Apparatus and method for the production of bi-material hollow bodies by means of injection overmolding

An apparatus for the production of bi-material hollow bodies by means of injection overmolding, comprising:

• a first hot channel connected to supply a base molding material to a number n+1 of base molding cavities or groups of base molding cavities, with n>1, said base molding material being intended for making a first layer of a bi-material hollow body;
• a second hot channel connected to supply an overmolding material to a number n of overmolding cavities or groups of overmolding cavities, said overmolding material being intended for making a second layer of said bi-material hollow body,
• wherein said base molding cavities or groups of base molding cavities and said overmolding cavities or groups of overmolding cavities are alternately arranged in a formation along a transverse direction, and wherein the cavities or groups of cavities located at the two ends of said formation are first and second end base molding cavities or first and second end groups of base molding cavities, respectively;
• a base plate on which there is mounted a core holder plate carrying a similar formation of a number 2n of cores or groups of cores,
• wherein said core holder plate is actuated to be moved alternately on the base plate in said transverse direction between two positions in which the cores or groups of cores are aligned respectively with first and second sets of cavities, each formed by said number n of overmolding cavities or groups of overmolding cavities and a number n of the base molding cavities or groups of base molding cavities including one or the other of said first and second end base molding cavities or first and second end groups of base molding cavities, respectively, and wherein said base plate is actuated to be moved in a longitudinal direction between a closed position, in which the cores or groups of cores are introduced in said first or second sets of cavities, and an open position, in which the cores or groups of cores are extracted from the first or second sets of cavities;
• valve means arranged in said first hot channel to alternately allow or interrupt the passage of base molding material towards the first and second end base molding cavities or first and second end groups of base molding cavities, according to the positions of the base plate and core holder plate;
• and
• ejecting means adapted to eject the finished hollow bodies only from those cores or groups of cores which have been extracted from overmolding cavities or groups of overmolding cavities.