Patent GB-633267-A (GB)
Title: Stitch-forming mechanism for sewing machines
IPC: D05B73/12
Filed: 1948-02-11
Abstract: 633,267. Sewing-machines. FAIRWEATHER, W. C. (Singer Manufacturing Co.). Feb. 11, 1948, No. 3995. [Class 112] Stitch-forming mechanism for an eyelet-hole sewing-machine comprises an upper needle, a lower needle carrying a thread-loop through that of the upper needle on one side of the work for penetration by the latter needle on the other side of the work, and a looper which takes the upper-needle thread-loop and travels in a path between the lower needle and the previous stitch, thus producing stitches of the kind described in Specification 633,270. Both needles are adjustable in their holders, the upper one laterally, and the stroke of the lower needle can be varied without altering its lowermost position. Overedge stitching; needles, driving. In the embodiment described the bar carrying the upper (straight) needle slides in a turret rotatable by a toothed sector in unison with the usual turret carrying the lower needle and looper, and is prevented from rotating in the turret by a member which is screwed to the turret and has a split lug, with adjusting screw, projecting into a keyway in the needle-bar. The needle is adjustable laterally to vary the size of eyelet, and is simultaneously adjusted vertically (see next - paragraph) to provide the proper size of loop. The lower (curved) needle 36, Fig. 8, is carried by a member 76 pivoted at 77 on a pillar on the turret 38, and is actuated from a pin 72 on a rod reciprocating along the axis of the turret by a link 73 connected to an arm 75 which is adjustably clamped to the carrier 76 ; sliding adjustment of the arm 75 alters the stroke of the carrier without affecting its lowermost position (shown), and the stroke is indicated by graduations on the upper face of the arm 75 in conjunction with an edge 88 on the carrier. The looper 116, Fig. 6, is fixed adjustably to a link 105 which is pivoted at one end to a lug 103 on a slide 100 and at the other to a member 106 provided with a pair of rollers 108 working in a cam groove formed in a plate 110 fixed to the turret : the cam groove imparts to the looper the necessary needle-avoiding movements as the slide 100 is reciprocated across the turret by a member 92 pivoted to the turret at 93 and having pivoted block and slide connections at 95 with the slide 100 and at 89 with the operating rod previously mentioned. This rod is reciprocated vertically by a toggle linkage at its lower end, connected to a crank on a shaft geared to the main shaft of the machine, the linkage passing over the straight-line position near the top of the stroke of the rod so that the looper and lower needle have a dwell and slight dip in their projected positions. The looper has integral with it a lower needle-guard portion 118 to assist in positioning the upper needle during the seizure of its loop. Needle holders. The curved needle 36, Fig. 8, is clamped in its carrier 76 by a shoe pivoted at 80 and pressed downwards by a screw 81. The straight needle 14, Fig. 13, is clamped by a grub screw 17 in a member 16 which is formed with an inclined rib fitting in a corresponding groove in a lug 18 on the lower end of the needle-bar and secured therein by a screw 19 passing through a slot in the base of the groove. The screw also passes through a slot in a pointer 24 pivoted to the lug 18 at 241 and indicating on a scale on the lug the outside diameter of the eyelet for which the needle is set. The combination of vertical with lateral adjustment ensures the production of a loop of the appropriate size. Eyelet-hole sewing-machines. The upper and lower turrets are rotated by toothed sectors linked to cranks on a vertical shaft actuated from the feed-cam. The lower turret carries an adjustable throat-plate with an elongated hole, to receive both needles, enlarged at one side at the end through which the curved needle passes. As described in Specification 146,587, [Class 112], the sewing operation is preceded by one revolution of a shaft which closes the clamp, puts the stop lever into the running position, and actuates the eyelet cutter, and is followed by one revolution of a shaft which carries a crank connected to the feed cam by a link and pawl to give the cam a rapid motion back to its initial position. Specifications 15049/15, [Class 112], and 633,268, also are referred to.