Patent attributes
A sewing machine includes a vertical shuttle and a middle shuttle presser disposed at a front side of the vertical shuttle. The sewing machine includes a presser frame, an optical upper thread detector and a stitch skipping detection processor. The presser frame is movably supported between a pressing position at which the middle shuttle presser is pressed and a retract position separated from the pressing position. The optical upper thread detector is provided at the presser frame and is configured to detect passage of an upper thread using detecting light which passes through passage portions formed in the middle shuttle presser and which crosses a front side of a bobbin case of the vertical shuttle. The stitch skipping detection processor is configured to determine whether the passage of the upper thread is present based on an amount of received light of the detecting light from the upper thread detector.
