| 摘要 |
<p>The speed of rotation of a welded tube is slowed down by an optical-magnetic device or by a contact, in a plant for coating tubes by the extrusion of a strip of thermoplastic material, so that the tension on the strip is diminished at the extrusion nozzle, and the thickness of the coating above the welded seam is the same as that on the same as that on the remainder of the outer surface of the tube. The additional thickness of the extruded strip corresponds to the point where the weld presents itself for the weld presents itself for the winding on, i.e. at the moment when the slowing down is commanded by the signal acting directly on the rollers driving the tube. Used to make possible the application of a coating of extruded material if minimal thickness on to the welded pipe, whilst ensuring at the same time that the zone covering the welded seam has the same thickness as the coating on the remainder of the circumference of the pipe.</p> |
