Nozzle for injection molding machines

A nozzle for injecting a first medium into a mold cavity of an injection mold, the mold cavity defined by a pair of opposed first and second mold surfaces of said injection mold, said mold cavity having a second medium present therein, the injection mold having a first bore located outside the first mold surface wherein the first mold surface is connected to the first bore via a second bore, said first bore being larger in diameter than said second bore, the nozzle comprising:

• an outer blowing needle located within the first bore and the second bore, said outer blowing needle having a first terminal end;
• an inner blowing needle located within said outer blowing needle, said inner blowing needle having a second terminal end and a central bore closed at said second terminal end, said inner blowing needle having near said second terminal end at least one opening communicating with the central bore;
• first displacing means for displacing said inner blowing needle axially relative to said outer blowing needle and axially relative to the first and second bores of the injection mold such the second terminal end of said inner blowing needle moves from a first position even with the first terminal end of the outer blowing needle to a second position located between said opposed first and second mold surfaces and back to said first position, whereby said first medium passes through said central bore, out of said at least one opening and into said second medium when said second terminal end is in the second position;
• and
• second displacing means for displacing said outer and said inner blowing needles axially relative to the first and second bores of the injection mold when said second terminal end of said inner blowing needle is moved back to said first position such that said second terminal end of the inner blowing needle and the first terminal end of said outer blowing needle are moved to third position even with the first mold surface,
• whereby the first and second terminal ends of said inner and outer blowing needles supplement the first mold surface to ensure that said mold cavity is smooth and seamless.