Patent GB-223124-A (GB)
Title: Thread cutter for sewing machines
IPC: D05B3/06
Filed: 1924-02-27
Abstract: 223,124. Fairweather, W., (Singer Manufacturing Co.). Feb. 27, 1924. Button-hole sewing-machines; thread-cutters and thread-end holders.-A button-hole machine is provided with a thread-cutter which is moved in a path transverse to the lead of the thread from the work so that a pointed blade grazes the surface of the work. The threads cut include the needle-thread, looper-thread, and stay cord. Means are also provided for cutting and nipping the needle thread, for removing the severed portion of needle loop and for pulling off looperthread at the completion of stitching so that it will not be under strain when severed. The thread-cutter comprises a ledger-blade 51 fixed to a movable blade 52 pivoted on a carrier 54 which is carried by a lever 58, Fig. 6, pivoted in the turret casing 60. The lever 58 is connected adjustably to a bell-crank, an arm 73 of which is linked to the button-hole cutter-lever fulcrum-pin so that when the cutter-levers are advanced the lever 58 is rocked and the threadcutters advanced to the thread-severing position. As this occurs a pin 74 on the blade 52 is moved by a cam-slot 75, in which it rides, to close the blades. The work-supporting plate is formed with the transverse slot 24b to accommodate the cutter blades. The needle-loop removing means comprises a gripper having jaws 78, 79 pressed together by a spring 84, the jaw 78 being secured to the carrier 54. The jaw 79 has an extension 85 adapted to be engaged by a latch 86 to hold the jaws open. The latch is mounted on a fulcrum-pin 87 having a lever thereon adapted to be engaged by a pin 90 on the lower cutterlever 43 to release the latch. The lever of the jaw 79 also carries an extension 91, which on retraction strikes a stop 92 and opens the jaws to release the severed loop. Means are provided for nipping the stay-cord during the initial stitches of a group. The cord passes through a guide 96, Fig. 22, between a nipper-jaw 98 and the framing and thence through guides, including a checkspring on the needle-throat. The jaw 98 is carried by a lever 100 actuated by a face cam 104, formed on a disc 105 mounted on the rapid feed-shaft 23, so timed that the cord is gripped during initial stitches and then released. Needle-thread nipper. A nipper is provided above the work together with an auxiliary cutter for reducing the length of needle-thread required to be absorbed during the formation of initial stitches and comprises the usual compound blade 119 pivotally mounted on the clamping-foot 25 or formed so as to nip and cut the thread. The blade is linked to a plate 129 stressed by a spring 133 to move the needle blade to nipping position. The plate 129 has an arm 135, Fig. 2, lying in the path of the nipper-opening rod 137. The plate 129 also carries a tooth 138 which can engage a tooth 139 of a latch-plate 140 which is moved to release the plate 129 when the cutter-levers are moved forward at the end of an operation. The rod 137 is pivoted to a lever 151 connected to a link 157 pivoted to a slide-plate 160. A spring 164 restores the slide-plate to lower position and the rod 137 to elevated position. The movements of the slide-plate and therefore of the nipper are controlled by a timing-cam 145 driven by a twoto-one gear from the needle-bar shaft, Figs. 2 and 27. A boss 159 on the slide plate receives a sliding pin 165 grooved at 167 and pressed toward the cam by a leaf spring 166. The pin is held during most of the sewing operation out of contact with the cam bv a latch-lever 168. When the stop-motion lever shifts at the close of an operation a lever 169 is rocked to engage a latch 171 and lift a tension-release bar 172 which by means of a pin 176 engages the latch-lever 168 and releases the pin 165 to engage the then stationary cam 145. On starting the machine a cam rise on the lower ledge 179 of the cam raises the pin 165 on to a ledge 180<1> and takes up lost motion in the connections to the lever plate 129. A further rise 181 causes the lever 129 to rock and opens the thread-nipper. On the further movement of the cam a cam projection 183 presses back the pin 165 so that it is latched by the lever 168. The ledge 182 then rides from beneath the pin and allows it to drop to the bottom ledge 179 where it rides idly. Threads, controlling otherwise than in stitchforming; thread-tensioning devices.-The needlethread passes from the supply through a light thread-check 185, between the tension-discs 175 and through guides beneath a pull-off bar 191 and thence to the hollow needle-bar. The pull-off bar 191 is connected to the clamp-closing lever 31 and operates prior to sewing to pull enough thread through the then open tension to allow the first stroke to be made without strain. The check 185 which is provided to control the thread while the tension is open comprises a spring-pressed disc 197 housed in a cylindrical body 195 and pressing the thread against a disc 198 carried by a pin 199 apertured at 201 to guide the thread between the discs. The looper-thread pull-off comprises a lever 108, Fig. 6, engaging the looper-thread and connected to a link 112 the grooved end of which is embraced by the forked end of a lever 114 actuated bv a cam on the disc 105 so timed that a complete oscillation from full to dotted lines and back, Fig. 6, is given when the sewing operation is completed. Specifications 142,561, 179,278, 183,873, 184,134, and 184,135 are referred to.