Abstract: An injection molding method and device, wherein, in order to minimize dimension errors of molded products, molten resin is injected from a nozzle (23) retaining therein pre-pressurized molten resin such as plastic into the cavity (3) via an annular gate (24).

Abstract: Disc storage case (1) for storing a plurality of discs (20) comprises a case body (2) having a cylindrical protuberance (4), the outer diameter 4a of which is encompassed by an elastic member (5), and a protrusion (10) that freely enters and exits the inner diameter (4a) of the protuberance (4).

Abstract: A valve pin (4) for controlling an injection amount of molten resin is inserted into a cavity (13), and then the molten resin is injected by way of a gate (10) along the surface of the valve pin (4) into the cavity (13) to be dropped therein, and tip ends of this dropping molten resin merges at a bottom (13a) of the cavity (13) to form a hollow portion (S) between the valve pin (4) and the dropped molten resin. Then, air is blown into the hollow portion (S) from the tip end of the valve pin (4), inflates the hollow portion (S), brings it into contact with the inner surface of the cavity (13), and cools and solidifies this molten resin, so as to attain a hollow molded product (40).

Abstract: A valve pin (24b) of a valve for injecting molten resin is inserted into a cavity (31) formed in a mold (22), then the molten resin is injected and filled by way of a gate (30) into a space formed between the valve pin (24b) and the cavity (31). Then the molten resin is cooled and solidified so as to provide a molded product of synthetic resin.