| 摘要 |
PURPOSE:To obtain an oval composite plastic tube inexpensively by a method wherein an annular passageway is provided between a die ring and a mandrel to pass molten synthetic resin and extrude an expandable resin to form a round tube, subsequently, the round tube is pushed and deformed to form the oval tube gradually. CONSTITUTION:A cap, consisting of a die ring 1 and a mandrel 2, is arranged at the tip end of an extruder E1 while the cap is provided with a round annular passageway. A round tube is formed while molten synthetic resin R, extruded out of the extruder E1, passes through the annular passageway and, simultaneously, an expandable resin H, extruded out of an extruder E2, is extruded out of the cap under a condition that it is interposed in the intermediate layer of said round tube. The sectional configuration of the round tube, extruded out of the cap, is deformed gradually from a round shape into an oval shape by pushing while the round tube is passed between a former 4 and a forming mandrel 5 whereby the desired oval tube may be formed. |
