Blind stitch sewing machine

A blind stitch sewing machine having an arc needle with a tip, main drive means to oscillate the needle along an arcuate path and a fabric deflector movable in a plane of motion intersecting the arcuate path to bear against a material being sewn comprising:

• (a) means to oscillate the fabric deflector in its plane of motion to contact the fabric being sewn to deflect the fabric into the arcuate path of the arc needle, the means including a stepping motor for adjusting the fabric deflector oscillation with respect to the arcuate path;
• (b) a sewing material sensor generating an output signal depending upon the thickness of the fabric;
• (c) a contact pickup to generate an electrical signal upon contact between the arc needle and the fabric deflector;
• (d) measurement window pickup means operatively associated with the drive means to generate a measurement window signal for each stitch commencing shortly before the tip of the arc needle reaches the plane of motion of the fabric deflector and ending with the onset of the motion of the fabric deflector away from the arcuate path of the arc needle;
• and,
• (e) control circuit means operatively connected to the stepping motor, the contact pickup, the sewing fabric sensor and the measurement window pickup means such that the stepping motor places the fabric deflector in a starting position displaced away from the arcuate path of the arc needle and, in the course of a subsequent sewing operation, moves the fabric deflector closer to the arcuate path until the contact pickup generates its signal during the measurement window signal and such that, at the end of the measurement window signal, the stepping motor moves in the opposite direction a predetermined number of steps dependent upon the output signal from the sewing fabric sensor to provide a minimum spacing for the fabric deflector.