Gas injection nozzle for gas assisted injection molding
 An improved gas injection nozzle for use in gas-assisted injection molding process is disclosed. The improved gas injection nozzle comprises: (a) a nozzle body, and a nozzle cap fixedly connected to the nozzle body; (b) a gas inlet provided in the nozzle body so as to allow gas to be injected into a mold cavity via a gas channel formed inside both the nozzle body and the nozzle cap; (c) a heating coil provided on the gas injection nozzle; and (d) at least one circumferential groove formed on the outer surface of the nozzle cap. The circumferential groove formed on the outer surface of the nozzle cap preferably has the shape of a spiral groove, with a depth between about 0.2 mm and about 0.5 mm and a length between about 50 mm and about 150 mm. The combination of the heating coil and the circumferential groove prevents the formation of micro cracks that are often formed in the interstices between the nozzle cap and the sprue bushing during the cooling stage of injection molding process. These micro cracks allow passageways to be developed for the inert gas to be leaked out and a fall-off of the gas pressure inside the mold cavity, resulting in sinks and/or warpages to be formed on the injection molded product. The prevention of gas leakage also eliminates the need for continuous gas and thus reduces the manufacturing cost. 
Industrial Technology Research Institute
B B
B29C B29C
inventional additional
Wen-Liang Long-Cheng Yung-Chih
Liu Cheng Chen