Method of and device for monitoring and/or controlling welding current in the high-frequency resistance pressure welding of pipes with longitudinal seams
First Claim
1. Method of monitoring and controlling welding current in high-frequency resistance pressure welding of pipes with longitudinal seams, comprising the steps of:
- detecting magnetic fields generated by the welding current with two sensors below edges of a skelp and in front of a welding point;
converting the detected magnetic fields into a voltage, each of said sensors being separately located below one edge of the skelp for inducing a voltage thereinto and having a coil with a coil axis transverse to a pipe axis, voltage in the coil of one sensor being measured independently of voltage in the coil of the other sensor;
monitoring oscillations in the voltage and comparing with reference voltages serving as references for width of oscillation; and
shaping a setting signal to correct the welding current when said reference voltages are exceeded.
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Accused Products
Abstract
It is necessary to determine welding temperature as precisely as possible in order to properly control the high-frequency welding of longitudinal pipes. Changes in welding temperature are proportional to alterations in the welding current that flows through the edges of the skelp. Magnetic-field sensors can be used to directly and precisely determine alterations in the current and hence changes in the temperature. Voltages induced in the sensors can be processed into setting signals to correct the high-frequency welding generator and disruptions in the current used to generate signals to mark the site of failure on the pipe for subsequent rejection.
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Citations
13 Claims
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1. Method of monitoring and controlling welding current in high-frequency resistance pressure welding of pipes with longitudinal seams, comprising the steps of:
- detecting magnetic fields generated by the welding current with two sensors below edges of a skelp and in front of a welding point;
converting the detected magnetic fields into a voltage, each of said sensors being separately located below one edge of the skelp for inducing a voltage thereinto and having a coil with a coil axis transverse to a pipe axis, voltage in the coil of one sensor being measured independently of voltage in the coil of the other sensor;
monitoring oscillations in the voltage and comparing with reference voltages serving as references for width of oscillation; and
shaping a setting signal to correct the welding current when said reference voltages are exceeded. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- detecting magnetic fields generated by the welding current with two sensors below edges of a skelp and in front of a welding point;
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11. Apparatus for monitoring and controlling welding current in high-frequency resistance pressure welding of pipes with longitudinal seams, comprising:
- a high-frequency welding generator, current-transmission means, and a welding-current setter, two sensors for detecting magnetic fields generated by welding current and converting detected magnetic fields into a voltage being inside the pipe immediately in front of the welding point and below edges of the skelp;
means for monitoring oscillations in the voltage and comparing with reference voltages serving as reference for width of oscillation;
a voltage measuring device connected to said sensors and containing integrated limiting-value generators; and
a reference-to-actual value comparator with means for shaping a setting signal to correct the welding current when said reference voltages are exceeded, said comparator being wired into controls connected to said welding-current setter each of said sensors being separately located below one edge of the skelp for inducing a voltage thereinto and having a coil with a coil axis transverse to a pipe axis, voltage in the coil of one sensor being measured independently of voltage in the coil of the other sensor. - View Dependent Claims (12, 13)
- a high-frequency welding generator, current-transmission means, and a welding-current setter, two sensors for detecting magnetic fields generated by welding current and converting detected magnetic fields into a voltage being inside the pipe immediately in front of the welding point and below edges of the skelp;
Specification