| 摘要 |
The shutter, having outer and inner walls (10) forming a hollow housing with one or more inner reinforcing elements (18), has each reinforcing element made with projecting tabs (66) on its edges that engage with slots (40) in the shutter walls before being welded in place. Each reinforcing element is in the form of a flat plate with one or more apertures, and it is welded in place from the outside of the shutter.
|
