Abstract: An over-lock sewing machine executing an over-edge chain stitch and a double-chain stitch includes a sewing machine motor for driving a needle bar so that the needle bar is moved upward and downward, a sewing needle mounted on a lower end of the needle bar, an upper looper and a lower looper forming stitches in cooperation with the sewing needle, and a stepping motor for driving the lower looper so that the lower looper is rocked.

Abstract: A lock stitch machine capable of being selectively set for either an overcasting mode or a hemming mode. A needle plate tongue is shifted between an operative position and an inoperative position in a region separated from the operating region of the looper, along a path substantially resembling a circular arc for a vertical displacement and a horizontal displacement greater than the vertical displacement, by turning an overcasting width adjusting knob which turns a control shaft. Thus, the needle plate tongue can be shifted between the operative position and the inoperative position regardless of the position of the looper thereby facilitating the stitching mode changing operation.

Abstract: This invention provides an overlock sewing machine with a threading mechanism that is both easier and more efficient to use. As shown in FIGS. 1 and 7, the overlock sewing machine has a vertically movable needle (6, 106), a looper carriage (18, 118) connected to a rotating shaft, and a looper (11, 111) on the end of the looper carriage. The looper extends laterally over the looper carriage and has a thread-receiving eye (11a, 111a). The looper and the needle cooperate to form a chain stitch. As shown in FIGS. 3 and 9, a thread-guiding member (25, 125) next to the looper pivots with the looper to guide a thread LT through the thread-receiving eye. A movable lever (30, 130) pivots with or relative to the looper. A thread-delivering member (39, 139) mounted on the movable lever that can be set in two positions: a first position corresponding to a first position of the thread-receiving eye, and a second position corresponding to the thread-guiding member.

Abstract: In this overedge sewing machine, when stitch width is adjusted, an adequate excess thread proportional to the adjusted stitch width is obtained. An overedge stitch can be steadily sewn without excessive stitch tension, even when the stitch width increases. By operating one adjustment member, the position of the lower knife holder and the stitch-support member can be easily adjusted, and the stitch width can thus be easily altered.

Abstract: A needle clamp includes a clamp screw, a square nut member having a threaded hole engageable with the clamp screw, and a needle clamp body having a first hole for receiving plural needles arranged in side-by-side relationship in a first direction within a predetermined plane, a second hole formed so that the clamp screw may move therein in the first direction, and a square cavity formed so that the nut member may move therein in the first direction. The cavity includes a pair of opposite internal walls which prevent the nut member from rotating about an axis of the clamp screw by engaging with corners of the nut member, and a third internal wall which prevents the nut member from moving away from the needles arranged in the first hole by engaging with a surface of the nut member opposite to a surface facing the arranged needles.