Sewing machine with a tensioning device having a plurality of tensioning rollers

Abstract

In order to permit a reliable alignment, in the direction transverse to the direction of rotation, of the edge 5 of the opening of a tubular workpiece 4 of medium-heavy to heavy sewing material which is drawn with considerable pre-tension over a tensioning device 3, each of the tensioning rollers 6, 7, 8 belonging to the tensioning device 3 has at least three alignment members 15 distributed uniformly over its circumference. Each alignment member 15 has an engagement side with a gripping surface. After optically scanning the edge 5 of the opening of the workpiece 4, one or more of the alignment members are displaced by a pulsating action of a pressure fluid, radially and axially, in the tensioning roller 6, 7, 8. In this way, the gripping surfaces of the alignment members 15 grip the inner side of the tubular workpiece 4 and displace it transversely to its direction of rotation.

Dependencies are inferred from the claim text.