| 摘要 |
<p>The invention relates to an extrusion head (10) for forming a tubular sheath. The extrusion head includes an annular chamber (18) having an upstream end and a downstream end (24), said upstream end comprising an inlet opening for injecting a polymer material loaded with a flow additive, said annular chamber (18) including two channels for forming two circumferential flows of polymer material in the molten state, said channels combining in a junction area (48), wherein the flow additive is concentrated in said junction area, and the junction of said two flows forms a weld joint, at which there is a concentration of flow additive, in said tubular sheath. According to the invention, said annular chamber includes an extraction pipe (52) leading into said junction area (48) in order to enable the extraction of a fraction of said polymer material, which is in the molten state and which has a concentration of flow additive, from said junction area (48).</p> |
