Process and sewing machine for sewing together layers of fabric according to a pattern

A sewing machine for two-dimensionally aligning and sewing together two fabrics having the same surface structure according to a pattern, the sewing machine comprising:

• upper and lower feed means, whose feed travels can be varied relative to one another by means of at least one adjusting means;
• an edge guiding device associated with one of the two fabrics which operates at right angles to the direction of feed and whose aligning movement can be performed by first and second aligning means;
• at least one edge sensor for determining the lateral distance between the edge adjacent to the seam to be produced in one of the fabric layers and the stitch formation site of the sewing machine, wherein the distance value determined is compared with a presettable nominal distance value, and the corresponding aligning means of the edge guiding device are actuated corresponding to the deviation;
• one surface sensor for each fabric producing a mask image for one fabric and a search image for the other fabric;
• a signal processing device which generates digital image data from said surface sensor for each fabric layer, said digital image data being made of picture elements of flat sections of the surface, said picture elements being arranged in rows and columns;
• said signal processing device also determines the mutual displacement of structural elements of the fabric layers by two-dimensional cross-correlation analysis of the digital image data of the search image and of the mask image shifted row by row and column by column, and actuates the adjusting means as a function of the value of the parallel displacement and actuates said first and second aligning means of the edge guiding device as a function of the value of the lateral distance between the edge adjacent to the seam to be produced and the stitch formation site for each of the two fabric layers, such that at a time when longitudinally extending structural elements are temporarily not recognized, the alignment of a particular fabric layer having an edge which has not since been aligned according to the structural elements at right angles to the direction of feed, is interrupted, after which the edge of said particular fabric layer is also adjusted, and the distance between the edge of said particular fabric layer and the stitch formation site of the sewing machine, which existed prior to the change from the pattern-oriented alignment to the edge-related alignment, is used as the nominal distance value;
• matrix camera means including a surface sensor, said matrix camera means being connected to an image memory associated with each fabric layer, one edge scanning sensor being provided for each fabric layer to determine the lateral distance between the edge of each of the two fabric layers, which edge is adjacent the seam to be produced, and the stitch formation site.

A sewing machine for two-dimensionally aligning and sewing together two fabrics having the same surface structure according to a pattern, the sewing machine comprising:

• upper and lower feed means, whose feed can be varied relative to each other;
• edge guiding means for moving one of the fabrics at right angles to said feed;
• upper surface sensing means for creating upper picture elements of the upper fabric of the two fabrics, said upper picture elements being aligned in rows and columns;
• lower surface sensing mans for creating lower picture elements of the lower fabric of the two fabrics, and lower picture elements being aligned in rows and columns;
• and
• signal processing means receiving said upper and lower picture elements and performing a two-dimensional cross-correlation analysis on said upper and lower picture elements, said two-dimensional cross-correlation analysis determining an alignment of the two fabrics, and said signal processing mans controlling said upper and lower feed means, and said edge guiding means, to perform said alignment determined by said two-dimensional cross-correlation analysis, said signal processing means also determining if the surface structure is recognizable, such that if said surface structure is not recognizable, then said processing means interrupts said two-dimensional cross-correlation analysis until the surface structure is recognizable, said signal processing means using previous alignment values for said alignment of the two fabrics at a time when the surface structure is determined to be unrecognizable, said previous alignment values being determined from said two-dimensional cross-correlation analysis performed previous to the time when said surface structure is determined to be unrecognized.