Patent GB-739815-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1953-05-06
Abstract: 739,815. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO., Ltd., and GERMANY, N. V. May 5, 1954 [May 6, 1953], No. 12549/53. Class 112. Work feeding. In a machine for sewing seams in leather soles and comprising a main cam shaft extending horizontally and transversely across the machine, a curved hooked needle and a curved awl, a work table, a presser-foot arranged to press a workpiece against the work table as the work is pierced by the awl and needle, an oscillating thread take-up, and a rotary shuttle lying above the table; the presser-foot and work table are arranged to move rectilinearly, on suitable supporting means, to feed the workpiece onwards whilst the needle and awl, which are arranged always to lie in the same plane, are both withdrawn from the workpiece. The invention is shown as a modification of the machine described in Specification 23478/10 as modified by Specifications 24331/12, 1021/14, 190,547 and 273,794, [all in Class 112], and consists essentially in substituting a clamp feed for the awl feed of said machine. The frame 2 of the machine carries a pair of brackets 38, 40, Fig. 1, provided respectively with aligned hollow spigots 39, 41. A curved hooked needle 32 is mounted on a carrier 34 journaled on the spigot 39. A curved awl 48 is mounted on a carrier 36 integral with a pin 35 which is journaled in the spigots 39, 41 and is adjustably fixed against longitudinal displacement. The awl is actuated by an awl driver 53 journaled on the spigot 41. A work table 54, Figs. 3 and 4, is mounted on a carrier 56 provided with trunnions 58 slidably journaled in the brackets 38, 40, and also with a tongue 62 slidably engaging a groove in the machine frame, whereby the table is. slidable laterally while its work-engaging upper face remains in the same horizontal plane. A presser-foot 76 is carried by an arm 74 of a double-armed lever 72 which is slidably journaled on a pin 70 fixed to the bracket 40. A tongue 90 projects downwardly from the hub of the lever into a groove 68 formed in the work table carrier 56, whereby lever 72 can pivot about pin 70 to raise and lower the presser-foot, while sliding movement of lever 72 on pin 70 is transmitted to the work table by means of the tongue 90. The hub of lever 72 is formed with a pair of opposed slots 88 engaged by coaxial pins 86 which are pivoted within the forked arm 82 of a bell crank lever 84, the other arm 94 of which is connected by a link 96 to a lever 98 actuated by a toggle link 102 for imparting feed and return movements to the work table and presserfoot. The other arm 80 of lever 72 carries a ball end 78 connected by a link 104 to a ball end 106 on one arm of a bell crank lever 108 pivoted at 110 on bracket 40. A link 114 connects lever 108 to a floating lever 118, being pivoted to the latter at 116. Lever 118 is pivoted at one end at 120 to a link 128 fixed adjustably by means of a bolt 132 in a slot 134 in one end of a bell crank lever 136, the other arm of which carries a roller which co-operates with a rotary cam. A longitudinally slidable rod 125, which may be fixed against sliding by locking means 126, is pivoted at 122 to the floating lever. When rod 125 is free, lever 118 fulcrums about the pivot 120, and when the rod is locked, lever 118 fulcrums about the pivot 122. The other end of lever 118 is connected by a link 130 to a rocking arm 142 and the latter is connected by a link 144 to one arm of a bell crank lever 148. A pin 151 carried by the other arm of the latter is secured to a tension spring 156 which thereby tends to urge the presserfoot against the work table. Pin 151 is disposed in a slot 152 at the end of a link 154 and in normal operation of the machine does not make contact with the ends of the slot. At the beginning of the work-feeding movement, lock 126 holds the rod 125 stationary and the presser-foot is urged downwardly by the action of the cam-actuated lever 136. At the end of the feeding movement the awl pierces the work and lever 136 then commences to lift the presserfoot against the resistance of the spring 156 by rocking the lever 118 about the pivot 122. As soon as the return movement of the presser-foot and work table is completed, lock 126 is released, whereby the presser-foot is urged against the work by spring 156 which acts to rock the lever 118 about the pivot 120, the lever 136 being held stationary by its cam. Lever 136 is next actuated in a direction to apply force to the presser-foot, but the latter is not moved since lever 118 rocks about the pivot 116 to relieve the tension in spring 156. The awl is now withdrawn from the work, having retained the latter in position during the time when the work was not clamped to the table by the presser-foot. As the movement of the lever 136 in the work-pressing direction is almost completed, lock 126 is applied and the completion of said movement serves to rock lever 118 about pivot 122 for applying a small positive pressure to the work. Another movement of the feed is then initiated under the action of the toggle link 102. On the stopping of the machine, link 154, which is pivoted to a lever 166, is raised initially .by the latter to release the lock 126, and further rocking of lever 166 brings the lower end of slot 152 against the pin 151 to rock lever 148 and thereby raise the presser-foot by rocking lever 118 about pivot 120. A hand lever 168 is connected by a link 170 to lever 166, whereby the operator may raise the presser-foot still higher if required. It is stated that the effort required to operate the hand lever 168, when heavy work clamping pressure is required, may be somewhat reduced by replacing spring 156 by a spring having one end secured to a downward extension of lever 118. Lock-stitching. A pair of thread locks is provided for the needle thread 203, Fig. 5, the arrangement being such that neither thread lock is opened during a normal stitchmaking cycle unless the other is fully closed, while both thread locks are open when the machine is at rest. The upper thread lock comprises a fixed jaw 204 formed with an aperture for the thread, and a movable jaw 210 pivoted to one end of a bell crank lever 216, the other arm of which is pivoted to a link 222 which passes freely into a hollow adjusting screw 226 threaded into a lug 228 in the machine frame. A spring 220, which encircles the link 222 and abuts the screw 226 and a collar 232 on link 222, serves to bias the jaws together. A link 238 has a ball and socket connection at one end with the bell crank lever 216, and is formed at the other end with a slot 248 engaged by a pin 246 on an arm 244 fixed to a shaft 250 journaled in the machine frame. An arm 258, also fixed to shaft 250, is pivoted to the strap 262 of an eccentric 264 mounted on the main cam shaft 4 of the machine. The arrangement is such that the pin 246 for the greater part of its travel moves freely in slot 248, the pin when moving in one direction not quite reaching the corresponding end of the slot, but in the other direction reaching the other end of the slot and moving link 222 a small distance in a direction to open the upper thread lock during a small portion of the stitch-making cycle.