Patent GB-181555-A (GB)
Title: Work-shifting mechanism for sewing machines
IPC: D05B81/00
Filed: 1921-04-21
Abstract: 181,555. Fairweather, W., (Singer Manufacturing Co.). April 21, 1921. Button-hole sewing-machines.-A button-hole sewing-machine is provided with a work-clamp movable for the purpose of spacing the buttonholes in a path of curvature variable between a given maximum and a straight line, the means for varying the curvature being operable while the machine is running. The work is shifted and the button-holes are cut by a lever 12 having a tubular boss 13 in which is fitted a guide-stud 14 secured in a plate 15 positioned by a jaw and stud 16, 17 and carrying a thrust block 20. A spring 19 is interposed between the base of the stud, which rests on the machine frame, and the boss 13, and holds the lever with the cutter 21 in raised position from which it may be depressed to bring the cutter and the block 20 into co-operation. The lever 12 is mounted at one end 23 on a slide-pin 25 slidably and rotatably mounted in bearings 26 of a yoke 27 which is pivoted on a fixed vertical stud 29. The lever carries at its other end a roller 34 engaging the underside of a rail 35. The rail 35 is secured to a slide 36 in which a rod 39 is slidably mounted, a spring 47 being interposed between the head 46 of the rod and the slide 36. A slide 42 mounted on the rod carries a stud 42 adapted to be engaged by a camrib on the main cam 9 to depress the slide 42 which acts through a spring to depress the rod 39 and hence the slide 36 and rail 35 which is turn depresses the lever 12 into nipping engagement with the work. A plunger 53 vibrated by a lever 54 and cam 58 works in a slot in the rail 35 and engages the roller 34 to depress the lever forcibly and cut the buttonhole at the time when the roller has been moved by the shift of the lever 12 to the cutting position. The shaft 59 of the cam 58 is driven by worm-gearing from the main shaft 3 of the machine and drives the cam 9 through gearing 60, 61. The mechanism for moving the lever 12 to shift the work comprises levers one of which is mounted on a rock-shaft 63 controlled by a spring 85. An arm 64 on the shaft carries a stud 65 engaged by a lever 67 fulcrumed at 68 and having a tappet member 72 projecting into the path of rollers 73 on the cam 9. An arm 75 is secured on the shaft 63 and has a sleeve 76 on which is mounted a lever 78 having a series of holes 79 arranged at an inclination to a series of holes 80 in the arm 75. The levers can be connected in different angular relations by a pin 81. A stop-screw 87 on the hub of the lever 78 is held by the spring 85 against a movable stop-plate 88 which is adjustable by a lever 89 as described in Specification 183,256. A ball stud on the lever 78 is connected by a link 83 to a ball stud on the lever 12. A collar 92, Fig. 3, secured on the sleeve 76 is provided at one end of a bar 93 extending forwardly to a hub 94 carrying a steadypin 95 journaled in the frame. A segmental crank-arm 96 extending upwards from the hub 94 has a slot 97 in which is movable a stud 98 carrying a ball-stud connected by a link 100 to a ball-stud carried by the boss 23 of the lever 12. A spring 103 attached to an extension 102 of the link tends to keep the stud 98 in contact with a stop 108 adjustable along the slot 97, and it may be lifted from this position against the action of the spring by the operation of a treadle-chain 106 attached to an extension 105 of the link. The crank-arms 96, 75 and their connections to the lever 12 are so proportioned that when the stud 98 is in its highest position, the effective lengths of these arms are equal and the consequent displacements of their respective connections to the lever 12 when the shaft 63 is rocked are also equal so that every point of the lever moves in a straight line. By adjusting the position of the stop 107, the degree of curvature of the path of the lever 12 and the cutting tool is varied, the adjustment of the length of the path being effected by the levers 75, 78. Specification 185,711 also is referred to.