| 摘要 |
<p>A method of forming a sheet metal door with intersecting stiffener ribs so as to rigidify the door and prevent it from flexing along mutually perpendicular axes by cutting slit means at each corner of a sheet of metal, each slit means being defined by a pair of spaced diverging side edges originating at a common point spaced interiorly from the outer edges of the sheet, forming an elongated rib shaped depression in the sheet parallel to each outer edge of the sheet and along an axis that intersects one of the side edges of a pair of slit means intermediate the ends thereof so as to cause the side edges of each slit means to move out of the plane of the sheet towards each other while maintaining the outer edges in the plane of the sheet, and finally welding the side edges of each slit means together.</p> |
