Patent ID: 6544459
Filing Date: 2003-04-08
Classification: B29B,B29C

Abstract:
A method of injection molding a multi-layered article by utilizing an apparatus including(i) a mold including a hot runner block and a cavity block having a cavity; (ii) at least a first injection cylinder and a second injection cylinder; (iii) a first resin-flow-passage located within said hot runner block and connecting said first injection cylinder and said cavity; (iv) a second resin-flow-passage located within said hot runner block and connecting said second injection cylinder and said cavity, wherein said first resin-flow passage and said second resin-flow-passage communicate with each other at a junction portion upstream of said cavity; and (v) a back flow device operable to allow a first molten resin in said first resin-flow-passage to flow into said second resin-flow-passage after a second molten resin has been injected into said cavity through said second resin-flow-passage, wherein said back flow device is operable in response to pressure exerted by the first molten resin located in said first resin-flow-passage against the second molten resin located in said second resin-flow-passage, said method comprising: injecting a first molten resin from the first injection cylinder through the first resin-flow-passage into the cavity, and then discontinuing the injection of the first molten resin into the cavity; injecting a second molten resin from the second injection cylinder through the second resin-flow-passage into the cavity, and then discontinuing the injection of the second molten resin into the cavity; and then injecting the first molten resin from the first injection cylinder through the first resin-flow-passage into the cavity, and allowing the first molten resin in the first resin-flow-passage to flow into the second resin-flow-passage in response to operation of the back flow device either during injection of the first molten resin into the cavity or after completion of the first molten resin into the cavity.