| 摘要 |
PURPOSE: To provide the high frequency foamed coaxial cable which has its foams made fine and uniform, and is stable in frequency characteristics, by letting refrigerant flow in the inside of a metallic pipe acting as the inner conductor of the foamed coaxial cable, and thereby letting a foamed insulator be so constituted as to be cooled from the inside and outside of the metallic pipe. CONSTITUTION: A metallic tape 2 is formed 3 into a cylindrical shape in the longer direction, and its end peripheries are joined by welding 4 so as to be formed into a metallic pipe 5. Subsequently, a formed insulator 7 is extruded into a filament over the metallic pipe 5 at the extrusion cross head 6 of an extruder. At this time, a refrigerant injection pipe 9 is inserted in as far as a cooling section (an entrance to a water tank 10) from the forming section 3 of the metallic tape 2, let refrigerant 8 flow in the inside of the metallic pipe 5, and as a result the foamed insulator 7 is thereby cooled from the outside and inside of the metallic pipe 5. |
