Patent GB-153377-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1919-07-31
Abstract: 153,377. British United Shoe Machinery Co., (United Shoe Machinery Corporation). July 31, 1919. Boot-sole sewing-machines; lock-stitching; feed by awl.-Adjacent stitches in a single line of simple lock-stitches are formed in one cycle of operations by means of two barbed needles piercing the work and drawing thread loops simultaneously and a shuttle having two horns which passes its thread through the needle-thread loops in turn. The first of the two stitches is set by the usual take-up devices and the second by the shuttle in which, for this purpose, the shuttle thread is periodically locked. The lock of the first stitch is made near the top of the work, Fig. 27, and the lock of the second stitch near the bottom. The method of operation is as follows : -After the two awls have risen through the work and the feed has taken place, the needles descend through the awl holes. The looper L, Figs. 19 and 27, moves to the left and the thread from the last preceding stitch is bent around a needle support 30 and laid over a thread hook 70, then in the barb of the left-hand needle, thence around a thread hook 71, between the two needles, and is finally laid in the barb of the second needle, all as shown in Fig. 19. The strain exerted by the thread upon the first needle is resisted by the needle support 30, which engages the side of the first needle as soon as it has descended through the work and just as the looper lays its thread in the needle-barb. The longer loop 300, held by the left-hand needle and the thread hook 70, is of sufficient length to permit the needle to move back and the thread to pass over the shuttle without reeving of the thread in the barb ot the needle or around the material between the first needle and the second needle. The second loop 310 is much shorter and is only sufficient to permit the needle to move back to its extreme position without the thread reeving in its barb. The other half of the thread for the loop 310 is drawn by the shuttle from below the work. After the needles have carried the loops through the work, a spreader or thread-lifter 220 lifts the outer sides of the needle loops and distends them to the positions shown in Fig. 23, in readiness to receive the shuttle horns. A rigid shuttle horn 171 and a spring-held horn 210 enters the needle loops, the horn 171 entering both loops and the spring-held horn 210 entering the left-hand loop only. The horn 210 in taking the loop 300 separates it from the loop 310, and the latter is cast off from the shuttle before the former. At the time the needles start upward, a lower thread retainer 91 is thrust forward between the two needles, and the thread extending on the lower side of the work from the first needle hole to the second needle hole is drawn up against this lower thread retainer and sufficient thread is retained thereby for the sinking of the lock of the second stitch in the work. Also an upper thread retainer 240 is thrust between the two loops 300 and 310, retaining sufficient shuttle thread between the last completed stitch and the second stitch being formed, position 5, Fig. 27, to allow the. setting of the look of the first stitch down into the work. The shuttle casts off the second loop 310 from the shuttle in the usual manner, and the thread is drawn through by the take-up; the needle thread being locked at this time, to prevent pulling off thread from the tension during the takeup operation. As the second loop 310 is pulled back through the work, it pulls back with it the shuttle thread. A loop of the shuttle thread is thus drawn out below the work, as shown in position 5 of Fig. 27, and thereupon the spring horn 210 yields under the tension of the thread and releases the loop 300 which is drawn back by the take-up. The upper thread retainer 240 is then withdrawn from under the shuttle thread and the needle thread engaging the slack shuttle thread above the work, pulls the lock down into the work, as shown in position 6 of Fig. 27, thereby setting the first stitch in the work, as shown. Now the lower loop retainer 91 is withdrawn from under the work, and the shuttle, on its backward movement, takes up the loop of shuttle thread, pulls the needle thread into the work, and sets the second stitch. In order to prevent the displacement of the threads in the second needle hole during this shuttle take-up operation, an abutment 250 is laid alongside of the shuttle thread, as shown in Positions 6 and 7, thus forming a support over which the shuttle thread reeves in setting the stitch. The needlethread control mechanism is shown in Fig. 6. It includes a tension wheel T, thread lock 101, thread measurer 102, thread lock 103, slack thread controller 105, a take-up arm 110, the thread passing twice over the slack thread controller and the take-up arm, and a terminal guiding eye 111. The slack thread controller is normally locked by a latch 143, but at the inner limit of its movement the take-up arm 110, by means of a projection on it and a pin 142 on the latch 143, releases the slack-thread controller and permits its spring to move it to take up any slack thread. The shuttle oscillates from the position shown in Fig. 19 through about threequarters of a revolution, and in the early part of its return movement it acts as a shuttle thread take-up to set the second stitch. For this purpose the thread is lead from the shuttle through an eye 182, Fig. 19, in an adjustable slide 181 by which the throw of the eye can be regulated. It is also led through eyes in a pivoted plate 176 on the spool case, the plate being pressed on to the spool case, to nip the thread, by means of a plunger 190 and a ball 191 when the latter is passing over the inwardly-projecting edge of the plate 192. The other parts of the machine are similar to those described in Specification 7793/92.