Injection moulding tool

A device for producing an injection molded part having an open end defining a peripheral edge and a hollow interior, the device comprising:

• a hot runner nozzle having an annular nozzle mouth sized to inject material about the peripheral edge of the open end of the part;
• a core plate positioned downstream of the hot runner nozzle and dimensioned to direct injection material from the hot runner nozzle to the peripheral edge;
• a hollow needle which is axially movable adjacent the hot runner nozzle and is dimensioned to reversibly block the nozzle mouth to admit or prevent flow of injection material through the annular nozzle mouth;
• a nozzle core which extends through and along an interior of the hollow needle and past the annular nozzle mouth to form the hollow interior of the part, the nozzle core including an outer core which defines an interior surface of the hollow interior of the part, and an inner cooling core which cools the outer core;
• a die which defines an exterior surface of the part;
• the nozzle core and the die defining therebetween a cavity open at the nozzle mouth, the cavity having the shape of the part to be molded;
• an insulating jacket interposed between and along the hollow needle and the nozzle core and terminating at the peripheral edge of the open end of the part, the jacket surrounding the nozzle core and peripherally surrounding an interior of the hollow needle adjacent to the nozzle core, to thereby reduce heat transfer from the hot runner nozzle through the hollow needle to the outer core and inner cooling core of the nozzle core, the insulating jacket formed of a low heat-conducting material.