| 摘要 |
By a method for connecting a plastic pipe end (4 and 4', respectively) to a plastic welding sleeve (1) a heater (3) of annealed expanded metal is initially mounted on the pipe end (4 and 4', respectively), whereafter the welding sleeve (1) is pushed over said pipe end. Subsequently the plastic welding sleeve (1) is pressed downwards to abut the heater (3) in question by means of a known clamping device and heat supplied from the outside. The heater (3) is then connected to a welding generator and a microprocessor measuring and controlling the current through the heater and the voltage across the heater (3) during the entire heating phase. During the first phase of the heating process the heater (3) is supplied with a constant current, and when the microprocessor registers that the increase in voltage per time unit has dropped below a predetermined level corresponding to a specific temperature, said microprocessor computes the ohmic resistance of the heater corresponding to a desired predetermined final welding temperature. This final welding temperature is kept constant for a period thereafter. In this manner a method is provided for connecting a plastic pipe end to a plastic welding sleeve by means of an extensible heater. During the fully automatized welding operation this heater is situated in the welding area, whereby a uniform distri bution of heat is ensured and results in a welding of high strength and quality. |
