| 摘要 |
<p>An extrusion head with an annular extrusion die gap or orifice for fabricating a hollow extrudate of thermoplastic material. The extrusion head has a central die core and outer die casing ring cooperating to define the die gap. The inner boundary of the die gap is formed by a wall of the die core, while the outer boundary of the die gap is formed by a wall of the casing ring. At least one boundary wall of the die gap comprises independently movable sections that move with respect to the other boundary wall to change the width of the die gap.</p> |
