Patent GB-918725-A (GB)
Title: Lock stitch sewing machine
IPC: D05B57/26
Filed: 1961-11-24
Abstract: 918,725. Sewing machines. SINGER MANUFACTURING CO. Nov. 24, 1961 [Dec. 12, 1960], No. 412074/61. Class 112. In a single-thread lockstitch sewing machine the looptaker bobbin can be wound while the needle and looptaker are operative, commencement of the winding being under manual control at the will of an. operator. The arm shaft 32 is driven by an electric motor 35 contained in the standard 23, and is coupled by a vertical shaft 74 and bevel gearing 75, 751 and 76, 76<1> to a hollow shaft 71 carrying a rotary hook 70. The latter comprises a cupshaped body 120 formed with a looptaker beak and fixed by a screw 122 to shaft 71. A circular groove 123 in body 120 journals a circular rib 127 on a hollow bobbin carrier 128 in which is journalled a bobbin 137 and which is formed with a rotation - preventing lug 129 disposed between a pair of fixed resilient abutments 131. Slidable in shaft 71 is a shaft 164 carrying at its end within body 120 a disc-shaped member 167. A radial arm 168 on the latter is slidably disposed in an opening 169 in body 120 and thereby keys shafts 71 and 164 together. When shaft 164 is displaced to move member 167 inwardly, a pin 171 on the latter enters one of a series of segmental grooves 173 in bobbin 137 to rotate the bobbin, while arm 168 engages the looptaker beak to clamp the needle thread thereon. Further rotation of shafts 71 and 164 then serves to draw the needle thread between a leaf-spring 177 and the side of a slot 176 in body 128 and to wind the thread on the bobbin 137. Operation of a control lever 151 serves to shift shaft 164 for initiating bobbin winding and also for rendering inoperative the thread takeup, the thread tensioner and the work feed. A crank-pin 43 on the needle bar-driving crank 37 is connected by a link 44 to a two-armed thread take-up lever, one arm 48 of which is pivoted at 49 to the machine frame and the other arm has a U-shaped end 46 formed with aligned thread-guiding eyelets 47, 47<1>. The presser bar-lifting lever 55 carries a pin 64 which, on operation of lever 55, engages an abutment 63 on a lever 59 pivoted at 61 to the machine frame, whereby an abutment 62 on lever 59 operates the tension-releasing spindle 58 of a thread tensioner 57 against the bias of a spring 60. The lower end of the control lever 151 carries a pin 154 engaged in the forked end of an arm 157 rigid with a pivoted shaft 154. An arm 220 on the latter is connected by a link 221 to an arm 222 at one end of a shaft 223, the other end of which carries arms 224 and 225. On operation of lever 151, arm 224 co-operates with abutment 63 for releasing the thread tension. Arm 225 carries a pin 226 engaged in the forked lower end of a vertically slidable bar 228. Pivoted at 238 to bar 228 is a bar the upper end 236 of which is slidably engaged between a pair of fixed abutments 234, 235, and the lower end of which is formed with a hook 239. When lever 151 is operated, pin 226 moves bar 228 upwardly, whereby hook 239 swings upwardly to engage the thread between the eyes 47, 47<1> and thereby immobilize the thread take-up. The feed dog 95 is carried by a feed bar 96 pivoted to an arm 98 rigid with a feed advance shaft 87 oscillated, via a pitman 84 from a cam 78 fast with the flat 75 on the arm shaft 32, the feed being controlled by a sliding block 88 mounted in a pivoted arm 90. The feed bar 96 is also connected by a link 103 to one arm of a double-armed lever 102 pivoted on the feed lift shaft 82 which is oscillated by a pitman 79 from an eccentric 77 fast with gear 75. The other arm of lever 102 is adapted to be releasably coupled to an arm 99 fast with shaft 82 by a plunger 108 slidable on a spindle 100 fixed to arm 99. Arm 157 is connected by a link 199 to one arm 195 of a bell-crank lever 194, 195 pivoted on a hollow boss 191 depending from the work-support 22. Arm 195 is also connected by a link 210 to one arm of a double-armed lever 211 pivoted at 212 to the machine frame. The other arm of lever 211 is pivoted to one end of a slidable bar 213 the other end 215 of which is coupled to the plunger 108. Operation of lever' 151 thereby serves to withdraw plunger 108 from lever 102 against the bias of a spring 109, when lever 102 is swung by a spring 111 to lower the feed dog 95 beneath the throat-plate 28. Arm 157 is also connected by a link 159 to one arm 160 of a two-armed lever pivoted.at 161 to the machine frame. A washer 163, slidable on shaft 164, is biased by a spring 165 against the other arm 162. Operation of lever 151 thereby shifts shaft 164 to engage arm 168 with the looptaker beak for initiating bobbin winding. A flange 181 fast with shaft 164 is formed with a cam lobe 182 adapted, when bobbin-winding, proceeds, to co-operate with a ball-headed stud 183 carried on pitman 79, whereby arm 168 is separated from the looptaker beak at each normal loop-taking position in order to insure initial clamping of the thread. A collar 197, fixed to the lower end of boss 191, has pivoted thereto at 203 a two-armed lever the inner end 204 of which is aligned with the axis of boss 191 and the outer end 201 of which is biased by a spring 205 to engage the lower surface of arm 195 adjacent a notch 200 therein. When lever 151 is operated, end 201 thereby enters notch 200 to hold the machine parts in the bobbin-winding position. A pin 250 on the arm 194 normally holds pawls 251 and 252 out of engagement with a ratchet-wheel 196, journalled on boss 191, against the. bias of respective springs 254, 258. Pawl 251 is pivoted at 253 to the machine frame. Pawl 252 is pivoted to one arm of a lever 257 also pivoted at 253, the other, arm being connected by a link 259 and ball-and-socket joint 261 to a stud 262 projecting radially from shaft 82. On operation of lever 151 the pawls will thereby engage the ratchet-wheel 196 to turn the latter counterclockwise, Fig. 3, and to wind up a torsion-spring 266. A spindle journalled in the hollow boss 191 carries at its upper end a disc 278, and at its lower end an arm 276 to which is pivoted at 274 a two-armed lever whose inner end 273 is aligned with the axis of boss 191 and underlies end 204, and whose outer end 272 carries a ball-headed stud 271 located in the path of movement of a cam block 270 depending from ratchet-wheel 196. Rotation of wheel 196 causes block 270 to engage stud 271 and thereby disengage end 201 from notch 200 to terminate the bobbin-winding operation. The length of thread wound is determined by the position of stud 271 as set by the disc 278. A two-armed lever also pivoted at 203 has its inner one end 291 aligned with the axis of boss 191 and its outer end 292 engaged by the upwardly-biased operating arm 293 of an electrical switch 294. A two-armed lever also pivoted at 274 has its inner end 296 aligned with the axis of boss 191 and underlying end 29<1>, while its outer end 295 carries a ball-headed stud 297 disposed adjacent stud 271 in the direction of approach of block 270. At the commencement of the bobbin-winding operation when end 201 rises into notch 200 arm 293 is released to close switch 294 for illuminating a signal lamp or sounding a bell or buzzer. Towards the end of the operation block 270 engages stud 297 to open switch 294. Switch 294 may also be arranged to disconnect the driving motor 35 towards the end of the bobbin-winding operation.