Automatic thread trimming device of sewing machine

An automatic thread trimming device of a sewing machine comprising:

• a holding disc including a groove in which a protrusion extending from a predetermined position of the groove, a receiving orifice formed on a predetermined position of the protrusion, an accommodation portion formed beside the receiving orifice, and a coupling portion formed on a side of the accommodation portion, wherein the groove has a first defining orifice and a second defining orifice which are formed on two predetermined positions of the groove, and a first connection portion and a second connection portion are formed on two ends of the groove, wherein the first connection portion has a first flexible connection element, and second connection portion has a second flexible connection element;
• wherein a cutter assembly is slidably received in the groove of the holding disc, and the cutter assembly includes a drive bar and a movable blade, wherein the movable blade has a guide rib extending from a side thereof, a tiled guiding face formed on a bottom of the guide rib, and an abutting section formed on a top of the movable blade, such that the movable blade is slidably aligned with the receiving orifice of the holding disc, wherein the cutter assembly further includes a trench corresponding to the second flexible connection element, and the cutter assembly includes a push face corresponding to the first flexible connection element, such that the trench of the cutter assembly is engaged with the first flexible connection element, and the push face of the cutter assembly abuts against the second flexible connection element;
• wherein a fixed cutter is mounted in the accommodation portion of the holding disc, and the cutter assembly includes an arcuate guiding face formed on an end of the cutter assembly and corresponding to the receiving orifice of the holding disc, wherein the arcuate guiding face has a fixed blade formed on an end thereof and corresponding to the movable blade, such that the movable blade moves to the receiving orifice with the fixed blade to cut a thread, wherein the arcuate guiding face contacts with the tiled guiding face of the movable blade after the movable blade moves, the fixed cutter further includes a fixing segment formed on an end thereof and corresponding to the coupling portion of the holding disc, and the coupling portion of the holding disc is screwed with the fixing segment of the fixed cutter by using a first threaded bolt;
• wherein a protective sheet includes multiple through holes corresponding to multiple defining orifices, such that the multiple defining orifices and the multiple through holes of the protective sheet are screwed by way of a second threaded bolt and at least a third threaded bolt, and the protective sheet covers the cutter assembly, wherein the protective sheet includes a stop face corresponding to the drive bar, such that the drive bar is limited on the stop face;
• wherein the protective sheet further includes an elastic extension extending therefrom and corresponding to the movable blade, the elastic extension has a flexible curved section bending downward from a front end thereof, and the flexible curved section has a flexible biasing segment formed on a distal end thereof and corresponding to the abutting section of the movable cutter, the movable blade is pressed longitudinally by using the abutting section and the flexible biasing segment of the elastic extension, such that the movable blade accumulates an elasticity to bounce away, and the movable blade produces a cutting force with the fixed blade, when moving to the fixed blade horizontally.