| 摘要 |
An extrusion process is described in which the variation in cooling of an extruded plastic pipe due to variations in wall thickness is measured and the measurement is used to control the extrusion process. The pipe is extruded through a nozzle, passes through a cooler in which an even flow of coolant around the walls of the pipe is guaranteed and thence through a measuring ring. As more heat is retained in thicker wall sections than in the thinner sections, the pipe surface at the thicker section will recover to a higher temp. than that at the thinner section. The variations in temp. are detected by series thermocouples around the circumference of the pipe. The signals transmitted are used to increase or reduce the feed rate and to position the central former of the nozzle. Existing methods for attaining correct and even wall thicknesses in extruded plastic tubes are complex and expensive. This process is simple but still enables an accurate tube to be formed so that the minimum of material is used. |
