| 摘要 |
<p>14 A mechanical connection for connecting together a juxtaposed first and second layer of malleable sheet material includes the use of a third layer of malleable sheet material overlying the first and second layers, with the second layer sandwiched between the first and third layers. The first layer has a first displaced pocket projecting away from the second layer, and the second layer has a second displaced pocket nesting within the first displaced pocket. The third layer has an aperture in registry with both pockets, the aperture resulting from the punching out of a disc or slug which is nested within the second displaced pocket. In a preferred embodiment, a length of duct with at least one flat wall has an intermediate lateral stiffener which includes a base leg defined by two juxtaposed layers of sheet metal, the base leg being connected with the flat wall against which it is juxtaposed by the mechanical connection described above.</p> |
