System of manufacturing injection molded article and metal mold

Abstract

In an injection process, molten resin is successively injected from a first flow channel and a second flow channel connected with each other in order into a cavity of a metal mold. High-temperature resin existing in the first flow channel is injected in advance into the cavity as a part of a single shot of molten resin to later form a skin layer of a molded article. other low temperature resin near a flowable limit existing in the second flow channel is subsequently injected into the cavity as another part of the single shot of molten resin to later form a core layer of the molded article. A low temperature resin remaining in the first flow channel when injection is completed is warmed to be a high-temperature resin before the next cycle, thereby allowing successive molding of molded articles.

What is claimed is: 
     
         1 . A system of manufacturing an injection-molded article comprising:
 a metal mold having a cavity to mold the injection-molded article; and   an injector to pump and inject molten resin into the cavity,   the injector injecting molten resin having a high temperature into the cavity in advance as a part of a single shot of molten resin to later form a skin layer of the injection molded article,   the injector subsequently injecting molten resin having a low temperature near a flowable limit into the cavity as another part of the single shot of molten resin to later form a core layer of the injection molded article.   
     
     
         2 . The system as claimed in  claim 1 , further comprising:
 a first flow channel to guide molten resin downstream; and   a second flow channel connected to the first flow channel to guide molten resin downstream,   wherein the high-temperature molten resin is prepared by warming molten resin in the first flow channel before the molten resin is pushed out into the cavity in advance,   wherein the low temperature molten resin is prepared by retaining temperature of molten resin in the second flow channel before the molten resin is subsequently pushed out to the cavity,   wherein the injector sends the single shot of molten resin from a molten resin supply source to the second flow channel and the first flow channel in order.   
     
     
         3 . The system as claimed in  claim 2 , wherein the first flow channel is located closer to the cavity than the second flow channel is,
 wherein the molten resin in the first flow channel is warmed until the high temperature to prepare the high temperature molten resin in at least one of:   when the metal mold is closed before molten resin is injected into the cavity,   when molten resin injected into the cavity is cooled, and   when the metal mold is opened and an injection-molded article is removed from the metal mold after the molten resin is cooled.   
     
     
         4 . The system as claimed in  claim 1 , further comprising:
 a nozzle section to send a single shot of molten resin supplied from a molten resin supply source; and   a cylinder,   wherein the high temperature molten resin is prepared by warming the molten resin either in the nozzle section or in the vicinity thereof,   wherein the relatively low temperature molten resin is prepared by retaining temperature of molten resin in the cylinder.   
     
     
         5 . A metal mold comprising:
 a high temperature flow channel section to warm molten resin injected in an early stage as a part of a single shot of molten resin until a high-temperature, the molten resin later forming a skin layer of an injection-molded article, the high temperature flow channel section having a first flow channel located just before a cavity of a metal mold; and   a low temperature flow channel section to retain temperature of other molten resin injected after the early stage of injection as another part of the single shot of molten resin at a low level near a flowable limit, the other molten resin later forming a core layer of the injection molded article, the low temperature flow channel section having a second flow channel connected to the first flow channel.   
     
     
         6 . The metal mold as claimed in  claim 5 , further comprising a molten resin supply source to push out the high temperature molten resin in the first flow channel in advance and the low temperature molten resin in the second flow channel subsequently to the cavity by pumping a single shot of molten resin to the second flow channel and the first flow channel in this order. 
     
     
         7 . The metal mold as claimed in  claim 5 , wherein the high-temperature flow channel section is enabled to warm the low temperature molten resin until the high temperature within a given period of time calculated by summing up a cooling period of time for cooling a molten resin filled in the cavity, a period of time for opening the metal mold and ejecting an molded article, and a period of time for closing the metal mold. 
     
     
         8 . The metal mold as claimed in  claim 5 , wherein the low temperature flow channel includes a heat retention manifold and the high temperature flow channel includes a warming manifold. 
     
     
         9 . The metal mold as claimed in  claim 8 , further comprising a heat transfer suppression section to suppress heat transfer from the warming manifold to the heat retention manifold, the heat transfer suppression section disposed between the warming manifold and the heat retention manifold.