Magnetic detection device for sewing machine workpiece

A device for detecting the passage of the edge (4a) of a piece (4) of material, not parallel to the advancing direction (A) of the material, for a sewing machine comprising more particularly a presser foot (2), a needle (1) and a needle plate (3), characterized in that it comprises means (7) for generating a magnetic field and means (10) responsive to this magnetic field, one of said means being coupled to said presser foot (2) so that they are, on the one hand, applied to said piece of material (4) at a point situated at a distance and in front of said needle (1) of the sewing machine relatively to said advancing direction (A) of the material, and, on the other hand, moved with respect to said presser foot (2) in a direction substantially perpendicular to the plane of said needle plate (3), the other means being mounted opposite the first means and fixedly in the sewing machine, under said needle plate.