| 摘要 |
A method and apparatus for manufacturing hollow plastic articles (20) having a wall (21) which at least partly consists of at least one core layer (24) and two outer layers (22,23) 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 (60), and an injection nozzle which, via an injection channel (63) in the mold, connects to the mold cavity and has a central material feed channel (32), a needle (40) of a controllable needle valve, which needle is active in the central material feed channel (32) and can close or release the part (32a) of the central material feed channel located adjacent the injection channel (63), and at least one further material feed channel (36), opening into the central material feed channel (32), wherein first a plastic material (M1) of a first type for forming the outer layers (22,23) is fed to the mold cavity and then at least one plastic material (M2) of a second type for forming at least one core layer (24). After the feed of the material (M2) of a second type and after the freezing of the material in the injection channel (63), material (M1) of the first type is fed to the central channel (32) in at least the space before the free end of the needle (40), and then, the needle is moved to the injection channel (63) for mechanically compressing, in the sprue of the plastic article located in the injection channel, the material located before the needle. |
