JPH07275545A - Needle thread tension control method and device for sewing machine - Google Patents

Abstract

PURPOSE:To automatically apply optimum tension to a needle thread, and form a neat stitch, even when selection is made between a stitch having long stitching length and a stitch having short sticking length during operation. CONSTITUTION:The needle thread tension control device of embroidery machine has a control device 30 common to a pre-reading means for reading stitch formation data in advance and a judgement means for making judgement as to whether a stitch to be formed next is a satin or walking stitch, on the basis of data available from the pre-reading means. Also, the device is equipped with a rotation driver 12 as an automatic operation means to weaken the tension of a needle thread 11, when the stitch to be formed next is a stain stitch, and to increase the tension of the needle thread 11 when the stitch to be formed next is a waking stitch, through the operation of a stitch balancing thread tension disc 3 on the basis of discrimination with the judgement means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle thread tension control method and device for a sewing machine.

[0002]

2. Description of the Related Art In many sewing machines, tension is applied to the upper thread by the thread tension. The tension depends on the type of needle thread,
Since the optimum value varies depending on various conditions such as the sewing speed and the stitch to be formed, the operator manually operates the thread tension and adjusts the tension according to these various conditions. Therefore, this adjustment requires experience, skill, and labor, and it is difficult to deal with the case where various conditions change during operation. Regarding the sewing speed among these various conditions, a technique for automatically adjusting the thread tension according to the sewing speed has been developed (JP-A-54-60047). However, there is no prior art that considers other conditions.

[0003]

Therefore, a particular problem occurs when a stitch having a long stitch length and a stitch having a short stitch length are switched during operation. For example, since the embroidery sewing machine mainly forms a so-called satin stitch that is sewn in a zigzag pattern, an operator operates the thread tension to weaken the tension of the upper thread in accordance with the satin stitch.
However, the embroidery sewing machine may switch during operation to form a so-called walking stitch that is sewn in a linear shape. In that case, if the tension of the upper thread remains weak for the satin stitch, the upper thread may be fed too much, and the walking stitch may float up in a loop from the work piece. In other words, it is better to weaken the tension when using a satin stitch with a long stitch length.
For walking stitches with short stitch length, it is better to increase the tension. Therefore, when the walking stitch is lifted up, it is troublesome for the worker to operate the thread tension to increase the tension of the upper thread in accordance with the walking stitch.

The object of the present invention is to solve the above-mentioned problems, and even when a stitch with a long stitch length and a stitch with a short stitch length are switched during operation, the optimum tension is automatically applied to the upper thread to clean the stitch. An object of the present invention is to provide a needle thread tension control method and device for a sewing machine capable of forming a stitch.

[0005]

According to the method for controlling the needle thread tension of the sewing machine of the present invention, the stitch forming data inputted to the control device of the sewing machine is preread, and the stitch to be formed next from the preread data is the stitch length. Of long stitches or short stitches, and based on that determination,
When the stitch to be formed next is a stitch with a long stitch length, the tension of the upper thread is weakened, and when the stitch to be formed next is a stitch with a short stitch length, the tension of the upper thread is increased.

The upper thread tension control device of the sewing machine of the present invention is a sewing machine having a tension applying means for adjusting the tension of the upper thread so that the stitch forming data inputted to the sewing machine control device can be pre-read. A pre-reading means, a judging means for judging whether a stitch to be formed next from the data pre-read by the pre-reading means is a stitch having a long stitch length or a stitch having a short stitch length, and the tension applying means is automatically operated based on the judgment made by the judging means. Automatic operation that reduces the tension of the upper thread when the next stitch to be formed is a stitch with a long stitch length, and increases the tension of the upper thread when the stitch to be formed next is a stitch with a short stitch length And means.

