Chain stitch sewing machine including a needle-thread pushing member

A sewing machine comprising:

• a machine bed;
• a presser foot disposed vertically and movably on said machine bed;
• a needle seat disposed vertically and movably on said machine bed and located over said pressure foot;
• a row of vertical stitching needles of different lengths mounted fixedly on said needle seat and arranged one behind another, a front one of each adjacent pair of said stitching needles having a lower end, which is located below that of the rear one;
• a power source disposed on said machine bed;
• a thread pushing device disposed on said machine bed behind said needle seat and including a needle-thread pushing member that is adapted to move gradually forward and downward between said presser foot and said stitching needles along a curved path so as to be adapted to push suspended needle threads away from said presser foot just before said presser foot moves downward toward a fabric to be stitched on said machine bed;
• and
• a thread cutting device adapted to cut a horizontal row of looper threads, after a stitching action has been finished,
• a linkage, which includes:
• a driving crank mounted rotatably on said machine bed and swung by said power source;
• a follower crank mounted rotatably on said machine bed;
• and
• an inclined coupler connected Pivotally to said driving crank and said follower crank and having a lower end that is connected fixedly to said needle-thread pushing member;
• whereby, said power source can drive said linkage to move said needle-thread pushing member along the curved path,
• two rotating elements mounted respectively and rotatably on said driving crank and said follower crank, each of said rotating elements rotating about a horizontal axis and having a hole, through which said coupler extends slidably;
• and
• two lock bolts for locking said coupler respectively and releasably on said rotating elements;
• whereby, the position of either of said rotating elements relative to said coupler can be varied by loosening said lock bolts to move said needle-thread pushing member on said machine bed.