Patent ID: 7138600

Claim:
An automatic pulse plasma welding method of forming a lap joint between membrane sheets, the method performing a pulse plasma welding operation by recognizing a flat part and a corrugated part of the lap joint between membrane sheets, through the steps of: dividing a corrugated part of the lap joint between membrane sheets having at least one flat part and at least one corrugated part into a plurality of regions, and setting optimal welding conditions according to the regions; installing a guide rail on the lap joint between membrane sheets, and welding a weld line for the flat part by moving a carriage along the flat part weld line by the guide rail; detecting a position where the lap joint changes from the flat part to the corrugated part by a photo sensor mounted on a front portion of the carriage; transmitting a corrugated part detection signal detected by the photo sensor to a controller unit; changing sensitivities of two touch sensors to “high” from “low” by the controller unit in response to the corrugated part detection signal of the photo sensor, causing a welding torch mounted on the carriage to incline at a forward angle of 6 to 7 degrees with respect to a travel direction of the welding torch, and detecting a rotation angle of the welding torch by switching a potentiometer to an “ON” state; recognizing the corrugated part of the lap joint between membrane sheets by the two touch sensors mounted to be collinear with the welding torch on the carriage in the travel direction (an X axis) of the welding torch; rotating an θ axis of the welding torch to be perpendicular to a weld part by operating a torch angle adjusting motor through a welding torch angle adjusting driver in response to a difference between output values of the two touch sensors; detecting the rotation of the θ axis of the welding torch by the potentiometer, and transmitting an output voltage value of the potentiometer corresponding to the detected result to the controller unit; recognizing a corresponding region and varying welding conditions corresponding to the region if a voltage signal corresponding to each of the regions is detected according to the output voltage value of the potentiometer, which is transmitted to the controller unit; and recognizing the lap joint as the flat part on the basis of a position where the welding torch comes to have a right angle to a horizontal surface, and welding the flat part again.