| 摘要 |
Bending preshaped sheet metal pieces that have a web and side flanges, by stretching on one side, and compressing on the other side, by utilizing opposed rollers. They can be, and are, selectively bent into cylinder shapes or cone shapes. The bending steps produce folds in the extended edges of the flanges, of circular cross sectional shape, and in one form, are of large dimensions on one side and of small dimensions on the other side, and adjacent pieces are interconnected by placing the large fold of one piece over and encompassing the small fold of the other piece, to form lids of great area.
|
