GB614811A - Thread trimming and pull-off mechanism for sewing machines - Google Patents

Abstract

614,811. Sewing-machines. SINGER MANUFACTURING CO. July 31, 1946, No. 22887. Convention date, April 25. [Class 112] Thread-cutters and thread-end holders-In a twothread sewing-machine the under thread-handling mechanism is so arranged that when the machine comes to rest the needle-thread and under-thread extend from the work to that mechanism, and a thread-severing element in a single stroke successively cuts the needle-thread and pulls off and cuts the under-thread. The mechanism is described in connection with a buttonhole sewing-machine which is adapted for tacking by arranging for the stitching to be stopped before one side of the buttonhole is completed, the thread-severing element being actuated by the rotation of the usual turret carrying the stitch-forming elements ; instead of cutting needle and under-threads it may be applied to cut two looper-threads in a three-thread machine. In the arrangement shown in plan in Fig. 3, the stitchforming devices, mounted on a turret 25, include a needle-loop detainer 28 on which the needle-loop remains when stitching ceases. The thread-severing device comprises blades 61, 68 (see Fig. 12) carried by arms 59, 65 on a vertical spindle 58 and a fixed blade 70 carried by an arm 71 which can be adjusted to some extent about the axis of the spindle 58. The spindle is rotated clockwise, as the turret rotates in the same direction, by an arm 80 engaging a cam member 83 and carrying a pinion 77 meshing with a toothed sector 76 on the spindle 58 ; the spindle is returned by a spring when the arm 80 leaves the cam 83, and on the return rotation of the turret the arm 80 pushes the cam aside against a spring. The end of the blade 61 has a sharp edge 62 and a blunt recessed portion 63, the latter engaging the free limb of the needle-loop to carry it clear of the part 62 which cuts the limb that remains attached to the work. The blade 61 and the arm 65 have notches to engage the under-thread to pull off a length during the continued rotation of the spindle 58, this thread being finally cut by the blade 68 engaging the fixed blade 70, after a travel which may be varied by adjusting the fixed blade The mechanism may be readily adapted for operation by the final reverse movement of the turret, the stitching being carried out along what would be the second side of a buttonhole. Threads, controlling otherwise than in stitchforming-A length of needle-thread is pulled off from the supply when the work-clamp is opened, by a rod, connected to the clamp, which releases a cam arm to allow a thread nipper to close and engages the thread between the nipper and the supply.