Patent GB-1128278-A (GB)
Title: Improvements in and relating to zig-zag sewing machines
IPC: D05B19/00
Filed: 1967-07-27
Abstract: 1,128,278. Sewing machines. B. TAKETOMI. 27 July, 1967, No. 34684/67. Heading DIG. A zig zag sewing machine comprises an axially-reciprocable needle bar mounted for universal movement transverse of its axis, a pair of cams selectively adapted to impart transverse movements to the needle bar, a pair of guide means adapted to be made selectively operable for guiding the needle bar during said transverse movement, and changeover means for selectively coupling one of the cams to the needle bar while making one of the guide means operative, or the other cam while making the other guide means operative. A U-shaped frame 19, pivoted about vertically-aligned pins 20 on fixed brackets 22, carries vertically-aligned pins 42 journalling a U-shaped bracket 17 slidably supporting a needle bar 16. A plate 14, slidable in grooves 22b formed in the upper bracket 22, has a V- shaped front surface 14a which is positioned in front of a straight surface 22a of bracket 22 when plate 14 is advanced, or at the rear of surface 22a when plate 14 is retracted. A torsion spring, connected between frames 17 and 19, biases frame 17 counterclockwise to engage a sleeve 15 on needle bar 16 with surface 14a when plate 14 is advanced, or with surface 22a when plate 22 is retracted. Movement imparted to frames 17, 19, by a link 27 pivoted to needle bar 16, thereby moves sleeve 15 either along surface 14a for the formation of V-shaped zig zag stitches, or along surface 22a for the formation of straight zig zag stitches. Link 27 is also pivoted at 31 to an arm 25 pivoted at 36 to the machine frame. A spring 30 biases arm 25 clockwise, whereby a roller 24, carried at one end of an arm 26, pivoted at its other end at 31 to arm 25, is engaged with a curved arm 23 pivoted at 40 to the machine frame. The arm shaft 35 is coupled by 4 to 1 reduction gearing 1, (2) to a shaft 5 carrying cams 3 and 4. A shaft 10, rigid with a handle 41, carries a triangular cam 9 engaged in a bifurcated arm 6c of a bell crank lever pivoted at 12 to the machine frame, the other arm 6b being pivoted to one end of a bar 6a carrying a roller 6 at its other end. Shaft 10 also carries a triangular cam 8 opposed to cam 9 and engaged in one bifurcated arm 7c of a T-shaped lever pivoted at 12, a second bifurcated arm 7d engaging a stud 13 on plate 14, and the third arm 7b being pivoted to one end of a bar 7a carrying a roller 7 at its other end. When handle 41 is turned clockwise to its extreme left hand position, the bell crank lever is turned clockwise to position roller 6 between cam 3 and a nose 23a on arm 23, while the T-shaped lever is turned counterclockwise to withdraw roller 7 and to advance plate 14. Cam 3 is formed with four concentric lobes spaced at 90 degrees apart and smoothly joined together by non-concentric portions. Two opposed lobes are of maximum and minimum radius respectively, and the other two opposed lobes are of equal and intermediate radius. When the machine operates and the highest lobe engages roller 6, link 27 will move sleeve 15 to an extreme right hand position on surface 14a and the needle penetrates the work. When a second and intermediate lobe engages roller 6, sleeve 15 is positioned at the centre of surface 14a and the needle again penetrates the work. When the third and lowest lobe engages roller 6, sleeve 15 is at an extreme left hand position on surface 14a and the needle penetrates the work. When the fourth and intermediate lobe engages roller 6, sleeve 15 is at the centre of surface 14a and the needle penetrates the work. When handle 41 is turned to its extreme right hand position, roller 6 and plate 14 are retracted, while roller 7 is positioned between cam 4 and nose 23a. Cam 4 comprises four lobes spaced at 90 degrees apart, one pair of opposed lobes being of equal radius greater than that of the other pair of opposed lobes of equal radius. The arrangement is such that sleeve 15 is located at an extreme right hand position on surface 22a when cam 4 engages the high lobes, and is located at an extreme left hand position on surface 22a when cam 4 engages the low lobes, a needle penetration occurring each time a lobe is engaged. Means for varying the stitch width comprises a bell crank lever 28 pivoted at 29 to the machine frame. One end 28a of lever 28 is connected to arm 26, and the other end is formed as a handle 33, manipulation of which shifts roller 24 towards or away from the pivot 40 of arm 23. A follower member 32 on lever 28 is adapted to cooperate with a rotary pattern cam 34 for varying the stitch width automatically. The throat plate is formed with the usual straight needle-passing slot (45), and also with a V- shaped slot (46) united at its apex with slot (45). Specimens of stitching producible are shown in Fig. 4.