JPH06233877A - Fray preventing method for seam and device therefor - Google Patents

Abstract

PURPOSE:To prevent a sewing thread from being frayed at a sewing end by a multi-thread chain stitch sewing machine or a covering chain stitch sewing machine. CONSTITUTION:A looper thread guard 3 longitudinally movable and capable of slidably holding a looper thread is provided. A sewing machine is temporarily stopped immediately before a sewing end, and a looper thread 5 is hooked and held by the looper thread guard 3. A needle thread and the looper thread 5 are cut after sewing is made by one stitch, and a sewing thread is removed from the sewing machine. Regarding a seam at the sewing end, the looper thread is removed from the loop of the needle thread, other-thread lacing is made at the sewing end, and the fray of a seam can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double chain stitch sewing machine, a flat stitch sewing machine and the like, and a method for preventing the fray of the seam at the end of sewing of a sewing machine for sewing with a looper thread and a needle thread, and an apparatus used therefor. Regarding

[0002]

2. Description of the Related Art In order to prevent fraying of a sewing thread from a sewing end portion of a sewing by a double chain stitch sewing machine or a flat stitch sewing machine using a needle thread and a looper thread, several stitches before the end of sewing are required. Performing sewing with a short distance between the stitches on the sewing cloth and making the needle thread and the looper thread entangled easily before and after the stitch, with the tension of the needle thread and the looper thread being loosened. , The second method of making the needle thread and the looper thread entangled or entangled between the front and back of the seam or for each seam by performing sewing for several stitches before the end of sewing, or the sewing cloth before the end of sewing A third method has been used in which the needle thread is tensioned by increasing the tension of the cut looper thread on the side connected to.

[0003]

However, in the case of the first method, the seam spacing is narrower than in the other seams, and in the case of the second method, the tension of the looper thread is relaxed so that the entire seam is tight. There was a problem that the seams at the end of sewing did not look good, such as disappearing. Further, the third method has a problem that wrinkles are generated in the sewing material due to the tension of the looper thread.

The present invention has been made in view of such circumstances, and in a sewing machine such as a double chain stitch sewing machine or a flat stitch sewing machine for sewing with a needle thread and a looper thread, the sewing machine is sewn up just before the end of sewing. Stop once near the dead point, move the looper thread hook provided on the back side of the sewing machine bed toward the front of the sewing machine, hook the looper thread passing through the back of the looper on this, and then move the looper thread hook back to its original position. After returning and sewing only one stitch, cut the needle thread and looper thread, remove the sewing cloth from the sewing machine while holding the looper thread in the thread trimming device, and loop the looper thread to the final loop of the needle thread with respect to the seam at the end of sewing. It is intended to provide a method for preventing the fray of the seam of the sewing machine at the end of the sewing without spoiling the appearance of the seam by removing it from the seam, and an anti-fray device used for the execution. To.

[0005]

A method for preventing fraying of stitches according to the present invention is a method for preventing fraying of stitches in a sewing machine for sewing using a needle thread and a looper thread. A looper thread hook that holds the looper thread slidably is provided at the rear, the sewing machine is stopped immediately before the end of sewing, the looper thread is held by the looper thread hook, and one stitch is sewn, and the needle thread and looper thread are cut. The looper thread is pulled out from the final loop of the needle thread with respect to the seam at the end of sewing by removing the sewing cloth from the sewing machine while holding the looper thread in the looper thread hook. Further, a stitch fray prevention device according to the present invention is a looper thread for slidably holding a looper thread behind a looper for entwining a looper thread with a needle thread in a sewing machine that uses a needle thread and a looper thread for sewing. It is characterized by having a hook.

[0006]

[Operation] When the sewing cloth is taken out of the sewing machine, the cut looper thread is slidably held in the looper thread hook.
As the sewing cloth moves away from the sewing machine, the looper thread gradually begins to come out of the final loop of the needle thread, and eventually comes out completely. When the looper thread is pulled out from the final loop of the needle thread, the last seam becomes the shape of the other thread lacing, and the fray does not occur.

