Patent GB-946671-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B93/00
Filed: 1959-01-27
Abstract: 946,671. Sewing machines. BRITISH UNITED SHOE MACHINERY CO. Ltd. (United 'Shoe Machinery Corporation). April 26, 1960 [Jan. 27, 1959], No. 2856/59. Heading D1G. The work-support in a sewing machine is provided with an electrically-heated threadsevering member in the former of a U-shaped plate, one arm of which is bonded to the work support and the other arm of which is connected to an electric circuit. As shown, the upper and lower threads in a "loop lock stitch" sewing machine for attaching soles to footwear are severed close to the work when the latter is raised from the work support at the end of a stitching operation. Starting and stopping Figs. 2, 4, 10. A rod 62 connects a treadle to a lever 298, and a rod 302 connects the latter to a swinging cam 68. Collars 304, 306 on rod 302 embrace the end of a lever 56 coupled to the main driving clutch. When the treadle is depressed, lever 56 is actuated for imparting drive to the main shaft 52, and cam 68 engages a roller 70 to rock a lever 72. The latter engages one arm of a lever 76 which is thereby rocked, against the bias of a spring 332, about a pin 326 which passes transversely through a pivoted shaft 322. The other arm of lever 76 is thereby moved out of alignment with a cam 74 on shaft 52. When the treadle is released, the main clutch is disengaged and lever 72 actuates clutch and brake means adapted to stop the machine with its parts in predetermined position, while the second arm of lever 76 moves into alignment with cam 74. Lever 76 is thereby rocked with shaft 322 and transmits motion, via a lever 78 and link 80, to a lever 82 pivoted at 84. One arm of lever 82 is engaged with a lever arm 86 on a shaft 88, and thereby rocks the latter against the bias of a spring 320, when a rod 92 connecting a lever arm 90 on shaft 88 to the presser foot raises the latter from the work support 12. An abutment on cam 74 co-operates with lever 76 to prevent shaft 52 from over-running its predetermined stopping position. A stud 346 on a lever arm 344, rigid with a pivot 342, is biased into engagement with lever 76 by a spring 348. A lever arm 34, also rigid with pivot 342, is thereby moved to position an abutment 338 thereon in alignment with an abutment 336 on lever 82, in order to hold the presser foot in the raised position. Stitch-forming Figs. 2, 3, 25. The machine, in its stitch-forming aspect, is a modification of the machine described in Specification 804, 854, and is adapted to sew a shoe welt 30 to an outsole 32 by 'loop-lock' stitching. An awl 4 pierces the work for the passage therethrough of a curved hooked needle 2, the thread 42 for which is laid in the needle hook by a looper 8. The loop of withdrawn thread 42 is expanded by a spreader 6, and a loop of locking thread 44 is inserted into the expanded loop by a thread-carrying finger 26, the locking thread loop then being engaged by a detaining finger 28 while the finger 26 is being withdrawn. The thread loop is detached from the needle hook, while the stitch is being set, by the bevelled lower end 424 of a finger 423. The loop spreader 6 is rigid with a shaft 442 oscillated by connections 446, 448, 450 from machine upper shaft 54. The loop shedding finger 423 is fixed eccentrically to a shaft 430 which is oscillated by the co-operation of a roller 438, mounted on an extension 436 of shaft 430, with a cam sector 440 carried by an arm rigid with shaft 442. The thread-carrying finger 26, which is arranged to rise and fall with the presser foot 14, is rigid with a bar 492 which is pivoted at 494 to a bracket 120, the latter being rigid with the presser foot 14 and being pivotally mounted on the work-feed carriage. Bar 492 is oscillated via connections 500, 502, 505 from the shaft 54. The locking thread 44 passes through the respective arms of a U-shaped bracket 212 and is deflected therebetween at each stitch by a roller 506 carried by one arm 510 of a threadmeasuring bell crank lever, the other arm 516 of which is connected by a link 518 to a lever 520 pivoted at 522 and oscillated from shaft 54. The hub 528 of lever 510, 516 has a cam-shaped end which co-operates with a pivoted finger 530 in order to clamp the thread 44 between the latter and a fired bracket 514 while the roller 506 is withdrawing thread from the supply. Needle guides. Fig. 3. The free end of the oscillating lever 520 is formed with a rack cooperating with a gear pinion 524 operatively connected to a needle guide 526 movable along the needle to stiffen it as it enters the work. Thread tensioners. Fig. 3. The locking thread passes under one arm of a torsion spring 228 the other arm of which is fixed to the bar 492 carrying the thread-inserting finger 26. Thread cutters, thread controlling, work holding. The needle and locking threads are adapted to be severed, closely adjacent the work, by their engagement with respective electrically heated elements. The work support 12, Figs. 