Joint construction for sheet metal ducts

An elbow for a sheet metal conduit, said elbow having at least two cylindrical sections the axes of which are inclined to each other and having abutting circular ends of identical diameter, wherein the end of one of said sections has a radially outwardly offset circumferential ridge having axially spaced circumferentially extending inclined walls at opposite edges thereof;

• said one of said sections, circumferential ridge and inclined walls all having substantially the same wall thickness;
• the end of the other of said sections having a radially outwardly offset circumferential flange having an inner diameter to closely and slidably seat over said ridge and a single skirt portion to closely seat over the adjacent one of said end walls;
• a parted band having a cross sectional shape complementary to said flange when said ridge and flange are fitted together;
• and means for closing the part in said band for drawing said band around said ridge and flange to form an air-leak resisting seal between said cylindrical sections.

A joint assembly for ducts comprising:

• a first duct section integrally including at one end an axially aligned and radially offset flange extending longitudinally parallel with the axis of said first duct section and spanned on either side by a pair of inwardly inclined walls with one wall joining said flange to said first duct section;
• said first duct section, radially offset flange and pair of inwardly inclined walls all having substantially the same wall thickness;
• a second duct section integrally including at one end an axially aligned and radially offset flange extending longitudinally parallel with the axis of said second duct section and having a radial dimension greater than said flange associated with said first duct section and a single inwardly inclined wall coupling said second named flange to said second duct section;
• and
• means for securing said first duct section to said second duct section with said first named flange seated within said second named flange.