Patent GB-498044-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1937-07-07
Abstract: 498,044. Sewing - machines ; toothed gearing. BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation) July 7, 1937, No. 18842. [Class 112] [Also in Group XXIV] Rotary horns; lockstitching by barbed needles; thread-tensioning devices.-In a McKay-type boot-sole-sewing machine, a thread finger is provided in the horn to allow each stitch to be set before the needle thread is drawn through the work during the formation of a succeeding stitch, and in order to allow of the use of a small needle and a slender horn a looper which is movable towards and away from the tip of the horn, as well as being rotatable, is used and the needle is rotated during its descent to a position depending upon the position of the horn so that it is always presented to the looper in the same way, the needle being reversely rotated during its ascent to a substantially fixed position in which the thread is easily engaged by the shuttle. The invention is described and shown as applied to a machine of the kind described in Specification 347,269, having driving means, oscillating shuttle, and actuating means for needle, presser-foot, feed-point and awl as described in that Specification. The horn 18, Fig. 16, is fixed to a hollow spindle 88 mounted in bearings 272 in the machine frame, and is rotatable without any limit in either direction ; the devices in the horn are actuated from a shaft 24 which is driven through gearing from a shaft 22 passing up through the horn spindle 88 and having an axial bore through which the thread passes. The gearing is arranged so that rotation of the horn has no effect on the shaft 24, and comprises a gear 134 on the shaft 22 meshing with a gear 132 carrying a planet wheel 128 which runs round a normally stationary sun wheel 140 and drives an internally-toothed ring 126 integral with a gear 120 meshing with a gear 118 on the shaft 24. The sun gear 140 is connected to a gear 138 meshing with a toothed ring 136 fixed on the machine frame, so that rotation of the horn causes the sun gear to rotate the planet 128 by the amount required to accommodate the rotation of the wheel 132 round 134 without affecting the ring 126 ; the driving forces between the gears 134, 132 and 138, 136 are equal and opposite, so that there is no tendency for the horn to rotate. The thread-handling devices in the horn comprise a take-up arm 188, a rocking thread finger 92 pivoted at 106 and formed with a slightly hooked end, and a hollow cylindrical looper 94 which oscillates on its axis and slides longitudinally towards and away from the tip of the horn ; the axis of the looper intersects the needle axis and the axis of rotation of the horn at an acute angle at the same point. The looper 94 has at its end an eccentric thread eye 98, Fig. 17, and a needle opening 99 which in the uppermost position of the looper is directly beneath the needle opening 90 in the tip of the horn; the end of the looper is bevelled so that in the position shown in Fig. 17 the thread lies on it parallel to the work-engaging surface of the horn. The thread finger 92 is rocked by a sliding member 100 which is connected by a pitman 108 to a pivoted arm 110 actuated by a cam-groove in the gear 118. The reciprocation of the looper 94 is produced by a forked lever 146 pivoted at 150 and actuated by a link 148, Fig. 26, from a crank-pin 149 on a disc on the shaft 24 ; the upper end of the lever 146 is connected to the looper by a disc 142 on the end of the latter rotatably engaging in a recess of T-section in a pivot pin 144. The rotation of the looper is produced by a sliding rack 154, parallel to the member 100, engaging long teeth 152 on the looper and actuated from the link 148 by a link 162, crank 158 and pitman 156. The take-up arm 188 is operated by links 194, 196 from a crank-pin 198 on the shaft 24, the link 196 being guided by an arm 200 pivoted in the horn at 202. Tne thread passes round a thread-lock before entering the horn, and then passes round a tension device on the pivot 190 of the take-up arm, a guide pulley 191, the take-up pulley, and a pulley 216 on the lever 146. The thread-lock, Fig. 15, comprises a disc 164 on a rock-shaft mounted in bearings 167 with blocks 180, 186 fixed to them, the shaft being rocked by an arm 168 engaging an internal cam formed on one of the gears driving the shaft 22 ; the thread passes between the parts 164, 180, which are pressed together by a spring 174 engaging a block 176 on the shaft when the shaft is in a position in which endwise movement is allowed by teeth on the block 176 coming opposite notches 184 in the block 186. The tension device, Fig. 21, comprises a pair of discs 214 on the pivot 190 of the arm 188 pressed together by a spring engaging a thimble 208 which is adjustable on the pin 190. The thread is also acted upon by a loopspreader above the work, which comprises a hooked finger 36, Fig. 5, slidable in a pivot pin 286 and guided