Patent GB-532026-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1939-07-05
Abstract: 532,026. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation). July 5, 1939, No. 19535. [Class 112] [Also in Groups XXIV and XXV] In a boot-sole sewing machine in which a curved hooked needle and a curved awl are arranged to lie always in the same plane and the work is fed by means of a work-support and a presser-foot arranged to clamp the work between them: (a) a yielding thread controller co-operates with the take-up to permit each needle loop to be passed around the thread case by the loop taker without substantial tension and to prevent slack in the needle thread loop during the passage of the loop from a position of maximum extension about the thread case to a position where the loop is free to be drawn from the loop taker by the take-up; (b) a needle thread pull-off is controlled by the presser-foot, with adjustable means by which the inter-locking portions of the needle and shuttle threads may be caused to lie closer to the surface of thin work substantially at the same distance from the surface of the work regardless of its thickness; and (c) the work support and presserfoot are arranged to move, whilst feeding, about an axis which is at an acute angle to the worksupporting surface on the work support. The thread controller is movable between two positions and holds the needle thread under a relatively light tension during the first part of its movement and then under an increasing tension during its continued movement. A thread tension device acts on the needle thread between the take-up and the work, and maintains a tension on the needle thread loop after the loop is freed from the loop taker and is being drawn towards the work. A thread lock is located between the pull-off device and the take-up, and is opened before the needle-thread loop is carried by the loop-taker to a condition of maximum extension about the shuttle thread case ; a second thread lock is located between the pulloff device and the thread supply. The second lock is closed while the take-up is setting a stitch and the first thread lock is closed while the thread is being strained by the take-up ; both locks are opened up for the stopping of the machine and permit the last loop to remain projecting from the work. The loop-taker has a shoulder for assisting in spreading the needle thread loop. The needle guide has a projection which deflects one side of the needle thread loop as it is being passed about the thread case. The take-up is rotary and is driven by gears providing cyclically variable motion and mounted in a housing which is adjustable in two directions. The presser-foot is automatically unlocked and lifted when the machine stops. Means are provided for lubricating the needle. Lock-stitching by barbed needle and rotary hook; thread - tension devices; perforating devices ; threads, waxing. In the machine shown the stitch-forming devices comprise a curved barbed needle 2, Figs. 8, 10, with guide 3, awl 4, looper 10, thread finger 12, thread-lifter 14, and rotary hook 6 making three revolutions per cycle. Thread passes to the stitching point by way of a thread lock 118, pull-off: 92, thread-lock 36, light spring controller 28, rotary take-up 20, and frictional thread-tension device 48. The threadcontroller 28 comprises a bent-wire arm with an eye engaging the thread between the threadlock 36 and a pulley 38, and is mounted on a block pivoted, with a biassing, spring, on a fixed spindle 32; its movement is limited to a range smaller than that of the usual auxiliary take-up by engagement with a recess in a saddle 43 on. the spindle 32, the saddle being adjustable angularly (see Group XXV). Its purpose is to control the thread loop passing round the thread-case between the position of maximum distension, and the position at which the take-up begins to act, and to yield thread between the latter point and that at which the loop becomes free to be drawn down by the take-up. The tension device, to prevent undue enlargement of the thread loop if, its passage is not resisted by the work and to control slack during take-up, comprises a plate 48, rocking on a fixed; bracket 52; and a friction member 54 carried by an arm, mounted on a pivot 68, which carries a thread pulley and threadretaining cage; the arm is actuated by the notched tail of the thread finger engaging a pin on a sliding, member which bears on the arm through a spring, to increase the tension to assist. laying of the thread in the needle-barb. The pull-off comprises a slotted arm 86 engaging the thread between, two eyes in, an, arm 92 and is actuated in a similar manner to that described in Specification 23478 / 10. [Class 112]. The arm 92 is connected by an arm 114 and link 116, Fig. 8, to an arcuate slotted lever 240 connected to the presser-bar as described below, the link being adjustable along the lever 240 from a lowest position in which the length of the needlethread loop is constant to an uppermost position in which the depth of stitch is uniform; the mechanism may thus provide automatically for placing the thread interlock deeper where the thickness of the work makes this possible without entering the joint between the sole and welt. The upper thread lock 36, Fig. 10, comprises a pulley round which the thread passes and against which it is clamped by a pivoted shoe 120 apertured at its free end for the passage of the thread, and the lower lock 118 is similar. The two locks are closed by cam arms 122, 142, movable about concentric, axes by linkages including longitudinally-movable members 126 which, are springe-pressed to the closing position. and are moved to the open position by camactuated levers. 