JP3499407B2 - Method and apparatus for preventing seam fraying - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for preventing fraying of a sewing thread at a sewing end of a seam in a sewing machine forming a double chain stitch.

[0002]

2. Description of the Related Art When a sewing machine having a needle and a looper is used to form a double chain stitch, for example, a stitch shown in stitch type 406 of JIS L 0120, when the looper thread is pulled from the end side of the stitch. The seams unravel one after another. As a method of preventing such sewing thread fraying of the cloth, Japanese Patent Laid-Open No. 6-233877 proposes a looper thread hook provided behind the looper of the sewing machine to prevent the fraying. The looper thread hook described in this publication holds the looper thread slidably, and holds the looper thread when the sewing machine is once stopped immediately before the end of sewing. In that state, the sewing machine is operated to sew one stitch, and then the needle thread and the looper thread are cut. The sewing manufacturer removes the cloth from the sewing machine while holding the looper thread with the looper thread hook. As a result, the entangled state between the needle thread and the looper thread is changed to make it difficult to fray.

However, this method has a drawback that the looper thread ends remain long on the fabric after the looper thread is cut, and the looper thread ends must be picked again in order to improve the appearance of the sewn product. It was

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent the thread from fraying from the seam end of the seam when forming a seam on a fabric by a double chain stitch sewing machine, and yet to prevent the seam from ending. It is an object of the present invention to provide a method for cutting a yarn end of a looper yarn connected to a short length and a device therefor.

[0005]

SUMMARY OF THE INVENTION A method for preventing seam fraying according to the present invention is such that at least one needle that moves a needle thread vertically through a needle thread is advanced and retracted between an advanced position and a retracted position. When sewing a cloth by a sewing machine having a looper that swings and inserts a looper thread that forms a double chain stitch with the needle thread, at the end of sewing, the looper that extends from the cloth to the looper is advanced to the forward position. The step of hooking the thread by the engaging means, and driving the sewing machine for one stitch while the engaging means is engaged with the looper thread to move the looper to the forward position again, the looper thread hooked on the engaging means is removed. The step of cutting at the engaging portion, the step of cutting a needle thread loop from the cloth through the looper to the needle between the cloth and the looper, and the end of the looper thread remaining on the looper side being formed on the cloth. Characterized by comprising the step of pulling out from the needle thread loop.

Further, according to the stitch raveling prevention method of the present invention, the needle thread is inserted, and at least one needle that moves up and down and the forward and backward positions between the advanced position and the retracted position with the needle interposed therebetween are swung forward and backward, When sewing fabric with a sewing machine having a looper that inserts the looper thread that forms a double chain stitch with the needle thread, when the sewing is completed, the looper thread that extends from the cloth to the looper is engaged with the looper advanced to the forward position. The step of hooking the looper thread with the engaging means and driving the sewing machine to move the looper to the retracted position with the engaging means engaged with the looper thread, and then pulling the looper thread hooked on the engaging means at the engaging portion. The step of cutting, the step of driving the sewing machine for half a needle to set the looper to the forward position, the step of cutting the needle thread loop from the cloth through the looper to the needle between the cloth and the looper, and the looper remaining on the looper side. Characterized in that it consists of a withdrawing from the final needle thread loop formed the end of the thread to the fabric.

The seam anti-ravel device according to the present invention is
A needle thread is inserted, and at least one needle that moves up and down and a looper thread that forms a double chain stitch with the needle thread are inserted and retracted between the forward position and the retracted position by sandwiching the needle. And a looper thread engaging means for engaging the looper thread between the needle drop in the sewing machine bed and the tip of the looper in the advanced position, and the looper thread at the engaging portion is cut. A first cutting device, a needle thread engaging means that engages a needle thread loop extending from the cloth through the looper to the needle between the cloth and the looper, and a second cutting device that cuts the needle thread at the engaging portion. And a looper thread pulling means for engaging the looper thread end on the looper side cut by the first cutting device with the looper thread continuing from the cloth to the looper and pulling it out from the final needle thread loop formed in the cloth. It is characterized by that.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cylinder bed portion of a double chain stitch sewing machine using the present invention. Cylinder bed 1
Is provided with a feed dog 2 which makes four movements in the vertical and forward and backward directions to feed the fabric in the direction of arrow F, a looper 3 which makes an elliptical motion in the left and right and forward and backward directions, and a needle plate (not shown) fixed to the screw holes 4. There is.
A needle bar 7 to which a left needle 5 and a right needle 6 are attached is provided above the cylinder bed 1. The tips of the left and right needles 5, 6 penetrate the needle plate by the vertical movement of the needle bar 7. The looper 3 swings forward and backward in an elliptical orbit between a forward movement position and a backward movement position with the tip portions of the left and right needles 5 and 6 penetrating the needle plate sandwiched therebetween.
The left and right needles 5, 6 and the looper 3 cooperate to form a double loop stitch S with the needle threads 8 and 9 and the looper thread 10, as shown in FIGS.

