Patent GB-746389-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1953-09-10
Abstract: 746,389. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation). Sept. 9, 1954 [Sept. 10, 1953], No. 25037/53. Class 112. In a shoe sole lockstitch sewing - machine of the kind described in Specifications 285,487, [Class 112], 516,539 and 610,199 and having a barbed needle, a loop-taker on the same side of the work as the needle, and a rotary shoe-supporting horn, a curved needle 12, Fig. 2, is arranged to enter the perforation formed by a curved awl 2 and to impart a feeding movement to the work, whereby a presser foot 14 may be arranged directly over the horn 6 to be close to the needle while the latter is piercing the work ; and the loop-taker is in the form of a rotary shuttle 98 having a plurality of loop-taking beaks, each arranged in turn to receive a loop of thread from the needle and to draw it through the work while a previously formed loop is retained on another beak, the shuttle being of a size substantially larger than those employed in the machines described in the above-mentioned Specifications, whereby the shuttle serves to act as its own take-up for setting the stitch provided by said previously formed loop. Feeding by needle; perforating devices.-The awl 2 and needle 12, Fig. 2, are mounted respectively on arms 4 and 10 provided with hubs which are journalled in aligned bearings 18 and 20, Fig. 17, attached to the machine frame by bolts 22. A spindle 30 passes through the hubs, the latter being fixed with respect to the spindle at a constant distance apart equal to at least the length of the longest stitch. A feed lever 24, Fig. 19, is pivoted between a pair of lugs projecting from bearing 18, one end of the lever being forked to engage a block 26 pivoted at 28 to one end of spindle 30. Actuating means for the feed lever comprise a link 32 pivoted at 33 to the other end of the lever and at 34 to a pair of links 36, 38. Link 36 carries a bolt 40 adjustably clamped within an arcuate slot 42 in the end of an arm 44 of a lever 44, 48 which is pivoted at 46 and is provided at the end of arm 48 with a roller 50 engaged in a slot 52 in a cam 54 carried by a vertical shaft 56 which rotates in unison with a main serving shaft 58. The arrangement is such that when bolt 40 is at the outer end of slot 42 the needle remains engaged with the work during the entire feeding stroke, and when the bolt is in an intermediate position, the needle withdraws from the work and is then moved idly by an amount necessary to bring the awl into alignment with the needle opening in the horn. A spacer 70, having radial holes 72, is interposed between the hubs of arms 4 and 10, and also has laterally projecting lugs 74 which enter notches in the ends of sleeves 76 and 77 mounted on said hubs and having flanges engaging the outer surfaces of the latter. Spindle 30, which passes through said sleeves and spacer, is screwed into sleeve 76 and is provided at its outer end with nuts 78. When the latter are loosened, sleeve 76 may be rotated by engaging a pin in successive holes 72 to change the alignment of the needle and awl with respect to the horn. The arms 4 and 10 are formed with laterally projecting lugs engaging radial slots formed in the hubs of cam levers 84, 86, said hubs being journalled on the outer surfaces of bearings 18, 20, and the levers having rollers engaging slots in opposite sides of a cam secured to shaft 58. This arrangement enables arms 4 and 10 to move in the direction of feed while being actuated to and away from the horn. Stitch-forming; loop-takers having two or more loop-taking points.-The shuttle 89 has four loop-seizing beaks formed by slots cut between peripherally arranged teeth 100, Figs. 3 and 7, the latter meshing with the teeth of a driver gear 102. The shuttle contains a bobbin-case 103, and is driven three-quarters of a revolution in each stitch making cycle, whereby each beak is brought in turn to receive a loop of thread from the threaded needle. The loop 104, Fig. 12, of a stitch being formed is extended by a loop-spreader 120 to engage a shuttle beak ; the forward side of the loop, as the latter is extended over the shuttle, then being furnished from the contracting previously formed loop 106, and the other side of loop 104 being furnished from the supply paid out by the horn. Said supply is furnished by a thread controller of the oscillating bell-crank type, such as described in Specification 516,539, the stroke, however, being reduced to furnish not more than half the thread needed from the time the needle is being looped until it reaches the top of its stroke, all the thread required by the enlarging loop 104 being drawn from the preceding loop 106, whereby the latter is contracted into the work and the stitch thereby set. A thread-measuring device, such as described in Specification 516,539, acts on the thread between the thread controller and a wax