in a horizontal plane by a part 282 of the machine frame ; the spreader is reciprocated in a direction approximately perpendicular to the line of feed, and at the same time oscillated, by a crank-pin 288 on a short shaft having teeth engaging a rack 294 which is reciprocated by a lever 296 actuated by a cam oscillated by connections from the rockshaft of the needle-bar actuating lever. In operation, as the looper 94 approaches its lowest position a loop of needle thread is being passed over the shuttle, which pulls the thread tight against the under surface of the work ; the thread finger 92 then descends in front of the looper (Fig. 16), the take-up pulls the loop off the shuttle, the work is fed, the thread-lock closes and the stitch is then set by the take-up, assisted by the movement of the wheel 216. The thread lock then re-opens, the take-up pulls off thread for the next stitch, and the looper rotates clockwise (looking downwards) to carry the thread round the finger 92 and commences to rise, the finger being raised just clear of the looper to permit this; the looper continues to rotate during the first part of its upward movement to carry the thread across the path of the needle to the same side as that from which it was laid round the finger 92, Fig. 17. During the upward movement of the looper, the take-up relieves the thread tension somewhat while the looper eye 98 is sliding rapidly along the sharplybent thread, the movement of the pulley 216 supplying part of the thread required by the looper and assisting in maintaining an even tension. When the looper reaches the upper end of its stroke, the needle descends and the looper starts to rotate anticlockwise, to carry the thread round the needle, and to descend ; the take-up has a short reversal of movement at this point, with the thread-lock closed, to pull the thread into the needle hook, and then the fmger 92 is further raised to give up its loop of thread to the rising needle, after which the take-up continues to give up thread as required, but at increased tension. In order to avoid the difficulties, in some positions of the horn, of properly threading the needle and of setting twisted thread loops, the needle is rotated during its descent to a position in which the hook faces directly away from the thread finger 92, so that it can be most easily threaded, and is rotated back during its ascent to take out any twist in the thread loop and to present it in a constant relation to the shuttle. The needlebar 40, Figs. 3 and 7, is rotatable about 180‹ to each side of a mean position in which it faces along the line of feed away from the completed stitches ; its upper end is formed with a series of teeth for engagement with a rack 224 supported and guided by links 226, 230, the latter being extended beyond its pivot 232 to carry a toggle link 236 which is pivoted at its lower end 238 to a pair of toggle links 234 suspended from the tail of the needle-bar actuating lever 52. The pivot 238 of the toggle links is connected by a link 240 to an arm 242 on a sleeve 244 surrounding the shaft 232 and carrying asecond arm 245 to which is pivoted a link 246 pressed to the right by a spring 264 abutting against a member 266 through which .the link passes. The other end of the link 246 is pivoted to an arm 248 on a shaft 250 which carries an arm 252 connected by a link 254 to a rocking lever 256, Fig. 8 ; the lever 256 is pivoted to the frame at 258, and its free end engages a helical cam 260 on the horn spindle 88, the ends of the cam face being connected by a step 262. When the horn is in a position in which the thread finger lies under the line of feed and under the completed stitches, so that the needle does not require to be rotated during its stroke, the lever 256 engages the middle of the cam face 260 and the toggle pivot 238 is coaxial with the pivot 54 of the lever 52, so that the latter cannot impart any movement to the needle-turning mechanism. When the horn is rotated one way or the other the toggle pivot 238 is shifted so that the movement of the lever 52 during the needle stroke causes the. required movement of the needleturning mechanism. When the horn is rotated more than 180‹ from its mean position the direction of turning of the needle is reversed, so that the needle never requires to turn more than 180‹, by movement of the lever 256 up or down the step 262 of the cam 260 ; to allow the lever to move up the step, it is raised at each stitch, while the needle is in its highest position, by a cam 268, Fig. 7, on the main shaft of the machine, slight movement of the horn past the position at which the lever 256 engages the cam step 262 being allowed during a stitch by a spring connection between the cam 260 and the spindle 88. The cam 268 also shifts the needleturning adjustment mechanism to produce a slight turning of the needle towards the shuttle after the thread loop is spread, in order to facilitate engagement of the thread by the shuttle and casting off from the nee