| 摘要 |
PURPOSE:To prevent the undersirable slenderization and the deformation of the diameter and the cross section shape of an exhaust pipe side part respectively, by heating the exhaust pipe side more than the other parts, pressing an inert gas to introduce thereinto, then fabricating said exhaust pipe side in a curved form. CONSTITUTION:A straight bulb 3 is heated, for example, up to about 800 deg.C, while transferring it up to position of a heating furnace 5. Just when the straight bulb 3 comes to the next position x in the heating furnace 5, here, the exhaust pipe side 3n of the straight bulb 3 is heated, for instance, at 850 deg.C. This temperature is higher than that of any other parts. In this case, the heating apparatus 7 such as a burner is used. While the straight bulb 3 moves to the position x, or from the position x to the next position g, an inert gas is pressed to introduce into the straight bulb 3; the diameter of the exhaust pipe side 3n is preparatorily processed larger than that of any other parts, and then the exhaust pipe side is facricated in a curved form. |
