Thread trimming mechanism for lock stitch sewing machines

Claim 1

IN COMBINATION WITH A LOCK STITCH SEWING MACHINE HAVING A THROAT PLATE, A RECIPROCATING NEEDLE ABOVE SAID PLATE, AND A CYLINDERICAL ROTATING LOOP TAKER HAVING A NEEDLE THREAD SEIZING BEAK AND MOUNTED BELOW SAID PLATE, THREAD TRIMMING MECHANISM COMPRISING AN ARCUATE BLADE CONFORMING AND DISPOSED IN CLOSE PROXIMITY TO THE OUTER SURFACE OF AND MOUNTED FOR OSCILLATION CONCENTRICALLY WITH SAID LOOP TAKER, SAID BLADE HAVING A POINT-LIKE PROJECTION IN THE DIRECTION OF ROTATION OF SAID BEAK ADAPTED TO ENTER THE SPACE ENCLOSED BY THE LOOP TAKER THREAD AND THE WORK LIMB OF THE NEEDLE THREAD LOOP, ON THE ONE HAND, AND THE TAKE-UP LIMB OF SAID LOOP, ON THE OTHER HAND, IN A PREDETERMINED POSITION OF SAID LOOP TAKER UPON DRAWING OUT OF THE NEEDLE THREAD LOOP BY SAID BEAK, WHEREBY TO SEPARATE THE LOOP TAKER THREAD AND WORK NEEDLE THREAD LIMB FROM THE TAKE-UP NEEDLE THREAD LIMB DURING THE FIRST HALF-WAVE OSCILLATING MOVEMENT OF SAID BLADE IN THE DIRECTION OF SAID BEAK, AND BLADE FURTHER HAVING A LATERAL HOOK-SHAPED PORTION IN THE DIRECTION OPPOSITE TO SAID PROJECTION PROVIDING A RE-ENTRANT RECESS WITHIN AND EXTENDING IN THE DIRECTION OF SAID PROJECTION, TO GUIDE AND TRAP THE SEPARATED LOOP TAKER THREAD AND WORK NEEDLE THREAD LIMB WITHIN SAID RECESS DURING THE SECOND HALF-WAVE OSCILLATING MOVEMENT OF SAID BLADE IN THE DIRECTION OPPOSITE TO SAID BEAK, OPERATING MEANS TO EFFECT A COMPLETE OSCILLATING MOVEMENT OF SAID BLADE, AND A STATIONARY CUTTING KNIFE ENGAGING SAID BLADE AT THE END OF SAID SECOND MOVEMENT, TO SEVER THE LOOP TAKER AND NEEDLE THREADS TRAPPED WITHIN SAID RECESS.