| 摘要 |
The present invention relates to a sheet metal member having an annular peripheral wall and a method of thickening an annular peripheral wall of the sheet metal member. The thickness of the annular peripheral wall is increased to be 2 or more times or 3 or more times that of a base plate. Teeth for a timing toothed belt, a gear, or the like are cut in the annular peripheral wall which is thickened in this way. In the method of thickening an annular peripheral wall of the present invention, a base plate integrally having a flange-shaped portion is held between a circular bottom pattern tool and a circular top pattern tool, the flange-shaped portion which projects outwardly and the circular top pattern tool is sequentially pressed in a radially inward direction by annular forming faces of circular rollers of plural kinds, thereby thickening the flange-shaped portion. The flange-shaped portion is then formed into a cylindrical shape which is concentric with the base plate. According to the method, it is not required to separately produce the peripheral wall and the base plate and then weld them together. The peripheral wall can be provided with the strength required for cutting teeth in the peripheral wall.
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