Patent ID: 11124908

Abstract:
The present invention provides a thread feeding device of a decorative stitching sewing machine. The thread feeding device feeds a needle thread, an upper looper thread, and a lower looper thread in the amounts required for sewing one stitch such that the position of a stitch looping point of the threads changes. The thread feeding device includes: a thread accumulator 500 having thread accumulating elements 13a to 13d and 14a to 14d which measure the thread accumulation amounts of predetermined lengths of the needle thread, the upper looper thread, and the lower looper thread, and thread accumulation amount control elements 15 to 18 which adjust the amounts of the threads required for sewing one stitch in an increasable and decreasable manner within the range of thread accumulation amounts of predetermined lengths at the time of fabric feeding, and which release the threads to a stitch forming device when a stitch is formed; a thread feed drive mechanism 600 which drives each of the elements; and a thread feed control unit having a program which dives the thread accumulation amount control elements for each stitch to feed the threads in an increasable and decreasable manner so as to increase or decrease the threads within the range of a total thread feeding amount that is maintained constant, including a fabric feeding amount, a fabric thickness and an overlocking width, thereby to change the position of the stitch looping point of the needle thread, the upper looper thread, and the lower looper thread, thus controlling the decorative stitching according to a stitching decoration pattern.