Patent ID: 8950229
Filing Date: 2015-02-10
Classification: B21D,E04F,F16L,F24F,Y10T

Abstract:
1. A metal duct blank formed from a metal sheet of bendable material having a leading end and side edges extending rearward from the leading end to opposed trail notches formed at the side edges at a distance rearward from the leading end so as to define a trailing end, said duct blank comprising: a body having inward and outer surfaces extending between said leading end, said side edges, and said trailing end, and having opposed lead notches formed at said side edges adjacent to said leading end, said trail notches bracketing a female portion of the body and the lead notches bracketing a male portion of the body, the body female portion including a leg part extending forward from said trailing end, a Z-bend extending forward from the leg part, and an offset part extending forward from the Z-bend, the Z-bend having an inward fold adjacent to the leg part and having an outward fold disposed inward of the inward fold, a trailing part of the outward fold being bent further inward to provide an insertion angle opening between the inward and outward folds toward said trailing end, the offset part having outward and inward bends such that the outer surface of the Z-bend substantially aligns with the outer surface of said body and such that a gap exists between a leading surface of the Z-bend inward fold and a trailing surface of the offset part inward bend; flanges extending substantially perpendicular to said body along said side edges between said lead and trail notches; and wherein each of said trail notches having a lead part and a trail part, the lead and trail parts extending from one of said side edges across the width of the adjacent flange, each of said trail notches further having a slot disposed between the lead part and the trail part, the slot extending partway across said body toward the opposed trail notch.