Abstract: A buttonhole closing device for a lockstitch bar tacking sewing machine comprises a feed plate for holding the buttonhole of a sewn product thereon, an arch clamp frame which is supported by the feed plate on the side thereof so as to be vertically swingable, a first and a second movable clamp feet which are swingably connected to the arch clamp frame by way of pins separately and which are arranged on the left and right sides of a center clamp foot at the clamp portions formed at the front ends thereof respectively, a clamp foot unit driving mechanism, pin portions and cam portions for converting the longitudinal movement of the clamp foot unit driving mechanism into the lateral swinging of the first and second movable clamp feet and driving units for driving the clamp foot unit driving mechanism forward or backward.

Abstract: In a bar tacking stitch pattern comprising lateral stitches formed in a sewn product in such a way as to cover the starting and ending portions of overedge chain stitches which are formed on the periphery of a button hole in the direction substantially at right angles to the extending direction thereof and zigzag stitches which cross the lateral stitches, a pair of stitches of the zigzag stitches are formed on both sides of an end portion of the button hole adjacent thereto in such a way as to be substantially symmetrical with regard to the button hole and a pair of stitches of the lateral stitches are formed on both sides of the end portion of the buttonhole adjacent thereto outside the area between a pair of line segments which respectively extends through the pair of stitches of the zigzag stitches in the extending direction of the button hole.

Abstract: A thread trimming device for a lockstitch bar tacking sewing machine is equipped with a thread trimming unit comprising a detecting member which is rotatably supported by a sewing machine body and has a detecting portion, a first position detecting means which is fixedly mounted on said sewing machine body in such a way as to be capable of facing the detecting portion of the detecting member and which produces a thread trimming signal for starting thread trimming when the detecting portion approaches thereto and a driving unit for driving a thread trimming cam link in such a way as to bring the contact portion of a thread cam link in contact with the cam surface of a thread trimming cam for trimming a needle and a bobbin threads based on the thread trimming signal. As a result, the mechanical components thereof becomes simple in structure and easy in adjustment, and those relating to the thread trimming operation are improved in durability.

Abstract: A device for use in a button sewing machine which uses a wire of elastic material for maintaining looseness to that portion of the needle thread between a button and material to which the button is to be sewn while preventing the needle thread from being pulled out of the eye of the needle and at the same time preventing the wire from being warped.

Abstract: A speed controller for controlling revolution speed of the upper shaft of a cycle sewing machine comprises a first disk shaped stop lever adjustment cam that has a small diameter portion, middle diameter portions and a large diameter portion. The cam is rotatably driven by an upper shaft. The small diameter portion establishes a neutral position at which a first driving clutch for low speed rotation and a second driving clutch for high speed rotation are disengaged from each other. The middle portions establish a position at which the first clutch is connected to a first driving wheel for low speed rotation. The large diameter portion establishes a position at which the second clutch is connected to a second driving wheel for high speed rotation. A first end portion of the large diameter portion is defined by a second cam. The second cam is secured to the first cam by an adjustable device which can vary the circumferential position of the second cam.