| 摘要 |
<p>The channel (1, 103) that feeds the plastic material into the part of the coextrusion head involved in, for example, forming the final layer of the parison, between the plug (2) and the die (102) of this part, divides into two or more suitably radiused descending channels (5, 7, 9 and 6, 8, 10) that continue in the form of identical fan-shaped channels (11, 12) which diverge in the downward direction and are of decreasing depth and open out to communicate with each other at the site of greatest diameter of the terminal conical mouth (14) that converges in the downward direction, from which emerges the outer layer of the multi-layer coextruded parison. The passive resistances are thereby minimized and the length of time required to change the colour of the extruded plastic is made much less than is required in the prior art. <MATH></p> |
