Patent GB-921681-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B19/00
Filed: 1960-01-07
Abstract: 921,681. Sewing-machines. E. FORSTER, and J. FORSTER, [trading as GEBRUDER FORSTER]. Jan. 7, 1960 [Jan. 9, 1959], No. 598/60. Class 112. In a zig-zag sewing-machine comprising a plurality of pattern cams mounted on a common rotary shaft, a plurality of operating members are mounted on a displaceable carrier member, and the arrangement is such that, on movement of the carrier member, the operating members are selectively brought into abutment with cam followers to establish a positive connection between the cams and means for influencing the stitch formation. As shown, the cam discs 50 are fixed to a rotary driving shaft 51, the two uppermost cams being adapted to influence the stitch length, and the other eight cams to influence the stitch width and position. A carrier drum 52, rotatable concentrically with the cam discs, is driven by gears 53, 54 from a shaft 56. The drum is formed with a series of circumferential slots 64, at one end of each of which is pivoted, at 61, a pawl 62. A projection 63 on each pawl, near the pivot 61, engages the exterior of the drum to limit outward movement of the pawl, and the nose 65 of the latter can pass through the slot 64 to engage a respective cam 50. An arm 67, pivoted at 68, carries a cam follower member 66 extending axially over the bottom eight cams. Arm 67 is connected by a link 69 to an arm 40 pivoted at 41. Releasably coupled to arm 40 are three bars 27, 29, 30, bar 27 controlling the stitch position and bars 29, 30 controlling the stitch width. An arm 45, also pivoted at 41, is connected to a bar 46 controlling the stitch length. A cam follower member 70, carried by arm 45, extends axially over the two top cams. On rotation of drum 52, the pawl noses 65 are selectively wedged between the cams 50 and the followers 66 and 70 to effect movement of the latter, and corresponding movement of the bars 27, 29, 30, 46, on rotation of the cams. A pulley 57 on shaft 56 is connected by a cord 59 to a pulley 58 on a rotary shaft 44. The latter is provided with cams adapted to lift the bars 27, 29, 30 selectively from engagement with the arm 40. A handle on shaft 44 has six positions of angular adjustment. In one position all the bars 27, 29, 30 are uncoupled to allow for manual control. In a second position bar 27 is coupled to provide for automatic control of the stitch position. In third and fourth positions bars 29 and 30 are respectively coupled to provide automatic control of the stitch width, bar 30 producing stitches twice the width of those produced by bar 29. In the fifth and sixth positions bar 27 is coupled with bar 29 and 30 respectively to provide automatic control of stitch position and width simultaneously. Shaft 44 is arranged to rotate three times for each rotation of shaft 56 to provide 18 alternative stitch-producing positions, in three of which the arms 27, 29, 30 are then coupled from the bar 40 and all the pawls 62 are uncoupled from the cam followers 66, 70 to provide for manual operation. A dial 71 carried by shaft 56 is formed at its periphery with stitch diagrams which correspond to the various positions of adjustment and which move successively behind a window in the machine frame. The needle bar gate 13, pivoted at 12, is also pivoted at 14 to one end of a bar 15, the other end of which is forked to embrace a three-lobed rotary cam 17. A block 21, pivoted on bar 15, is slidable in a slot 22 formed in a member rigid with a shaft 23 which may be turned by a handle (not shown) for manually varying the stitch width. Shaft 23 is journalled in one arm 24 of a double-armed lever, pivoted at 25, the other arm 26 of which is connected to the stitch position controlling bar 27. A handle (not shown) is provided for swinging lever 24, 26 to vary the stitch position manually. A crank 32 on shaft 23 is connected by a link 31 to one arm of a double-armed lever, also pivoted at 25, to the other arm 28 of which is connected the stitch-width controlling bars 29, 30, the point of connection of the former being farther from pivot 25 than that of the latter. The stitchlength controlling bar 46 is connected via a bellcrank lever 47 and link 48 to the manual stitch-length adjusting means 49.