Patent GB-792784-A (GB)
Title: Zig-zag sewing machine for making diverse fancy seams
Inventor: FISCHER ERNST
IPC: D05B19/00
Filed: 1956-03-29
Abstract: 792,784. Sewing machines. VEB NAHMASCHINENWERK WITTENBERGE. March 29, 1956, No. 9784/56. Class 112. [Also in Group XXIV] Needles, shifting laterally. In a zig-zag sewing machine the rocking levers 11, 8, Fig. 1, determining the position of the centre-line and the amplitude of the zigzag, carry cylindrical members 18, 19, fitted with sets of longitudinally arranged strips 20, 21, the edges of which are shaped to the desired pattern, and the selected ones of which make point contact with a singlethread worm 23 mounted on a shaft 64 which is turned step-by-step through ratchet gearing to actuate the rocking levers. The ratchet wheel is mounted on the worm shaft and is engaged by a pawl mounted on a loose pinion 26 engaged by a toothed segment 27 oscillated by a cam 30 on the arm-shaft 7. The magnitude of the step-by-step movement may be varied by an eccentric 32 Figs. 9 and 10 (not shown), adapted to move the segment away from the cam. In a modification, Fig. 17 (not shown), the worm 23 is made up from a number of discs with projections staggered to form a helix. In Fig. 19 (not shown) the worm is replaced by a cam disc mounted on an axis at a right angle to the axes of the members 18, 19, and provided with two or more projections only one of which is in engagement with a particular strip at one time. A further modification consists in using a rocking member instead of a rotary worm, the strips being curved to follow the arc of movement. The members 18, 19 can be rotated from outside the machine and have blank spaces which may be presented to the worm when it is desired to dispense with automatic control. Manual control is effected by cams 70, 75 Fig. 11, operable by levers 73, 77, to move radially arranged pins to actuate the rocking levers. Feeding work. The work feed is controlled by a cylindrical pattern member 39, actuated by a worm 37 driven through a loose pinion 63 and ratchet gearing by pinion 26. Feeding is effected by an eccentric 50, Fig. 15, on the arm shaft 7. The rock arm 46 moving the feed bar 35 is connected by a link 47 to the eccentric rod 48. The pivotal connection 51 is guided by a slide block arranged in a guide 52 pivoted at 53 and connected by a link 60 to a slide block arranged in a second guide 54 pivoted at 55. The second guide has a toothed sector 56 engaged by worm 57 adjustable by a knob 59. The pattern member actuates rod 42 contacting link 60 to vary the inclination of guide 52 to control the feed. Automatic control ceases when pattern member 38, Fig. 11. is turned by a knob 89 so as to present a blank space to the worm 37. Buttonhole stitching. The spindle 64. Figs. 3 and 11, carrying the manual control cams 70, 75 carries a third cam 78 adapted to adjust the rocking levers 11, 8, and the feed control rock arm 40 through pins 81, 82, 83 respectively. The cam may be moved by lever 80 to one of four positions 0, I. II, III, by lever 80. Positions I and III are used to produce reinforcements along the buttonhole, stitched in a forward and reverse direction respectively. Position II is used to produce long stitches at the ends of the buttonhole. Position 0 is used to produce a few final straight stitches. In an arrangement for automatic production of a buttonhole, Fig. 14 (not shown) a cam corresponding to cam 78 may be clutched to the worm 22 so as to be driven from the arm shaft.