Method and apparatus for forming a multi-layer preform

A preform mold assembly for the injection molding of a multi-layer preform for use in the blow molding of containers said preform mold assembly comprising:

• a preform mold having a gate for receiving molten plastic material, said preform mold having a cavity defining an inner surface, said cavity having a longitudinal axis;
• a core-pin situated within said cavity and spaced from said inner surface;
• a preform cavity formed between the inner surface of the cavity and the core-pin for receiving molten plastic from the gate;
• a threadsplit portion situated within said cavity at a location remote from said gate;
• and
• said inner surface of the cavity having a plurality of flutes formed beginning substantially proximate said gate and extending substantially upstream from said gate past an end of the threadsplit closest to the gate, said flutes formed generally parallel to said cavity longitudinal axis within said cavity inner surface.

A method of injection molding a multi-layer preform for use in the blow molding of containers, said method comprising the steps of:

• providing a first preform mold assembly having a gate for receiving molten plastic material and a cavity defining an inner surface having a remote end opposing said gate, a core-pin situated within said cavity, and a preform cavity formed between the inner surface of the cavity and the core-pin for receiving molten plastic material from the gate, said inner surface of the cavity having a plurality of flutes, said flutes beginning substantially proximate said gate and extending longitudinally along the inner surface of the mold substantially upstream from said gate to a location substantially proximate said remote end;
• injecting a first molten plastic material through said gate and into the preform mold cavity to form a thin preform substrate;
• injecting a second molten plastic material over said preform substrate to form the second layer of a multi-layer perform;
• and
• removing the multi-layer preform from the second injection mold.

A method of injection molding a multi-layer preform for use in the blow molding of containers, said method comprising the steps of:

• providing a first preform mold assembly having a gate for receiving molten plastic material, a cavity defining an inner surface, a core-pin situated within said cavity, a preform cavity formed between the inner surface of the cavity and the core-pin for receiving molten plastic material from the gate, and a threadsplit portion situated within said cavity at a location remote from said gate, said inner surface of the cavity having a plurality of flutes, said flutes beginning substantially proximate the gate and extending longitudinally from the gate to the cavity inner surface and extending substantially upstream from the gate to a location past an end of the threadsplit closest to the gate;
• injecting a first molten plastic material through the gate, into said cavity and along said flutes to the location passed the end of the threadsplit closest to the gate, to form a thin preform substrate;
• removing the thin preform substrate from the mold;
• inserting the thin preform substrate in a second injection mold;
• injecting a second molten plastic material into the second injection mold and over said preform substrate to form the second layer of a multi-layer perform;
• and
• removing the multi-layer preform from the second injection mold.