Patent GB-120411-A (GB)
Title: Improvements in or relating to Sewing Machines.
IPC: D05B15/00
Filed: 1917-10-06
Abstract: 120,411. Roberts, W. T. B., and British United Shoe Machinery Co. Oct. 6, 1917. S e w i n g - machines; chain-stitching by devices comprising b a r b e d needles.-In inseam sewing-machines of the type comprising a curved hooked needle and tubular looper, means are provided for automatically rethreading the looper in the event of the thread breaking. The invention is described as applied to a chain-stitch welt sewing-machine with automatic stopping-mechanism as described in Specification 5453/12. The looper consists of two sections 34, 32, Fig. 6, hinged together and closed against the action of a spring-pressed plunger 42 by a wedge 40. The lower ends 36 of the sections are shaped to form a thread passage which is opened along planes 38, Fig. 7, tangential to the thread passage and e:;- tending in a direction opposite to that in which the thread moves in the operation of the machine. When the thread breaks, the machine is stopped and the thread tension released in the usual manner. The wedge 40 which is held in its locking position by a spring is raised through a rod 54, Fig. 2, and cam-actuated lever 52. The loose end of the thread which passes through a guide in an arm 90 is clamped between this arm and an abutment 112 on the frame. The arm 90 is pivoted to the frame and its rear end is connected by a link 94 and buffer spring 114 to a cam-actuated lever 96. The thread extending from the clamp 90, 112 to the take-up 214 is carried down and into the open looper by a finger 63 which is connected to a plate 70 by rollers 72 running in a cam-groove 74 in a fixed plate 66. The plate 70 is connected by a link 76 to a camactuated lever 78. During the return movements of the parts, the thread between the looper and the take-up passes into the opening in the arm 90 which is open at the side and closed by a spring for this purpose. The cams for actuating these levers are mounted on a shaft 88 which can be driven through the gearing 104, 118 from a shaft 120 carrying a continuously driven loose pulley 122 and adapted to be connected thereto by a spring-controlled clutch 130. The clutch is withdrawn by a lever 134 controlled by a latch-lever 136 which has a projection 138, Fig. 5, adapted to be engaged by one of two pins 139 on the gearwheel 104 and held in contact therewith by a spring 140. The threading devices are set in operation by a hand-lever 142 which, through the lug 148, pushes up the rod 150 and releases the latch lever 136, allowing the clutch springs to connect the shaft 120 with the pulley 122. In one half-revolution of the shaft 88, the threading-devices act to place the thread in the looper and the second pin 139 then breaks the connexion between the shaft 120 and its pulley. The machine is then started and a lever 190 which is actuated by a cam on the main shaft 172 acts through the lug 188 on the end of the rod 150, which has been moved into register therewith by a pin-and-slot connexion with the lever 98, to free the clutch 130 and allow the shaft 88 to be given another half revolution to restore the threading-devices to their normal positions. The shaft 88 is then again unclutched from its driving pulley by the first pin 139. The tension is released during the initial stitches by a rod 238 having a. collar 240 acting on the brake-lever 176. This rod is connected to one arm of a lever 242, the other end of which is held by a spring 246 in contact with an edge cam on the shaft 88. The hand-lever 142 is controlled by a spring-plunger 160 and stops 158, 156, 162, 164, and to prevent movement of the lever until the machine is stopped, a detent 166, connected with the usual stop-levers 168, 170 is adapted to come in the way of a stop 167 on the lever. To prevent the operation of the stitching mechanism while the threading-devices are in operation, a pawl 200 carried by a spring-controlled three-armed lever is adapted to engage ratchet teeth on the main cam. When the lever 134 is moved to unclutch the shaft 88 after its first half-revolution, the pawl 200 is retracted by the engagement of its end with the arm 196. When the clutch of the shaft 88 is thrown in for its second half-revolution, the movement of the junction of the levers 170, 168 consequent on starting the machine brings the pivot pin 206 against the end 208 of the arm 194 and prevents the pawl 200 from engaging the ratchet teeth on the main cam. The tension device is adapted to act as an auxiliary take-up as described in Specification 120,541.