| 摘要 |
<p>A welding sleeve for connecting pipes formed of thermoplastic material includes an electrical conductor in the form of an electrical resistance wire. The resistance wire extends around the sleeve and has a pair of opposite ends for conveying current through the wire. The opposite ends of the wires can be connected directly to a source of electrical current, for instance a 220 DEG V DIFFERENCE line. It is not necessary to provide transformers or timing relays. A melting material is incorporated into the conductor between its ends and it melts through when the energy necessary for welding the sleeve has been developed. After the current is supplied through the resistance wire, the welding process is completed when the predetermined melting material melts through. Such sleeves can be manufactured in a mass production operation, and the sleeves are much safer than the conventional devices used to-date.</p> |
