Abstract: A lifting rocker which is pivotally supported by a link is engaged with an eccentric ring which is fixed to a main shaft of a sewing machine. By the rotation of the eccentric ring, the lifting rocker rocks up and down about a fulcrum defined by the link while causing the link to rock. A feed bar having thereon a feed dog is slidably supported by the lifting rocker, and moves in back and forth directions through the rocking of the arm to constantly maintain a definite amount of feed without respect to variation of the rotational speed of the main shaft of the sewing machine.

Abstract: A hemming apparatus for a sewing machine includes a hem folding attachment which guides a cloth edge portion into the sewing machine and an aiding apparatus which prefolds the cloth edge portion into an S-shaped hem before it reaches the hem folding attachment. The aiding apparatus includes a rotatably supported free roll, a ring thereon for setting the position of the cloth edge portion, a fitting mechanism engageable with the top of the hem, an under guide plate engageable with the bottom of the hem, and a base guide spaced above the under guide plate. As the edge portion of the cloth extending between the hem folding attachment and free roll and defining the upper fold of the hem is advanced toward the hem folding attachment, an adjacent portion of the cloth is moved by the fitting mechanism gradually further into the region between the base guide and the under guide plate so that the hem assumes the prescribed S-shape.

Abstract: A top feed device for a sewing machine has an upper feed dog movable horizontally and vertically in synchronism with operation of a lower feed dog. The upper feed dog is vertically moved by a spring for depressing an upper feed arm to which the upper feed dog is attached, and a crank engages the upper feed arm and is vertically swingable, the crank being held in engagement with the upper feed arm at all times to prevent striking engagement therewith. A swingable shaft to which the crank is fixed and a lever angularly movably mounted on the swingable shaft and swingable in coaction with a drive shaft have abutments projecting axially in confronting relation. The abutments on the shaft are urged by a spring to angularly move in one direction. The abutments on the lever which are held against the other abutments are disengaged therefrom in a circumferential direction when the upper feed dog reaches a throat plate and stops its downward movement.

Abstract: A thread chain sewing method and device for use in a two-needle overlock sewing machine. An inner chaining-off finger is held in an advanced position during sewing directly on fabric material. The inner finger is also advanced during the period at which thread chains are formed right after the sewing process passes the trailing edge of fabric material. The inner chaining-off finger is retracted from its advanced position alongside an outer chaining-off finger, in a direction opposite to a fabric material feeding direction, during other periods. The thread chains formed are wrapped only around the outer chaining-off finger before the leading edge of fabric but bridge over the inner and outer chaining-off fingers right after the trailing edge. The needle threads are automatically tightly tensioned during the sewing of fabric, the tension of the needle threads being automatically changed over to slightly tensioned for production of extensible thread chains.

Abstract: A thread chain sewing method and device for use in the two-needle overlock sewing machine comprising an inner chaining-off finger arranged to be retractable from an advanced position in which it is positioned alongside an outer chaining-off finger. The inner chaining-off finger is retractable in a direction opposite the fabric material feeding direction. The inner chaining-off finger is held in its advanced position during sewing over the fabric as well as during a thread chain forming period after the trailing edge is stitched. Thread chains formed before the start of sewing are wrapped only over the outer chaining-off finger, while thread chains formed after the trailing edge of the material passes are bridged over the inner and outer chaining-off fingers.