Patent GB-419923-A (GB)
Title: Lock-stitch sewing machine
IPC: D05B3/08
Filed: 1934-05-14
Abstract: 419,923. Sewing-machines. FAIRWEATHER, W. C., 65, Chancery Lane, London.- (Singer Manufacturing Co. ; Elizabeth, New Jersey, U.S.A.) May 14, 1934, No. 14453. [Class 112.] Buttonhole-sewing machines.-In sewing a pyramid-purl lock-stitch buttonhole, at high speed, an eye-pointed laterally vibrating needle co-operates with an under thread in such a way that the loop taker seizes thread loops from the needle below the work, expands these loops for passage about the bobbin and the take up draws up the needle thread and pulls the under thread loops through the work to the upper side so that in the finished seam the needle thread lies in a straight centre line between the rows of zig-zag needle punctures while the loops of under thread are threaded by the needle thread and lie between this and the needle punctures, Fig. 29. For this purpose, the tension on the under or bobbin thread is light while that on the needle thread is very strong. Needles, vibrating laterally.-The needle bar 9 is journalled in the usual needle-bar gate 10 fulcrumed at 11. The take-up crank 6 actuates the usual bell-crank take-up lever 12, Fig. 6, which is anchored by the link 13 to the head- 4. The needle-bar vibrating mechanism comprises a gear 14 on the main shaft 5 which drives a gear 15 of double the number of teeth carrying two diametrically opposed pins 16, Fig. 5, meshing with the star wheel 17 fixed to the vertical shaft 18 which is given a step-by-step rotary motion. Through a train of upper gears 19, 20, 21, 22, the shaft 18 drives the shaft 23 and imparts a half-rotation to this shaft for each step of movement of the shaft 18. The shaft 23 has a head 24 at its upper end in which is mounted a slide block 25 carrying a crank pin 26 connected by a link 27 to a lever 28 which in turn is connected by a link 29 to the needle-bar gate 10. The shaft 23 is hollow and contains a vertically movable pin 30 having an inclined head 30<1> engaging a slot in the slide block 25. The amplitude of the vibrations depends on the position of the control rod 30 in the shaft 23. The control rod 30 is connected at its lower end to an arm of a lever fulcrumed to the goose neck. This lever has a nose bearing on the upper face of a gear 34, which is driven from the shaft 18 through the usual trains of reduction gears 37 and makes one complete rotation per buttonhole producing cycle. Cam-blocks are fixed to the upper face of the gear 34 and pass under and elevate the nose to increase the amplitude of the vibration of the needle during the sewing of the barring stitches at the opposite ends of the buttonhole. Work clamps.-The work clamp is of usual construction and comprises the upper clamp foot 39 carried by the lever 40 fulcrumed at 41 on the longitudinal slide-frame 42 mounted in the cross-slide frame 43. The frames 42, 43 are actuated by the usual connections with the longitudinal and lateral feed cam-grooves in the feed wheel 36. The clamp lever 40 has a tail 46 passing under a roller 47 on the vertically movable bar 48 on the clamp-lifting arm 49 journalled to move relatively upon the stop-motion controlled rock-shaft 50. Starting and stopping.-The stop motion device comprises the usual tight and loose belt-pulleys 56,57 on the main shaft 5, the latter carrying a gear 58 meshing with a gear 59 in a 2-to-1 speed reducing ratio. The gear 59 carries the double-notched stop-cam 60 which co-operates with the usual spring-pressed stop-plunger 61 carried by the tilting stopmotion lever 62. Lock-stitching by shuttles.-The bobbin-case flange 87 is held in the bearing groove of the shuttle body by the removable member 90 screwed thereon. The bobbin-case 88 has a guard flange 89 to prevent contact of the front limb of the needle loop with the oiled bearing rib 87. The shuttle body has a smoothly rounded throat 91, Fig. 12, behind the shuttle beak 85, which draws out the needle-loop and causes the limbs of the loop to engage the tapered front and rear loop-spreading walls of the case 88. The case 88 has a circular cavity for the bobbin 94 which is journalled on the arbor 95 and held by the latch 96. A spring 101 bears lightly on the bobbin and prevents its overrunning and spilling thread. The case 88 has a needle-clearance channel with inner and outer needle guide walls 106, 107. The spring 108 applies a light tension to the thread. The front wall of the bobbin case has notches 111 for the reception of the free hook-shaped ends of the rotation restraining arms 112, 113. These arms are carried by rock shafts 114, 115 journalled in sleeves carried by a bracket fixed to the tubular stud 118. The rock shafts 114, 115 each carry a fork actuated by cams to cause the arms 112, 113 to move into and out of the notches 111.