This sewing machine has a needle drop in the sewing machine bed,
That is, a first cutting device 11 having the following configuration is provided on the left side of the position where the two needles 5 and 6 move up and down.
The first receiving knife 13 is fixed to the rear portion of the cylinder bed 1 with a screw 12. The tip of the first receiving knife 13 extends near the needle drop along the lower surface of the needle plate. First
The hook knife 16 is attached to the front side of the cylinder bed 1 so as to be rotatable with the step screw 14. A hook (looper thread engaging means) 15 is formed at the tip of the first hook knife 16. In addition, the first receiving knife 13
A pressing spring 17 is attached to the. This presser spring 1
7 moves the hook 15 by the rotation of the first hook knife 16.
When the hook reaches below the tip of the first receiving knife 13, the hook 15 is pressed against the lower surface of the receiving knife 13. A long hole 18 is provided at the rear end of the hook knife 16.

An air cylinder 19 is attached to the left end of the cylinder bed 1. An operating piece 21 is fixed to a piston rod 20 of the air cylinder 19 with a screw 22 so that its position can be adjusted. The pin 2 is provided on the upper surface of the operating piece 21.
3 is provided. The pin 23 is fitted in the long hole 18 of the first hook knife 16. The air cylinder 19 is also connected to a high pressure air source (not shown) via a pipe 24. Due to the aerodynamic force from the high-pressure air source, the operating piece 21 fixed to the piston rod 20 moves back and forth in the direction of arrow A. By the forward / backward movement of the operating piece 21, the first hook knife 16 rotates around the step screw 14 in the direction of arrow B.

On the right side of the needle drop inside the cylinder bed 1, a second cutting device 25 having the following structure is provided. The second cutting device 25, like the yarn cutting device described in Japanese Examined Patent Publication No. 5-68280 (US Pat. 4,726,305), has a working position approaching the movement path of the looper 3. Can be switched to a standby position (FIG. 8) where the looper 3 is separated from the moving path. Second hook female 28
Moves back and forth between the forward position and the backward position along the upper side of the blade portion 3b of the looper 3 in the acting position. Two hooks 26 and 27 are juxtaposed at the tip of the second hook knife 28. Further, the second receiving knife 30 is provided at the operating position so as to stop. A pressing spring 29 is attached to the second receiving knife 30. The second hook knife 28 is pressed against the second receiving knife 30 by the pressing spring 29, and cooperates with the second receiving knife 30 to cut the yarn at the retracted position of the second hook knife 28. The second hook knife 28 is driven by a driving device (not shown) such as a solenoid or an air cylinder.

A method for preventing the fraying of the sewing thread at the end of sewing according to the present invention will be described with reference to FIGS. 2 to 8. As shown in FIG. 2, in this sewing machine, the cloth W has a feed dog 2
Is sent in the direction of arrow F. In the sent fabric W,
Left and right needles 5, 6 and needle threads 8, which are respectively passed through the looper 3,
9 and looper thread 10 form a seam S of stitch type 406. When the needles 5 and 6 are almost at the top dead center and the looper 3 is almost at the left dead center or the forward position as shown in FIG.
Is activated to rotate the hook knife 16 clockwise. First
By the rotation of the hook knife 16, the hook 15 moves across the upper part of the blade portion 3b of the looper 3 from the rear of the looper 3 to the front. By this movement, the hook 15
3 hooks the looper thread 10 connected to the eyelet 3e of the looper 3 from the cloth W as shown in FIG.

