Projection-welding method for insulation-coated surfaces

Claim 1

A PROCESS FOR WELDING TOGETHER TWO METAL PARTS, OF WHICH AT LEAST ONE IS COATED ON THE SURFACE TO BE WELDED WITH AN INSULATING LAYER, COMPRISING PROVIDING ON THE SURFACE OF ONE OF SAID PARTS PROJECTIONS FACING THE OTHR PART, SUPPORTING ONE OF SAID PARTS ON A SUPPORT PERMITTING MOVEMENT OF SAID PART AGAINST A SELECTED ELASTIC FORCE IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO THE SURFACE TO BE WELDED, PRESSING THE OTHER OF SAID PARTS AGAINST SAID ONE PART IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO SAID SURFACE, SUBJECTING ONE OF THE TWO PARTS TO A SUB-ULTRASONIC VIBRATORY MOVEMENT WITH REFERENCE TO THE OTHER IN A DIRECTION SUBSTANTIALLY PARALLEL TO SAID SURFACE TO MAKE SAID PROJECTIONS BREAK THROUGH CORRESPONDING AREAS OF THE COATING LAYER, STOPPING SAID VIBRATORY MOVEMENT AND ACCURATELY POSITIONING SAID PART RELATIVE TO ONE ANOTHER WITH SAID PROJECTIONS IN SAID BROKEN-THROUGH AREAS AND FEEDING AT LEAST ONE SHORT ELECTRIC PULSE THROUGH THE CONTACT POINTS BETWEEN SAID PROJECTIONS AND THE AREAS OF THE COATED PART WHERE THE COATING LAYER HAS BEEN BROKEN THROUGH WHILE THE PARTS ARE PRESSED TOGETHER TO WELD ONLY SAID PROJECTIONS OF ONE PART TO THE OTHER PART.