Apparatus for precutting metal strip in the manufacture of spiral strip pipes, e.g. ventilation ducts

Apparatus for uninterruptedly manufacturing spiral strip to be used for fabricating spiral strip piping, said apparatus being positioned along a feed path for operating on continuous strip material having a longitudinal axis and opposite edges extending parallel with said axis, the apparatus comprising in combination:

• strip cutting means comprising an upper driven knife wheel and means for driving the upper driven knife wheel to rotate about a rotative axis thereof;
• and a lower freely rotating, circular, substantially horizontal support roller with a substantially vertical rotation axis for cooperating with the upper driven knife wheel for cutting the strip fed to the cutting means;
• feed means for feeding a strip into the cutting means in a continuous length thereof;
• the feed means feeding the strip in a feed direction past the strip cutting means;
• punch means positioned upstream from the strip cutting means, with respect to the feed direction;
• table means supported for swiveling in rotative orientation with respect to the direction of feeding of the strip;
• the cutting means being supported on the table means for swiveling therewith;
• means for adjusting the swivel orientation of the table means, prior to the feeding of the strip and the cutting thereof, for adjusting the location of the upper driven knife wheel around the support roller knife, which adjusts the angle of the cut across the strip for a selected pipe diameter;
• means for translating the table means across the feed direction of the strip for enabling the strip to be cut at an angle to the feed direction thereof so that said cutting means cuts the strip along a straight line extending from a first point on one edge of said strip to a second point on the opposite edge of said strip longitudinally spaced from said first point;
• the punch also being placed at the side of the apparatus from which the table means commences its translation by the translating means;
• the punch thus being positioned at the edge of the strip to be cut before the strip is fed to the strip cutting means;
• the punch being shaped for making triangular stampings in the edge of the strip at the starting points for each cut, with the stamping having a side extending perpendicular to the longitudinal axis of said strip, wherein the stampings act as cutting location marks for the upper knife eliminating the free, projecting, triangular plate tip which would otherwise be formed at the beginning of the cut strip;
• said cutting means being positioned so that each cut is made coextensive and parallel with another side of the triangular stamping in said strip.