Abstract: A method for the production of a molded article having a hollow portion by utilizing a gas compression apparatus having a gas source, a compressor composed of a piston and a cylinder, and a discharge valve for controlling the flow of pressurized gas discharged from the cylinder, the method comprising introducing the pressurized gas through the discharge valve into a molten resin injected into a cavity of a mold, under the control of the discharge valve while carrying out, in one molding cycle, the intake step of supplying gas from the gas source to the cylinder and the compression step of compressing the gas by movement of the piston in the cylinder, at least twice each on the basis of predetermined compressor operation conditions, and thereby forming the hollow portion in the molded article.

Abstract: An injection-molding method using an injection molding machine having a mold apparatus comprising(A) a fixed mold member,(B) a movable mold member movable in the mold opening and closing directions,(C) an intermediate mold member which is provided between the fixed mold member and the movable mold member and is slidable in the mold opening and closing directions between the fixed mold member and the movable mold member, and(D) at least one intermediate mold member sliding means for sliding the intermediate mold member in the mold opening and closing directions,the method including the steps ofinjecting a molten resin into a cavity formed of cavity wall surfaces of the fixed mold member, the intermediate mold member and the movable mold member, andincreasing the distance of the cavity by moving the movable mold member in the mold opening direction with keeping the intermediate mold member in intimate contact with the fixed mold member or the movable mold member by the intermediate mold member sliding means, an

Abstract: A process for the production of a molded article having a hollow structure, using an injection molding machine equipped with a mold apparatus having a mold provided with a cavity, said process comprising the steps of(a) positioning a plug in its forward end position in the cavity with a plug-moving means before a molten resin is injected,(b) moving the plug toward its backward end position nearly in parallel with a flow-axis direction of the molten resin, with the plug-moving means or under a pressure of the injected molten resin, after the injection of the molten resin is initiated,(c) introducing a pressurized fluid into the molten resin in the cavity through a pressurized fluid introducing portion while the plug is moving, and(d) moving the plug up to its backward end position nearly in parallel with the flow-axis direction of the molten resin with the plug-moving means or under the pressure of the molten resin and/or the pressurized fluid introduced into the molten resin, and then, cooling and solidifying