Patent GB-190804417-A (GB)
Title: Thread Cutting Mechanism for Sewing Machines.
Inventor: FAIRWEATHER WALLACE
Filed: 1908-02-27
Granted: 1908-10-01
Abstract: 4417. Fairweather, W., [Singer Manufacturing Co.]. Feb. 27. Buttonhole - sewing machines ; thread - cutters; stopping - gear, automatic; governing needle and under thread.-Thread-cutting mechanism for sewing-machines which cuts both upper and lower threads is arranged to avoid leaving the cut ends upon the face of the work, and is described as applied to buttonhole-sewing machines, such as that described in Specification No. 5621, A.D. 1904. The upper thread cutting mechanism is actuated automatically in connexion with automatic stopping- gear of the kind described in Specifications Nos. 261 and 5621, A.D. 1904. Figs. 1 and 3 show views in elevation, and Figs. 2 and 4 show under and upper views of the machine. The upper thread-cutter comprises a pivoted blade 25, Fig. 13, working beneath a pivoted thread-nipper 24 and co-operating with the sharp edge of the lower surface of a slot 26 in the work-clamp 14, which is carried by spring arms 16, Fig. 3, and is pivoted on an horizontal pin 18. An horizontal spring-pressed rod 31, Fig. 11, moves in a guide 33, and actuates the upper threadcutting mechanism through a crank 28. The tension of a spring 34 is gradually increased by the ordinary feed-motion of the plate 12, a spring- pressed latch 39 pivoted on a lever 38 being meanwhile in position to act as a stop and prevent the motion of the rod 31. The spring 34 then actuates the cutting-mechanism when the latch 39 is suddenly withdrawn by the automatic stopping of the machine. The lever 38 is fixed on a rock-shaft 36, Fig. 4, carrying an arm 45 provided with a hollow cylindrical piece 46, in which slides a spring-pressed pin. When the pin 22<x> on the rotary feed-plate 22, Fig. 2, actuates the lever 61 and releases the vertical rod 62, the automatic stopping-gear of the kind described in the above-mentioned Specifications comes into operation, and the spring-pressed plunger-rod 52, Fig. 3, rises and rocks the shaft 36 by means of a collar thereon actuating the arm 45, Fig. 4, through the pin in the cylinder 46. The tension of the needle thread is released immediately after the nipping and cutting operation to prevent the thread from being pulled out of the nipping- device This is effected by the wedge-shaped end 68, Fig. 3, of a spring-controlled pivoted lever 66 entering between the tension disks 69, the lever 66 being actuated by connexion with an arm 71 fixed on the rock-shaft 36. The nipping-operation takes place before the cutting - operation because the nipping-member is set slightly in advance of the cutter, a pin in the one member projecting into a recess in the other to maintain their relative positions. The nipper and cutter are formed separately, and are detachable, a portion of the lower part of the work-clamp 14 being made removable to facilitate the removal of the nipper and cutter. The lower thread-cutter comprises a spring knife-edged portion 76, Fig. 2, of a laterally sliding plate 73, and co operates with the edge of the needle throat to effect the cutting operation. A pull-off lever 78 is pivoted by a pin 79, and is actuated by connexion with the plate 73 so that a requisite length of thread is drawn off by this lever 78 before the cutting operation. The plate 73 is actuated by a pivoted arm 86 controlled by a spring 99. When the work-clamp is raised for removal of the work by depression of a treadle &c. attached. to a chain 92, fig. 1, a loose boss 90 on the shaft 36 is rocked, and an attached arm 89 then actuates the lever 86, Fig. 2, to effect the cutting-operation immediately before the work is removed. After the upper thread is cut, the tension of the lower thread draws the cut end of the upper thread downwards, and the action of the pull-off lever for the under thread, subsequently to the cutting of the upper thread and before the cutting of the lower thread, ensures the withdrawal of the cut thread end from the face of the material.