Patent GB-160920-A (GB)
Title: Sewing machine
IPC: D05B23/00
Filed: 1919-12-29
Abstract: 160,920. Fairweather, W., (Singer Manufacturing Co.). Dec. 29, 1919. Straw-plait sewing-machines. - Relates to a machine forming stitches as shown in Fig. 14<b>. The loopers are mounted on the presser bar and on separate axes at rightangles one to the other. Two needles, one eyed and one barbed, enter the work from below and are actuated by a variable stroke mechanism controlled by the position of the presser-foot. The mechanism is such that no lock is necessary to prevent alteration of the stroke of the needles due to any resistance the needles may experience in penetrating the work, and such resistance serves to increase the pressure of the presser on the work. Needles, driving.-An eccentric 74 on a continuously rotating shaft 67 oscillates a lever 77 which has an arcuate slot 79 embracing a slide block 80 linked to the needle bar. The position of the block 80 in the slot is determined by the thickness of the work by means of a link 97 connected by linkages, with the presser bar. When the needles enter the work, the slot is inclined as shown, and the resistance of the work to the needles tends to move the block towards the pivot 76 with a corresponding downward movement of the presser bar, which is resisted by the work underneath it. Loop-stitching.-Loopers 10, 11, Fig. 15, are adjustably secured upon carriers 31, 14 respectively, which oscillate about pivots 38, 16 in the presser-bar 7. The carrier 14 is oscillated from a shaft 22 bv means of an arm 21 and a pin 20<1> having a head 20 slidingly engaging a rod 18 on the carrier. The sliding connection 20, 18 permits vertical movement of the presser, as the thickness of the work varies, without materially altering the action of the loopers. The carrier 31 is oscillated from the carrier 14 by means of a pitman 42 of adjustable length and with ball-joints 44. The shaft 22 is oscillated bv means of a compound eccentric 25, the eccentricity of which varies in each revolution. The parts are shown separated in Fig. 16. The eccentric block 200 is pivoted upon a pin 204 on a disc 205 secured to the shaft 67, and has an elongated hole 203 through which the shaft passes. A crank 207 is mounted upon a fixed eccentric sleeve 208 and is rotated with the shaft because a pin 206 upon it enters a hole 202 in the eccentric block 200. In the rotation the distance of the pin 206 from the centre of the shaft varies and causes the block 200 to swing about the pin 204, and thereby the eccentricitv of the block 200 is varied. Presser-bar lifting devices.-To permit the lifting of the presser foot incidental to the introduction and handling of the work, the linkages connecting it to the link 97, Fig. 6, include a telescopic arm which during stitching is held from extension by a spiral spring. The movement of the link 97 is limited by suitable stops, and in lifting the presser by the usual lifting lever after the link 97 has moved the full amount permitted by stops, further movement of the lifting lever extends the telescopic connection. An additional lifting lever with a ratchet detent is conveniently mounted on the head of the machine to enable the operator while stitching to turn corners conveniently. Feed by dogs.-The feed-rock shaft 140, Figs. 4 and 5, is oscillated by an eccentric 169 and rod 136, adjustably connected to a slotted arm 138 fast on the shaft and to which the feed-bar 116 is pivoted at 141. The slide block 137 is engaged by the forked end of an arm 145, Fig. 5, pivoted on the shaft 67. A forward extension 150 of the arm carries a handle 155 having pins 158, which, when the arm has been adjusted, enter sockets and lock the arm in place. Vertical movements are imparted to the feed-dog by means of an upright link 127 pivoted to the feed-bar at 129 and to an eccentric rod 123 at 126. The pivot pin 126 is guided in a slot in a revolubly adjustable disc 124<1> and the inclination of the slot determines the lift given to the feed-dog. The pin 129 extends through a long boss which projects laterally from the feed bar, and to accommodate this the eccentric rod 123 and the link 127 are cranked, the off-set upper part of the link 127 being guided by a plate. The feed-dog is secured in a block 112 adjustable upon the feed-bar, and fine adjustment of its position is effected by a screw 109. The feeding surface is gouged out in the line of the seam and has two prongs standing above the general serrations which insure against slip of the work. Governing needle thread. - The stroke of the take-up lever and the timing of the thread lock are varied automatically as the length of feed is varied. The take-up arm 162, Fig. 5, is integral with a lever 164 pivoted near its middle on the free end of a lever arm 166. The lower end of the lever 164 is connected directly to the rod of an eccentric-rod on the shaft 67 and the upper end is connected by a link 170 with an eccentric sheave 169 which actuates the feed shaft. A thread lock, Fig. 10, comprises an eccentric actuated member 175 and a spring- pressed member 186, the position of which is determined by a containing sleeve 180. The sleeve has an oblique slot engaged by a pin 182 and is so connected to the feed regulator that the sleeve is turned and, consequently, moved axially as the feed is raised. The combined effect of the adjustments of the take-up and the thread lock is to cause the take-up to operate as a pulloff when the stitches are long and as a take-up when the stitches are short.