Patent GB-335092-A (GB)
Title: Thread-cutting mechanisms for sewing machines
IPC: D05B65/00
Filed: 1929-10-26
Abstract: 335,092. Fairweather, W., (Singer Manufacturing Co.). Oct. 26, 1929. Buttonhole - sewing machines; thread-cutters and thread-end holders.- A button - sewing machine is provided with a thread cutter which not only cuts the needlethread close to the work at the end of a sewing- operation and holds the end for the beginning of the next sewing operation, but also retrims the beginning end of the needle-thread close to the work. The invention is illustrated as applied to a " straight " lock-stitch buttonhole sewing machine. The needlebar 7 is carried in a gate 6 and actuated by suitable connections from the main shaft 9, the period of action being controlled by a stop-motion device 10. A tilting lever pivoted at 11 carries the spring plunger 12 which, when shifted into range of the stop-cam 13 on the gear 13', is first depressed by the portion 14 and then projected upwards by the spring 15 into a stop-notch 16 in the cam. The gear 13<1> is rotated at half the speed of the main-shaft by the pinion 17. The plunger 12 carries an arm 18 which, when the lever 11 is released from its running position (dotted lines Fig. 2), strikes the plunger 19, driving it endwisa into its carrier boss 20 on the arm 21 fixed to the rock shaft 22. When the plunger 12 is depressed by the eccentric 14, the arm 18 is carried below the plunger 19, which is then projected rearwardly. When the plunger 12 is projected upwards by the spring 15 into the stop-notch 16, the arm 18 lifts the plunger 19 and thereby gives a rocking impulse to the shaft 22. This lifts a latch extension above the end of a rod 38, releasing the rod to allow the spring 40 to draw it rearwards to close the jaws 35, 36 to cut and nip the end of the needlethread after the stitching of the buttonhole. To trim the long thread end so left, a disc 46 with timing holes is carried by a feed cam shaft 45. A pin 48 on the cam 49 loosely mounted on the shaft 45 enters one of the holes and is pressed forwards by the spring 50. The cam 49 is lifted and turned for adjustment, the pin 48 entering the desired hole. The cam 49 engages the lever 52 pivoted on the plate 54 and connected to the lever 56 by a link also pivoted to the plate 54. An upturned end 58 of the lever 56 engages the block 59 secured to the threadcutter operating rod 38 and pushes the rod forwardly to open the thread cutter. When the point of the cam 49 passes the lever 52, the rod 38 is released and the thread cutter closes upon and retrims the end of the needle-thread. The cam 49 is so timed that the beginning end of the thread will be held nipped until after the first barring stitches are formed, after which the end is released and retrimmed early in the sewing of the second or return side of the buttonhole. When the machine is started, the beginning end a of the thread is nipped as shown in Fig. 8. The sewing continues down one side of the buttonhole with the end a held till the first barring stitches c, Fig. 11, are formed, whereupon the blades 35, 36 are actuated to release and return the end a, leaving only the short end d. The feed shaft 45 makes one rotation per buttonholeproducing cycle and is driven from the mainshaft 9 by suitable gearing. The work clamp and feed-frame are of usual construction.