Patent ES-269349-A1 (ES)
Title: Blind stitch sewing machine
IPC: D05B1/24
Filed: 1961-07-24
Abstract: A chain stitch sewing machine comprises a needle moving in a curved path, a looper moving in a closed path comprising two vertically-displaced curves the ends of which are higher than the intermediate ends and the plane of which is transverse to the needle path, and means for displacing the looper slightly to permit its operation during backwards sewing. Stitch forming. The arm shaft 4 drives a horizontal shaft 7 connected by a crank pin and a link 8 to a crank 9 on a horizontal shaft 10 carrying an oscillating needle bar 11. Shaft 4 also drives a vertical shaft 14 journalled in a sleeve 15 suspended at its upper end by pivots 15b from fixed lugs 3b. Shaft 14 is connected by a crank pin and a link 16 to one end of a looper bar 17 slidable in a sleeve 20. The latter is biased downwardly by a spring 22 and is connected by a link 21 to one arm 23 of a double-armed lever, the other arm 25 of which serves as a follower to a cam 26 on shaft 4, whereby sleeve 20 is vertically reciprocated. The free end of bar 17 is formed with a pair of vertically spaced offset jaws 17b, 17c stepped on their respective upper faces, the lower jaw being formed on its lower surface with an inclined threadguiding groove. A plate 18, pivoted at c between said jaws, has on one side a nose e, and on the other side noses d,f,g. Nose d abuts a leaf spring 19 rigid with the jaws, whereby the noses e,f and g normally project from the latter. The jaws follow a closed path, transverse to the needle path and consisting of two vertically-spaced curves the opposite ends of which are higher than the intermediate points. The upper curve lies slightly above the needle path, whereby the jaws take the loop from the needle, said loop being retained during forward feed in front of the forward nose g. When the machine is adjusted for reverse sewing nose 31a on a lever 31 engages a lever 28, whereby an abutment 151 on the latter pivots sleeve 15 to position the looper slightly rearwards. A link 29 connecting lever 28 to a lever 30 swings the latter to engage an abutment 70 rigid therewith with nose e on the forward movement of the looper to retract nose g,whereby the loop is retained behind the latter. During the return movement of the looper an abutment 73, linked to abutment 70, engages nose f, whereby nose g is withdrawn to release the loop. Feeding, blindslilching. A feed shaft 47 has pivoted thereon a casing T, and drives a pair of spaced work-feeding wheels 52, 53, journalled in casing T, via gears 49, 50, 51. A member 62, rigid with casing T, is pivoted to the ends of a cranked link 63 which is pivoted at its apex to a crank 57 on a shaft 56. A two-armed lever 60, rigid with shaft 56, is engaged on one arm by a spring 61 to bias casing T into work-engaging position. The other arm of lever 60 abuts a screw 59 which thereby serves to adjust the vertical position of casing T for regulating the depth of the stitches. A lever 55 rigid with shaft 56, serves to lower casing T. Shaft 47 carries ratchet wheels 45 and 46 having oppositely-positioned teeth, wheel 45 cooperating with a pawl 44c for forward feed, and wheel 46 co-operating with a pawl 44d for reverse feed. Said pawls are rigid with the lower end of a bar 44, the upper end of which carries a pair of studs 44a, one of which is slidable in a vertical groove 43a formed in a block 43 in screwthreaded engagement with a spindle 42 turnable by a knob P. The other stud 44a is engaged in a slot 411 formed in an arm 41 which is pivoted at 40a to the machine frame and has a notch 41a embracing an eccentric 39 on shaft 4. Arm 41 is thereby oscillated to impart vertical reciprocation to bar 44, the extent of which may be varied by adjusting the position of block 43. A lever 38, pivoted at 38b to the machine frame, has a forked lower end lying within studs M and M1 on pawls 44c and 44d respectively. Swinging of lever 38 thereby serves to engage one or the other pawl with its respective ratchet wheel. Lever 38 is pivoted to one end of the lever 31 pivoted at 32 to the machine frame. A plunger 33, carrying an external knob A, is pivoted to lever 31 and is biased by a spring 34 for positioning.lever 38 such that pawl 44c engages ratchet wheel 45 for forward sewing. If knob A is pressed inwards, lever 38 is moved to the position in which pawl 44d engages ratchet wheel 46 for reverse sewing. Plunger 33 is retained in the retracted position by the engagement of a notch 331 in plunger 33 with the nose 36b of a pivoted member 36. A notch 36a in the latter engages a pin 35a on a plunger 35 which is thereby moved outwardly against the bias of a spring 37. Forward sewing is restored by pressing inwardly a knob R on plunger 35, thereby releasing nose 36.