Abstract: The invention concerns a device for detecting variations in the physical state of the plastic material in a coupling piece used for welding pipes and incorporating a heating resistor, cavities which the softened material can enter and sensors for detecting the state of the material within the cavities. According to the invention, in order to obtain a weld of high quality, it is necessary for the distance between the bottom of the cavities and the part of the resistor nearest this bottom on the one hand, and for the linear dimension in the cross-section of these same cavities near their bottom on the other, to be less than or equal to the thickness of the material which is softened during the heating of the pieces. The invention applies to the control of the welding of sections of piping, particularly for the gas industry.

Abstract: The invention relates to the automatic welding of plastic parts possessing a built-in winding. In order to carry out an automatic welding operation without risking damaging the parts by subjecting them to an excessive welding temperature, there are regulating means for varying the electrical energy supplied to the winding, in order, during the welding phase, to maintain the temperature of the winding between a minimum temperature, below which welding cannot be carried out, and a maximum temperature, beyond which the parts will be damaged. The invention is used particularly for the production of systems for the distribution of gas under pressure by means of plastic pipelines.

Abstract: The invention relates to the conducting and to the monitoring, using an automatic machine, of the temperature rise of electrically heated components with which there is associated an identification chart comprising parameters which can be used for conducting and for monitoring this heating, the machine comprising apparatus for reading the chart and for initiating the determined heating program.According to the invention, the chart is divided into a number of zones into some of which are entered, in addition to the said parameters, additional data concerning some of them, the parameters and their associated data are read off using the said reading apparatus, and provision is made for at least some of these parameters to undergo conversions which are induced by some of the other associated zones as a function at least of the data which are contained therein.The invention applies particularly to the monitoring of welding together of plastic components.