US 9,810,447 B2
Duct blank seam and apparatus for making a duct blank seam
Michael C. Borwig, Swisher, IA (US)
Assigned to MESTEK MACHINERY, INC., Westfield, MA (US)
Filed by Mestek Machinery, Inc., Westfield, MA (US)
Filed on Jan. 7, 2015, as Appl. No. 14/591,070.
Application 14/591,070 is a division of application No. 13/959,999, filed on Aug. 6, 2013, granted, now 8,950,229.
Prior Publication US 2015/0118513 A1, Apr. 30, 2015
Int. Cl. B21D 5/04 (2006.01); F24F 13/02 (2006.01); B21D 39/02 (2006.01); F16L 9/00 (2006.01); F16L 9/17 (2006.01)
CPC F24F 13/0209 (2013.01) [B21D 5/04 (2013.01); B21D 39/02 (2013.01); F16L 9/003 (2013.01); F16L 9/17 (2013.01); Y10T 428/12229 (2015.01)] 5 Claims
OG exemplary drawing
 
1. A method for forming a duct blank from a 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 method comprising the steps of:
forming opposed lead notches at said side edges adjacent to said leading end such that said lead notches bracket a male portion of a body of said sheet and said trail notches bracket a female portion of said body;
bending said side edges to form flanges extending substantially perpendicular to said body between said lead and trail notches;
folding said body female portion to form a leg part extending forward from said trailing end, a Z-bend extending forward from said leg part, and an offset part extending forward from the Z-bend;
wherein the Z-bend includes an inward fold adjacent to the leg part and having an outward fold disposed inward of the inward fold, the outward fold being bent further inward to provide an insertion angle opening between the inward and outward folds toward said trailing end;
wherein the offset part has outward and inward bends such that the outer surface of the Z-bend substantially aligns with an 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;
wherein each of said trail notches has 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.