GB832726A - Improvements in or relating to thread severing devices in sewing machines - Google Patents

Abstract

832,726. Sewing machines. PFAFF A.G., G. M. Oct. 1, 1957 [Oct. 11, 1956], No. 30635/57. Class 112 Thread cutting, stitch forming, starting and stopping. In a single-thread chain-stitch sewing machine having a rotary looper, a loop-deflector which serves to locate the preceeding loop with each stitch has arranged thereon a threadseverer and is adapted, after the last stitch of a series, to perform a thread-severing movement which deviates from its normal loop-deflecting movement A shaft 6 driving a rotary looper 7 carries a cam 8 which co-operates with a follower 10 on a shaft 9 to rock the latter. Shaft 9 carries an arm 26 to the free end of which is secured on opposite sides, by means of a screw 28, a loop-deflecting finger 27 and a thread-cutting blade 29. Shaft 9 is so biased axially by a spring 34 that the base of arm 26 normally abuts a bearing sleeve 32. In normal operation each preceding loop 67 is deflected to one side by being engaged between arm 26 and finger 27, so as to position the loop accurately for entry of the looper beak carrying the succeeding loop 68 from the needle 66. When the machine is stopped, shaft 9 is displaced axially, so that the point of arm 26 enters loop 67, whereby blade 29 engages and severs one arm of the loop close to the throat plate. It is stated that the blade may be replaced by a hook or the like adapted to break the thread instead of cutting it. Shaft 9 at its rear end is provided with a lug 35 which is normally disposed outside an aperture 37 in a disc-like member 36 journalled on shaft 9. Member 36 is connected by a link 41 to one arm of a bell crank lever 43, the other arm of which carries a stud 46 disposed adjacent the lower end of a starting and stopping lever 18 journalled on a shaft 58. The upper arm of a lever 57, also journalled on shaft 58, is drawn by a spring 60 into engagement with a stud 65 carried by a bracket 63 fixed to the upper arm of lever 18. A surface 59 on the lower arm of lever 57 lies adjacent an arm of a lever 51, the other arm of which carries a stud 55 disposed adjacent the end of shaft 9. The lower end of lever 18 carries a notched block 17 which, in the running position of lever 18, is engaged by the pawl end 16 of a lever 15. The other end of the latter carries a follower 14 which is engaged, at the end of a stitching cycle, by a stopping cam 13 carried on the periphery of a pattern cam wheel 12. Lever 18 is thereby released, and swings to move a fork 19 for shifting a driving belt 20 from a fast pulley 22 to a loose pulley 21. A member 23 on lever 18 also engages a rotary disc 14 and after running down an inclined portion in the latter, engages a groove therein to stop the machine. During the first part of the movement of lever 18, spring 60 serves to swing levers 57 and 51 for shifting shaft 9 axially, and during the final part of said movement lever 18 engages stud 46 to rock shaft 9, via-lever 43, link 41, member 36, a face 38 of aperture 37 and lug 35, for severing the thread.