Patent GB-1128430-A (GB)
Title: Bobbin thread replenishing mechanism for sewing machines
IPC: D05B57/26
Filed: 1967-08-22
Abstract: 1,128,430. Sewing machines. SINGER CO. 22 Aug., 1967 [29 Aug., 1966], No. 38613/67. Heading D1G. A lock stitch sewing machine, adapted to wind a bobbin in situ, comprises a bobbin case carrying a bobbin thread-tensioning spring and formed, with a gapped bearing rib, a rotary looptaker having a gapped raceway for the bearing rib. a loop-seizing beak at said gap and at one side of the raceway, and a thread loop-manipulating surface extending from the beak to a throat disposed on the other side of the raceway, means for preventing rotation of the bobbin case with the gaps open to each other at loop seizure, means for rotating the bobbin in the bobbin case, means for influencing the position of the seized loop across said surface to extend on the throat side of the raceway when the gaps overlap, whereby the seized loop is manipulated completely about the bobbin case for the formation of lock stitches. and means for simultaneously rendering effective the bobbin rotating means and influencing the position of the seized loop across said surface to extend on the beak side of the raceway when the gaps overlap, whereby the seized loop is manipulated entirely across one side of the bobbin case and on to the bobbin. A stub shaft 42. journalled in a fixed bush 41, journals a gear 44 secured by screws 47 to the base 49 of a cup-shaped looptaker body 48. Gear 44 meshes with a gear 29 rigid with a driving shaft 25. The side wall 50 of body 48. is formed with inward projections 52 which support a radial rib 73 on a bobbin case 53 having a cylindrical wall 71 enclosing a bobbin 95. An annular member 60, sprung into body 48, has a radial flange supported by wall 50 and an axial flange co-operating with the projections 52 to provide a raceway for rib 73. Member 60 is secured to body 48 by pins 66 to position a gap 63 in member 60 above a trapezoidal notch 54 in wall 50. One end of gap 63 is constituted by a loop-seizing beak 64 which is positioned adjacent a throat 55 of notch 54. Member 60 is also formed, diametrically opposite gap 63, with an inwardlyextending thread-camming fin 65. Rib 73 is formed with a gap 74, one end of which is constituted by a shoulder 75. A leaf spring 79, adapted to tension the bobbin thread, is secured at one end by a screw 80 to rib 73. has an upturned free end 87 and is formed intermediately with a thread-guiding notch 82. A disc 105, located between base 49 and bobbin case 53, is rigid with shaft 42 and has ah upstanding projection 111 located in gap 74 to prevent rotation of bobbin case 53. An axial bore in shaft 42 journals a shaft 120, the upper end of which slidably carries a tongue 122 supported on a compression spring 125. and the lower end of which is rigid with a disc 127. A shaft 140, journalled in a fixed bush 141, is rigid at its upper end with an arm 152, the face end of which carries a plate 153 spacing a plate 154 from arm 152. The lower end of shaft 140 is rigid with a first arm 162 which is located above disc 127 and carries a pin 168 engaging a slot in an arm 170 rigid with shaft 42. A second lower arm 164 rigid with shaft 140 is located beneath disc 127. A spring 166 acts on arm 164 to bias arm 152 to a normal latched position S for straight stitching. Notch 82 is then located in position S<SP>1</SP> at one side of the mean position of the needle 23. For zig-zag stitching, an arm 180, rigid with a journalled shaft 181, is engaged with arm 152 to locate the latter in position Z, when notch 82 is located in position Z<SP>1</SP> opposite the mean position of needle 23. During stitching, a needle thread loop seized by beak 64 is guided into throat 55 and is entered by shoulder 75 on further rotation of body 48. The limbs of said loop are thereby directed respectively above and below the bobbin case 53. For bobbin winding, arm 152 is located in a latched position W, when notch 82 is located in a position W<SP>1</SP> on the other side of the mean position of needle 23, shoulder 75 is located closely adjacent the needle position, and arm 164 engages a projection 128 on disc 127 to raise the latter into engagement with a rubber ring 129 mounted coaxially on the hub 130 of gear 29. Consequent raising of shaft 120 engages tongue 122 with a notch 100 in bobbin 95, and raises the latter into engagement with plate 154. On operation of the machine, throat 55 will be closed by rib 73 before the loop seized by beak 64 can be engaged by shoulder 75, and the loop will therefore remain above the level of rib 73. The upper limb becomes engaged with plate 153 in the space between arm 152 and plate 154. The lower limb is initially engaged by a notch 86 in spring 79 adjacent end 87, and then passes successively under end 87 and up a ramp 90 connecting rib 73 with the upper rim of wall 71. The upper limb then passes into bobbin 95 while inclined between the upper rim of wall 71 and the base of a notch 91 formed therein, to be engaged in one of a series of peripheral notches formed in a washer 103 located radially in bobbin 95. Rotation of the latter in the reverse direction to that of looptaker body 48 then serves to stretch the lower limb for engagement with the cutting edge 89 of a triangular member 88 projecting upwardly from rib 73. Thread severing then occurs and the single limb is drawn into notch 82, while thread winding continues. Spring 79 can thereby control bobbin thread tension during both bobbin winding and stitching. In a modification, an arm (207), fast with the bobbin-winding shaft, has three fingers (208), (209), (210), the middle finger (209) of which is engaged between two fingers (213). (214) on an arm (215). fast with shaft 140. An arm (220) has a bifurcated free end engaging a peripheral groove in the bobbinwinding shaft, and has a loose connection with shaft 140 permitting vertical movement of said bifurcated end. A coil spring (212). connected between finger (209) and arm (220), encloses a rod (224). A spring (218) acts on arm (215) to bias arm 152 to the sewing position, when finger (209) is located directly above arm (220) and rod (224) engages finger (209) and arm (220) to depress the bobbin-winding shaft. When arm 152 is moved to the bobbin-winding position, rod (224) is disengaged from finger (209) and arm (220). Spring (212) thereby raises the bobbin-winding shaft to engage a tongue (201) thereon with the bobbin, and to mesh a gear (202) fast thereon with gear 29.