Patent GB-1314156-A (GB)
Title: Upper feed mechanism in a sewing machine
IPC: D05B27/04
Filed: 1971-04-26
Abstract: 1314156 Feeding work SINGER CO 26 April 1971 [1 May 1970] 11337/71 Heading D1G A sewing machine has a drive shaft (20, Fig. 2 not shown) a lower feed dog 30, an upper feed dog 40 and upper feed mechanism comprising an auxiliary shaft 78 driven from the drive shaft, a pitman 72 oscillated by the shaft 78, means 70 connecting the pitman 72 to a rocker arm 68, 58 connected by a linkage 50, 46, 42, 56 to the upper feed dog to provide feed advance and return movements thereto in timed relation to the lower feed dog, (which is also driven from the drive shaft;) a stud shaft 116 rotatably mounted in the machine frame and driven from the shaft 78, having an eccentric 118 engaging the linkage to impart lifting and dropping movements to the dog 20. The eccentric engages one arm 54 of a bell crank lever biassed by a spring 120, the other arm 50 being part of the linkage. The device 70 comprises a feed regulating mechanism comprising a frame 86 having pivoted thereto at 96 one end of a link 98, the other end embracing a pin 102 connected to the pitman 72. One end of a second link 104 embraces the pin 102, the other end receiving a pin 108 engaging the end of the rocker arm 68. The frame 86 is pivotable about pins 93 by mechanism 170, 162; when the axes of the pins 96 and 108 are aligned no motion is given to arm 68 by the pitman 72; as the axes separate the arm 68 is increasingly oscillated by the movement of the pitman. Feed adjustment and indication. (Figs. 1 and 5). The concentric shafts 140, 148 are rotatably mounted in the frame. At one end of shaft 148 is secured an arm 172 connected by linkage 174, 176, 180 to a chain 184 depressable by a treadle (not shown). To the other end is secured a lever 162 connected to the frame 86 of the upper feed dog feed regulating mechanism. To one end of shaft 140 is secured a crank 142 connected by a link 138 to a spring biassed indicator bracket 130 movable by a screw 134 and connected by a link 136 to feed advance regulating mechanism (not described) for the lower feed dog. At the other end of shaft 140 (see Fig. 5) is secured a crank 144 adjustably connected by a screw 156 to a pin 154 at the end of a plate arm 153 on a bush 151 rotatable on shaft 140 and carrying an arm 160 engageable with link 170 by a resilient coupling comprising a pin 166 and a spring 168. Adjustment of knob 134 adjusts the feed advance of both dogs together, that of the lower dog through link 136, that of the upper dog through link 138, shaft 140, cranks 144, 150, 160 and link 170. A pointer 132 on the bracket 130 indicates the feed advance set. Adjustment of knob 156 varies the relative position of the arms 144, 153 to vary the feed advance of the upper dog alone. A pointer 188 co-operates with a scale 190 to indicate the difference between the feed values of the upper and lower dogs, the pointer being moved by a pin 200 secured to a lever 196 pivoted at 194 to a block 192 fast on shaft 140. A follower 202 on arm 153 engages a cam surface 198 on the lever 196 to pivot the latter as the arm 153 is moved relatively to shaft 140 as screw 156 is adjusted. To change the upper feed advance while the machine is operating the treadle is depressed to rotate shaft 148 directly, lever 162 actuating the adjuster frame 86 while spring 168 yields. On release of the treadle spring 168 returns the lever 162 to its original position.