GB957587A - Improvements in or relating to sewing machines - Google Patents

Abstract

957,587. Sewing machines. HUSQVARNA VAPENFABRIKS A. B. June 19, 1962, No. 23623/62. Heading D1G. In a zig-zag sewing machine the swinging movements of the needle bar gate are derived from a rotary cylindrical cam having a cam groove comprising two parallel parts and a cross over part therebetween,the cam consisting of asting of a material having a lower casting temperature and better sound-deadening properties than iron, preferably a synthetic plastic material, and the cam follower being spring-biased to one side of the groove and being adapted to oscillate an arm formed with a longitudinal slide engaged with a member adjustable therealong and operatively connected to the needle bar gate. The needle bar 14 of a zig-zag sewing machine is mounted in a suspended gate 13 oscillated by means of a connecting rod 33 against the bias of a spring 35. The farther end of rod 33 carries a roll 32 displaceable in a guide slot 31 in a swing- ing arm 28, one end of which is rigid with a pin 29 Journalled in a fixed bush 30, and the other end of which pivotally carries a pin 27 rigid with a follower 26 co-operating with a cam 20 on the machine arm shaft 12. Cam 20 is cylindrical and is formed with a peripheral groove having two parallel portions 24, 25 interconnected by a crossover portion 22. The arrangement is such that when roll 32 is at one end position 46 co-incident with the axis of pin 29 the machine produces straight stitching b along a mid line M. Displacement of roll 32 produces symmetrical zig-zag stitching a, the width of which is greatest between the lines L and R at the other end position 47 of slot 31. Arm 28 is also formed with open-sided guide tracks 50 and 51 which are adapted to cooperate with roll 32, upon axial displacement of the latter, under the bias of spring 35, and which are so arranged that when roll 32 in position 46 engages track 50 straight stitching c is produced along line L, and when engaging track 51 straight stitching d along line R is produced, while in intermediate positions along tracks 50 and 51 zig-zag stitching e and f is produced respectively displaced to the left and right. A notch 36 in rod 33 is engaged by a roll 37 adjustably mounted on an eccentric pin 60 carried by a bar 38 projecting from a crank 39 on a spindle 40 turnable or axially slidable by a knob 45 thereon for shifting roll 32 laterally or axially. Spindle 40 turns with, but is axially displaceable relative to, a dial 41 provided with a scale 42 co-operating with a fixed mark 48 for indicating the stitch width. A sleeve 43 rigid with dial 41 is formed with patterns 53 which correspond to the stitching a, e and f respectively, and which co-operate with an aperture 54 in knob 45 to indicate the position of the stitching field. An arcuate spring-member 55, carried by crank 39, engages a notch in bush 30 at each of the three positions of axial adjustment of spindle 40. A member 59 straddling bush 30 brakes the turning of spindle 40. Cam 20 and follower 26 are preferably made of synthetic plastic. The respective sides of a buttonhole may be sewn by engaging roll 32 succesively with tracks 50 and 51, the stitch width being adjusted to half the maximum width.