Patent GB-106310-A (GB)
Title: Thread Cutting and Controlling Mechanism for Sewing Machines.
Inventor: FAIRWEATHER WALLACE
IPC: D05B57/02
Filed: 1916-05-15
Abstract: 106,310. Fairweather, W., (Singer Manufacturing Co.). May 15, 1916. Sewing-machines; buttons, attaching; threadcutters and thread-end holders.-In a sewing- machine for forming successive groups of stitches between which the thread is severed, such as is described in Specification 4051/04, means are provided for simultaneously clamping the needle-thread above and severing it below the work, and also for providing a sufficient amount of slack in the needlethread to ensure the formation of the initial stitches in each new operation. The invention is described as applied to a machine for attaching flat buttons and having a single chain-stitch rotary looper, but is stated to be applicable to other types of machine. The thread-severing device 438, Fig. 5, is formed at the end of the long arm 437 of a bent lever which is pivoted to a bracket 434 attached to the underside of the throat-plate 433 and which carries on its short arm 436 a pin 439 engaged by the slotted end 440 of an arm 441 of the cutter-bar 442 supported in bearings under the bed-plate and extending to the rear of the machine. The rear end of the bar has a pin 444, Fig. 1, which is engaged by a slot in one arm of a bell-crank lever, the other arm 448 of which is adapted to be operated automatically by the stop lever 417 at the ccmpletion of each group of stitches. The thread-clamping device consists of two plates 454, 455, Fig. 6, secured to the faceplate of the machine, the inner plate having slotted lugs 456 embracing the outer plate and providing a guide for the thread. The plates are normally spaced apart and are moved together to clamp the thread at the completion of the stitching operation by a lever 460, pivoted to the block 459, and operated by an inclined face on the stop-lever 417 engaging the rear end of a push-bar 462 in two parts with an interposed cushioning spring 465. The slack-thread producing device comprises a lever pivoted to the bracket 470 concentrically with the tension disks 469, and having an arm 473 with a thread-eye 474 engaging the thread between the take-up on the needle-bar and n fixed threadguide 472. An arm 475 of this lever is connected through the link 476 to one end of a rocking lever pivoted at 478, the other end of which is pressed against the periphery of the usual control camdisk by a spring and engages, during the final stitches of a group, a stepped cam 480 by which the arm 473 is progressively raised and the amount of thread drawn off the supply proportionately increased. The rock-lever end drops off the high end of the cam 480, at the beginning of a new group of stitches, in one step leaving a sufficient amount of slack thread to ensure the formation of the initial stitches before the take-up comes into action. The stop-lever 417 is pivoted on a cross-pin 418 in a rocking plug 419 mounted in a socket 420 and carries at its upper end a spring-pressed plunger adapted to engage the stop cam 413 secured to the fast pulley 412. It is held out of contact therewith against the action of a spring by a spring catch 426 which is tripped at a predetermined time by a projection on the inside of the control cam-disk thus allowing the stop-lever to come into register with the stop cam 413 and shift the belt to the loose pulley 411. At the same time, a slot in the tail 417<1> of the lever engages the arm 448 of the bell-crank lever operating the cutter-bar. The lever 417 is thrown sideways against the action of a buffer-spring when its end contacts with the stop on the cam 413 to stop the machine in the required position, and this movement simultaneously operates the threadclamp and cutter mechanism. The parts are restored to their working positions by a treadleactuated lever 428 which bears on the rear side of the stop-lever.