| 摘要 |
<p>A method and apparatus for electrically heat welding a thermoplastic fitting having an electric resistance heating element disposed therein whereby a regulated quantity of electric power is supplied to the heating element during the welding process and the making of a high quality weld is insured. In accordance with the method, a controlled electric power is supplied to the resistance heating element of the fitting. The initial magnitude of the current flowing through the heating element is sensed and compared with predetermined current levels for various sizes of fittings whereby the size of the fitting as well as the total time the controlled electric power should be supplied to the heating element of the fitting for the making of a high quality weld are determined. The magnitude of the current flowing through the heating element over the time the controlled electric power is supplied thereto is sensed at predetermined time intervals and compared with predetermined current levels for the size of fitting being welded to thereby determine if the welding process is proceeding abnormally at such time intervals. The electric power supplied to the heating element is terminated when it is determined that the welding process is proceeding abnormally or otherwise at the end of the total time determined to be required for the making of a high quality weld.</p> |
