Patent GB-479484-A (GB)
Title: Buttonhole sewing machine
IPC: D05B73/12
Filed: 1937-08-20
Abstract: 479,484. Sewing - machines. FAIRWEATHER, W. C. (Singer Manufacturing Co.) Aug. 20, 1937, No. 22824. [Class 112] In apparatus for sewing an eyed and barred pyramid purl lock-stitch buttonhole, the needle moves endwise and laterally and the feeding means move the stitch forming devices and work-holder relatively to sew round the buttonhole, the stitch-forming devices turning about an axis normal to the plane of the work. The buttonhole cutting mechanism and stop mechanism is of known construction. In operation, the work is placed in the open work-clamp 114, 130 and the starting button pressed. This exerts a down-pull on the starting rod 290 and initiates the action of the clamp-closing mechanism. The three-armed lever 269, Fig. 1, receives one oscillatory impulse from the camgroove 289, Fig. 8, in the fly wheel 288. In the down. - motion of the forwardly extending arm of the lever, the work-clamp is closed and in the return movement of the lever its.depending arm depresses the arm 267 on the rock-shaft 266 and trips the latch 234, Fig. 36, to effect the coupling of the cross-shaft 153 to the rapid-feed shaft 231. The connected feed and pattern wheels 126, 152 are then rapidly driven to effect a rapid forward shift of the work - clamp from its initial retracted position to a position at which the stitching begins. When the work-damp reaches the sewing position, the cam incline 173, Fig. 3, on the pattern wheel 152, engages the follower nose 172 on the lever 170 and shifts the stopmotion device 163 to the dotted-line or running position, in which position it is retained by the latch 174. At the same time the tripping point 264, Fig. 36, acts on the lever 262 to trip'the latch-lever 256, Fig. 10, and effect the throw-out of the rapid feed mechanism. The sewing then proceeds down the first side of the buttonhole, round the eyelet hole and back along the return side of the buttonhole, during which sewing the feed - and pattern - wheels are driven more slowly and in step-by-step fashion through the clutch-mechanism 179, 177, Fig. 14, with the shafts 8 and 5 which drive the stitchforming mechanism. When the stitching along the return side of the buttonhole reaches a point even with the initial stitches, the bevelled nose 158 of the block 157, Fig. 36, on the pattern-wheel shifts the lever 147 to centralize the work-clamp relative to the vibrating needle 18 and, simultaneously, shifts the lever 161 to move the lever 57 and increase the amplitude of the needle for the bar-stitching operation. The shift of the lever 57, Fig. 10, effects the tripping of the latch 199 and allows the clutch-lever 194 to spring upwards to disconnect the feed- and pattern-wheels from the main sewing shaft 5 so that they come to rest. Also, the up-motion of the clutch-lever 194 permits the spring-biassed holding-pawl 240, Fig. 3, to rise and start the bar-stitch counting mechanism consisting of a toothed sector 212, stop arm 214, pawl 220 and lever 221. The number of barring stitches is determined by setting the pointer 218 at the appropriate place on the scale marked on the frame. The position of the pointer and consequently of the lever 215 determines when the constantly reciprocating push bar 226 is engaged by the latch 234 to connect it with the barring mechanism. When a given number of bar-stitches have been sewn, the shoulder 244 of the toothed sector 212 engages the latch 174 and trips the stop-motion device, allowing the stop-motion lever 163 to spring back to the full-line or stopping position, Fig. 3, to stop the stitching mechanism. The rising and falling of the stop-motion tooth 165 effected by its engagement with the notched stop-cam 166, Fig. 1, - imparts an impulse to the rapid feed trip arm 270 which engages and shifts the arm 268 on the rapid feed start-control shaft 266 to throw in the rapid feed and effect the rapid return of the work-damp to its initial position in rear of the stitch-forming mechanism. In this action, the movement of the slide-rod 251, Fig. 10, to the left carries the stud 253b against the inclined edge 261 of the clutch control lever 194 and depresses the latter to reconnect the feed- and pattern-wheels to the main-shaft 5 for the next buttonhole-producing cycle. The down-motion of the lever 194 also carries the arm 240 of the bar-stitch-counting mechanism downwardly to the position shown in Fig. 3, and thus disengages the pawls 220 and 237 from the toothed ,sector 212 which springs back into engagement with the stop 214. Buttonhole cutting. When the work-clamp reaches its initial or retracted position, the tripping point 315, Fig. 5, on the gear wheel 154 swings the lever 316 about its fulcrum 317 and shifts the cutter-shaft-control gate 285 inwardly to initiate the action of the cutter-shaft 280 which performs one complete rotation and effects the cutting of the buttonhole slit s, Fig. 2. By providing for circular adjustment of the tripping points 173, 264, 157 on the pattern wheel 152, square-barred eyelet-end buttonholes of various lengths may be produced. Alternatively, a set of interchangeable pattern-wheels 152 may be provided for this purpose. The buttonhole cutter levers are provided with a punch and die of proper length for the hole to be made. Take-up mechanism. The needle thread t, Fig. 23, runs from the supply to the tension 300, thence to the tension 299, thence round the guide-pin 318 and through the check spring 319 to the take-up 294. From the take-up 294 the thread leads forwardly through the stationary guide 320 adjacent the upper end of the hollow thread-conducting needle - bar 13, and thence down through the needle-bar and through a hole in the needle clamp-block 20 to the needle 18. The shuttle. mechanism is of known kind. The needle-vibrating mechanism may be as described in Specification 483,533. The needle block carrier has a pinion 23 engaged by a sector 129 worked in unison with the turret 65 for turning the needle about a vertical axis when sewing round the eyelet-end of the buttonhole.