GB509592A - Thread-cutting mechanism for sewing machines - Google Patents

Abstract

509,592. Sewing-machines. FAIRWEATHER, W. C. (Singer Manufacturing Co.). April 6, 1939, No. 10739. [Class 112] In a sewing-machine having thread-cutting and thread-gripping means mounted on a carrier-lever, the cutting means is arranged to be adjustable independently of the gripping means so that its path of operation may be varied. The invention particularly relates, and is shown applied, to a buttonhole sewing-machine in which the work-clamp and stitch-forming devices are relatively movable, in the longitudinal direction of the buttonhole, between cutting and stitching positions and in which a loop of needle-thread is drawn out after stitching by the return of the parts to their initial positions, this loop then being severed close to the work and gripped close to the loop-retaining means ; the position of the gripping means is fixed by that of the loop retaining means, but the cutting point is determined by the position of the last stitch, which is variable according to the length of the buttonhole, and the cutting means therefore requires to be adjustable. In the arrangement shown, the cutting and gripping means are mounted on a carrier arm 27 actuated from a cam on the pattern shaft 18. The member 43 carrying the cutter-blades 24 has a slotted base member 44 formed with a rib fitting into a channel 53 in the carrier 27 so that it is located laterally, but slidable longitudinally. The member 39 carrying the gripper jaws 33, 34 has a channelled base 48 fitting over the part 44, and is secured to the carrier 27 by a bolt 46 which also clamps the member 43 in its adjusted position. One edge of the member 44 rests on a wedge 54 slidably adjustable on the carrier 27 so that the members 39, 43 can be tilted slightly to adjust the radius of action of the cutting and gripping devices. A spatulate guide plate 26 is secured to the fixed scissor blade 24 ; the pivoted blade 25 is actuated by a pin engaging a cam slot in a fixed member 57. The pivoted gripper jaw 34 is normally held open against a spring by a latch 36 on a rock-shaft carrying an arm 40 with a pin engaging fixed cam members 42 so that the jaw is released to close at the end of the upward movement of the carrier 27 and is closed (its tail being bevelled so that the latch can ride on to it) at the end of the return movement ; the turret carrying the lower stitch-forming devices and needle throat-plate 11 also carries a leather wiperblade which removes the waste-thread from the gripper during the return rotation of the turret after a buttonhole-sewing cycle.