Patent GB-976937-A (GB)
Title: Improvements in or relating to chain stitch sewing machines
IPC: D05B57/02
Filed: 1963-10-11
Abstract: 976,937. Sewing machines. G.M. PFAFF A.G. Oct. 11, 1963 [Oct. 13, 1962], No. 40122/63. Heading D1G. In a chain stitch sewing machine comprising needle and bottom feed, and a looper having loopseizing and shedding movements in the direction of feed and transverse needle-avoiding movements derived from two eccentrics on a rotary shaft, the looper and needle have synchronized oscillatory movements in the feed direction, and the angular position of the eccentric controlling looper movements in the feed direction is adjustable on said shaft in order to maintain a substantially constant loop-seizing relationship between the looper and needle for varying rates of feed. A needle bar 35 carrying a needle 36 reciprocates in a pivoted gate 34 oscillated by a crank 39 on a shaft 38 rocked via a crank 43 from an adjustable eccentric 45 on the main arm shaft 24. Adjustment of eccentric 45 is effected by engaging a spring-biased pin 50 with a notch 46 in an adjusting ring 47 of eccentric 45, and then turning a handwheel 28 on shaft 24. Shaft 38 is coupled by cranks 51, 54 and a link 52 to the feed-advance cork shaft 53. Shaft 24 is coupled by a belt 64 to a shaft 65 coupled by a key 67 to a flange 88 fast on a shaft 61. An eccentric 70 on the latter is connected by a linkage 71 to one arm of a bell crank lever 73, the other arm of which carries a block 77 slidable in a slot 74 in a crank 76 on a shaft 75 carrying a looper 59. Rotation of shaft 61 thereby causes axial reciprocation of shaft 75 to impart transverse needle-avoiding movement to the looper A sleeve 79, journalled on shaft 61, carries at one end an eccentric 80 connected by its pitman 81 to crank 76. Rotation of sleeve 79 thereby serves to oscillate the looper in the feed direction for loop seizing and shedding. A forked crank 83 on the other end of sleeve 79 embraces a block 84 journalling an eccentric 85 at one end of a shaft 86 journalled in flange 88. The other end of shaft 86 carries a fork 92 engaging a pin 94 on a disc 93 concentric with and rotatably mounted on flange 88. Turning of disc 93 thereby serves to rotate eccentric 80 relative to shaft 61. A crank 89 on shaft 86 carries a spring-biased pin 90 adapted to enter any one of a series of holes 91 in flange 88 to hold eccentric 80 in the desired position of adjustment. Flange 88 is provided with a scale corresponding to the stitch-length scale associated with the handwheel 28. In a modification, Fig. 4, cranks 101, 102 on shaft 53 are coupled by a link 103 to a frame 106 pivoted on a shaft 107 which carries the eccentric 70 and is belt-driven from shaft 24. A shaft 105, journalled in frame 106, carries a pinion 111 meshing with a pinion 110 fast with shaft 107. Shaft 105 carries eccentrics 112, 113 which are displaced 120 degrees apart and are connected by rods 114, 115 to similarly displaced eccentrics 116, 117 fast on the sleeve 79 which carries the eccentric 80 and which is journalled on shaft 107. The angular position of eccentric 80 relative to shaft 107 is thereby automatically adjusted in accordance with the rate of work feed. It is stated that several loopers and needles may be provided.