| 摘要 |
<p>In order to provide a tube of thermoplastic material with a groove and a thickened end, the tube is heated to plasticity, whereupon the heated tube end is upset until the tube end is confined between an outer and inner mould. After cooling the outer side of the tube end until a solid skin is formed, the outer mould is removed. After cooling, the heat content in the plastic material is sufficient for reheating the complete tube end to a temperature allowing further deformation of the plastic, whereupon the tube end is provided with a socket and with a groove.</p> |