In these needle thread tension control methods or apparatuses, the following can be exemplified as a combination of a stitch having a long stitch length and a stitch having a short stitch length. Satin Stitch and Walk Stitch Long Stitch Walk Stitch and Short Stitch Walk Stitch Long Stitch Satin Stitch and Short Stitch Satin Stitch

[0008]

According to the method and apparatus for controlling the upper thread tension of the sewing machine of the present invention, even when the stitch having a long stitch length and the stitch having a short stitch length are switched during operation, the stitch forming instruction input to the sewing machine controller is used. Data is read in advance, and it is determined from the read data whether the stitch to be formed next is a stitch with a long stitch length or a stitch with a short stitch length. In this case, the tension of the upper thread is weakened, and when the stitch to be formed next is a stitch having a short stitch length, the tension of the upper thread is increased, so that a clean stitch can always be formed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a needle thread tension control method and device for an embroidery sewing machine will be described with reference to the drawings. First, FIG. 1 schematically shows a main part of an embroidery sewing machine incorporating a needle thread tension control device. A thread tensioner 3 as a tension applying means is attached to the front surface of a mounting base 2 of the yarn path device provided above the sewing machine head 1.

As shown in FIG. 2, the thread tensioner 3 has a hollow tension shaft 5 fixed to a mounting cylinder portion 4 of a mounting base 2 and a thread take-up spring 6 mounted on the outer periphery of the middle portion of the tension shaft 5. And a pair of front and rear tone discs 7 mounted on the outer periphery of the front portion of the tone shaft 5,
8, a conical coil-shaped tone spring 9 for urging the front-side tone disc 7 toward the rear-side tone disc 8 and a front-side outer periphery of the tone shaft 5 screwed together to adjust the compression amount of the tone spring 9. Tone nut 10
It consists of and. The upper thread 11 fed from the upper side to the thread tensioner 3 is wound between the tension discs 7 and 8 and then hooked on the thread take-up spring 6 to be fed further downward.

An adjusting shaft 28, which rotates together with the nut, is attached to the adjusting nut 28.
A rotary shaft 13 of a rotary driver 12 such as a rotary solenoid or a pulse motor as an automatic operation means of the thread tension member 3 is connected by a joint 14 to the hollow portion of the rotary shaft 13 extending rearward.

As is well known, the sewing machine head 1 has a hook-shaped upper thread guide 15 which folds the upper thread 11 fed from the thread take-up spring 6 upward, a balance 16 through which the upper thread 11 fed from the upper thread guide 15 passes, and a balance. A sewing needle 17 for passing the upper thread 11 passing through 16 is provided. Further, below the needle plate 19 of the sewing machine table 18, there is provided a shuttle 21 for feeding the lower thread 20 and entwining it with the upper thread 11.

An embroidery frame 24 having a work piece 23 stretched is attached to a drive frame 22 provided immediately above the sewing machine table 18. The drive frame 22 is for the X-axis pulse motor 26 of the drive means 25 and the Y-axis. XY by the pulse motor 27
Driven axially.

The control device 30 of the embroidery sewing machine is a CPU
A microcomputer 34 including 31, a memory 32, an input / output interface 33, etc., and a keyboard, a floppy disk drive, an IC card reader,
A data input device 35 such as a CD-ROM drive is provided. By inserting a floppy disk, an IC card, a CD-ROM or the like in which data for stitch formation is stored in the data input device 35, the data is input to the control device 30. An encoder 38 for detecting the rotation angle of a sewing machine spindle 37 driven by a spindle motor 36 is connected to the input side of the control device 30, and the X-axis pulse motor 26 and the Y-axis motor 26 are connected to the output side of the control device 30. A shaft pulse motor 27 is connected.

Further, the control device 30 of this embodiment is similar to that of FIG.
As shown in, the pre-reading means for sequentially pre-reading the input stitch forming data for each 10 stitches and the data for 10 stitches pre-read by the pre-reading means determines whether the stitch to be formed next is a satin stitch or a walking stitch. It also has a determining means for performing.

