Patent GB-429991-A (GB)
Title: Improvements in and relating to buttonhole sewing machines
IPC: D05B73/12
Filed: 1935-01-11
Abstract: 429,991. Buttonhole-sewing machines. HUGHES, R. M., 72, Cannon Street, London.- (International Button Hole Sewing Machine Co. ; 502, Harrison Avenue, Boston, U.S.A.) Jan. 11, 1935, No. 1021. [Class 112] In a moving stitch-frame buttonhole-sewing machine, the needle thread is broken and the under-thread and stay cord cut, after completion of the buttonhole. As shown, the machine comprises the usual work frame 1 on which the work 2 is clamped by the plates 3 and 4, the usual needle 7 and looper mechanism 9 mounted in the turret 10 below the work. The stitch-forming mechanism is carried in the frame 11 which moves to-and-fro on the bed frame 1. The turret 10 and needle bar 12 are rotated at the ends of the buttonhole by the usual rock-shaft 100 and segment gears 101 and 102. Disrupting the needle thread. When the stitch-forming mechanism comes to rest at the end of formation of a buttonhole, the needle is raised, Fig. 1, and there is a loop 27 of needle-thread retained by the loops 9 beneath the throat plate, Fig. 14. The needle thread is subjected to the usual tension device 28 which is operative during both the stitching and cutting operations. The forward movement of the stitch-frame and throat plate from sewing to cutting position consequently imposes an additional tension on the needlethread loop 27 which causes a breakage in the leg 30 of the loop. The broken end of the thread is pulled back from the work and held ready for the next cycle by a pull off arm 31 having a small piece of felt 35 at its end 33. This arm is actuated by a projection 98 on the cutter lever 19. Needle thread controlling. Surplus thread is drawn through the tension 28 during the stitching of the buttonhole by a member 36 which gives up the surplus before stitching begins on the next buttonhole. Cutting under thread. The under thread and stay cord are cut by a member 39 after the stitch frame has moved to buttonhole cutting position and the needle thread withdrawn from the work. The cutter is mounted on a rock-shaft and has a cutting edge and a finger. The curved edge is so positioned that when the sewing on the buttonhole is completed the needle opening is in close proximity to the edge, Fig. 14. When the stitch frame moves from stitching to buttonhole-cutting position, the under thread 25, stay cord 26 and the two limbs of the needle loop 27 will lie closely adjacent to the curved edge. As the throat plate moves, the threads are carried round the curved edge and the cutter placed between them and the work. When the buttonhole is cut and the clamps released, the rock-shaft is turned to cause the cutter to sever the under thread and stay cord, the upper thread having been pulled back by the arm 31. Under thread controlling. The under thread is led through the usual tension 59 mounted in the turret 10 and thence through a guide 60 and an eye 61 in a pull off arm 62 to the looper. The arm 62 is made of spring wire coiled about a stud 63 on the turret 10. When a length of under thread has been drawn out by the movement of the stitch frame, the thread is gripped against the under face of the throat plate by the gripper 74, placing tension on the spring arms 62. Cord guides. The stay cord is led to the sewing opening through a guide in a finger 67 Fig. 7 pivoted to the turret at 68 and acted on by a spring. The finger 67 has a gripping flange 72 so that although the cord can pass freely forward sewing, it cannot move backward and the end is securely held for the next cycle after being cut.