Patent ID: 7493685

Claim:
A method for producing in a single pass a hollow, generally conically shaped hollow sheet metal part ( 16 ) for a HVAC duct, the part including a conically shaped hollow portion having a first circular edge and a cylindrically shaped hollow portion attached to said edge, said method comprising the steps of (a) providing an elongate strip ( 12 ) of metal sheet material, said strip having (i) a first edge portion ( 13 ) to be laterally tapered and rolled into a hollow first round cylindrical configuration having a selected diameter, (ii) a second portion ( 14 ) connected to said first edge portion to be laterally tapered and rolled into a hollow conical configuration, (b) providing first and second opposed rotating rollers each rotating about an axis of rotation and including (i) an outer conically shaped surface to engage and taper laterally said second portion ( 14 ), and (ii) an outer cylindrically shaped surface to engage and taper laterally said first edge portion ( 13 ) and cant said first edge portion with respect to said second portion; (c) feeding said strip ( 12 ) of material through and between said pair of rollers (i) to work simultaneously said second portion and said first portion, (ii) to taper laterally said second portion and said first portion such that said first portion has a minimum thickness less than the minimum thickness of said second portion, (iii) with said first edge portion canted and in a different plane with respect to said second portion, (iv) to cause, when said strip of material exits said rollers, said strip of material to curve about one of said axes of rotation of said rollers, said one of said axes spaced apart from said conically shaped hollow portion and said cylindrically shaped hollow portion, and (v) to produce in a single pass through said pair of rollers the hollow generally conically shaped sheet metal part ( 16 ).