Patent GB-944391-A (GB)
Title: Lock stitch sewing machine
IPC: D05B57/36
Filed: 1962-07-31
Abstract: 944,391. Sewing machines. SINGER CO. July 31, 1962 [Aug. 25, 1961], No. 29487/62. Heading D1G. In a single-thread lock stitch sewing machine in which the bobbin is wound while in position in the looptaker, the needle thread is directed by guide means into the bobbin to be held by threadgripping means provided thereon, and the limit of thread extending between said thread-gripping means and an anchorage on the sewing machine is severed by means associated with the guide means, whereby the other limit is wound on the bobbin as the latter is rotated. A vertical axis rotary hook 40 is driven by gearing 44 from a bed shaft 45 coupled by gearing 42, 43 and a vertical shaft 46 to the arm shaft 19 carrying a gear 21 driven by an electric motor. Thread passes from a bobbin 23 supported on a horizontal pin 24 over a thread guard 25 on pin 24, through a light pre-tension device 28 to prevent spilling from the bobbin, and through the main tensioner 29 and take-up lever 22 to the eye of the needle 18. A control dial is adapted, when turned by a predetermined amount, to release the thread tension, to immobilize the work feed, and to shift a lever 51 to the bobbinwinding position. Dial 50 then rotates back to its initial position, at which bobbin winding is terminated. The rotary hook comprises a body 60 fixed to a hollow driving shaft 44, and formed with an annular bearing rib 61 and with a loop-seizing break 62. A bobbin case 64 comprises a portion which is formed with a raceway 65 receiving rib 61, and which extends over less than 180 degrees, the periphery of the bobbin case being completed by a rib 66. A plate 71, slidable on the machine base, has noses 69, 70 in which engage abutments 67, 68 on the bobbin case to prevent rotation of the latter and to hold it on the bearing rib 61. A leaf spring 74, fixed to plate 71, is interposed between nose 70 and abutment 68. A bobbin has an upper flange 76 resting on a seat 75 in the bobbin case, and a hub portion 80 which is formed with a lower flange 80 and is secured to the flange 76 by a screw 77. The upper end of hub 80 is formed over half its periphery with a thread-gripping bevel 82 and over the other half with a thread-passing groove 83. A bobbin-winding member has an upper circular flange 101 surrounding flange 81, and is fixed to the upper end of a spindle 102 which is slidable in shaft 41 and carries at its lower end a lug 104 engaged in a recess 105 in the gear 44 fast with shaft 41. Spindle 102 is connected by a leaf spring 107 to lever 51, whereby, on actuation of the latter, spindle 102 is raised to shift a pin 108 on member 100 into driving engagement with a slot 84 in flange 81. At the start of bobbin winding the thread extending from the needle to the work is held either by the lowered presser foot 15 or by separate thread-gripping means. Beak 62 seizes an initial loop in the normal manner, but when said loop is shed and is being shortened by the takeup, it i s directed by a downwardly-projecting cam portion 115 on the bobbin case rib 66 into positive engagement with the upper rim of the raised circular flange 101, to be gripped by a hook 110 formed in the latter. Further rotation of member 100 then serves to wind the thread on hub 80, the thread initially passing freely through groove 83 and then being gripped in bevel 82 when hook 110 arrives adjacent the needle 18, as shown in Fig. 6. Further rotation of member 100 causes the thread limb extending between bevel 82 and the fixed anchorage to be severed by a knife edge 111 provided at the base of hook 110. On continued rotation of member 100, thread is drawn through the needle eye and is wound on limb 80, this thread passing through a notch formed in the lower surface of rib 66 to prevent its engagement with flange 101. Rib 66 is formed, adjacent the needle, with a bevel 117 over which thread may be led to the needle from a pre-wound bobbin. Specification 876, 190 is referred to.