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Arrangement for monitoring the quality of electric welds

  • US 5,291,423 A
  • Filed: 06/21/1991
  • Issued: 03/01/1994
  • Est. Priority Date: 12/16/1988
  • Status: Expired due to Fees
First Claim
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1. An apparatus for monitoring the quality of electric welds on can bodies, each can body having a weld seam formed by a plurality of welds extending continuously along the length of a can body each weld being associated with a welding parameter of a given value, said apparatus comprising:

  • means for receiving weld signal indicative of the value of the welding parameter as measured for each weld, with a set of said parameter values of each weld seam;

    at least one means for determining from said weld signals an average welding parameter profile (Fm) computed from a group of acceptable weld seam parameter value sets measured on a plurality of acceptable welded can bodies;

    store means to store the average welding parameter profile;

    a comparator to compare the average welding parameter profile with welding parameter profiles measured later on subsequently welded can bodies for determining a degree of agreement between the average welding parameter profile and each of said subsequently welded can body welding parameter profiles; and

    evaluation means for providing statistical evaluation of said subsequently welded can body welding parameter profiles and determining a reject limiting-value band (Fg±

    ) from computed mean welding parameter values for each weld in said group of acceptable weld seam parameter value sets and from the product of a standard deviation of said welding parameter values for each weld in said group of acceptable weld seam parameter value sets assumed to be normally distributed and at least one weld quality sensitivity factor;

    the comparator further generating output signals indicative of whether each welding parameter value of said subsequently welded can body welding parameter profiles lie within the reject limiting-value band (Fg±

    ).

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