The rotation driver 12 is connected to the output side of the control device 30, and the rotation driver 12 automatically rotates the tone nut 10 via the adjusting shaft 28 based on the discrimination by the discriminating means. Thus, the tension of the upper thread 11 is adjusted. That is, when the stitch to be formed next is a satin stitch, the amount of compression of the tension spring 9 is reduced to weaken the bias of the tension disc 7 to weaken the tension of the upper thread, and the stitch to be formed next is a walking stitch. At this time, the amount of compression of the tension spring 9 is increased and the bias of the tension disc 7 is increased to increase the tension of the upper thread. In parallel with this adjustment, the control device 30 drives the embroidery frame 24 through the control of the X-axis pulse motor 26 and the Y-axis pulse motor 27, and the sewing machine head 1 is synchronized with the rotation of the sewing machine main shaft 37 and the stitches are stitched one by one. Form stitches. Each time one stitch is sewn, as shown in FIG.
The pre-reading means pre-reads the data for the next 10 stitches.

The needle thread tension control method and device of the present embodiment constructed as described above operate, for example, as follows. As shown in FIG. 4, the needle drop points N1 to N11 on the work piece 23 are satin stitches S, and the needle drop point N1.
2 to N27 is the walking stitch W, and the needle drop point N
Assume an embroidery example in which 28 to N37 are satin stitches S. FIG. 5 shows the sewing needle 17 in this embroidery example.
The relationship between the movement of the needle tip, the movement of the embroidery frame 24, and the tension of the upper thread 11 is shown.

Before the sewing needle 17 falls to the needle drop point N1, the control device 30 as the prefetching means and the discrimination means prefetches 10 stitch forming data for 10 stitches, and the next stitch to be formed is the satin stitch S. I have decided. Then, as shown in FIG. 2A, the rotation driver 1
In No. 2, the tension nut 10 is automatically rotated based on the discrimination by the discriminating means to weaken the tension of the upper thread 11. In this state, the sewing needle 17 drops to the needle drop point N1, and the embroidery frame 24 moves each time the needle tip of the sewing needle 17 comes near the top dead center.
The satin stitch S from the needle drop points N1 to N11 is formed. After the sewing needle 17 has dropped to the needle drop point N2,
The control device 30 starts pre-reading the data of the walking stitch W after the needle drop point N12, but stores the data at the same point and does not change the tension of the needle thread until after the needle drop point N11.

Next, when the sewing needle 17 passes the needle drop point N11, the control device 30 determines that the stitch to be formed next is the walking stitch W from the data that is read in advance and stored. Then, as shown in FIG. 2B, the rotation driver 12 automatically rotates the tension nut 10 based on the discrimination by the discriminating means to increase the tension of the needle thread 11. In this state, the sewing needle 17 drops to the needle drop point N12, and every time the needle tip of the sewing needle 17 comes near the top dead center, the embroidery frame 24
Moves, a walking stitch W from the needle drop points N12 to N27 is formed. The sewing needle 17 has a needle drop point N.
After falling to 18, the control device 30 starts prefetching the data of the satin stitch S after the needle drop point N28, but at the same time, only by storing the data, the needle thread of the needle thread is reached until reaching the needle drop point N28. Do not change the tension.

Next, when the sewing needle 17 passes the needle drop point N27, the control device 30 determines that the stitch to be formed next is a satin stitch S based on the above-mentioned data stored in advance.
Is determined. Then, the rotation driver 12 automatically rotates the tension nut 10 based on the discrimination by the discriminating means and weakens the tension of the upper thread 11. In this state, the sewing needle 17 drops to the needle drop point N28, and the embroidery frame 24 moves each time the needle tip of the sewing needle 17 comes near the top dead center.
Satin stitches S from 28 to N37 are formed.

The change of the needle thread tension from and to the above is performed when the needlepoint of the sewing needle 17 is near the bottom dead center at the needle drop point N12 or N28. That is, when the needle tip is at the bottom dead center, the balance 16 is also lowered and the upper thread 11 is loose. At this moment, the rotary driver 12 automatically rotates the tension nut 10 to switch the tension of the upper thread 11 and then pull up the balance 16.

