GB1005076A - Lock stitch sewing machines - Google Patents

Abstract

1,005,076. Sewing machines. SINGER CO. Aug. 21, 1964 [Aug.30, 1964], No. 34410/64. Heading D1G. A sewing machine comprises work-feeding means, a needle bar gate shiftable in the workfeeding direction, a shaft driven from the main shaft at a lesser speed than the latter shaft, a variable eccentric on the former shaft, and a linkage between said eccentric and the needle bar gate, the arrangement being such the needle-jogging movement in the feed direction is greater than the movement imparted by the work-feeding means during the formation of each stitch. A needle bar 23, carrying a needle 27, reciprocates in a gate 24 pivoted at about 25 about an axis perpendicular to the direction of work feed imparted by dogs 50. The feed advance shaft 54 is driven by a pitman 60 from a variable eccentric 61 on the arm shaft 18. Adjustment of eccentric 61 is effected by engaging a spring-biased plunger 62 with a notched flange 63 and turning the hand wheel 64. A plate 80, closing an opening 82 in the machine arm 16, carries a pair of bearings 83 journalling a shaft 85 coupled by gearing 86, 87 to the arm shaft 18 for rotation at half the speed of the latter. A variable eccentric 88 on shaft 85 is adjustable by engaging a spring-biased plunger 90, carried by a cover plate 92, with a notched flange 89 and turning the hand wheel 64. Eccentric 88 is connected by a pitman 94 to a crank arm 96 on a lock shaft 33, and a crank arm 31 on the latter is slidably connected to a pin 28 first with the gate 24. The arrangement is such that the needle is jogged prior to one stitch in the direction of work feed and prior to the next stitch in the opposite direction, the needle jogging amplitude being approximately one and a half times the feed provided by the dogs 50, whereby needle penetrations are made at A, B, C and D in succession to effect backward stitches AB and CD, the lengths of which are the difference between the needle jogging movement and the feed dog movement, and a forward stitch BC the length of which is the sum of the needle jogging and feed dog movements. It is stated that the seam is extensible and is therefore suitable for uniting knitted fabrics. The stitches are formed over a finger 100, carried by the presser foot 66, to prevent the needle from penetrating the thread of a previously formed stitch. Specification 435, 360 is referred to.