CS277666B6 - Sewing machine for thread cutting machine - Google Patents

Abstract

The device comprises a fixed knife (5) cooperating with a movable knife (11) and a holding spring (9) with a support (22) of the movable knife (11). These parts are mounted on a common supporting body (2), while the arm (16) of the movable knife (11) is connected by means of an adjustable rod (19) to the swing lever of the control device.

Description

Field of technology.

The invention relates to a device for a sewing machine for cutting threads, consisting of a movable knife cooperating with a fixed knife and a holding spring.

Prior art

In a known device of this kind, a movable knife rotatably mounted on a pin is movably connected to one arm of an angled two-arm lever, the other arm of which is pin-connected to a rod adapted for reciprocating rectilinear movement derived from the cam cams different kinds of movements. The disadvantage of this device lies in the complexity of adjusting and adjusting the position of all individual functional parts in the machine?

Another known solution derives the movement of the movable knife from the core of the electromagnet by a relatively small number of mechanical coupling members, none of which is formed as a cam. Although this solution is simpler to manufacture, it is not perfectly secured against malfunctions of the cutting process itself, eg in the event of a collision of the cutting knife with the needle, which can occur due to instability of electrical elements due to fluctuations in electrical voltage in the supply network. In addition, adjusting this device directly in the machine is also relatively complicated.

The essence of the invention

These disadvantages are eliminated by a thread cutting device consisting of a movable knife cooperating with a fixed knife and a holding spring, the essence of which consists in that the movable knife, fixed knife with holding spring and movable knife support are mounted on a common support body. it is connected by means of an adjustable rod to the pivoting lever of the control device.

The device according to the invention can be set as a whole before the actual assembly into the sewing machine, where the actual fine adjustment is then performed easily by operating only a single adjustable drawbar.

Overview of pictures in the drawing

The invention is explained in more detail with the aid of the drawing, in which FIG. 1 shows a view of the arrangement of the thread cutting knives, FIG. 2 shows the control device of the thread cutting device and FIG.

Examples of embodiments of the invention

The sewing machine (Fig. 1) comprises a base plate 1 in which a support body 2 is mounted. A thread cutting device fixed to the base plate 1 by screws 2. A groove 4 is formed in the support body 2 for fixing a fixed knife 5 with a cutting edge 6. by means of a screw 7 and another groove 8 in which a flat retaining spring 9 is fixed by a screw 10. To the support body 2 is further fixed a pin 12 which carries a rotatable movable knife 11 formed by a two-arm lever, one arm of which is provided with a point 13; in which a recess 14 with a cutting hole 15 is formed and the second arm 16 is provided with a pin 17 fitting into the fork 18 of the adjustable rod 19. The adjustable rod 19 is kinetically coupled, for example, by levers to a control device, formed in this case by a cam 31 (Fig. 2) and an electromagnet 30. A shaft 20 carrying a hook 21 is further rotatably mounted in the base plate 1. The support body 2 is provided in the space below the movable knife 11 with a support 22, the bearing surface for supporting the movable knife 11 being at the same level as the bottom surface of this movable knife 11.

The sewing machine is further provided with a device for stopping the machine in a preselected needle position.

By moving the adjustable rod 19 from the rest position to the active position, the movable knife 11 is tilted around the pin 12 away from the fixed knife 5 by means of a fork 18 threaded on a pin 17 in the arm 16 of the movable knife. knives 11 so that the lower thread emerging from the hook 21 and the upper thread of the last stitch pass along the outside of the tip 13 of the movable knife 11 and move into the recess 14 with the cutting hole 15. At this point the movable knife 11 begins to return towards the fixed knife 5. by the action of the adjustable rod 19. The two threads, which were in the recess 14, approach the cutter edge 6 of the fixed knife 5 with further movement of the movable knife 11. To ensure reliable thread cutting, the outer part of the movable knife 11 a support 22 of the support body 2, which is flush with the lower surface of the movable knife 11. The movement of the movable knife 11 relative to the fixed knife 5 is completed via cutting the upper and lower threads and returning them to the starting position. In this initial rest position of the movable knife 11, the lower thread is held by a flat holding spring 9 on the lower surface of the movable knife 11 and is thus prepared to form the first stitch of the next seam. This completes the entire thread cutting cycle.

Claims (1)

PATENT CLAIMS Sewing machine device for thread cutting, consisting of a movable knife cooperating with a fixed knife and a holding spring, characterized in that the movable knife (11), the fixed knife (5) with the holding spring (9) and the support (22) of the movable knife (11) are mounted on a common support body (2), the arm (16) of the movable knife (11) being connected by means of an adjustable rod (19) to the pivoting lever of the control device. -