Method for joining plastic pipes, a joint ring used in the joining and a pipe joint provided with the method

A method for joining a first tubular member having an outer surface to a second tubular member having an inner surface, said method comprising:

• (a) providing a stretchable and compressible welding ring comprising a flexible inner ring, a resistance coil wound around the inner ring and at least one layer of plastic coating the resistance coil, said welding ring being sufficiently stretchable to stretch over a rib of a ribbed pipe having a plurality of ribs or a corrugation of a corrugated pipe having a plurality of corrugations whereby it can be placed in a space or groove between the ribs or corrugations, said inner ring comprising a material that imparts pressure against the outer surface of the first tubular member and the inner surface of the second tubular member with the welding ring encircling the first tubular member and compressed between the first and second tubular members;
• (b) arranging the first and second tubular members in overlapping relation with an end of the first tubular member inserted into an end of the second tubular member and with the welding ring encircling the first tubular member and compressed between the respective ends of the first and second tubular members;
• (c) applying electric energy to the resistance coil to melt the at least one layer of plastic so that, upon cooling, the respective ends of the first and second tubular members are welded to the welding ring.