Patent GB-937299-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B73/12
Filed: 1959-12-23
Abstract: 937,299. Sewing machines. B. TAKETOMI. Dec. 23, 1959 [Dec. 27, 1958; Sept. 23, 1959], No. 43749/59. Class 112. [Also in Group XXIV] In a zig-zag sewing machine, a driven pinion mounted on the machine bed engages a buttonhole-shaped endless rack connected to one part of a work-feeding bar, another part of which, adapted to feed the work, is disposed under the presser foot of the machine. As shown in Figs. 1 and 2, the work-supporting plate 18 of a zig-zag sewing machine is formed with a recess 19 in the base of which is journalled a shaft 3. The upper end of the latter is formed with a flange 4 supported in a recess in said base, and is also formed with a gear pinion 5. A washer 7, secured to the lower end of shaft 3 by a screw 9, supports a double-armed lever 8 pivoted on shaft 3. A spring 16, acting on one arm of lever 8, biases the end 8<SP>1</SP> of the other arm against the oscillatory feed-advance lever 1<SP>1</SP> of the normal work-feeding mechanism. An aperture formed in lever 8 houses a roller adapted to become wedged between said aperture and shaft 3 for transmitting intermittent uni-directional rotation to the latter on oscillation of lever 8. A member 10, disposed in recess 19, is formed with an internal, endless rack 11 corresponding to the shape of the desired buttonhole. Pinion 5 meshes with rack 11, and a pin 6, concentric with pinion 5, engages a groove 11<SP>1</SP> formed in member 10 parallel to rack 11. A flat, workfeed bar 12 is formed at one end with an aperture 12<SP>1</SP> which is engaged with member 10, is formed intermediately with a slot 27 engaging a pin 14 projecting upwardly from plate 18, and is formed on its upper surface at the other end with work-engaging teeth 22. The work is compressed between the usual presser foot 15 and the toothed end of bar 12. The length of the individual zig-zag stitches is controlled in the normal manner by varying the extent of oscillation of the lever 1<SP>1</SP>. In a modification, Figs. 6, 7, a plate 30, adapted to be secured within a recess in the work-supporting plate by two screws passing through holes 23 therein, is formed with a depending boss 34 and journals the shaft 3 carrying flange 4, pinion 5 and pin 6. A collar 44, fixed by a screw 45 to the reduced lower end of shaft 3, is formed with a flange 42 supporting a plate 40, and is also formed with a circular spigot 43 which enters a circular hole in plate 40. Said hole is extended peripherally to accommodate a friction pawl 38 secured by a screw 37 to a plate 47 which rests on plate 40 and is formed with a clearance hole for shaft 3. An arm 46 extending from plate 47 carries an adjustable eccentric member 50. A spring 35, connected to screw 37 and by a screw 36 to plate 30, turns plate 47 to bias member 50 against a reciprocating member 51 of the workfeed mechanism. Pawl 38 is adapted to be clamped against spigot 43, to rotate shaft 3, during movement of plate 47 in the direction R<SP>2</SP>. A spring washer 33, disposed under flange 4, holds shaft 3 stationary during the return movement in direction R<SP>1</SP>. The amplitude P of the drive movement is varied by adjusting member 50. A screw 57, passing through plate 30, carries an arm 58 which, on rotation of screw 57, engages a pin 59 on arm 46 to shift member 50 clear of part 51. The friction pawl 38 and co-operating spigot 43 may be replaced by a normal pawl and ratchet wheel. In a further modification, Fig. 12, a plate 75, secured in a recess in the work-supporting plate 18, carries a pin 67 which journals a double-armed lever. One arm 66 of the latter is biased by spring means against one end of a slidably mounted pin 65 the other end of which abuts a cam 64 carried by the shuttle-operating shaft 63. Rotation of the latter thereby effects oscillation of the double-armed lever, the other arm of which carries a pawl co-operating with a ratchet wheel 71 rigid with the pinion 5.