Patent GB-525292-A (GB)
Title: Thread and cord trimmers for buttonhole sewing machines
IPC: D05B3/06
Filed: 1939-02-17
Abstract: 525,292. Sewing-machines. SINGER MANUFACTURING CO. Feb. 17, 1939, No. 5268. Convention date, Sept. 8, 1938. [Class 112] In a buttonhole sewing-machine, the needlethroat member is moved downwardly and away from the last stitch, after the sewing is completed, to draw a length of under-thread through the throat, means being provided to cut the thread ; the stay-cord, if used, is drawn out and cut by the same means. The invention is particularly applicable to a machine of the kind in which the hole is cut first and the sewing operation does not include barring, and is directed to the elimination of the waste thread and cord connecting successive buttonholes while leaving sufficiently long ends to be effectively secured by the barring operation subsequently performed on another machine. Since the scissors cutting the under-thread act at a distance from the last stitch, scissors clearance slots in the work clamp plates, which interfere with the uniform clamping and spreading of the work, are unnecessary. In the machine shown the usual feed-cam 17 and pattern cam shaft 28 are used, with rapid and step-by-step feed mechanisms arranged and controlled as described in Specification 507,318. Work - clamps.-The lower work - plates 56, Fig. 6, are mounted for spreading on a plate 75 which is movable laterally and longitudinally of the machine; the clamping feet 57, carried on arms 58 pivoted to the plates 56 at 59, Fig. 1, are lowered against springs by cams on connected rock-shaft sections 61 actuated by the lever 64 engaging an arm 63 on one of the shafts 61, which also carries a finger-piece 62. The clamps are held closed by a spring latch 66, fixed on a shaft 68, engaging behind an abutment 67 on the shaft 61. The shaft 68 carries a spring-pivoted transverse arm 72 arranged to be engaged by an arm 206 on the actuating lever for the under-thread scissors. The clamps are spread by toggle mechanism 77, 79, 80 actuated by a lever 83 operated from a cam on the buttonhole-cutter shaft 129, the front ends being spread by a wedge 91 actuated by a lever 89 and link 87 from the lever 83; the clamps are unspread when the arm 72 is actuated, by this arm engaging an abutment 208 on the link 87. The work-plates 56 carry cord-positioning plates 209, 211. Threads and cord, controlling, cutting and holding.-The lower stitch-forming devices, Figs. 14 and 19, comprising a threaded looper 6, non- threaded looper 7 and complementary loopretainers 8, 9, are carried by a turret 10 operated as usual from the feed-cam. The needle throat member 31, having an elongated needle hole and cord-guiding holes 32, Fig. 23, which keep the cord clear of the thread handling and needle-thread cutting devices and holds it in the throat member, is also carried on the turret 10 by a yoke 33 pivoted at 34 to the turret and held in the normal position by a spring latch 35, pivoted at 37, engaging a tail 36<SP>1</SP> on the yoke 33; the pivot 37 has an arm 49 with a spring-pivoted member 51, biassed against a stop 52, which rides over a cam 54 on the machine frame during the rotation of the turret but operates the latch 35 only on the return rotation of the turret. The yoke 33 is operated from a cam on the shaft 28 through a lever 43 connected to a lever 38 which has a forked end engaging a pin 36 on the yoke; the cam is formed so as to give the yoke a slight movement at the moment of unlatching, to prevent relatching when the member 51 rides off the cam 54, the main movement of the yoke and throat member taking place when the rotation of the turret is completed. The movement of the throat member 31 to the position shown in Fig. 19 pulls off looper thread and cord ready for starting the next cycle, carries the looper thread past a horn 135 on the needle-thread cutter blade 133 if it is not already engaged therewith, so that the end of the looper thread is held against the loop detainer 9 for starting the next cycle, and draws the thread and cord away from the underside of the work to facilitate cutting. The return motion of the throat member 31 engages the end of the cord between the positioning plates 209, 211 on the clamps, as shown in Fig. 23, and draws some of the slack cord through the throat; the underside uf the plate 209 may be roughened to assist this. The scissors comprise a fixed blade 144, Figs. 4 and 14, and a moving blade 149, both carried on a pivot pin 148 on a lever 145, the blade 144 being adjustably fixed by a clamping screw 157 and the blade 149 being operated by a pin 150 on it engaging a member 151 which is pivoted at 152 on the lever 145 and has a pin 154 engaging a cam slot 155 in a fixed plate 156. The lever 145 is actuated by a link 159 and arm 160, Fig. 1, from a cam on the shaft 28. An arm 206 rigid with the arm 160 moves the arm 172 on the clamp latch shaft 168 aside during the advance of the scissors, but engages this arm on the return motion to release the clamp latch and unspread the clamps. The cord passes through a tension device 178, Fig. 1, on an arm 179 frictionally pivoted at 180 and moved up, to give slack cord 'during the formation of the buttonhole eye and before cutting, by pins 186 on a disc 187 on the shaft 28 engaging a branch 184 of the arm, the return movement being effected by similar pins on the other side of the disc engaging a branch 183 of the arm. The looper thread passes over an ordinary double-disc tension device 165, Fig. 4, which is released during the rapid feed by an arm 167 on a lever 166 pivoted at 168 and actuated by an arm 170 on a rock-shaft 171 which is operated by the stop gear 5. The needle thread passes from the tension device 202, Fig. 1, through the take-up eye and then through a thread nipper comprising a post 192 with a thread-hole and a sliding spring-pressed nipping collar 198 operated by a lever 196; a sliding rod 200 connected to the clamp-closing lever 64 has a horizontal end engaging under the lever 196 and over the thread, so that when the clamp is closed the nipper is closed and a measured length of thread is pulled off and on recovery of the lever 64 the nipper is opened for the pulled-off thread to pass to the needle. The needle thread is cut, early in the return rotation of the turret 10, by a blade 133, Fig. 14, with cutting edge 134, on an arm 136 pivoted to the turret at 137 and carrying a spring-pivoted member 140 similar to the member 51 to engage a fixed cam block 143. A hook 135 on the blade 133 catches and holds the looper thread on the return movement.