Abstract: A cloth cutting knife 16 is structured such that the length of the cutting edge thereof is set shorter than the length of the side sewing portions of a buttonhole to be formed, and a buttonhole having a length corresponding to the length of the right and left side sewing portions can be formed by moving up and down the cloth cutting knife 16 two or more times. The cloth cutting knife 16 is moved up and down at least once during formation of the stitches of the right and left side sewing portions. Also, the cloth cutting knife 16 is moved up and down once each time a given number of stitches of the right and left side sewing portions are formed. The given number of stitches is set in accordance with both of the length of the cutting edge of the cloth cutting knife 16 and the length of the buttonhole to be formed.

Abstract: A method is disclosed where a knot is formed in chain-stitching, and a first loop formed by a stitch to an article to be sewn, two stitches ahead of a final stitch, is drawn through a second loop which is formed by a stitch one stitch ahead of the final stitch, whereby a knot where the first loop is fastened by the second loop is formed, such that a third loop is inserted through the second loop and is then cut.

Abstract: A knot is formed in chain-stitching, and a first loop, formed by a stitch to an article to be sewn two stitches ahead of a final stitch, is drawn through a second loop which is formed by a stitch one stitch ahead of the final stitch, whereby a knot is formed where the first loop is fastened by the second loop, such that a third loop is inserted through the second loop and is then cut.

Abstract: A apparatus for forming a knot where a knot is formed in chain-stitching. In the method, a first loop is formed by a stitch to an article to be sewn, two stitches ahead of a final stitch, is drawn through a second loop which is formed by a stitch one stitch ahead of the final stitch, whereby a knot where the first loop is fastened by the second loop is formed, such that a third loop is inserted through the second loop and is then cut. The sewing machine including a single needle and a rotary looper and including a yarn feed adjusting device for adjusting a degree of feed of a yarn to the single needle. The yarn feed adjusting device sets a fed volume of the yarn during formation of the second loop to a value larger than that of the final or third loop and the first loop.

Abstract: A needle thread guide provided at a needle bar frame and located adjacent to the needle entry protects the needle thread from being stuck by the needle when the workplace is fed during button holing. The guide guides the needle thread outwardly when the needle descends, thus the needle thread positioned lower than the needle eye is protected from being stuck by the needle. The guide is associated with the oscillating motion of the needle, but its direction of oscillation is opposite to the direction of needle oscillation, and its amplitude is almost twice the amplitude of the needle.

Abstract: A presser foot control for a sewing machine comprises a solenoid and two springs having different spring constants arranged in series with a transmitting lever and a starting lever. A first weaker spring is set in a "previously-pulled" condition and is connected in series with a second, stronger spring. The solenoid force first pulls on the stronger, unloaded spring. Thereafter, the weaker spring, which has been pulled previously into a loaded condition, is pulled and presses the presser foot causing the workpiece to be pressed against the table. Despite variations of thickness in a workpiece, the invention is effective to clamp the workpiece with a substantially constant pressure value.