Patent GB-774294-A (GB)
Title: Zig-zag control device for sewing machines
IPC: D05B19/00
Filed: 1954-03-19
Abstract: 774,294. Sewing machines. VITTORIO NECCHI SOC. PER AZIONI. March 19, 1954 [April 11, 1953], No. 8080/54. Class 112. [Also in Group XXIV] Automatic mechanism for control of the stitching in a zig-zag sewing-machine comprises one or more exchangeable cams driven intermittently from the rotary needle-bar shaft and each cam actuating means to displace the control member for the mean position of the needle, the amplitude of the lateral movement of the needle, or the feed mechanism ; the intermittent movement is derived from a camoscillated member through a helical torsion spring surrounding the cam shaft and tightened to transmit motion while the member moves in one direction only. In the machine described, the needle vibration is derived from a cam 23, Fig. 3 (plan), on a vertical shaft 24 geared to the needle-bar shaft, this cam engaging between walls on an arm 21 pivotally mounted at 20 on an arm 21a fulcrumed at 19. The arm 21 has on its underside a channel receiving a block 28 pivotally carried by a link 29 which is pivoted at 36 to an arm 35 on a shaft 37, the pin 36 also connecting these members to the link 39 by which movement is transmitted to the needle-bar gate ; the shaft 37 transmits to the shuttle movement corresponding to that of the needle. The block 28 is shifted along the arm 21, to vary the amplitude of the needle vibration, by an arm of a lever 33 lying below the link 29 and mounted on a fixed pivot, the other arm of this lever being upwardlycranked ; a finger-lever 13 mounted on the same fixed pivot carries an adjustable eccentric contact-member 13a whereby its movements are transmitted to the lower arm of the lever 33 in one direction against the action of an adjustable spring surrounding the fixed pivot. Adjustable stops are provided to limit the movement of the lever 13. In order to shift the mean position of the needle laterally, the arm 21a is moved angularly against a spring 21b by an arm 18, with adjustable finger-piece 12, engaging a pin 20a on the arm 21a. The mechanism for adjusting the feed is shown in. Fig. 8 ; the feed-shaft derives its movements from the needle-bar shaft 8 through a cam 44 engaging the forked end of a lever 43 which is pivotally mounted on a link 42 connected at 40a to a lever 40 on a fixed pivot 41, the position of the pivot 40a determining the amount and direction of feed. A lever 14b also pivotally mounted at 41 and having, a lug engaging the pivot 40a, so that the lever 40 is moved with it against the action of a spring 40c, has a pin (not shown) engaging a tapering slot 14c in a sleeve on the spindle of a rotatable knob 14. The pin on the lever 14b is normally held against one side of the slot by the action of the spring 40c so that rotation of the knob 14 varies the forward feed of the work ; a push-button 14a acts on the lever 14b to swing it so that its pin engages the other side of the slot which similarly controls the feed, now reversed. For variable automatic movement of the 'control members to produce various patterns of zig-zag stitching, the shaft 8 carries a cam 46, Fig. 10, actuating against a spring, a lever 47 ; this lever carries with it a spring-returned arm 53, after lost-motion determined by a longitudinally-slidable member 54 with an inclined flange limiting return of the arm. The lever 53 operates a spiral gear 56 through a one-way drive comprising a helical torsion spring anchored to the hub of the lever 53 and wound round the spindle of the gear 56 so as to be tightened, and thus transmit motion, only when the lever 53 moves in one direction [see Group XXIV] ; the gear 56 drives a vertical spindle 58 having keys to receive three cams (absent in the drawing) which are held thereon by a pivoted arm 62 with spring catch 62a. Three cam-follower bars 64, 65, 66 are slidably mounted on pins 67, 68 to be actuated by the respective cams. The bar 64 is notched to engage a pin 69 on a lever which is adjustably connected to an arm mounted in the same bearing 71a, and a second arm rigid with the latter arm has a notch.72 engaging a pin 33a, Fig. 3, on the arm 33 controlling the amplitude of needle vibration. The bar 66 similarly engages a pin 81 on a lever which is adjustably connected to a member similarly having an arm with a notch 84 engaging the pin 20a of the arm 21a, Fig. 3, whereby the mean position of the needle is adjusted ; and the bar 65 actuates a lever connected by a cable 77 to the feed-control lever 40, Fig. 8. The bars 64, 65, 66 are held against the respective cams by the springs acting on the control mechanisms to which they are connected; the bar 65 is biased away from its cam by a spring on the pivot of the lever which it actuates, to keep the cable 77 taut. All the control mechanism shown in Fig. 10, except the cam 46, is carried by a plate 50 which is removable from the machine. The cams may be placed on the spindle 58 in a plurality of positions determined by the keys on the shaft, and may be inverted, thus giving several different stitching patterns without exchanging any of them for other cams.