Patent GB-906397-A (GB)
Title: Lock stitch sewing machine
IPC: D05B65/00
Filed: 1961-02-22
Abstract: 906,397. Sewing-machines. SINGER MANUFACTURING CO. Feb. 22, 1961 [March 4, 1960], No. 6450/61. Class 112. In a single-thread lockstitch sewing - machine, means associated with the looptaker are adapted to withdraw all the thread from the looptaker bobbin at the end of a sewing operation, and further means then sever both bobbin and needle threads adjacent the work. As shown, the machine is a clamp-feed group-stitch machine. A rotary hook 32 is carried by a hollow shaft 31 driven by a belt 30 from the upper shaft 24. The machine is controlled by a rotary cam disc 23 journalled in the base 22 of the machine and driven from the upper shaft 24 by a vertical shaft 40. A cam groove 61 in disc 23 co-operates with a follower roller 62 carried on a lever 63 which is coupled by a link 64 to an arm 65 on the lower end of a pivoted shaft 66. A forked arm 67 on the upper end of shaft 66 embraces a block 68 pivoted to a slide-bar 60. The arrangement is such that the final movement of cam 23 shifts bar 60 to operate the bobbin threadextracting means and then to position thread-severing blades adjacent the threads. Pivoted at 70 to bar 60 is a lever 69 connected by a link 71 to a lever 55 adapted to raise the upper jaw 51 of the work clamp. Actuation of lever 55 thereby serves to effect final movement of bar 60 for severing the threads. The rotary hook comprises a body 83 fixed by a screw 82 to the driving- shaft 31 and formed with a loop-taking beak 93, a gib 85, and a tubular member 101 formed with a circumferential thread-camming edge 102. A bobbin case 88 is formed with a radial flange 87 journalled between body 83 and gib 85, and also with a notch 90 which is engaged loosely by a fixed lug 91. A bobbin 92 is journalled within the bobbin case. Edge 102 is formed with an inclined notch 103 and also with a circumferential, needle-passing notch 105. Slidably mounted in gib 85 is a plate 107 biased rearwardly by a spring member 114 fixed to the rear face of body 83. Bar 60 carries a lug 121 and also a finger 123 formed with a hooked end 124. The arrangement is such that when bar 60 moves for wardly, lug 121 engages spring 114 to shift plate 107 forwardly, when hook 124 becomes aligned with edge 102 and a notch 109 formed in plate 107 becomes aligned with notch 103. A shaft 95, slidable within shaft 31, carries a member 94 positioned within body 83 and adapted, when shaft 95 is moved forwardly, to engage the rear face of bobbin 92 for directing thread on to the latter during the bobbin-winding operation. A bracket 128, fixed under the work support 21 by a bolt 129, carries a stud 127 on which is j ournalled a member formed with a gear segment 126 and, diametrically opposite the latter, with a cam groove 130. A rack 125, fixed to an end of bar 60, engages segment 126. A follower pin 131, engaged in groove 130, is carried on an arm 132 fixed to one end of a spindle 133 journalled in a block 135 attached by a bolt 136 to bracket 128. The other end of spindle 133 carries a curved finger 134 the end of which is adapted to enter a notch 140 in the bobbin case 88 when spindle 133 is pivoted. Lug 91 is formed on block 135. A thread-cutting blade 141, rigid with gear segment 126, has a knife edge 143, a thread-deflecting lug 144, and a thread-deflecting finger 146. Disposed in a shallow recess 152 in the lower surface of the work support 21 is a thin ledger blade 153, one end of which is pivoted at 154 to support 21, the other end of which is formed with a knife edge 160, and the centre portion of which is formed with an aperture 158 which embraces a cam 159 rigid with gear segment 126. The needle passes through a hole 151 in a throat plate 150 fixed to the support 21. On the last stroke of the needle, follower 62 moves inwardly to the position F9, Fig. 3, whereby slide 60 moves inwardly to shift plate 107. The bobbin thread B thereby passes into the aligned notches 103, 109 and rotation of the hook then serves to draw the bobbin thread out of the bobbin, hook 124 being so positioned as to support said thread. At position F10 follower 62 commences to move outwardly until it finally comes to rest at position F12 opposite a radial opening 72 in the outer wall of cam groove 61. During this motion bar 60 is moved progressively outwards, whereby finger 134 engages notch 140 and the last-taken loop of needle thread passes up finger 134 to rest against a flange 138 at its upper end, the ledger blade 153 swings to position the knife edge 160 adjacent the needle hole 151, and the blade 141 swings to position knife edge 143 adjacent hole 151 and lug 144 opposite the thread loop on finger 134, while finger 146 deflects the bobbin thread B to a position between the knife edges 143, 146. Finally, when lever 55 is operated to open the work clamp, follower 62 passes through opening 72 and slide 60 moves further outwardly to swing the knife blades, when lug 144 enters the needle thread loop to deflect the limb NS leading to the needle away from the knife edges 143, 160 which then sever the limb NW leading to the work and the bobbin thread B. Specification 906,398 is referred to.