Subsequently, the left and right needles 5 and 6 are attached to the looper thread 1
0, the blade portion 3b of the looper, and the needle threads 8 and 9 descend into the triangle of the thread. As the needles 5 and 6 descend,
The looper 3 moves on the front side of the needle and retracts to the right. As shown in FIG. 4, the looper thread 10 is engaged with the hook 15 at a position closer to the needle 5 than the needle 5, and the loop 10L is slightly longer.
To form. After that, the looper 3 moves to the left behind the needles 5 and 6 via the right dead center, that is, the retracted position, and moves forward to the left, while the new needle thread loops 8L and 9L are formed by the needles that rise through the bottom dead center. (Fig. 5 (a)). That is, FIG.
(A) shows a state in which the needle has advanced by almost one stitch from the state in FIG. Long loop 10 of looper thread engaged with hook 15
L is maintained slightly above the looper 3 as it is.

At this time, by operating the air cylinder 19, the first hook knife 16 rotates counterclockwise. The rotation of the first hook knife 16 causes the hook 15 to move.
Reaches below the tip of the receiving knife 13, and the engaging portion of the looper thread 10 engaging with the hook 15 is cut. By driving a driving device (not shown) at this cutting time, the second hook knife 28, the second receiving knife 30, and the presser spring 29 are switched to the operating position, and the second hook knife 28 is moved leftward. Exercise. As a result, the hooks 26 and 27 move to the left of the needle drop along the upper part of the blade portion 3b of the looper 3 (FIG. 6).

Next, when the second hook knife 28 is moved backward to the right, the hook 26 hooks the looper thread 10 connected to the looper 3 from the cloth W, and the hook 27 passes from the cloth W through the blade portion 3b of the looper and the needle. Hook the two needle thread loops 8L and 9L connected to each other. The second hook female 28 is
The respective yarns move backward to the right while the hooks 26, 27 remain engaged with each other (FIG. 7). Then, the two needle thread loops 8L and 9L in the engaged state are cut when the hook 27 reaches the second receiving knife 30.

The looper thread 10 in the engaged state is gradually bent by the backward movement of the second hook knife 28. When this bending progresses to a certain extent, the separated thread end 10e becomes the final needle thread loop 8L formed on the fabric.
It is pulled out to the right through L and 9LL. And
The second hook knife 28, the second receiving knife 30, and the pressing spring 29 are switched to the standby position. The pulled-out yarn end 10e side is clamped by the hook 26 and the pressing spring 29 as shown in FIG. That is, the thread end 10f of the looper thread connected to the fabric W remains short, and the thread end 10e of the looper thread remaining on the looper 3 side is the final needle thread loop 8LL, 9L.
It is pulled out from L. In this way, unless the cut thread end 10f is pulled out from the final needle thread loop 8LL, the sewing end end of the cloth is not frayed.

In the above-described embodiment, the long loop 10L of looper thread engaged with the hook 15 has the loop 15L after looper 3 has scooped new needle thread loops 8L and 9L, as shown in FIG. It is cut by reaching below the tip of the receiving knife 13. However, this cutting may be performed in a state in which the looper 3 shown in FIG. 4 is in the retracted position in which the half-needle sewing machine has been driven from the forward position of the looper 3 in FIG.
That is, with the long loop 10L of looper thread formed, the hook 15 is received below the knife 13 and the engaging portion of the looper thread 10 engaged with the hook 15 is cut (FIG. 5 (b). )). Then, after scooping new needle thread loops 8L and 9L with the looper 3, the hooks 26 and 27 juxtaposed at the tip of the second hook knife 28 are removed from the needle drop along the upper part of the blade portion 3b of the looper 3. Move it to the left. By doing this, in the state of FIG.
Even if 0L is cut, the same state as in FIG. 6 is obtained. If the method after FIG. 6 is performed as described above, fraying does not occur at the sewing end end of the cloth.

