Patent ID: 9663884
Date: 2017-05-30
CPC Classifications: D05B

Claim:
1. A method for preventing seam ravel of multi-thread chain stitches formed by catching a needle thread loop formed below a needle plate by a needle moving up and down while holding a needle thread, by a forward movement of a looper movable forward and backward in a direction substantially orthogonal to a vertical movement path of the needle, and by interlooping the needle thread loop with a looper thread held by the looper, the method comprising the steps of: after a normal sewing is terminated with the looper set in a forward movement state, maintaining a state in which the needle thread loop caught by the looper is subjected to position holding at a position closer to a forward movement end of the looper than a descent position of the needle until the needle descends through the needle thread loop caught by the looper; and thereafter, selflooping the needle thread loop with the needle thread held by the needle by releasing the position holding of the needle thread loop to permit a sewing action for at least one stitch which includes a descent of the needle through the needle thread loop, under conditions that feed of a fabric is suspended, or that feed has a lower feed rate than during the normal sewing; concurrently or substantially concurrently with subjecting the needle thread loop caught by the looper to the position holding at the position closer to the forward movement end of the looper than the descent position of the needle, subjecting a looper thread extending from the looper to the fabric to position holding at a position ahead of or behind the descent position of the needle, and then suppressing feed of the looper thread to the looper; and making setting so that execution of suspension of the feed of the fabric or the feed having the lower feed rate than during the normal sewing in the sewing action for the at least one stitch for the self-looping is started at a certain stage before the needle thread loop is positioned closer to the forward movement end of looper than the descent position of the needle.