WELD QUALITY INDICATOR

• US 3,582,967 A
• Filed: 02/10/1969
• Issued: 06/01/1971
• Est. Priority Date: 02/10/1969
• Status: Expired due to Term

• Current Assignee: George Beckman, Tracy B. Gunderman
• Original Assignee: George Beckman, Tracy B. Gunderman
• Inventors: Beckman, George, Gunderman, Tracy B.
• Application Number:
  US04/797,802
• Time in Patent Office: 841 Days
• US Class Current: 219/109
• CPC Class Codes: B23K 11/25 Monitoring devices

Abstract

Apparatus is disclosed for developing a signal proportional to the total energy supplied to a weldment by the electrodes of an electrical welding machine during the welding cycle. The input signal to the apparatus is the AC voltage signal across the electrodes of the welding machine. The signal is rectified, and time integrated over the duration of the weld cycle. The integrated signal, which is proportional to the total energy delivered to the weldment, is compared to preset high and low reference levels. The result of the comparison indicates whether sufficient energy was supplied to the weldment to make a lasting weld.

Claims

1. In combination with an electric spotwelding machine having two electrodes through which energy is supplied to a weldment during the welding cycle, a device for monitoring the total energy supplied to the weldment during the weld cycle, said device comprising:

a. means connected to said two electrodes for rectifying the voltage across said electrodes, b. gating means connected to said means for rectifying for generating a start and end welding cycle signal, c. integrating means connected to said rectifying means and said gating means for integrating the output of said rectifying means between said start and end signals to develop a signal which is proportional to the energy supplied by the electrodes between the start and end signals; and

d. indicator means coupled to said integrating means for indicating the integrated output from said integrating means.

2. A monitoring device as claimEd in claim 1 wherein said integrating means comprises a capacitive storage means responsive to said rectifying means output and said gating means for storing a charge proportional to the total energy supplied to the weldment during the weld cycle.

3. A monitoring device as claimed in claim 2 wherein said gating means further comprises a timing means responsive to said start signal for generating a reset signal a predetermined time after the occurrence of said start signal, and said integrating means further comprises switching means responsive to said start, end, and reset welding cycle signals for controlling the charge and discharge times of said capacitive storage device.

4. A monitoring device as claimed in claim 3 wherein said capacitive storage means comprises an operational amplifier with a feedback capacitor.

5. A monitoring device as claimed in claim 4 wherein said switching means comprises a first transistorized switch connected between said rectifying means output and said operational amplifier input for connecting said rectifying means output to said operational amplifier input in response to said start signal and disconnecting said rectifying means output from said operational amplifier input in response to said end signal.

6. A monitoring device as claimed in claim 5 wherein said switching means further comprises a second normally open transistorized switch, connected across said feedback capacitor, responsive to said reset signal for closing and discharging said feedback capacitor.

7. A monitoring device as claimed in claim 6 wherein said indicating means includes display means connected to said integrating means, for comparing the output of said integrating means with predetermined reference levels, and generating a failure indication if the integrator output is outside said reference levels.

8. A monitoring device as claimed in claim 7 wherein said display means further comprises a meter having a needle and two positionable meter photodiodes on the face thereof, said photodiodes being positioned to indicate said predetermined reference levels, said needle being deflected in proportion to the output of said integrating means, a light source positioned to illuminate said photodiodes, and detection means responsive to the interruption of the illumination of said photodiodes for indicating whether the integrating means output is inside or outside said reference levels.

9. A monitoring device as claimed in claim 8 wherein said display means further comprises a plurality of indicator means responsive to said gating means and said detecting means for giving visual and audible indication that the output of said integrating means is inside or outside said reference levels.

10. A monitoring device as claimed in claim 9 further comprising means for generating a feedback control signal whereby said welding cycle will be continued until said meter photodiode output indicates that the output of said integrating means is within said preestablished reference levels.