The data read in advance by the control device 30 is not limited to 10 stitches and can be changed as appropriate. In the present embodiment, the needle thread tension is always changed every time the satin stitch and the walking stitch are switched, but when the data of the satin stitch or the walking stitch does not continue for a predetermined stitch or more, the needle thread tension is changed. Is set so as not to change the rotation drive 1
It is also possible to prevent the 2 from working too often.

Next, FIG. 6 shows a modification of the automatic operating means of the thread tension element 3. In this modification, the pressing shaft 42 of the pressing driver 41 such as a push solenoid or a fluid pressure cylinder is in contact with the end of the adjusting shaft 40 extending rearward from the adjusting shaft 5. The pressing driver 41 automatically operates and stops based on the judgment made by the judging means. That is, when the stitch to be formed next is a satin stitch, it operates as shown in FIG. 6B to press the tone shaft 5 forward, weakening the bias of the tone disc 7 by the tone spring 9 and the upper thread. Decrease the tension of 11. Further, when the stitch to be formed next is a walking stitch, the stitch is stopped and the tension shaft 5 is returned to the rear to increase the tension of the upper thread as shown in FIG. 6A.

The present invention is not limited to the above-described embodiments, but may be embodied with appropriate modifications, for example, as follows, without departing from the spirit of the invention. (1) Use a device other than the thread tensioner as the tension applying means. (2) Be embodied in various sewing machines other than embroidery sewing machines.

[0025]

Since the method and apparatus for controlling the needle thread tension of the sewing machine of the present invention is configured as described above, even if the stitch having a long stitch length and the stitch having a short stitch length are switched during the operation, the stitching is automatically performed. It exerts an excellent effect that a proper stitch can be applied to the upper thread to form a beautiful stitch.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a main part of an embroidery sewing machine incorporating a needle thread tension control device according to an embodiment of the present invention.

FIG. 2 is a side view of a thread tensioner serving as a tension applying unit and a rotary driver serving as an automatic operating unit in the control device.

FIG. 3 is a flowchart showing a needle thread tension control method by the control device.

FIG. 4 is a plan view schematically showing an embroidery example by the embroidery sewing machine.

FIG. 5 is a time chart showing the relationship between the movement of the needle tip of the sewing needle, the movement of the embroidery frame, and the tension of the upper thread in the same embroidery example.

FIG. 6 is a side view showing a modified example of the automatic operating means.

[Explanation of symbols]

 3 Thread tension as tension applying means 11 Upper thread 12 Rotation driver as automatic operating means 30 Control device as pre-reading means and discriminating means 41 Pressing driver as automatic operating means S Satin stitch W Walking stitch

Claims (4)

[Claims] 1. A stitch forming data input to a control device of a sewing machine is preread, and it is determined from the preread data whether a stitch to be formed next has a long stitch length or a short stitch length, and the determination is made. Based on the above, when the stitch to be formed next is a stitch with a long stitch length, the tension of the upper thread is weakened, and when the stitch to be formed next is a stitch with a short stitch length, the tension of the upper thread is increased. A method for controlling the needle thread tension of a sewing machine. 2. A sewing machine having a tension applying means for applying tension to a needle thread in an adjustable manner, the pre-reading means pre-reading data for forming stitches input to a control device of the sewing machine, and the data pre-read by the pre-reading means. The stitch forming means for discriminating whether the stitch to be formed next is a stitch having a long stitch length or a stitch having a short stitch length, and the stitch to be formed next by automatically operating the tension applying means based on the discrimination made by the discriminating means. The needle thread tension of the sewing machine with an automatic operation means that weakens the tension of the upper thread when the stitch is a long stitch and increases the tension of the upper thread when the stitch to be formed next is a stitch with a short stitch length. Control device. 3. The needle thread tension control method according to claim 1, wherein the stitch having a long stitch length is a satin stitch, and the stitch having a short stitch length is a walking stitch. 4. The needle thread tension control device according to claim 2, wherein the stitch having a long stitch length is a satin stitch, and the stitch having a short stitch length is a walking stitch.