JPH0214778Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial technical field] This invention relates to a thread cutting device for a sewing machine, and in particular, a movable knife is reciprocated with respect to a fixed knife that is fixedly arranged, and when the movable knife moves back, the fixed knife cuts. This invention relates to a thread cutting device for a sewing machine that shears thread using a blade and a blade portion of a moving scalpel.

[Conventional technology]

In the conventional thread cutting device of this type, the fixed knife and the movable knife are always elastically pressed into contact with each other.

[Problem to be solved by the invention] For this reason, in conventional thread cutting devices, the cutting blade of the fixed knife is always connected to the moving knife even at the beginning of the forward or backward movement of the moving knife, which does not require shearing action. Since the cutting blade of the fixed scalpel is in pressure contact with a surface other than the blade, it has the disadvantage that the cutting blade of the fixed scalpel wears quickly and has poor durability.
On the way to the shearing position after being captured by the moving knife, the thread touches the blade of the stationary knife and is cut, and the length from the needle to the cut end of the thread becomes shorter, and then the thread ends at the beginning of sewing. There were disadvantages such as the thread coming out of the needle hole and not being able to form stitches.

[Means for solving problems]

This idea uses an engagement member formed relative to the fixed knife and the movable knife to separate the cutting blade of the fixed knife from the movable knife when the movable knife moves forward, and moves the cutting blade of the fixed knife when the movable knife moves backward. It was configured to be brought into pressure contact with the female.

〔Example〕

Examples of this invention will be described below with reference to the drawings.

1 is a fixed scalpel made of an elastic plate, the base 2 of which is fixed to the machine frame (not shown) with screws 3;
A cutting blade 4 is formed at the tip by extending the tip, and a slope 5 as one of the engaging members is formed on the side.

Reference numeral 6 denotes a movable scalpel, whose base is rotatably supported with respect to the machine frame by a step screw 7, and whose tip has a branching part 8 that cuts into the needle thread loop to be cut, and one side of the loop. a jaw portion 9 that captures the blade, a blade portion 10 that faces the cutting blade 4 of the fixed knife 1, and an engaging portion 11 that faces the slope 5 of the fixed scalpel 1 and constitutes the other engaging member.
Form by bending.

The movable knife 6 is reciprocated about the stepped screw 7 by appropriate means.

This invention has the above-mentioned structure, and the state at the time of thread cutting will be sequentially explained below with reference to the drawings.

FIG. 1 is a plan view when the moving knife is in a normal position, and FIG. 1A is a sectional view taken along line 1A-1A in FIG.

When the moving knife 6 rotates clockwise from the state shown in FIG. 1 to the position shown in FIG. The stationary knife 1 is pushed up and bent, and the cutting blade 4 at the tip is separated upward from the movable knife 6. Further, the branch portion 8 of the moving knife 6 is inserted into a needle thread loop (not shown).

When the moving knife 6 further rotates from the state shown in FIG. 2 to the position shown in FIG.
As shown in the figure, it passes below the slope 5 of the fixed knife,
As a result, the fixed knife 1 returns to its original lower position by its own elastic force, and one of the needle thread loops enters inside the jaw 9 of the movable knife 6.

When the moving knife 6 starts returning from the state shown in FIG. 3 and rotates counterclockwise to the position shown in FIG. When engaged upward, the fixed knife 6 is bent and pushed down, and the cutting blade 4 of the fixed knife 1 is elastically pressed against the blade part 10 of the movable knife 6, and in this state, the thread caught in the jaw part 9 is removed by the cutting blade. 4 and the blade part 10.

Furthermore, when the moving knife 6 moves back counterclockwise and the engaging portion 11 passes through the slope 5 of the moving knife and comes off,
The fixed knife 1, which had been pressed downward, returns to its original position above as shown in FIG. 1A by its own elastic force.

[Other Examples]

In the illustrated embodiment described above, the slope 5 as one of the engaging members is formed on the fixed knife 1, and the engaging portion 11 as the other engaging member is formed on the movable knife 6. It is also possible to form one of these engaging members, the slope 5, on the movable scalpel 6, and provide the other, the engaging portion 11, on the fixed knife 1.

[Effect of idea]

As described above, this invention uses an engaging member to separate the cutting blade of the fixed knife from the blade of the moving knife when the moving knife moves forward, and press the cutting blade of the fixed knife against the moving knife when moving back. Compared to conventional models where the cutting blade of the fixed knife is always in pressure contact with the moving knife, the cutting blade of the fixed knife has less wear and can be used for a long period of time, resulting in excellent durability. In addition, the shearing force is stronger and the thread is cut more reliably, and the thread can also be cut at a predetermined position, so if the length of thread from the cut needle to the cut end is too short, it will not be possible to cut the thread at the beginning of the next sewing. This provides the effect that accidents such as failure to form stitches due to the thread end coming out of the thread hole of the needle do not occur.

[Brief explanation of the drawing]

Figures 1, 2, 3, and 4 are plan views sequentially showing the movement of the moving knife, and Figure 1A is the 1st diagram in Figure 1.
A cross-sectional view of the A-1A section, Figure 2A is 2A in Figure 2
- A cross-sectional view of the 2A section, Figure 3A is 3A in Figure 3.
A cross-sectional view of part 3A, Figure 4A is 4A-4 in Figure 4.
FIG. 3 is a cross-sectional view of part A.

Claims (1)

[Scope of Claim for Utility Model Registration] A fixed scalpel consisting of an elastic plate fixed to a base and a machine frame and having a cutting blade formed at its free end, and a fixed scalpel whose base is rotatably supported on the machine frame and when rotating back to the free end. A moving knife formed with a blade part that produces a shearing action in cooperation with a fixed knife, an engaging part formed on the fixed knife or moving knife, and a slope formed on the fixed knife or moving knife on the side that does not form the engaging part. , , and when the movable knife moves forward, the fixed knife is deflected by the engagement between the engaging part and the slope, and the cutting blade of the fixed knife is separated from the moving knife surface, and when the moving knife moves forward, the cutting blade of the fixed knife and 1. A thread cutting device for a sewing machine, characterized in that the device is configured to generate a shearing action by bringing the blade of a moving knife into contact with the blade.