In the above-described double chain stitch sewing machine, the retracted position of the looper is on the right side of the needle drop. However, even with a double chain stitch sewing machine in which the retracted position of the looper is on the left side,
It is possible to prevent fraying at the sewn end of the fabric by equipping it with the equivalent of the second and the second cutters. Further, although the double chain stitch sewing machine described above is provided with two needles, it is not limited to this. A second embodiment of the above-described method for preventing the fraying of the sewing thread will be described with reference to FIGS. 9 to 16. As shown in FIG. 9, this sewing machine also has the cloth W with the feed dog 2 and the arrow F.
Sent in the direction of. In the sent fabric W, the needle thread 8x and the looper thread 10 passed through the needle 5x and the looper 3x, respectively.
A stitch Sx of the stitch type 401 is formed by x. The hook knife 16x is rotated counterclockwise when the needle 5x is almost at the top dead center and the looper 3x is almost at the right dead center, that is, in the forward movement position, near the end of sewing of the cloth.
By the rotation of the hook knife 16x, the hook 15x moves across the upper part of the blade portion 3xb of the looper 3x from the rear of the looper 3x to the front. By this movement, the hook 15x hooks the looper thread 10x connected to the eyelet 3xe of the looper 3x from the cloth W as shown in FIG.

Subsequently, the needle 5x is the looper thread 10x, the looper blade portion 3xb, and the thread 3 formed by the needle thread 8x.
It descends into a polygon. As the needle 5x descends, the looper 3
x moves on the front side of the needle and retracts to the left. The looper thread 10x is engaged by the hook 15x at a position closer to the needle 5x than the needle 5x as shown in the retracted position state of the looper 3x shown in FIG. 11 in which the half-needle sewing machine has been driven from the forward position of the looper 3x shown in FIG. Form a rather long loop 10xL. At this time, by operating an air cylinder (not shown), the first hook knife 16x rotates clockwise as shown in FIG. By the rotation of the first hook knife 16x, the hook 15x reaches below the tip of the receiving knife 13x, and the engaging portion of the looper thread 10x engaged with the hook 15x is cut.

After that, the looper 3x passes through the left dead point and passes the needle 5
While moving forward on the rear side of x to the right, a new needle thread loop 8xL formed by a needle rising through bottom dead center is scooped (FIG. 13). At this time, the second hook knife 28x, the second
The receiving knife 30x and the pressing spring 29x are switched to the operating positions, and the second hook knife 28x moves forward to the right. As a result, the hooks 26x and 27x move to the right of the needle drop along the upper part of the blade portion 3xb of the looper 3x (FIG. 14). Then, when the second hook knife 28x is moved backward to the left, the hook 26x hooks the looper thread 10x connected to the looper 3x from the cloth W,
The hook 27x is from the cloth W to the blade part 3xb of the looper.
Hook a needle thread loop 8xL that continues to the needle via. Second
The hook knife 28x of FIG. 15 moves backward to the left while each thread remains hooked on the hooks 26x and 27x (FIG. 15). The needle thread loop 8xL in the engaged state is cut when the hook 27x reaches the second receiving knife 30x.

The looper thread 10x in the engaged state is gradually bent by the backward movement of the second hook knife 28x. When this bending progresses to a certain extent, the separated yarn end 10xe is pulled out to the left side through the final needle yarn loop 8xLL formed in the fabric. Then, the second hook knife 28x, the second receiving knife 30x, and the pressing spring 29x are switched to the standby position. As shown in Fig. 16, the pulled-out yarn end 10xe side is hook 26x.
And the holding spring 29x. That is, the thread end 10xf of the looper thread connected to the cloth W is shortened and remains, and the thread end 10xe of the looper thread remaining on the side of the looper 3x is pulled out from the final needle thread loop 8xLL. With this arrangement, the cut thread end 10xf is the final needle thread loop 8xLL.
The fabric will not fray at the end of the stitch unless it is pulled out from.

Although the driving of the sewing machine for one or half stitches and the control of starting each cutting machine have not been described in detail,
A known means for controlling the rotation of the sewing machine motor or a means for controlling by a signal from a rotation detector provided on the main shaft of the sewing machine may be used. Further, if the tips 10e and 10xe of the looper threads that are separated and sandwiched become long, the hook 2
6, 26x may reach the second hook knife 28, 28x to cut the tips 10e, 10xe of the looper thread.

[0023]

As described above, according to these inventions, among the separated looper thread ends, only the looper thread ends connected to the looper are pulled out from the final needle thread loop formed on the fabric. Therefore, it is possible to prevent the looper thread from fraying from the end of the seam. Moreover, according to the present invention, since the looper thread end connected to the sewing end is shortened, it is possible to obtain a high-quality sewn product without adding a step of picking up the thread end.

