Patent GB-1061662-A (GB)
Title: Improvements in or relating to automatic underthread winding apparatus for lockstitch sewing machines
IPC: D05B59/00
Filed: 1965-07-29
Abstract: 1,061,662. Sewing machines. G. M. PFAFF A. G. July 29, 1965 [July 30, 1964], No. 32386/ 65. Heading D1G. The looptaker of a lockstitch sewing machine is provided with a pair of bobbins, the arrangement being such that a preselected quantity of thread is drawn from one bobbin during stitch formation, whereupon a further preselected quantity of thread is wound on the other bobbin while the machine is stopped, and on resumption of stitching thread from said other bobbin is drawn after exhaustion of the remainder of the thread on the first bobbin. A rotary hook 12 has an outer body 14 fast with a hollow shaft "11", Fig. 4 not shown, carrying a gear 10 meshing with a gear on a driven bed shaft 8. Body 14 is journalled on a stationary outer bobbin case 15 releasably holding an inner bobbin case 26. The side walls of the bobbin cases are formed with respective aligned apertures 20, 34 with which an aperture 25 in the side wall of body 14 is aligned when the needle 13 is fully raised. Bobbin case 26 has a central pin (27) Fig. 4, on which is journalled a first bobbin 28, the hub of which has an extension 40 journalling a second bobbin 29. Each bobbin, is provided, adjacent its inner flange with a resilient annular disc 48 formed with a radial thread-guiding slot 51, Fig. 7 not shown. A hollow shaft (53), Fig. 4, slidable in shaft 11, carries at its outer end a coupling disc 60. A shaft "54", slidable in shaft 53, carries at its outer end a coupling disc 61. Shafts (53, 54) are movable inwardly, against the bias of a spring 62, into driving engagement with bobbins 29 and 28 respectively. A blade 112 is secured to a leaf spring 113 rigid with a block 114 carrying pins 116, 117 slidable in horizontal slots 118 in a pivoted body 120 biased upwardly by a spring 124 against an adjustable stop 127. The inner ends of slots 118 have upwardly in dined extensions 121. Blade 112 is aligned with the apertures 20, 34 and is formed with a pair of fingers 110, 111 aligned with bobbins 28 and 29 respectively. Blade 112 normally closes a micro-switch 128. A pin 129 on block 114 is embraced by the forked arm 130 of a bell crank lever, the other forked arm 133 of which embraces a pin on a bar 134 connected to the armature of a solenoid 135 and biased away from the latter by a spring 136. One arm of a two-armed lever 138 is pivoted to bar 134, and the other arm abuts disc 61. A motor 90 is coupled by reduction gearing 89 to a shaft 86 carrying a gear 87 and a cam disc 96. Gear 87 meshes with a gear 71 on a shaft carrying a slidably keyed sleeve 67 rigid with a coupling disc 66. An axially-slidable shaft 74 carries a pin 75 biased by a spring 77 into engagement with a face cam 70 rigid with gear 71, and a yoke member 78 on shaft 74 engages a circumferential groove in sleeve 67. The arrangement is such that, on operation of motor 90, disc 66 is shifted into engagement either with disc 60 and a surface 81 on a disc 82, driven by a motor 83, for rotating bobbin 29, or into engagement with disc 61 and a surface 84 on disc 82 for rotating bobbin 28. A circumferential cam groove 72 in gear 71 is engaged by one arm of a two-armed lever (103), Fig. 2 not shown, the other arm of which is connected by a link (101) to one end of a lever (99). The other end of the latter is pivotally connected to a radial cam groove formed in disc 96, and an arm (106) projecting laterally from lever (99) carries a threaded needle 107 aligned with the apertures 20, 34. One arm 148 of a bell crank lever carries a pin 149 engaged with a sliding cutter blade 151, and the other arm 147 is biased by a spring 145 against a fixed stop 146 to position blade 151 over an aperture 154 formed in a fixed blade 153 and aligned with needle 107. At the end of a sewing operation when a treadle is released to stop the machine, a switch contact 170 is shifted from a contact 171 to a contact 169. A relay 172 is thereby energised, via slip rings 156, 157 on the arm shaft 4 and brushes 158, 159, to open contact 172b in series with a winding 179 of a relay 180, and to close a contact 172a to energise a slow-running control solenoid 175. Shaft 4 then turns slowly until an insulating segment 160 on ring 157 engages brush 159 to stop the machine with the needle fully raised. Winding 179 is thereby momentarily energised via a capacitor 177 to close a holding contact 180a for energising a winding 183 of relay 180, and to close a contact 180b for energising solenoid 135. Arm 130 thereby moves blade 112 through the aligned aoertures 25, 20, 34. If one of the bobbins carries sufficient thread, the associated finger 110, 111 is engaged by the thread mass, and blade 112 is deflected upwardly by the yielding of spring 113 to open micro-switch 128. Relay 180 and solenoid 135 are thus de-energised, and blade 112 withdraws. If neither of the fingers 110, 111 engages a thread mass, body 114 moves forwardly until the pins 117 engage adjustable stops 122 at the end of the inclined extensions 121 for positioning the fingers 110, 111 at a distance from the bobbins equal to the depth of fully-wound thread mass required. Movement of arm 130 also shifts arm 147, whereby blade 151 uncovers aperture 154. Movement of lever 138 serves to shift discs 60, 61 into driving engagement with the bobbins. Final movement of bar 134 serves to close a micro-switch 142, whereby a relay 190 is energised to close a holding contact 190a thereof, and to close a contact 190b for starting motor 90 to drive cams 70, 72, 96. It is stated that the latter are so designed that needle 107 passes through the aligned apertures 154, 25, 20, 34 to engage between the resilient disc 48 and the adjacent inner flange of the empty bobbin, and then to withdraw, leaving the thread end clamped between said disc and flange, while disc 66 is shifted to couple disc 82 via the relevant disc 60 or 61 to the empty bobbin. A cam on shaft 86 then closes a microswitch 94 to energise a relay 196 for closing a holding relay 196a thereof and shifting a movable contact 196b from engagement with a contact 198 in series with motor 90 to a contact 199 in series with motor 83. The latter then rotates the empty bobbin to wind thread thereon until the thread mass engages the associated finger 110 or 111 to open micro-switch 128 for de-energising relays 180 and 196. Solenoid 135 is thereby de-energised, whereby blade 112 withdraws and arm 147 is released for blade 151 to co-act with aperture 154 to cut the bobbin thread. Motor 83 is also stopped, and motor 90 is restarted to run until a cam on shaft 86 opens a micro-switch 92 to de-energise relay 190. It is stated that the thread on the partly-wound bobbin is first used up at the commmencement of the next sewing operation, to be followed by the thread from the newly-wound bobbin, the thread being guided during this operation by a slot (23), Fig. 6, not shown, in the bobbin case 15 below a tensioning spring (21), and a protective flange (22). It is also stated that means may be provided to prevent the threadsensing means from operation after each stoppage of the machine, or to arrest the machine, for bobbin winding, after a predetermined sewing period.