Patent GB-543805-A (GB)
Title: Improvements in and relating to sewing machines and a method of sewing
IPC: D05B1/04
Filed: 1940-07-09
Abstract: 543,805. Sewing machines. AMERICAN MACHINE & FOUNDRY CO. July 9, 1940, No. 11439. Convention date, Aug. 12, 1939. [Class 112] Running-stitch machines. The stitch is formed by a double-ended needle 70, Fig. 8, which is passed to and fro between needle holders 55, 56. When the needle is above the work the thread on the free thread side of the needle is engaged by a roller 158 on a pull-off arm 156 operated by a cam and on the other side by a spring-actuated tension finger 159 frictionally engaged with the arm 156 but initially held back by engagement with the lever actuating the upper needle-holder. When the needle is below the work, the thread is engaged by a puller 274, and the free end is drawn through the last two perforations and laid under a band 194 on a stationary drum 178, the band being lifted by a cam on the puller. Fig. 8 shows the position immediately after the needle has passed downwards through the work. It has made a slight upward movement to form a loop L in the thread. The free thread lies under the band 194 and near to the needle it has been gripped and raised by a device 248 and placed within an open thread guide 272. The thread puller 274,' which rotates continuously but at varying speed around the drum 178, passes into the thread loop and engaging the thread carries it to the right, the device 248 having previously moved to a lower position out of the track of the puller. The free thread reeves around the puller and the roller 158 until the free end has been drawn through the last two perforations and the free thread is laid under the band 194. Prior to the slight upward movement of the needle, the thread is gripped on to the needle at its eye by a pair of tongs 229 and remains gripped during the thread pulling movement. Feed by dogs. The feed bar 128, Fig. 16, is carried at one end by an idler lever 142 and at the other end receives feed-lift movements from a cam-actuated lever arm 131 and feed advance movements from a lever 115 and a bar 114 which has a vertical movement determined by the horizontal movement of its lower end, produced by a crank-pin on a shaft 107 engaging a slot in the bar 114, and the inclination of a guide 120 embracing a pin on the bar 114. The stitch length is varied by turning the guide 120. When stitches of two specific lengths are required at different parts of the work, a stop member comprising two adjustable screwed heads 318,319 which embrace a fixed part 314 is carried by a feed-adjusting rod 310 and the latter may be connected to a treadleoperated lever 304. When alternate long and short stitches are required, an arm integral with the guide 120 is moved between two positions by a cam rotating freely upon the shaft 107 at half the speed of this shaft. Starting and stopping. A belt-pulley 20 driven by a motor 14 forms one element of a clutch of which the other element 21 is carried by a slidable shaft 36 bearing also a pulley 22 connected to the machine and a brake drum 35 engageable with a fixed member 37. The shaft 36 is moved longitudinally by an arm 33 of a lever 30 connected to a treadle rod 29 and a return spring 39.. To ensure stopping of the machine in a particular position, the lever 30 is connected by a link 280 with a lever which has a roller running on the face of a disc rotating with the machine and formed with a notch at the required position, the treadle being operable only when this notch is opposite the roller.