instant second feed dog 34 is lifted and executes a feed motion alone while needle 10 is in a position outside the workpiece 73 and moves upwardly and executes along with the lowered first feed dog 31 a rearwardly directed motion opposite to the feed direction v fig4 shows the instantaneous motion conditions at the end of the second feed step the second feed dog 34 having reached the end point of its advance motion is going to be lowered while the first feed dog 31 having reached the end point of its return motion is going to be lifted at the same time needle 10 approaches the workpiece 73 again in this manner workpiece 73 is advanced by two feed steps during each stitch forming operation which steps add to a large total advance resulting in a long stitch since at the same time feed members 10 31 34 travel along relatively short distances the sewing machine can run at the maximum speed for example at 6 000 rpm of main shaft 4 and produce seams having 7 mm long stitches for securing the thread at the end of the seam the feed direction of the feed members 10 31 34 can be reversed during the run of the sewing machine by actuating switch lever 74 due to the phase opposition between lifting eccentrics 37 38 and push eccentrics 41 42 the drive elements actuated by these eccentrics and at the end of the train also the two feed dogs 31 34 execute mutually opposite motions as a result of these motion conditions the dynamic forces produced by.