Electric seam weld monitoring apparatus and method

• US 4,242,561 A
• Filed: 02/07/1979
• Issued: 12/30/1980
• Est. Priority Date: 02/07/1979
• Status: Expired due to Term

• Current Assignee: Crown Cork & SEAL Company Incorporated (Crown Holdings Incorporated)
• Original Assignee: Crown Cork & SEAL Company Incorporated (Crown Holdings Incorporated)
• Inventors: Long, George
• Primary Examiner(s): Shaw, C. C.
• Application Number:
  US06/010,029
• Time in Patent Office: 692 Days
• Field of Search: 219/61.5, 219/64, 219/82, 219/83, 219/86.41, 219/108, 219/109, 219/110
• US Class Current: 219/109
• CPC Class Codes: B23K 11/25 Monitoring devices

Abstract

An improved weld monitoring apparatus and a method for its use are disclosed. Specifically, the invention relates to the application of integrating voltmeters to the monitoring of a resistance seam welding process applicable to cans and the like, wherein a blanking pulse generator is used to direct a voltage signal from the welding process to suitably adapted integrating voltmeters.

Claims

1. A method for monitoring an electric welding process for welding a series of parts of the type wherein the welding current is applied to the part to be welded by welding electrodes as a series of pulses, comprising the steps of:

integrating the voltage across the welding electrodes over the length of each pulse;

comparing the value thus obtained to predetermined maximum and minimum limits;

producing an alarm signal when said value does not fall between said limits;

using said alarm signal to trigger a reject means for removing the part from the series of parts; and

controlling the time during which the voltage across the electrodes is compared to said predetermined limits in accordance with the position of the part with respect to the welding electrodes, wherein

a blanking pulse generator directs the voltage across the electrodes to a plurality of integrating voltmeters, wherein each said integrating voltmeter is adapted to generate an alarm signal if said voltage does not fall within the predetermined limits, and wherein said blanking pulse generator directs the voltage to the particular integrating voltmeter corresponding to the stage in the welding process at which the voltage across the electrodes is measured.

2. A method for monitoring an electric welding process for welding a series of parts of the type wherein welding current is applied by welding electrodes to the part to be welded as a series of pulses, comprising the steps of:

integrating the voltage across the welding electrodes over the length of each pulse;

comparing the value thus obtained to predetermined maximum and minimum limits;

producing an alarm signal when said value does not fall between said limits;

using said alarm signal to trigger a reject means for removing the part from the series of parts; and

controlling the time during which the voltage across the electrodes is compared to said predetermined limits in accordance with the position of the part with respect to the welding electrodes,

wherein the voltage across the welding electrodes is directed to each of a plurality of integrating voltmeters, each said voltmeter being adapted to produce an alarm signal when the voltage is not between predetermined limits corresponding to desired welding conditions at a point in the welding process, and wherein the blanking pulse generator is used to prevent any given voltmeter from giving an alarm signal except during the part of the welding process corresponding to the predetermined limits.

3. Apparatus for monitoring a welding process of the type wherein a pulsed current is applied to parts to be welded by welding electrodes, comprising:

a plurality of integrating voltmeters connected in parallel to the electrodes, and adapted to integrate the voltage across the electrodes during each pulse, to compare the value thus derived with preset limits, and to provide an alarm signal when said value is not between said limits;

a blanking pulse generator adapted to prevent any one of said plurality of voltmeters from producing an alarm signal except during the part of the welding process corresponding to said limits; and

reject mechanism means adapted to be actuated by said alarm signal.

4. Apparatus for monitoring a welding process of the type wherein a pulsed current is applied to parts to be welded by welding electrodes, comprising:

a plurality of integrating voltmeters adapted to integrate the voltage across the electrodes during each pulse, to compare the value thus derived with preset limits, and to provide an alarm signal when said value is not between said limits;

a blanking pulse generator adapted to prevent any one of said one or more voltmeters from producing an alarm signal except during the part of the welding process corresponding to said limits; and

reject mechanism means adapted to be actuated by said alarm signal,

wherein the blanking pulse generator directs the voltage across the electrodes to each of the plurality of integrating voltmeters in a sequential order in accordance with the position of the part to be welded with respect to the welding electrodes.

5. Apparatus for welding the seams of each of a stream of cans, by application of a series of pulses of electric current to said cans by electrodes, wherein the current desirably applied to said cans varies along the length of each can, comprising:

an integrating voltmeter adapted to compare the integral of the voltage across said electrodes during each said pulse with predetermined maximum and minimum limits and to provide an alarm signal when the value of said integral is not between said limits;

reject means for removing improperly welded cans from said stream of cans in response to said alarm signal; and

blanking pulse generator means adapted to prevent said voltmeter from producing said alarm signal in response to said comparison except during the welding of the portion of the seam of each can corresponding to said predetermined maximum and minimum limits,

wherein the variation in current desirably supplied to said electrodes over the length of each can is such that the integral of the voltage across said electrodes during each pulse applied to said can does not fall within said limits at all times during the welding of each such can.