Patent GB-756403-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B19/00
Filed: 1954-06-18
Abstract: 756,403. Sewing-machines. HUSQVARNA VAPENFABRIKS AKTIEBOLAG. June 18, 1954 [Sept. 1, 1953], No. 18026/54. Class 112. [Also in Group XXIV] Needles, shifting laterally.-The needle-bar gate of a zig-zag sewing-machine receives its oscillations from a cam which is rotated once for every six or a greater even number of needle reciprocations; the cam may be one of a set selectively engageable with a follower, or may be arranged to be replaceable by such a set. Means may be provided for automatically rendering two or more adjacent cams alternately effective. In the machine described the needle-bar, which may carry two needles, reciprocates in a guide which is pivoted at its upper end and is pressed towards the standard of the machine by a leaf-spring. A member 40, Fig. 2 (plan), pivoted to the guide is formed with a nose 37 slidably engaging a groove in an arcuate arm 38 pivoted at its upper end on a pin 39 and formed at its lower end with a follower nose 27 for engagement with the cam or cams; an extension 40a of the member 40 is connected by a link 46 to a manually-actuated arm 45 arranged low in the standard of the machine whereby the nose 37 can be moved along the arm 38 to vary the amplitude of needle movement produced by a given movement of the arm, and the pivot-pin 39 of the arm is mounted on the vertical arm 47 of a lever 47, 48, pivoted at 52 on a fixed bracket 53 and adjustable by a finger-knob 51 with an eccentric pin 49 engaging a notch in the end of the arm 48 to vary the lateral position of the needle in relation to the cam. When the nose 37 of the member 40 is moved above the pivot 39 the arm 38 is tilted by the needle-bar guide spring away from the cam, so that straight-line sewing is produced or shifting of the cams is permitted; the same effect may be produced by moving the needle-bar guide to the left against its spring by hand or by a suitable manually-operated member if the arm 38 is lightly biased away from the cams by its weight or otherwise. In the mechanism shown, a fixed stub shaft 19 carries a sleeve 16 with a worm-gear 17 by which it is rotated from the needle-bar shaft, and several cams 15 are held on a flanged sleeve 21 by a nut 25, the cams being apertured to receive a tube 32 carried by the flange of the sleeve 21 and the tube receiving a pin 31 on a flange of the sleeve 16 whereby the cams are rotated with the latter sleeve; the nut 25 has a spring detent 26 engageable with any of a series of grooves in the long head of a screw 20 in the end of the shaft 19 to locate the cam unit with any selected cam opposite the follower 27, a scale 34 being provided to indicate which cam is in operative position. In this form the cams are shifted by using the nut 26 as a finger-knob, and the nut thus needs to project through a hole 22 in the rear wall of the machine arm; in a modification, Fig. 12, the cam unit is shifted by a finger 100 on a rod 101 slidably mounted in the hub of the finger-knob 51, the arm 100 being spring-biased into engagement with a peripheral groove in the nut 25<1> so as to be unaffected by movement of the knob 51 and to allow it to be pushed back when it is desired to remove the cam unit through a covered aperture in the rear wall of the machine arm. The rod 101 is held in the required position, as indicated on a scale 104 on the knob 51, by a spring-pressed pin 106 in the hub of the knob engaging a series of notches in the rod. The cams are formed so that at one portion of their peripheries the radius is the same for all, permitting movement of the set relatively to the follower without retraction of the latter, and as the arrangement allows manual movement of the cams during operation of the machine means are provided to prevent such movement except when the follower is opposite that portion of the cam peripheries. This means comprises a disc 113 fixed to the cams and a plate 110 notched to receive the disc in any operative position of the cams, the disc being notched at the appropriate point to allow it to be shifted along the plate 110 with the cams only when the latter are in the proper position; the plate 110 is pivotally mounted on a pin 117 so as to yield in case the disc is not completely shifted during the time allowed, and is normally spring-pressed against an abutment 119. The rod 101 and finger 100 may be replaced by similarly-acting means actuated by a lever having a knob which projects through a slot in the front wall of the machine. Means for automatically putting adjacent cams into operation for alternate revolutions comprises a sleeve 70, Fig. 9, fitting over the nut 25 of the arrangement shown in Fig. 2 so as to hold the detent 26 disengaged and arranged for axial and rotary movement with the cams 15, the sleeve being formed with a switch-cam groove 71 for engagement by a follower 73, whereby at each revolution the cams are shifted axially so as to bring two adjacent cams alternately opposite the follower 27. The follower 73 is formed on the end of a retractible and oscillatable pin 74 with a collar 76 which may lie on either side of a depending flange on a pivoted arm 78 according to whether the follower is required to be held in or out of action. A scale on the arm 78 shows which cam is in action at any time. In order to allow a simple zig-zag machine to be converted later for ornamental sewing, it may be constructed with a single cam clamped on a plain sleeve by a simple nut to take the place of the cams, sleeve 21, and nut 25 of Fig. 2, the cam having a hole for the pin 31 and the sleeve being held on the sleeve 16 by a simple screw; the rear wall of the machine arm is formed with an aperture 22 for the nut 25 of Fig. 2 and the aperture is closed by a disc. Instead of shifting the cams axially, as in Fig. 2, the arm 38 with the follower 27 may be shifted along the set of cams, for example by a finger carried by a rod which is slidable by means of a pin and helical slot connection with a manually-rotated sleeve; the arm 38 may slide on its pivot 39, or the lever 47, 48 on its pivot 52. The rotary camselecting knob may have a pointer moving over a disc provided with removable inserts each bearing a diagram of the stitching pattern produced by the corresponding cam. Feed.-The feed may be varied cyclically by controlling the feed mechanism by a separate set of pattern cams arranged similarly to the set for shifting the needle.