ES310542A1 - Zig-zag sewing machine with single manually operable setting device for both overstitch width and stitch length - Google Patents

Abstract

In a zig zag sewing machine in which the stitch width and length are adjustable by means of respective cams and co-operating followers, relative movement between said cams and followers is alone controlled by a single manually-operable device to effect simultaneous adjustment of the stitch width and length. The stitch length adjustment means is connected by a link 24 to a U-shaped bracket 32, the arms 33a, 33b of which are pivoted on a shaft 31 journalled in walls 29, 30. An arm 35, rigid with arm 33b, carries a pin 36 embraced by the forked end 38 of a link 37 pivoted to a crank 39 on a shaft 40 journalled in walls 29, 30. The intermediate portion of shaft 40 is polygonal in cross section, and journals a sleeve 41 provided intermediately on a member 42. The lower end of the latter carries a conical-shaped follower 50 which is normally biased into engagement with the upper edge 52 of a cam slot 51, formed in bracket 32, by a spring associated with link 24. The forked upper end 54 of member 42 embraces a cylindrical sleeve 56 eccentrically journalled on a shaft 7 which is journalled in the walls 29, 30. A U-shaped bracket 44, which embraces sleeve 41, is non-rotatably mounted on shaft 40 and carries an arm 45 ending in a knob 46. The latter thereby serves either to shift member 42 axially of shaft 40 and follower 52 along slot 51, or to rotate shaft 40 for engaging follower 52 with the lower edge 53 of slot 51. Edge 52 corresponding to forward feed, has a first inclined portion 52a for adjusting stitch length from a maximum to a minimum value, a second horizontal portion 52b corresponding to the minimum value, a third inclined portion 52c increasing stitch length to the maximum, and a fourth inclined portion 52d for decreasing stitch length to the minimum. Edge 53, controlling reverse feed, has corresponding portions 53a, b, c, d. Rotation of sleeve 56, by means of a knurled disc 57 rigid therewith, serves to move follower 50 into and out of slot 51 for fine adjustment of the stitch length. A sleeve 60, journalled on shaft 31, carries a pin 61 embraced by the forked end 62 of a lever 64 pivoted at 63 on wall 30 and biased by a spring 65 towards a stop 66 adjustably mounted on wall 30. Lever 64 has an aperture 67 providing clearance for shaft 31, and a slot 68 embracing a pin 69 which pases through a slot 70 in wall 30 and is carried by a sleeve 71 jornalled on shaft 31. Sleeve 71 is connected by a link 72 to a disc 73 journalled in the free end of a crank arm 75 on shaft 31. A diametrical slot 76 in disc 73 slidably embraces a block 77 connected by a link 78 to a crank arm 79 on shaft 7. Link 78 is oscillated by a pitman 80 actuated by a triangular cam 83 driven by gears 81, 82 from the machine arm shaft 12. Shaft 7 is connected via a crank 8 to the needle bar gate, and extent of oscillation of the latter is thereby governed by the inclination of slot 76 as controlled by the angular adjustment of sleeve 60, straight-line stitching corresponding to the engagement of lever 64 with stop 66. Sleeve 60 is formed with cam surfaces 59b, 59c, 59d co-terminous with cam edges 52b, 52c, 52d, and co-operating with a follower nose 58 on member 42. Inclined surface 52b governs an increase of stitch width to a maximum, horizontal surface 52c governs maximum stitch width, and inclined surface 59d governs decrease of stitch width to zero. A printer 48 on arm 45 moves over a pictorial representation, provided on a cover (47), of the stitching produced by progressive lateral movement of knob 46. An arm 87, rigid with shaft 31, carries a lug 90 selectively engageable in any one of three notches 88 formed in a pivoted, spring-biased arm 89. Arm 87 is used in buttonhole sewing for positioning the stitching field either to the left, or centrally, or to the right. It is stated that the stitching field can be controlled simultaneously with the stitch length and width.