SEWING THREAD TWIST-BACK PREVENTER, SEWING MACHINE, TWO- NEEDLE SEWING MACHINE, AND CATCH-STITCHING MACHINE

摘要

PROBLEM TO BE SOLVED: To prevent a sewing thread from being twisted back and loosened during the sewing operation such as back stitching, and to prevent any thread breakage or irregular stitch attributable to the loosening. SOLUTION: This sewing thread twist-back preventer comprises a re-twisting mechanism 12 for twisting the sewing thread 10 in the same direction as the twisting direction of the sewing thread to the sewing thread 10 which is drawn out of a bobbin 11 and leading to a sewing needle 4, a sewing direction detection part for detecting the sewing direction during the sewing operation, and a twist- back preventive means for driving the re-twisting mechanism 12 according to the result in detection of the sewing direction detection part. When the sewing direction detection part detects that the sewing direction is a predetermined one, the re-twisting mechanism 12 is driven, and the sewing thread 10 is continuously re-twisted in the same direction as the twisting direction. Twist-back and loosening of the sewing thread 10 during the sewing operation and thread breakage and irregular stitch of the sewing thread 10 attributable to the loosening can be prevented.