the wedge shaped cam section 51 of the cam 50 now moves toward the lever 55 of the one way coupling 53 and thus pivots the lever arm 54 which releases the thread tensioning mechanism 42 for the needle thread via the bar 51 the angle lever 62 and the push rod 63 in such a way that the releasing pin 49 is axially displaced by the oblique surface 64 of the releasing member 65 as a result of which the tensioning disk 45 is lifted off from the tensioning disk 46 against the force of the tension spring 48 at the same time the thread catcher 8 pulls thread from the shuttle thread reserve and the needle thread reserve due to the movement of the drive mechanism 21 to the right until the cutting blade 9 fastened on the lower side of the base plate 1 cuts off both threads shortly before the end of this movement immediately thereafter the cam section 52 of the cam 50 moves past the lever 55 of the one way coupling 53 and the lever 55 can drop in behind the cam section 52 under the pressure of the torsion spring 60 so that the lever arm 54 can come into contact with its lateral contact surface 54a with the axially parallel surface of the cam section 52 of the cam 50 this dropping off of the lever 55 from the cam section 52 brings about immediate closure of the thread tensioning mechanism 42 via the tensioning release linkage during the further residual rotation of the main shaft 4 until the sewing.