[0007]

The present invention will be specifically described below. FIG. 1 is a schematic plan sectional view showing the device of the present invention, and FIG. 2 is an operation explanatory diagram when the device of the present invention is viewed from the left side surface. 1 and 2, the outline arrow direction is the front side of the sewing machine. In FIG. 1, 6 is a sewing machine bed, in which a sub-feed base 13 and a main feed base 14 are arranged in parallel with each other in the front-rear direction, and a screw is provided on a side surface of the sub-feed base 13. The base of the auxiliary feed dog 15 is attached by 17 and the base of the main feed dog 16 is attached by a screw 18 to the left side surface portion of the main feed base 14. The main feed dog 16 is located on the rear side and the sub feed dog 15 is located on the front side. The sub feed dog 15 and the main feed dog 16 both operate to feed a sewing cloth (not shown) to the rear side of the sewing machine by the feed mechanism (not shown) arranged in the sewing machine bed 6 when the sewing machine operates. A longitudinal groove 16a of the sewing machine is provided at the boundary between the base of the main feed dog 16 and the feed dog portion.

A looper 1 having a U-shape in front view (see FIG. 5) is disposed below the sub feed dog 15 and the main feed tooth 16 and moves leftward and rightward. FIG. 1 shows a state in which the looper 1 moves to the leftmost. 5 is a looper thread, and the looper thread 5
Passes through the upper side of the looper 1 from right to left, and continues from the position near the left end of the upper side to the seam. A needle plate mounting plate 8 having an inverted U shape in plan view is provided so as to surround the auxiliary feed tooth 15 and the main feed tooth 16 from the front surface to the left side surface of the sewing machine and to the rear surface. A groove 8a is provided in the front-rear direction of the sewing machine at a position corresponding to the groove 16a.

Further, on the rear surface of the needle plate mounting plate 8, a groove 8a is formed.
A cylinder mount 9 is provided at a position corresponding to.
As shown in FIG. 2, the cylinder mounting base 9 has a vertical mounting plate portion at a position slightly separated from the rear wall of the sewing machine bed 6, and the air cylinder 11 is mounted on the cylinder mounting base 9 with the rod 11a moving forward and backward in the front side. is there. A looper thread hooking attachment piece 12 is attached to the tip of the rod 11a.
A looper thread hook 3 having a round bar shape and an upward hook-shaped thread hook portion 3a is screwed onto the tip of the hook. The looper thread hook 3 has flexibility and is inserted into the groove 8a and the groove 16a of the main feed dog 16. When the rod 11a of the cylinder 11 is in the most retracted state, the hook-shaped thread hooking portion 3a at the tip of the looper thread hook 3 is at a position separated from the looper 1 by a certain distance. Further, in the most advanced state of the rod 11a, the thread hooking portion 3a is at a position where the looper thread 5 passing through the back surface of the looper 1 is hooked.

FIG. 2 (a) shows a non-use state of the looper thread hook 3. Immediately before sewing is finished, the sewing machine is temporarily stopped, and the air cylinder 11 is operated to move the rod 11a forward as shown by the arrow in Fig. 2 (b), and the looper thread 5 passing through the rear side of the looper 1 is threaded. Hook on the hanging part 3a. Thereafter, as shown in FIG. 2 (c), the looper thread hook 3 is retracted to hold the looper thread 5 slidably on the thread hooking portion 3a. A hydraulic cylinder or solenoid may be used instead of the air cylinder 11.

FIG. 3 is a block diagram of a control system of a sewing machine equipped with the device of the present invention. Looper thread hooking signal 20 generated by operating a switch (not shown), stepping signal 19a and stepping back signal 19 generated by pedal switch 19
b, the needle position signal 21 obtained when the needle is at the top dead center, the thread trimming signal 27 generated by the thread trimming switch, and the needle thread wiping signal 28 generated by the needle thread wiping switch are input to the control unit 22. It Upon receiving these, the control unit 22 operates the air cylinder 11, controls the rotation and stop of the sewing machine motor 23 that is the drive source of the sewing machine main shaft, operates the cylinder 24 for lifting and lowering the work clamp, and operates the needle thread and the looper thread. The thread cutting cylinder 25 is operated to activate the air wiper 26 that flips up the cut needle thread.

Next, a method for preventing fraying will be described. 4 is a time chart showing the operation timing of the device of the present invention, FIG. 5 is a perspective view showing a state where the looper thread hook pulls out the looper thread, and FIG. 6 is a perspective view showing a state where the looper thread is pulled out and only one stitch is sewn. FIG. 7 is a schematic perspective view showing a state in which the looper thread is pulled out and only one needle is sewn, and then the needle thread and the looper thread are cut, and FIG. 8 shows the state in which the needle thread is wiped and the sewing cloth is taken out from the presser foot. 9 is a schematic perspective view showing a state, FIG. 9 is a perspective view of the back side of the seam at the end of sewing, and FIG. 10 is an explanatory view of the seam.

