US Patent 7234734 Integral transverse flanges for a duct connecting system

An integral transverse flange for a duct includes a first upturned portion extending substantially perpendicularly from a duct wall of the duct. The flange further includes a second portion bent rearwardly from the first upturned portion, and a third return portion turned toward the duct wall and rounded back toward the first upturned portion from the second portion. A fourth L-shaped portion extends from the third return portion, the L-shaped portion having a first arm arranged adjacent to and in close relation with the second portion and a second arm arranged adjacent to and in close relation with the first upturned portion. A bead is formed in the first upturned portion.