METHOD FOR DETECTING SKIPPING STITCH AT SEAM IN SEWING MACHINE

摘要

PROBLEM TO BE SOLVED: To surely detect skipping stitches at seams in sewing. SOLUTION: In this sewing machine, an upper yarn 5 scooped up by a bayonet 3 of a shuttle body 2 during one up-and-down movement of a sewing needle 1 is looped and passed once through the shuttle body 2, while a surface-side yarn portion 7 of the looped upper yarn 5 traverses the surface 9 of a bobbin case 8 stored in the shuttle body 2. A photoelectric detector which is sensitive to a reflected light detects in noncontact relation whether the traversed surface- side yarn portion is present or not.