BUTTON HOLE SEWING MACHINE

摘要

PROBLEM TO BE SOLVED: To provide a button hole sewing machine of a general type easily changing thread feeding for alternately creating single thread chain stitch and double thread chain stitch. SOLUTION: This button hole sewing machine is provided with a needle thread feeding mechanism 33 for guiding a needle thread through a cam disc 41 while once rotating during two stitches of a needle. Along the periphery thereof, the cam disc 41 has a curve so as to satisfy a condition for alternately sewing single thread chain stitch and double thread chain stitch with the tension and release of the needle thread while sewing a zigzag button hole seam. The cam is provided with two cam blocks made different for tensioning or releasing the needle thread while being extended over the surrounding angle of 180 deg..