extension which carries at least aportion of thedifferent geometrical profile, such as a thread. In one embodiment, the cavityextensioncomprises a pair of cavity portions which are mounted adjacent the core tolaterally moveableslides on a movable plate, that can be a stripper plate. During molding of thefirst layer, thecavity extension elements are moved "out" of alignment with the first cavityand duringmolding of the second layer the cavity extension elements are moved "in" toform thecomposite cavity with the second cavity so that only the second layerreplicates thegeometrical profile of the composite cavity. In another embodiment of theinvention, thecavity extension is a single element which is moved between a disengagedposition whereinthe core can be inserted into the first cavity and an engaged position whereinthe core isinserted into the composite cavity.
展开▼
