Thread tensioning for chain stitch sewing machine

Abstract

In a multi-needle double chain stitch sewing machine, when forming a thread chain after forming a seam without using upper cover thread, formation of loop or excess looseness of the right needle thread is prevented. A U-shaped guide having a pair of thread eyes at both opposing ends is fixed at the lower end of a needle bar, and a thread take-up cam extending in the vertical direction is fixed on the sewing machine frame between said thread eyes. The upper half of the cam working surface has a linear shape and the lower half has a sloping curve. The right needle thread passed between the thread eyes is brought into contact with the cam, and when the U-shaped guide descends together with the needle bar, the right needle thread is gradually bended.