Patent GB-775710-A (GB)
Title: Improvements in or relating to sewing machines
IPC: F16H53/04
Filed: 1955-02-10
Abstract: 775,710. Sewing-machines. PFAFF AKT.- GES., G. M. Feb. 10, 1955 [Feb. 10, 1954], No. 4061/55. Class 112. [Also in Group XXIV] In a zig-zag sewing-machine, automatic control giving a number of different stitching patterns without requiring pattern cams to be changed is provided by a rotary control disc, or two such discs, carrying a plurality of pins which can be displaced parallel to the axis of the disc into and out of positions in which they can come into engagement with an element for adjusting the width of the zig-zag or its lateral position or with elements for both these purposes ; by moving different selections of the pins into operative position the equivalent of cams of different forms may thus be produced. The invention is shown in Fig. 2 as applied to a machine wherein the width of the zig-zag is varied by angular adjustment of a spindle 84 mounted in the end of a lever by which the zig-zag is shifted laterally. A plate 89, mounted on the spindle 84 and guided by a pin-and-slot 88 so as not to rotate with the spindle, carries a locking member 100 for engagement, under spring action, with notches in the edge of a fixed plate to hold the mechanism in the required position of adjustment for lateral position of the zig-zag against the force of a spring attached to the pin 88 ; a toggle-lever 101 is arranged to hold the locking member 100 out of action when automatic variation of zigzag position is required. The member 84 is engaged by the forked limb of a plate 24 which is pivoted at one end on the shaft of a control disc 49 and which carries a second rotary control disc 50 and gearing connecting the latter disc to that shaft ; the shaft is movable axially to engage it with or disengage it from a gear 16 driven from the needle-bar shaft through double bevel and worm gearing. The pins 57 of the disc 49 may be moved axially to a position for engagement with the upper end of a lever 76 pivoted on the plate 24 and formed with a toothed sector 80 whereby it rotates a disc 83 fixed to the spindle 84 to alter the width of the zig-zag; a pin 81 on the lever 76, moving in a slot in the plate 24, abuts the edge of a member 40 pivoted behind the plate 24 at 39 and serving for manual adjustment of the stitch width, for which purpose it is provided with a locking screw 43. The pins of the disc 50, when in operative position, come into engagement, as the disc rotates, with horizontal surfaces on a fixed bracket 96, whereby the disc 50 is caused to move upwards, carrying the plate 24 and thus shifting the spindle 84 to vary the lateral position of the zig-zag. Each pin of the discs 49, 50 is spring-urged to the inoperative position, and carries a spring latch to engage the back of the disc and hold it in the operative position ; each pin is lettered or numbered, and the machine is set for a required pattern according to instructions specifying which pins are to be made operative. Each disc has a back-plate, with a flange 69 covering the edge of the disc, having clearance holes for the pins and arranged to have limited rotation, against a spring, on the disc and, when operated, to engage and release the latches of all the pins in operative position, when it is desired to change the pattern. The upper part of the mechanism behind the discs 49, 50 is enclosed by a cover closing the top of the machine arm; the lower part of the mechanism is covered by a plate carried on spacers 103 from the machine arm and having markings on its outer face for indicating the lateral position of the zig-zag in conjunction with a pointer carried by a stud 105 on the plate 89. In a different arrangement, Fig. 11, the two control discs are combined at 145, and the pins (not shown) have two operative positions, in one of which they can act only on a pivoted follower 213 to affect the lateral position of the zig-zag, while in the other they can act also on a follower 184 to affect the width of the zig-zag. The pins are set for the required pattern by pressing against them a template comprising spaced plates perforated at the appropriate places so that both pass over those pins which are not required to be operative and one passes over those which are required only to be in the first operative position ; the pins are frictionally held in any set position, and are withdrawn by moving axially a resetting disc which engages under the heads of the pins. The disc is driven by ratchet mechanism including a spring-urged pawl mounted on a vertically-sliding member spring-pressed downwards against a cam on the needle-bar shaft ; a spring latch controlled by a fingeroperated cam can engage a notch in the sliding member to hold it clear of the cam or can limit its downard travel by engaging a shoulder on it to reduce the stroke of the pawl. The cam-follower 184, pivoted at its lower end, carries a rotatable knob 196 with an offset pin for engagement in a vertical slot 203 in a slidable bar 199 ; the pin can thus be arranged to connect the follower 184 to the bar 199 at either the top or the bottom of the slot 203 to give the bar two different strokes for a given movement of the follower 184. The bar 199 has a notch 205 for engagement with a pin 206 on an arm connected to the means for adjusting the zig-zag width (so that the latter means is shifted according to the movements of the cam-follower 184) but may be held depressed clear of the pin (against a spring) by a snap-action finger-lever 231 engaging an arm 204 of the bar 199. The cam-follower 213 is pivoted directly to a bar 220 arranged similarly to the bar 199 to be held down by a finger-lever 232 or allowed to engage a pin 225 on a member 226 connected to the means controlling the lateral position of the zig-zag; the pin 225 is eccentrically mounted for adjustment in the member 226.