pat, and comprises a pair of thread locks between which the thread is engaged by a pulloff device actuated by mechanism under control of the presser foot, while engaging the work. Both thread locks are closed while each loop is drawn through the work by the needle, the pulloff arm then moving to provide slack thread between the thread locks. The upper thread lock opens to release the measured thread after the loop is disengaged from the needle and spreader. Means are provided for releasing the thread locks manually, when thread may be drawn through the latter, e.g. for re-threading the machine. The needle is supported laterally by an arm 89, Fig. 2, which engages the needle adjacent the barb, said arm being pivoted at 90 to arm 10 and having an upstanding finger engaging the side of the latter. Arm 89 is biased downwardly by a tension spring 92 and its movement is limited by a set-screw 94 which engages arm 10. As the needle approaches the work, arm 89 engages a shoulder 96, Fig. 12, provided on the presser foot, the latter being carried by a slidable bar 16. The loop-spreader 120, Fig. 2, is an angular arm projecting forwardly and downwardly from one end of a shaft 122 journalled in the machine frame, the end of arm 120 being forked to engage the side of the loop which extends to the preceding loop on the shuttle. Shaft 122 is mounted at an angle to the line of feed and carries at its other end an arm 124 connected by a link 126 to a cam lever 128 engaging a cam on a shaft 130 rotating in unison with shaft 58. The driving gear 102 has three-quarters of the teeth on the shuttle and is connected by a train of gears 134, 136, 140 to a shaft 142. The latter carries a crank which is connected by a swinging link to a crank secured to a further shaft which is offset from shaft 142 and rotates at the same speed as shaft 58. The arrangement is such that shaft 142 is driven at variable speed in such a manner that the shuttle is accelerated as each beak receives a loop of thread, and is retarded after the loop reaches its position of maximum extension. To prevent broken thread from becoming entangled in gear 102, the latter is formed with a circumferential groove engaged by the bevelled edge 214 of a stationary plate 212. The bobbin-case 103 has a base 152, and a side wall formed with two circumferential grooves, one of which, groove 154, provides a bearing for a circular rib on the rear detachable flange 156 of the shuttle, the other groove housing a leaf spring 172 adapted to tension the thread. The bobbin 160 fits over a central hub 164 of the bobbin case and is retained thereon by a pair of spring catches 162 mounted in said hub. The bobbin-case is also formed with a radial flange 166 having a thread-guiding groove 168 ending in a thread-guiding eye 170. A removable wear block is provided in the wall of the bobbin case and is formed with an opening 173 for the thread from the bobbin, a tongue 182 against which the thread is pressed by spring 172, and a thread-guiding groove 180 communicating with grooves 168. The bobbin-case is prevented from rotating by means of the alternate engagement of pins provided at the ends of levers 192, 194 with apertures 184, 186, Fig. 12, provided diametrically opposite each other in the bobbin-case. The levers are pivoted on a pin 196 mounted in a cover 198 for gear 102, the upper ends of the levers carrying rolls 200 engaging face cams 202, 204 on gear 102, the levers being pressed against the cams by coil springs 206. The bobbin is removable from the case by means of an ejector lever 217, Fig. 2, pivoted at 218 on the machine frame, the curved lower end of the lever being movable against the bias of a spring 220 to pass through a hole provided in the base of the bobbin-case. Flange 166 is so formed as to ensure escape of each needle loop from the shuttle beak and to enable each loop to move smoothly towards the work. For this purpose the flange has a flat outer surface which projects radially beyond the outer edge of the shuttle, said surface beyond the flat portion being bevelled, and the outer edge of the flange being formed with a helix, the inclination of said edge to the radius of the bobbin case being greater than the inclination of the slots forming the shuttle beaks. To retain the loops within the slots of the shuttle during rotation of the latter, the shuttle rotates within a two-part raceway 222 fitting between the side flanges 156 and 224 of the shuttle. To prevent the contracting loop 106 being carried about the shuttle a second time, the pin 190 at the end of lever 194 is retained in the bobbincase until engaged by the contracting loop. To prevent slack in the latter while it is being disengaged from the shuttle, a friction spring plate 226, secured at 228 to the machine frame, presses against the outer surface of flange 166, plate 226 being provided with a hole for pin 190 and also with a slot 230 overlying the threadguiding groove 168.