Abstract A locked seam is formed in ducting formed by convoluted metal strip and seam locking adjacent edges of adjacent convolutions, in which one edge is folded to form a pair of inwardly facing channels and the other is folded to form a generally T-shaped flange and the arms of the T-shaped flange are locked within the channels. The seam may be formed by folding the edges of the strip before it is convoluted to provide along one edge an open U-shaped element facing out of the plane of the strip. A complementary flange is formed along the other edge, generally of similar U-shape or L-shape and after the strip is convoluted and the edges are mated the U-shape is deformed to form the seam. Apparatus for forming the seam comprises a mandrel removably mounted on a frame and two pairs of forming means disposed about the mandrel, one pair being fixed in its location relative to the frame and the other pair being movable with the mandrel, whereby the mandrel can be changed without requiring adjustment of the forming means.
A tube formed from helically wound ductile strip material with adjacent edges of the strip joined together by a locked seam wherein said locked seam comprises a pair of generally oppositely directed channels formed in one edge of said strip and disposed on opposite sides of a longitudinal medial plane of the seam with their mouths facing, and a complementary flange of generally Tshaped cross section formed in the other edge of said strip with its arms disposed one within each of the said channels.
Claim 2
Dependent Claim
85 words
A tube formed from helically wound ductile strip material with adjacent edges of the strip joined together by a locked seam wherein said locked seam comprises a pair of generally oppositely directed channels formed in one edge of said strip and disposed on opposite sides of a longitudinal medial plane of the seam with their mouths facing, and a complementary flange of generally Tshaped cross section formed in the other edge of said strip with its arms disposed one within each of the said channels.
Claim 3
Dependent Claim
24 words
A tube as claimed in claim 1, wherein the channels are directly facing one another and the arms of the flange are substantially coplanar.
Claim 4
Dependent Claim
41 words
A tube as claimed in claim 1, wherein the channels are disposed to face slightly outwardly of the tube and their directions of facing intersect at an included angle slightly less than 180*, the arms of the flanges being correspondingly angled.
Claim 5
Dependent Claim
34 words
A tube as claimed in claim 1 wherein the shank of the flange lies approximately on a longitudinal medial plane of the seam and is disposed transverse of the elongate dimension of the tube.
Claim 6
Dependent Claim
34 words
A tube as claimed in claim 2 wherein the shank of the flange lies approximately on a longitudinal medial plane of the seam and is disposed transverse of the elongate dimension of the tube.
Claim 7
Dependent Claim
34 words
A tube as claimed in claim 3 wherein the shank of the flange lies approximately on a longitudinal medial plane of the seam and is disposed transverse of the elongate dimension of the tube.