METHOD AND APPARATUS FOR DETERMINING HTE AMOUNT OF ADVANCE OF A PLURALITY OF METERIAL PLIES IN A SEWING MACHINE

摘要

Method and apparatus for determining and regulating the amount of advance of a plurality of workpiece plies at a sewing machine which is affected by scanning the individual plies while recording the stitches being formed between two separate feed points and actuating top and bottom feed devices to achieve a desirable feed of each ply. Signs present or to be applied at any desired point of the workpiece plies are scanned at two successive points, and pulses generated by a pulse generator connected with the main shaft of the machine are summed during this period of time. The pulse sum is compared with a number of pulses which depends on the mutual spacing of the scanning points and on the adjusted stitch length. For two work plies the pulse sums formed between the recognition of the signs are compared directly. As signs to be scanned are used either imprinted marks, the jags of a pinked workpiece edge, or the bright, dark structure of a surface section of the workpiece.