Patent ID: 9505078
Filing Date: 2016-11-29
CPC Classification: B23K

Claim Text:
1. A spot welding method for spot-welding a stacked assembly constructed such that plurality of high-resistance workpieces are stacked with a low-resistance workpiece, wherein all of the workpieces include metal sheets and the low-resistance workpiece is the thinnest among all the workpieces in the stacked assembly, the method comprising the steps of: holding a first welding tip in abutment against the low-resistance workpiece which is disposed on one side of the stacked assembly; holding a second welding tip in abutment against one of the high-resistance workpieces which is disposed on another side of the stacked assembly; engaging a branch current electrode to an inner workpiece that is another of the high-resistance workpieces and positioned adjacent to the low-resistance workpiece to establish electrical communication between the inner workpiece and the branch current electrode, the branch current electrode being either a ground electrode or an electrode which has a same polarity as the second welding tip; directing a larger amount of electric current from the first welding tip through the inner workpiece toward the branch current electrode than toward the second welding tip by pressing the stacked assembly with a first pressing force, wherein the first pressing force is commensurate with intensity for contacting the low-resistance workpiece with the inner workpiece and for contacting the high-resistance workpieces to each other at positions aligned with the first welding tip and the second welding tip; and directing a larger amount of electric current toward the second welding tip than toward the branch current electrode by pressing the stacked assembly with a second pressing force which is larger than the first pressing force.