Patent GB-1099590-A (GB)
Title: Stitch forming mechanism for sewing machines
IPC: D05B57/14
Filed: 1966-08-26
Abstract: 1,099,590. Sewing machines. SINGER CO. Aug. 26, 1966 [Aug. 30, 1965], No. 38367/66. Heading D1G. A lock stitch sewing machine comprises a looptaker journalled in a supporting member and formed with a loop-seizing beak, a pinion rotatable with the looptaker, a stationary member formed with gear teeth in mesh with the pinion, and means for imparting oscillatory or reciprocatory movement to said supporting member to move the loop-seizing beak in a non-circular curvilinear path in timed relation with the reciprocation of a thread-carrying needle. A baseplate 11 carries a vertical plate-like frame (14) comprising a column portion, a horizontal arm portion and a head portion, and journalling a driven shaft 20 carrying an eccentric 21. A bellcrank lever 30, pivoted at 31 to frame (14) has a vertical arm 33 formed with ears 35 embracing eccentric 21, and a horizontal arm 32 connected by a link 36 to a needle bar 37 slidable in a groove formed in frame (14). An arm 50, pivoted at one end to a pin 51 carried by frame (14) and passing through a clearance slot 52 in arm 32, carries intermediately a roller 53 engaging a slot 54 in arm 32 for receiving oscillation from the latter, and is formed at the other end with a thread take-up hook 55. An arm 72, pivoted at one end on a vertical pin 73 carried by baseplate 11, is formed at its free end with a vertical counterbore 71 extending beyond said end to form an opening 115 in the latter. A shuttle 70 has an arcuate bearing rib 113 which is journalled in counterbore 71 and is held therein by a cover plate 116. One end of rib 113 is formed with a beak 114 adapted to project from opening 115 to seize the thread loop from the reciprocating needle 40. A shuttle driver 74, fixed to a shaft 75 journalled in a bore 76 formed in arm 72 concentric with counterbore 71, has an arcuate flange 120 disposed between the ends of rib 113. A pinion 77, rigid with shaft 75, meshes with an arcuate gear 81 on an arm 80 which is pivoted on pin 73 and is secured in adjusted angular position by a clamping screw 82. Arm 72 is connected by a link 103 to a plate 98 slidably mounted on baseplate 11. Plate 98 is connected by a link 95 to one end of a lever 92 pivoted at 93 to frame (14), the other end being pivoted at 90 to arm 33. The arrangement is thereby such that when shaft 20 rotates, arm 72 oscillates about pin 73 and shuttle 70 oscillates in counterbore 71, whereby beak 114 moves in a substantially epicycloidal path. The shuttle is formed with an upstanding circular wall 110, the axis of which is offset from the axis of rib 113. Wall 110 houses a bobbin 130 journalled on a pin rising from the base of the shuttle. Wall 110 is formed with a slot 140 terminating in an eyelet 141. Bobbin thread issuing from the latter passes to a notch 143 in wall 110 over a recess 142 in the outer surface of wall 110. A two-armed lever, pivoted on wall 110, has an upper arm 147 disposed over recess 142 and in alignment with notch 143, and a lower arm 146 located in a slot in wall 110. A leaf spring, secured at 149 to wall 110, has a lower arm 151 which biases arm 146 against the bobbin to brake the latter. Arm 147 is thereby biased against an upper spring arm 150 to tension the bobbin thread passing therebetween. Loop seizure occurs while arm 72 and shuttle 70 are both turning counterclockwise. When loop shedding occurs, arm 72 is still moving counterclockwise, whereby the shuttle is carried away from the shed loop, and the action of the thread take-up therefore need be less intrical than if the shuttle rotated about a fixed axis. At the end of the counterclockwise swing of arm 72, the bobbin thread is stretched diametrically across the upper surface of the bobbin, whereby lever arm 147 is drawn away from spring arm 150 to release the bobbin thread tension, and lever arm 146 moves away from the bobbin to release the braking thereof. In a modification, rectilinear movement is imparted to the shuttle-carrying member, and the shuttle-driving pinion meshes with a rack, whereby the loop-seizing beak moves in a substantially cycloidal path.