| 摘要 |
Polymer material is injection moulded using a tool comprising an ingot nozzle (1) with a flow channel (2) for molten thermoplastic, preferably a heater (3) for keeping the thermoplastic warm, and optionally a pin for closing the flow channel. The nozzle is placed into the tool with its opening (6) communicating with the moulding region (7) inside the tool. At least one cooling cavity (11) is provided in the tool between the nozzle and the part of the moulding region surface (8) immediately adjacent to the nozzle opening. A compressed liquified gas (preferably carbon dioxide) is supplied as a coolant to the coolant cavity via at least one coolant channel. A pre-determined amount of coolant is injected into the cavity via a first coolant channel (12) or a first group of these channels (12`) and as the carbon dioxide temperature falls suddenly due to the pressure drop, it temporarily solidifies inside the cavity before subliming as it absorbs heat. The sublimed gaseous carbon dioxide is then evacuated via a second channel or a second group of channels (12``). In this way heat generated by the thermoplastic heater and any friction-generated heat created during injection of the molten thermoplastic is nullified by the cooling action to prevent it from affecting the mould cavity surfaces immediately adjacent to the nozzle opening. |
