Patent GB-190307748-A (GB)
Title: Thread-cutting Devices for Sewing Machines
Inventor: MACDONALD JOHN KING
Filed: 1903-04-03
Granted: 1903-06-18
Abstract: 7748. Macdonald, J. K., [Singer Manufacturing Co.]. April 3. Sewing-machine thread-end holders; thread-cutters for buttonhole-sewing machines, button-attaching machines, and the like. Reference is made to the buttonhole-sewing machine described in Specification No. 21,637, A.D. 1896. A lever 24 is pivoted at 25 to a bracket 23 on the shank 22 of one of the presser-feet of the machine, and has two fingers 26, 27, projecting at a slope downwards from it towards the cloth plate. The lower finger 26 is a cutting-blade, while the upper 27 forms part of a holding-device for the end of the upper thread. Two blades 29, 30 are carried on an arm 28 pivoted on the lever 24 at A. The lever 24 is rocked by a rod 31 loosely attached to a lever 32 and urged towards the front of the machine-the right hand in Fig. 1-by a spring 35. The lever 32 is controlled by a stop 45 and by a collar 57 on a rod 56 connected with the mechanism for shifting the driving-band from the loose pulley 15 to the fast one 16. The lever 28 is rocked by a rod 36, which is urged towards the rear-the left of Fig. 1-by a spring 37, and is further controlled by a lever 38, which is actuated by a cam on the main driving-shaft 14. The lever 38 is engaged at the proper times by a fixed stop 43 and a catch 50, which is moved so as to disengage the lever by a pin 55 on the shaft 14. The rod 53, which connects the pin and the catch, is engaged with the pin when the belt shifter 17 shifts the belt on to the loose pulley. The action is as follows :-Just before the machine is started, the levers 24, 28 are in the positions shown in Figs. 7 and 11. The fingers 26, 27 (the latter of which is not shown in Figs. 4, 5, 6, and 7) and the blade 30 coincide, and are situated in the path of the needle, the position of which is shown by a small dotted oval, representing the hole in the cloth plate, in the last-named Figures. The upper thread end is held between the finger 27 and the blade 30, as shown in Fig. 11. The act of starting the machine causes the collar 57 to shift the lever 32, and move the cutting and holding devices into the position shown in Fig. 4, in which they retain their relative positions, on account of the connection of the lever 28 and the rod 36 being in nearly the same vertical line as the pivot of the lever 24. They are, however, clear of the path of the needle. After two or three stitches, the lever 38 is moved by its cam so as to bring the cutting-blades into the position shown in Fig. 5, thus releasing the upper thread. At the same time, the lower end of the lever 38 is engaged with the catch 50. The sewing then proceeds until the driving-belt is shifted on to the loose pulley. The collar 57 then releases the lever 32 and the spring moves the levers 24, 28 into the position shown in Fig. 6. The momentum of the parts causes the formation of another stitch, which, however, is laid round the fingers 26, 27 and the cutter 28. At the same time, the upper thread is held fast by a thread gripper 58 on the rod 56, so that no more thread can be drawn from the spool to form the stitch. The take-up 62 thus pulls the lower thread up through the fabric, as shown in Fig. 12. The pin 55 then releases the catch 50, and the rod 36 is pulled suddenly to the left by the spring 37. The blade 29 then cuts the lower thread, and the blade 30 and the finger 26 cut the upper one, the loose end of which is gripped between the finger 27 and the rounded upper edge of the blade 30, as shown in Fig. 11. The series of operations is repeated for the next group of stitches, on re-starting the machine.