2, 21, is formed with a work-supporting surface 106 intersected by an opening 108 allowing passage of the needle 2 and awl 4. A U-shaped heating element 94 has one leg secured by a screw 97 to the support 12 and the other leg, which is insulated by a porcelain coating thereon from the support 12, is connected to an electric cable. The base projects through an opening in the support 12 and is aligned with the side of the opening 108. A double-armed lever 112 is pivoted to the support 12, one arm being connected by a link 248 to the armature 252 of a solenoid 256. The latter is energized at the end of a stitching operation, whereby the corrugated face end of the other arm deflects the needle thread 42 against the heated element 94 and, after severing the thread against a closed thread lock, clamp the thread against a corrugated shoulder 115 of the support 12. A similar heating element 116, Fig. 3, is earned by the face end of a bar 118 fixed to the bracket 120 which is rigid with the presser foot 14. Element 116 is so positioned that when the work is raised from the full line to the dotted line position shown in Fig. 3, the locking thread 44 engages the heated element 116, when continued movement of the work serves to sever the thread. Element 116 is situated at a distance away from the thread finger 26, when the machine is at rest, equal to the amount of thread required for one stitch. A deflector plate 122, adapted to shield the body of the work from the heated element 116, is secured to the bar 118 and is forked in the vicinity of element 116, one arm of the fork being extended into contact with the presser foot 14. In a modification, Fig. 37, one leg of a U-shaped heating element has a boss 458 sweated into a hole in the work support while the other leg, which is connected to an electric cable 472, rests on a porcelain coating 468 on the support and is fixed to the latter by an insulating plug 464. The work is shielded from the heated base of the element by a U-shaped bar 480 having a porcelain coating on its undersurface and its legs detachably engaged in holes 474 in the work support. The elements 94 and 116 are respectively energized through double-throw switches 312, 313, Fig. 4, operated by an extension of the lever 298 associated with the starting and stopping treadle. The arrangement is such that when the treadle is depressed and the machine is operating, the elements are maintained at a comparatively low temperature, and when the treadle is released to stop the machine the elements are heated to thread-severing temperature for a period of about 8 seconds, when time delay relays act to switch off the elements. The solenoid 256, operating the lever 112, is controlled by a switch 350, Figs. 4, 10, which is closed, when the treadle is released, by an arm 352 pivoted on shaft 88 and held in engagement with the front edge of lever 86 by a spring 356. Arm 352 is retained in the switch-closing position by a latch plate 360 pivoted at 362 and connected by a link 364 to a pivoted arm 366 carrying a roller 372 engaging a disc 374 on shaft 52. A cam lug 376 on disc 374 is adapted to rock arm 366 for releasing the latch after the first stitch of a new seam has been inserted. A needle thread pull-off, actuated at the end of a stitching operation, comprises a bar 150, Fig. 33, slidably mounted on a fixed block 166. One end of bar 150 is arranged to engage the thread 42 at a point in its passage from a wax pot 146 to a pulley 144, to deflect the thread against an adjustable measuring arm 152. A bar 182, fixed to the lower end of lever 82, Fig. 33, has pivoted thereto at 180 a finger 176, whereby, when lever 82 swings on release of the treadle for stopping the machine, an abutment 178 on finger 176 engages a plate 174 adjustably fixed to bar 150 and moves the latter to its operative position. The movement of bar 150 is limited by the engagement of the curved front end of finger 176 with a finger 164 fixed to block 166, whereby finger 176 is raised to disengage abutment 178 from plate 174, when a spring 188 returns bar 150 to its inoperative position. A locking-thread pull-off, actuated at the end of a stitching operation, comprises a lever 210, Figs. 2, 3, 8 which is pivoted at 232 and is connected to the armature 262 of a solenoid 258 by a link 244, the connection between which and lever 210 is adjustable. Solenoid 258 is energized, when the treadle is released to stop the machine, by a lever arm 293, Fig. 4, on shaft 88 moving to close a switch 316. Lever 210 then swings to deflect the thread 44 on its passage between a fixed plate 208 and the upper arm of the U-shaped bracket 212. Lever 210 is retained in the displaced position by the engagement of an abutment on the armature 262 with a notch in a latch plate 268 adjustably fixed to an arm 234 also pivoted at 232. A flexible wire 282, enclosed in a sheath 284, has one end coupled to the lever arm 293 and its other end positioned freely adjacent the arm 234. When the treadle is depressed to start the