| 摘要 |
<p>FR--94389 E The extrusion nozzle has two concentric annular slit nozzles from whose centre (16) plastics are extruded to form a compact skin or sheath (137), while a second partly expanded thermoplastic material (139) is extruded from the inner annular nozzle (126) around a central mandrel (118) so that initially a cavity is formed which fills as the expandable material expands inwards. The calibrating vessel has an inner bore of circular or polygonal e.g. rectangular, profile of the required dimensions and slightly greater than the diameter of the extruded sheath as it leaves the nozzle (116); this bore is perforated and communicates with the annular vacuum chamber (133), so that the plastic sheath (138) is pulled against the bore to give it the correct dimensions, while the material extruded via the inner nozzle (126) expands to fill the interior. In a further embodiment, a core of metal or other material is pulled through the centre of the mandrel to give a reinforcement member as in the rectangular profile product, where the metal cord (240) is surrounded by the foamed plastic (241) the whole being enclosed by and bonded to the sheath (242). The calibrating vessel is water-jacketted to give controlled cooling of the product.</p> |
