METHOD AND APPARATUS FOR DETECTING SKIPPED STITCHES FOR A CHAINSTITCH SEWING MACHINE

摘要

Apparatus and method for detecting skipped stitches for chainstitch sewing machines (100) having a looper assembly (124) using a needle thread movement sensor (140) and/or a looper thread movement sensor (141) in combination with a shaft rotation sensor (130). Needle thread movement is correlated with needle shaft rotation per stitch cycle to detect instances when there is no needle thread movement during a stitch cycle (C). Similarly, looper thread movement may be correlated with needle shaft rotation per stitch cycle to detect instances when there is no looper thread movement during a stitch cylce (A). The invention includes methods for detecting needle loop (1B) and triangle skips (1C) by detecting instances of substantially no needle thread or looper thread movement during certain respective portions of the stitch cycle.