GB328899A - Stitch-forming mechanism for sewing machines - Google Patents

Abstract

328,899. Fairweather, W., (Singer Manufacturing Co.). Sept. 17, 1929. Needles, vibrating laterally.-A compensating mechanism for ensuring co-operative relation between the loop-taker and needle during the lateral vibrations, which is ineffective for a predetermined extent of the vibration and active for vibrations beyond this extent, is incorporated in the machine described in 646/15. The needlebar 9 reciprocates in a frame 11 supported in a fulcrum 12 and swung in the usual way by the crank arm 21. To limit the extent of the needle vibration, a link 39 is pivoted to the twisted link 46 joined to an arm 47 of a lever having its other arm 48 provided with an arcuate slot of which the centre of curvature coincides with the axis of the lever 47, 48. This lever is fixed on a short shaft 50 journaled in a bushing 51 adjustably fixed in an aperture in the standard 2 by a screw 52. Integral with the bushing 51 is a segment 53 provided with a slot 54 of T-shaped crosssection to receive the beaded pin 55 secured in adjusted position by a nut 56. Spaced from the nut 56 is a nut 58. On the outer end of the shaft 50 is the hub 59 of an arm 60 carrying a screw 61 engaging the periphery of the plate 53 to secure the shaft adjustably against movement and so ensuring a constant amplitude of vibration of the needle. When the screw 61 is released, the arm 60 normally engages the nut 56 so that the arm 80 is manually shiftable between the nuts 56, 58, or by the usual treadle, to change the amplitude of the needle vibration. The segment lever 29, 30 has a hub 62 fulcrummed on a shaft 63 eccentrically journaled in a bush 64 rotating in a bearing 65 in the standard 2. The bush 64 is held against axial movement by collars 66, 67. Secured to the collar 67 is a handle 68 with a stud 69 entering apertures 70. 71 in the flattened face of the standard 2. When the stud 69 is in the upper aperture, Fig. 1, the shaft 65 occupies a position such that the needle vibrates equal distances across its zero-position of non-vibration in accordance with the extent of vibration selected by moving the block 27 in the guideway 28. When the fulcrum of the lever 29, 30 is shifted by manipulating the handle 68 so that the stud 69 enters the aperture 71, the zero-position of non-vibration is at one side of the vibration path thereof. The effect of shifting the fulcrum axis of the lever 29, 30 is shown in Figs. 8 and 9 which correspond respectively to the upper and lower positions of the handle 68; a represents the fixed axis of the shaft 22, a, b the lever-arm 25, c the position of the fulcrum axis of the lever 29, 30, d that of the shaft 33 and d, c, e the levers 29, 30. The centre line d, c of the lever arm 30 passes through the axis d, and the arc c, e has the point b as centre with the link 26 as radius, in Fig. 8. In the other position, the fulcrum axis of the lever 29, 30 is shifted to c<1>, thereby displacing the point b' and accordingly the zero-position. The rotary-hook or looptaker 73 is journaled in a bobbin-case 75 and is carried by the end of a shaft 76 rotating in bearings 77, 78. When the slide block 27 is shifted a sufficient extent to cause the screw 114 to engage the stud 113, the manually initiated movement of the lever 47, 48 is transmitted to the lever 111, 112, shifting the slide block 107 off the axis of the rock shaft 22 and causing actuation of the link 106 to vibrate the loop-taker shaft 79 laterally to an extent adjustably determined by the connection between the lower end of the link 106 and the rock-shaft crank-arm 104. The reciprocating movements of the link 106 are not transmitted to the lever 111, 112 because of the groove 109.