Patent GB-781221-A (GB)
Title: Improvements in or relating to zig-zag sewing machines
Inventor: ZINK HERMANN
IPC: D05B3/08
Filed: 1955-06-17
Abstract: 781,221. Sewing machines. PFAFF AKT.- GES., G. M. June 17, 1955, No. 17498/55. Class 112 in a zig-zag sewing machine a control element is adapted to co-operate with a pair of abutment surfaces, either the element or the surfaces being movable to positions corresponding to selected stitch widths whereby engagement of the element with one or other of the surfaces corresponds respectively to the minimum and maximum stitch widths of a range, the relative positions of the element and surfaces being adjustable to vary such minimum and maximum stitch widths, and the surfaces, being fixed relative to one another whereby the ratio between .the minimum and maximum stitch widths is constant. As shown in Figs. 2 and 4, needle vibration is effected by means of a lever 6 one end of which embraces a rotary cam 5 driven by gears 3, 4 from the main shaft 2 of the machine, the lever being pivotally mounted by a sliding block 7 in an eccentric head 8 of a spindle 9, and the latter being turnable by means of a knob 10 for varying the stitch width manually. Spindle 9 is journalled in a lever 11 which is rockable about a fixed spindle 12 for varying the non-vibratory position of the needle. A bush 30 journalled on spindle 12 is provided with arms 34, 37, the former being connected by a link 35 to knob 10 and the latter being connected to a link 38, movement of which is utilized in effecting automatic variation of the stitch width. A frame 15, which is journalled in the machine frame, is turnable by means of a lever 27 engageable in one or the other of notches 28, 29 in the machine frame. Frame 15 is also movable along its pivotal axis by means of a knurled disc 17. When lever 27 is in notch 28, an abutment surface 24 on frame 15 is located below a control arm 31 provided on bush 30. If frame 15 is then at its lowest position, knob 10 can move through its entire range, but if frame 15 is moved to its highest position, when knob 10 is turned fully clockwise to the non-vibratory position, surface 24 abuts arm 31 to prevent movement of the knob. Lever 27 may be moved to notch 29 to position an abutment surface 23 on frame 15 below arm 31. Surface 23 then determines a smaller stitch width and surface 24 a larger stitch width, the actual size of said widths, which are in a fixed ratio to each other, being determined by the axial position of frame 15. In a modification, Figs. 7 and 9, knob 10 carries a supplementary knob 68 rotation of which serves to move a slide 60 radially with respect to knob 10 and thereby moves a control tongue 61, carried by slide 60. upwardly or downwardly in a notch 54 formed in a plate 52. When tongue 61 lies in the upper part of notch 54, an edge 55 of the latter determines the non-vibratory portion of the knob 10 and the other edge 56 the maximum stitch width. An abutment 47, biased by a spring 42, projects from edge 55 into the lower part of notch 54. When tongue 61 lies in said lower part, abutment 47 determines the minimum stitch width and edge 56 the maximum stitch width, said widths being at a fixed ratio to each other. Abutment 47 may be moved clear of edge 55 by tongue 61, when force is applied to knob 10, to enable straight stitching to be effected in any portion of tongue 61.