| 摘要 |
A method and apparatus for manufacturing hollow plastic articles having a wall which at least partly consists of at least one core layer and two outer layers covering the core layer on both sides, in particular suitable for manufacturing preforms for bottles, wherein use is made of an injection-molding machine with a mold comprising at least one mold cavity, and an injection nozzle which, via an injection channel in the mold, connects to the mold cavity and has a central material feed channel, a needle of a controllable needle valve, which needle is active in the central material feed channel and can close or release the part of the central material feed channel located adjacent the injection channel, and at least one further material feed channel, opening into the central material feed channel, wherein first a plastic material of a first type for forming the outer layers is fed to the mold cavity and then at least one plastic material of a second type for forming at least one core layer. After the feed of the material of a second type and after the freezing of the material in the injection channel, material of the first type is fed to the central channel in at least the space before the free end of the needle, and then, the needle is moved to the injection channel for mechanically compressing, in the sprue of the plastic article located in the injection channel, the material located before the needle.
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