After sewing is started to the required position after the start of sewing, the sewing machine is temporarily stopped with the pedal depressed at S _{1 in} FIG. 4, that is, with the needles 2a and 2b at the top dead center as shown in FIG. Then, at S ₂ , the looper thread hooking signal 20 is turned on to operate the air cylinder 11 to advance the rod 11a, and the looper thread 5 passing through the back surface of the looper 1 as shown in FIG. 2 (b).
Hook. Then, the looper thread hooking signal 20 is turned off, the rod 11a is retracted, the looper thread hook 3 is returned to the original position, and the looper thread 5 is held slidably (FIGS. 2 (c) and 5). Next, at step S ₃ , the pedal is depressed to sew only one stitch of sewing cloth (not shown). Then, as shown in FIG. 6, the looper thread hook 3 holds the looper thread inserted in the loop of the penultimate needle thread. After that, stepping back is performed, and then the thread trimming signal 27 is turned on at the time of S ₄ , and as shown in FIG. 7, before the looper thread is inserted into the loop of the final needle thread, the needle threads 4a, 4b and looper thread 5 is cut, and the looper thread 5 is held in the thread cutting device 7 and kept in a predetermined position until sewing is restarted.

Next, at S ₅ , the needle thread wiping signal 28
Is turned on to operate the air wiper 26, and as shown in FIG. 8, the needle threads 4a and 4b on the sewing machine side are flipped up onto the sewing cloth. Next, the cylinder 24 is operated to raise the work clamp (not shown),
Remove the sewing cloth from the sewing machine. Then, since the looper thread 5 on the sewing cloth side is slidably held by the looper thread hook 3, as the sewing cloth moves away from the sewing machine, the looper thread 5 in FIG. 9 (a) gradually changes to the final loop 4c of the needle thread. , 4d begins to come out, and eventually, as shown in FIGS. 8 and 9 (b), only one looper thread 5 passes through.

The stitches are formed by the other thread looping as shown in FIG. 10 (a). The seam at the end of the stitch is formed from the other thread looping shown in FIG. 10 (a) by the series of operations described above. Modification of b) and other thread lacing. In the other thread lacing, the loop of the needle thread is tightened by pulling the end of the looper thread, which fastens the looper thread. Therefore, according to the method of the present invention, the sewing thread is not frayed, and wrinkles are not generated. Also, the seams are the same as the other parts.

[0016]

As described above, according to the method of the present invention, the fraying can be prevented by a simple operation, the wrinkles of the sewing cloth are not generated, and the appearance of the stitches is not bad. Further, the device of the present invention can be constructed by adding a few parts, and the method of the present invention can be easily implemented.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing a device of the present invention.

FIG. 2 is an operation explanatory view when the device of the present invention is viewed from the left side surface.

FIG. 3 is a block diagram of a control system of a sewing machine including the device of the present invention.

FIG. 4 is a time chart showing the operation timing of the device of the present invention.

FIG. 5 is an operation explanatory view of looper thread hooking.

FIG. 6 is an operation explanatory view of looper thread hooking.

FIG. 7 is an operation explanatory view of looper thread hooking.

FIG. 8 is an operation explanatory view of looper thread hooking.

FIG. 9 is a perspective view showing a seam at the end of sewing from the back surface.

FIG. 10 is an explanatory diagram of seams.

[Explanation of symbols]

 1 looper 3 looper thread hook 3a thread hook 5 looper thread 6 sewing machine bed 8a groove 11 air cylinder 11a rod

Claims (2)

[Claims] 1. A looper thread hook for slidably holding a looper thread behind a looper for entwining the looper thread with a needle thread in a method for preventing seam fraying in a sewing machine for sewing using a needle thread and a looper thread. , The sewing machine is stopped immediately before the end of sewing, the looper thread is held in the looper thread hook, and one stitch is sewn, the needle thread and the looper thread are cut, and the looper thread is held in the looper thread hook A method for preventing fraying of the seam, characterized in that the looper thread is pulled out from the final loop of the needle thread with respect to the seam at the end of sewing by removing the thread from the sewing machine. 2. A sewing machine for sewing using a needle thread and a looper thread, wherein a looper thread hook for slidably holding the looper thread is provided behind a looper for entwining the looper thread with the needle thread. A feature to prevent the fraying of seams.