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Induction compensating method and apparatus for weld nugget resistance sensing leads of spot welders

  • US 4,403,132 A
  • Filed: 07/20/1981
  • Issued: 09/06/1983
  • Est. Priority Date: 07/31/1980
  • Status: Expired due to Fees
First Claim
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1. In an electrical spot-welding machine having a welding head including a pair of relatively movable electrodes for gripping the work to be welded and main welding current conductors, a method of compensating for inductive coupling between the main welding current conductors and the electrical sensor leads that monitor weld nugget resistance across the work to be welded, said method comprising the steps of:

  • (a) temporarily connecting the sensor leads to the welding electrodes and positioning said sensor leads along paths away from said current conductors so that there is no inductive coupling therebetween;

    (b) performing a welding cycle and recording the instant during the cycle at which the weld nugget voltage drop as represented by the sensor lead signal indicates the weld termination point, when there is no inductive coupling between the sensor leads and the current conductors;

    (c) re-positioning the sensor leads so that they are connected to the current conductors at desired final points of connection and laid along desired final paths such as are appropriate when the machine is in commercial use;

    (d) connecting into one of said leads an inductive compensating coil that is mounted on the welding head close to at least one main current conductor in an angularly adjustable manner; and

    (e) performing welding cycles and adjusting the angular position of the compensating coil until an angular orientation of the coil is achieved at which the weld termination point as indicated by the sensor lead signal representing weld nugget voltage drop occurs at the same instant in a welding cycle when said sensor leads are repositioned as when said sensor leads are temporarily positioned along paths away from said conductors.

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