| 摘要 |
PURPOSE:To make a foaming ratio of a molded article uniform by eliminating irregularity in casting pressure of a foaming agent, by a method wherein pressure of molten resin and that of the foaming agent is detected always and the casting pressure of the foaming agent is controlled based on the comparison between both of the pressure. CONSTITUTION:Resin pressure in the inside of an injection cylinder 1 is detected by a resin pressure sensor 82 and gas pressure of a foaming agent is detected by a gas pressure sensor 81 in the above flow path 63. These two pressure are being examined electrically always by a comparator 83, when a variation is generated on a pressure difference preset by a pressure difference presetting device 85, a proportional pressure valve 75 is a hydraulic pressure circuit is controlled by a pressure presetting device 86 of a pressure valve actuating through a signal from the comparator, through which hydraulic pressure to a pressure transducer 72 is adjusted. When gas pressure is detected low based on comparison with the resin pressure, the proportional pressure valve 75 is preset high, circuit pressure is raised and the pressure transducer 72 is pressurized. The pressure is transformed into flow path pressure further and is improved until the pressure of the foaming agent comes to the preset pressure difference by a proportional flow control valve 65. |
