| 摘要 |
The heating element (1) comprises a perforated metal band, e.g. a grid or sieve, the perforations (4) of which have a spacing less than the hole diameter. Independent claims are made for: (a) a method for connecting two pipe ends by resistance welding using an electric welding socket (5) with the claimed heating element (1) in which the socket is pushed onto both pipe ends; the heating element is inserted between the pipe and the welding socket walls; the socket is shrunk onto the pipe ends by heating and electric current is fed to the heating element for the welding stage; (b) an electric heating socket/sleeve with a larger diameter than the pipe end diameter. Preferred Features: The round holes (4) have a diameter of 2-6 mm and spacing of 0.5-2 mm and holes in adjacent rows are offset from each other. Angled connectors at the ends of the metal band allow connection to the welding transformer. A heating element is located at each end of the socket and the connectors are cut off after welding. Space between the socket and pipe wall is filled with foam after welding. The shrinkable central area (11) of the socket has a larger diameter than the ends and has filling holes with plugs (13) for introducing foam and purging air. |
