초록 ▼

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. I

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, electric power is supplied to the resistance heating element of the fitting. The impedance and optionally, the resistance of the heating element are measured using low voltage electric power and the size of the fitting to be welded is determined therefrom. The initial magnitude of the current flowing through the heating element is sensed and compared with predetermined current levels for the size of fitting to be welded at various temperatures whereby 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 is 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 insure the welding process is proceeding correctly.

대표청구항 ▼

A method of electrically heat welding a thermoplastic fitting having an electric resistance heating element disposed therein whereby a predetermined 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 com

A method of electrically heat welding a thermoplastic fitting having an electric resistance heating element disposed therein whereby a predetermined 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 comprising the steps of: (a) connecting said heating element of said fitting to an electric power source; (b) sensing the initial temperature of said heating element and said fitting; (c) supplying alternating current electric power to said heating element at a minimum voltage level for measuring the impedance of said element without significantly heating said element; (d) measuring the impedance of said heating element; (e) determining the size of said element and said fitting by comparing the impedance measured in step (d) with predetermined impedances for various sizes of elements and fittings; (f) supplying electric power to said heating element at a controlled voltage whereby said element is heated; (g) sensing one or more characteristics of said heating element over the time said controlled voltage electric power is supplied thereto, comparing at least one of said characteristics and said initial temperature of said element and fitting with predetermined characteristics for the size of element and fitting determined in step (e), and comparing at least one of said characteristics at predetermined time intervals with pre-determined characteristics for the size of element and fitting determined in step (e) to thereby control the welding process, determine its duration and determine if the welding process is proceeding abnormally at such time intervals; and (h) terminating the supply of electric power to said heating element of said fitting at the duration of said welding process or when it is determined that said welding process is proceeding abnormally in step (g).