| 摘要 |
A hollow body formed of a thermoplastic resin and having uniform inner diameter and thickness and an excellent inner surface smoothness, and, in particular, a pipe-shaped hollow body having a bent portion is manufactured by injection molding. A method of manufacturing a hollow body includes injecting a molten resin 8 into a mold cavity 2 of a mold 1, the mold cavity 2 having on its one end a pressure port 4 provided with a floating core 6 and on its other end an outlet 5, pressure-injecting a pressurized fluid through the pressure port 4 after the injection of the molten resin 8, and moving the floating core 6 toward the outlet 5, and, at the same time, extruding the molten resin 8 from the outlet 5. In the method, the floating core 6 is constituted of a columnar portion and a top portion, which is continuously connected to one surface of the columnar portion and has a shape that a cross-sectional area perpendicular to a central axis of the columnar portion gradually decreases from one surface side of the columnar portion. When a diameter of the columnar portion is represented by A, the height of the columnar portion is 0.1 A to 1 A, and the height of the top portion is 0.3 A to 1.6 A.
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