Stitch-length correcting sewing machine and stitch-length measuring presser foot assembly used therein

摘要

A stitch-length correcting sewing machine and a stitch-length measuring presser foot assembly used therein are disclosed. The sewing machine and presser foot assembly enables stitches of a predetermined length to be sewn, without the necessity of stitching a trial stitch on a piece of fabric and adjusting the sewing machine to compensate for variations in fabric type and thickness. The presser foot assembly utilizes a presser foot which is detachably securable to a presser bar. A movable presser frame slides on the presser foot as fabric is fed. A potentiometer is fixed to the presser foot and responds to sliding of the presser frame so as to enable distance moved by the presser frame to be ascertained by detecting the resistance of the potentiometer. The presser foot assembly can be used as a fabric sensor responsive to fabric motion in an electronic sewing machine. This enables fabric feed (and, optionally, needle swing) to be varied in accordance with actual motion of the fabric to sew stitches of a predetermined length and to further sew patterns which are properly balanced, independently of fabric type and fabric thickness.