Patent ID: 7781707

Claim:
An injection nozzle unit for the moulding of plastics materials, comprising: a nozzle with a tubular metal core forming a central longitudinal injection duct and a substantially cylindrical, outer, lateral surface, and a heater/diffuser device comprising: a metal heat diffuser element of tubular cylindrical shape with an open annular cross-section, mounted around the cylindrical outer surface of the nozzle core, with a substantially cylindrical internal surface fitting the cylindrical outer surface of the nozzle core, with two facing longitudinal free edges which are spaced apart circumferentially, are free of one another, and define between them a longitudinal space extending along the cylindrical surface of the heat diffuser element, and with a recessed, channel-like seat formed in said internal surface of the heat diffuser element that is in contact with the cylindrical outer surface of the nozzle core, and a wire resistor housed in the channel-like seat, wherein said metal heat diffuser element of tubular cylindrical shape comprises one bent metal plate, so that said longitudinal space along the cylindrical surface of said heat diffuser element is defined by two opposed ends of said one bent metal plate; wherein said wire resistor is housed is said channel-like seat with said metal plate being initially unbent; wherein the heat diffuser element has an internal diameter smaller than that of the cylindrical outer surface of the nozzle core, wherein the metal heat diffuser element is mounted on the outer surface of the nozzle core with radial interference for gripping the nozzle core resiliently, and wherein when the injection nozzle unit is heated by the supply of electric current through the wire resistor, the distance between the longitudinal free edges of the heat diffuser element provides for the heat diffuser element being substantially free to expand thermally by extending in the circumferential direction around the nozzle core without moving radially away from the outer surface of the nozzle core.