Patent ID: 6931729

Claim:
A method for manufacturing a filler neck comprising the following steps: forming a mouthpiece having a body with a circumferential wall portion in a sectional circular shape, forming a feeding pipe having a circumferential wall portion in a sectional circular shape, fitting the circumferential wall portion of the mouthpiece in the circumferential wall portion of the feeding pipe in a closely overlapped condition, and welding the circumferential wall portions at a welding area W defined in a range of an overlapped area S defined by the overlapped circumferential wall portions; wherein that: the step a welding is executed by a seam welding utilizing an internal welding electrode and an external welding electrode; the internal welding electrode being a cylinder having an outer diameter smaller than an inner diameter of the circumferential wall portion of the mouthpiece, said internal electrode having an electrode region on a side face of the cylinder and wherein the internal welding electrode is inserted in the mouthpiece to press the electrode region against an inner face of the circumferential wall portion of the mouthpiece at a predetermined pressure, the external welding electrode being a flat disk having a thickness equivalent to a width of the welding area W, said external welding electrode having an electrode region on a circumference face of the disk and wherein said external welding electrode presses the circumference face thereof against an outer face of the circumferential wall portion of the feeding pipe at a predetermined pressure, and both welding electrodes together holding the overlapped circumferential wall portions of the mouthpiece and of the feeding pipe within the welding area W therebetween, allowing the mouthpiece and the feeding pipe, the internal welding electrode, and the external welding electrode to respectively rotate at synchronized peripheral speed, applying a predetermined electric current to the internal welding electrode and the external welding electrode, and to thereby integrate the mouthpiece and the feeding pipe.