| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-stage device for detecting a welding defect of a nut, which is built in a resistance welding equipment and applicable to the welding of a nut having different diameters. SOLUTION: A first stepped part 6a, corresponding to the diameter of a nut to be welded, and a second stepped part 6b are provided with a predetermined distance at the tip of a guide pin 6 which is movable back and forth and penetrates through a lower electrode 3 of a resistance welding equipment 1. When a nut 5 having a large diameter is welded, the supplied nut 5 is accepted at the first stepped part 6a, an upper electrode 2 is lowered and its lower end face is butted to the nut 5, and the normal or abnormal state is checked by detecting the position of the tip of the guide pin 6 inserted into a relief hole 2a of the upper electrode 2. When the state is normal, a plate material 4 and the nut 5 are clamped between the upper electrode 2 and the lower electrode 3, and a welding work is performed by energizing. For a nut having a small diameter, the second stepped part 6b of the guide pin 6 is used.
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