Patent GB-949926-A (GB)
Title: Bobbin thread replenishing mechanism for lock stitch sewing machine
IPC: D05B59/00
Filed: 1962-11-23
Abstract: 949,926. Sewing machines. SINGER CO. Nov. 23, 1962 [Dec.11, 1961], No.44509/62. Heading D1G. A sewing machine rotary hook carries a bobbin case journalling a bobbin which is formed with axially-spaced flanges and which is adapted to be wound in situ, while the machine operates, by means comprising a thread-deflector supported by means externally of the rotary hook, means for shifting the thread-deflector into a position extending opposite the space between the flanges of the bobbin to deflect on to the bobbin thread loops taken from the needle, and means for maintaining the thread-deflector in said position during successive penetrations of the needle, the machine also being provided with means for severing a limit of a loop of thread deflected on to the bobbin. The rotary hook 15 comprises a body 40 fixed to the bed shaft 19 and formed with a loop-taking beak 41 and a raceway 42, and provided with a gib 43 which complements the raceway and is formed with a thread-detaining tail 46. A bobbin case 45 has a rib 44 journalled in raceway 42, and a centre post 47 covered by a nylon sleeve 49. The bobbin case is held from rotation by a bracket 55 having its lower end engaged within a slot formed in post 47 and its upper end disposed between a pair of fixed abutment springs 57. A bobbin 50, journalled on sleeve 49, has a pair of end flanges 51 and 52. The thread-deflector 60 has a pair of obliquely-inclined fingers 61, 62 and is fixed to one end of a slidably-mounted plunger 64 biased by a spring 67 to position the fingers 61, 62 within the annular space between the flanges 51, 52 and the rim of the bobbin case 45. The other end of plunger 64 abuts one arm 69 of a bell crank lever, pivoted at 68, the other arm 70 of which carries a follower pin 71. Pivoted at 24 to the machine bed 11 is an extension 24 carrying a bracket 72 formed with a cam end 74 which, when extension 24 is lowered, engages pin 71, whereby lever 69, 70 is rocked clockwise to shift plunger 64 for positioning the fingers 61, 62 clear of the looptaker. Raising extension 24 serves to free pin 71 for positioning the fingers 61, 62 within the looptaker. To initiate bobbin winding, the end of the free limb Tf of the needle thread is secured in a clamp 29, the extension 24 is raised, and the machine is operated. The limbs of needle thread which would otherwise pass over the outer surface of the bobbin are thereby directed on to the bobbin by the fingers 61, 62. Winding continues until the extension 24 is lowered, when limb Tf is severed by a knife blade 93 and sewing recommences. The thread-severing blade 93 is carried by an arm 92 which is pivoted on a fixed pin 91 and is normally biased by a spring 94 against the head 96 of a fixed screw. A U-shaped member 97 embracing arm 92 and pivoted thereto by a pin 95, is biased against bar 92 by a spring 98 and carried a depending pin 99. A bracket 101 fixed to extension 24 carries a pin 102 which is aligned with pin 99. The arrangement is such that when extension 24 is lowered, pin 102 engages pin 99 for swinging arm 92, blade 93 thereby severing the thread limb Tf. On continued movement of pin 102, pin 99 is disengaged therefrom and bar 92 returns to its original position. When extension 24 is subsequently lowered, pin 102 engages pin 99 and thereby swings member 97 away from bar 92 to permit disengagement of pin 99 without moving bar 92.