130, or by connection, to the stopgear (see below) ; the cam arms approach, a, position radial to the pulleys in the locking, position to clamp, the thread effectively. The locks are opened alternately, the upper one. being, opened before the needle-loop reaches, its. maximum, extension round the bobbin-case and closed, immediately after the take-up, reaches, its lowest stitch-setting position. The thread lifter 14, is clamped in one end of a link 444, Fig. 8, connecting its actuating; cam lever 446, and an arm 450. The looper is carried and actuated by similar mechanism arranged in a horizontal plane. The thread-case of the rotary hook is somewhat larger than that previously used and is formed with a grooved shoulder and other surfaces to assist in spreading the needle loop. The hook body, to assist in the required greater spreading of the loop, has a somewhat blunter beak with a shoulder more nearly parallel to the hook axis than the rear edge of the beak its, also has a projection at the base of the beak to force the thread out of the needle barb. The needle guide is formed with a projection, which engages the thread passing across the face of the thread-case to deflect it out of the path of the needle. The needle and awl are supported by bracket 288, Fig. 17, the needle segment 460 being mounted on a sleeve integral with the bracket and in turn carrying the needle guide 3, while the awl segment 462, is integral. with a pivot pin 484 the awl driver 466, mounted partly on a sleeve integral with the bracket 288 and partly on the pin 464, is formed in two parts embracing the awl segment 462 so that the latter can be adjusted axially without affecting the driver. The needle segment and awl driver are located by a flange on a bush 472, and the awl segment is adjusted by screws 468, 470 threaded in this bush and the bracket 288 respectively and bearing on the ends of the pin 464. The take-up comprises a rotating arm 20, Fig. 10, on a shaft 22 which is driven at a cyclically variable rate link connecting an arm on this shaft to an arm on a uniformly-rotating shaft offset from it ; the latter shaft is driven through -helical gears of which one is axially movable against a spring to take up any shock due to the irregular motion. of the take-up (see Group XXIV). The train of gears includes an idler wheel carried by a housing which encloses the whole train and is carried on an eccentric bush on one of the end shafts of the train for adjustment of the mesh of all the gear (see Group XXIV). The take-up arm rotates between a fixed shield, with an enclosing rim, and a cover 370 hinged at 372,. Figs. 8 and 10 ; the cover is locked by a lug 386 on a member pivoted at 388 and having a portion 384 shielding the looper mechanism and other parts. The cover is electrically heated, and the take-up roller is heated by conduction therefrom through a button which is carried on the stud of the. roller and is spring-pressed into contact with the cover. Feed by co-operating jaws ; presser-bars ; work supports and guides; channelling. The work support 16, Figs. 8, 10, 16, is adjustable on a feed carriage 180 which is fixed to a shaft 182 and is guided by hooked portions engaging fixed plates, 188, Fig. 8. The presser-foot 18 is carried by a lever 190 pivoted on a horizontal pin 192 on the feed-carriage, which has a stop 284 to limit downward movement of the foot in the absence of work... The feed carriage 180 is oscillated by a toggle linkage connected to rearward extension of the carriage, the middle point of the toggle being connected to a cam-actuated arm ; the other end of the toggle is pivoted to a yoke which is adjustable to vary the feed, about an axis approximately in line with the middle joint of .the -toggle .when the feed-carriage it at one end of its movement. The presser is actuated and locked through an arm extending' rearwardly from the pin 192 and connected by way of a universally-jointed link 224, crank 226 and link 230 to a floating lever 232 and to a link 236 attached to a three-armed lever 240 acted on by a presser spring 244 ; the spring is attached at the front end to an arm 246 which is adjustable by worm gear from a finger knob 251. The lever 232 is connected at its upper end by an adjustable link