Patent ID: 7775076

Claim:
An apparatus for producing lock-seam tubing from a metal strip having longitudinal leading edge portions and longitudinal trailing edge portions, comprising: I. means for feeding said strip to a forming head; II. means for forming said strip into a tube of tubular form in said forming head and for bringing said leading edge portions and said trailing edge portions of said tubular form into engagement with each other to provide a forming lock-seam tube; III. a clinching assembly for clinching said leading and trailing edge portions of said forming lock-seam tube to form a lock-seam on said forming tube formed in said forming head such that said lock-seam comprises a leading edge margin, a trailing edge margin and a transverse seam width between said margins; IV. means for feeding said forming lock-seam tube out of said forming head; and V. pinching means for effecting compression of portions of said seam to form a series of pinches, wherein said pinching means is constructed and arranged such that each of said pinches is formed substantially across at least one of said leading edge margin and said trailing edge margin, without extending completely across said transverse seam width, such that each of said pinches comprises an interlock, wherein said interlock is constructed and arranged to minimize the movement of said leading and trailing edges with respect to one another.