[Brief description of drawings]

FIG. 1 is a perspective view of essential parts of a sewing machine according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a process at the end of sewing in the first embodiment.

FIG. 3 is a perspective view showing a process at the end of sewing in the first embodiment.

FIG. 4 is a perspective view showing a process at the end of sewing in the first embodiment.

5 (a) and 5 (b) are perspective views showing a process at the end of sewing in the first embodiment.

FIG. 6 is a perspective view showing a process at the end of sewing in the first embodiment.

FIG. 7 is a perspective view showing a process at the end of sewing in the first embodiment.

FIG. 8 is a perspective view showing a process at the end of sewing in the first embodiment.

FIG. 9 is a perspective view showing the process at the end of sewing in the second embodiment of the present invention.

FIG. 10 is a perspective view showing a process at the end of sewing in the second embodiment.

FIG. 11 is a perspective view showing a process at the end of sewing in the second embodiment.

FIG. 12 is a perspective view showing a process at the end of sewing in the second embodiment.

FIG. 13 is a perspective view showing a process at the end of sewing in the second embodiment.

FIG. 14 is a perspective view showing a process at the end of sewing in the second embodiment.

FIG. 15 is a perspective view showing a process at the end of sewing in the second embodiment.

FIG. 16 is a perspective view showing a process at the end of sewing in the second embodiment.

[Explanation of symbols]

3: Looper, 5, 6: Needle, 8, 9: Needle thread, 8L, 9L:
Needle thread loop, 10: looper thread, 11: first cutting device, 1
5: hook (looper thread engaging means), 16: hook female,
19: Air cylinder, 25: Second cutting device, 26, 2
7: Hook, 28: Hook female, 29: Presser spring, 3
0: Receiving knife, W: Cloth

Claims (3)

(57) [Claims] 1. A needle thread is inserted through the needle thread, and the needle thread and the double chain stitch are oscillated by moving back and forth between at least one needle that moves up and down and an advance position and a retract position with the needle interposed therebetween. When sewing a cloth by a sewing machine having a looper for inserting the looper thread to be formed, the step of hooking the looper thread connected to the looper from the cloth by the engaging means with the looper advanced to the forward position at the end of sewing, and the engaging means In the state where the looper thread is engaged, the sewing machine for one stitch is driven to move the looper to the forward position again, and then the looper thread hooked by the engaging means is cut at the engaging portion, and the looper is removed from the cloth. It is characterized by a step of cutting a needle thread loop continuing to the needle between the cloth and the looper, and a step of pulling out the end of the looper thread remaining on the looper side from the final needle thread loop formed on the cloth. Stitch fray prevention how to. 2. A needle thread is inserted through the needle thread, and the needle thread and the double chain stitch are oscillated back and forth between at least one needle that moves up and down and between the forward position and the backward position with the needle interposed therebetween. When sewing a cloth by a sewing machine having a looper for inserting the looper thread to be formed, the step of hooking the looper thread connected to the looper from the cloth by the engaging means with the looper advanced to the forward position at the end of sewing, and the engaging means After the looper thread is driven to the retracted position while being engaged with the looper thread, the step of cutting the looper thread hooked on the engaging means at the engaging portion, Drive the looper to the forward position and cut the needle thread loop from the cloth through the looper to the needle between the cloth and the looper and the end of the looper thread remaining on the looper side to the final position formed on the cloth. Needle thread loop Seam fray prevention method characterized by comprising a step of pulling Ri. 3. A needle thread, which is inserted through the needle thread, and oscillates forward and backward between at least one needle that moves up and down and between an advance position and a retract position with the needle interposed therebetween to form a double chain stitch with the needle thread. In a sewing machine having a looper for inserting a looper thread, the looper thread engaging means for engaging the looper thread between the needle drop in the sewing machine bed and the tip of the looper at the forward position, and the engaging portion A first cutter for cutting the looper thread, a needle thread engaging means for engaging a needle thread loop extending from the cloth through the looper to the needle between the cloth and the looper, and cutting the needle thread at the engaging portion. A looper thread that is pulled out from the final needle thread loop formed on the fabric by engaging the looper thread end on the looper side, which is cut by the second cutter and the first cutter, with the looper thread that is continuous from the cloth to the looper. A device for preventing seam fraying, which is provided with a traction means.