Patent GB-707286-A (GB)
Title: Skip-stitch mechanism for blind-stitch sewing machines
IPC: D05B73/12
Filed: 1952-12-19
Abstract: 707,286. Sewing-machines. FAIRWEATHER, W. C. (Singer Manufacturing Co.). Dec. 19, 1952, No. 32171/52. Class 112 Blind-stitching machines. A ridge-forming element 74, Fig. 9, is mounted on a tubular shaft 75 journalled on an eccentric portion or portions 77 of an inner shaft 78 mounted in the work-table, the two shafts being oscillated at different frequencies so that the ridgeforming element moves in a range which is raised and lowered at intervals relatively to the needle, so that anchorstitches (penetrating all layers of work) and skip-stitches (missing the lowest layer of the work) are formed. In the machine shown in Fig. 2 the frame comprises a base with a housing 20 at one side, a standard 21 at one end of the housing, and an L-shaped arm 22, 23 extending sideways and forwards from the standard to carry a curved needle 32, looper 33, and feed-dog 34 actuated from a main shaft 30 in the arm portion 22; the work-table comprises an arm 27 of tubular section at one end, lying beneath the end of the arm 23, as shown in Fig. 9, and enlarged at the other end where it is pivotally mounted on a bracket 45 on the housing 20 by a spindle 42. Members 25, on either side of the ridge-former 74, to engage the underside of the work and press it against a stationary presser-plate 24 carried by the arm 23, are pivoted to an arm 29, Fig. 9, which is mounted on a pivot 26 in the work-arm 27 and urged upwards by a spring 28. The ridge-former 74, which moves in the direction of feed on its upstroke, is. oscillated by an eccentric 91, Fig. 2, on the main shaft 30, connected to an arm 83 on the tubular ridge-former shaft by a pitman 90, bell-crank 89, 85 (free on a shaft 86), and pitman 84. The inner shaft 78, on which the ridge-former shaft is mounted, is oscillated, to raise and lower periodically the field of movement of the ridge-former, by an eccentric 95, on the shaft 86, connected by a pitman 93 to an arm 92 on the shaft 78; the shaft 86 is driven from the main shaft 30 by belt gearing (not shown), of which the sprocket-wheels are dimensioned to rotate the shaft 86 once for every two revolutions of the main shaft to produce alternate anchor-stitches and skip-stitches, or once for any chosen larger number of revolutions of the main shaft to give two or more skip-stitches between each anchor-stitch and the next. The spindle 42 on which the work-arm 27 is pivotally mounted has eccentric end portions 41 engaged by sockets in the work-arm and its main portion is journalled in fixed bearings, so that by angular movement of the spindle the work-arm may be raised or lowered bodily; this adjustment is made by means of a thumb-disc 73 rigid with a screw 71 arranged in the top of the standard 21 to move a lever 64 which is pivotally mounted in the standard at 65 and is connected by a link 63 to an arm 62 clamped on the spindle 42. The work-arm is urged upwards about the spindle 42 by a spring 56 anchored by an adjusting screw 57 and connected by a link 58 to a two-armed lever 60 which is linked at 61 to the skirt 48 of the work-arm and is so formed that the mechanical advantage of the spring is greatest when the work-arm is in its upper position; lowering of the work-arm about the spindle 42, to allow insertion or removal of work, is effected by a knee- or treadle-operated lever as described in Specification 706,759. The upper position of the work-arm is determined by an adjustable stop-screw 47 carried by the skirt 48 and engaging a fixed part of the frame.