JP2013048710A - Device for detecting stitch skipping of sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect stitch skipping without the need for adjusting sensitivity of a sensor and others even if a thickness, a kind and the like of a thread are changed, and without being affected by dust and the like.SOLUTION: A sewing machine including: a needle bar 11 which is connected to a sewing machine upper shaft and is moved vertically; a shuttle which is rotated in an interlocking fashion with the sewing machine upper shaft to form a seam in an interlocking fashion with the needle bar; a stitch tension unit 4 which is arranged on the route from a bobbin to a balance and imparts tensile force to a needle thread; and a thread take-up spring 5 which is attached to the stitch tension unit, and swings between an initial position B and an operation position A by receiving the tensile force of the needle thread, and has a thread hooking part, comprises: detecting means 21 for detecting whether or not the thread take-up spring is located at the initial position B; and control means for detecting stitch skipping on the basis of the behavior detection of the thread take-up spring by the detecting means. The control means determines the stitch skipping on the basis of the detection of the initial position of the thread take-up spring 5 by the detecting means 21, within the range of a prescribed upper shaft angle (a balance bottom dead point+60°) from the balance bottom dead point, to output an alarm signal or stop the drive of the sewing machine.

Description

  The present invention relates to an apparatus for detecting a skip of a sewing machine.

  For example, Patent Literatures 1 to 5 are known as devices for detecting the skip of a sewing machine.

  Patent Documents 6 to 10 are known as a method for detecting the thread take-up spring in the thread tension portion.

Japanese Utility Model Publication No. 62-199065 Japanese translation of PCT publication No. 6-503007 US-A1 -470951 JP 50-54457 A JP 2005-246060 A JP-A-3-77583 JP-A-5-115654 Japanese Utility Model Publication No. 60-50974 JP-A-9-84982 Japanese Patent Laid-Open No. 3-6069

However, Patent Document 1 is designed to detect the thread passing through the outer periphery of the hook. However, it varies depending on the color and thickness of the thread, and is erroneously detected due to dust, and dust is attached to the sensor detection unit. There was a problem that would not be detected in some cases.
In Patent Document 2, the movement of the yarn is detected by an optical sensor in the sewing machine jaw. Similarly, since the sensor response changes depending on the color and thickness of the yarn, the yarn replacement is performed. Sometimes it was necessary to readjust the sensor, and it was necessary to readjust every time a process change occurred.
Moreover, since patent document 3 detects the presence or absence of the movement of an upper thread | yarn using a strain gauge, the cost of an apparatus becomes expensive.
In addition, the type in which the detection device is provided in the jaw portion of Patent Document 4 and Patent Document 5 is troublesome to thread.
In Patent Document 5, it is necessary to separately adjust the tension that can be detected without affecting the stitching every time the thread is replaced. Otherwise, malfunction may occur.

In addition, Patent Documents 6 to 9 that perform the detection operation of the thread take-up spring are all for detecting needle breakage or thread breakage.
Furthermore, Patent Document 10 relates to a chain stitch sewing machine, and in order to detect various sewing failure states including stitch skipping, it is necessary to newly provide a detection spring that is not included in the chain stitch sewing machine, which increases costs. It is had. Further, the detection spring disclosed in Patent Document 10 swings between an initial position and an operation position (point A at which the slack amount of the yarn becomes 0) where the yarn slack is eliminated against the urging force. When the detection spring moves to the operating position, the electrode contacts the electrode and outputs a detection signal. However, in the detection at the operating position, the needle bar top dead center, which is the normal stop position of the needle bar, passes, and a warning is issued. And post-processing such as stopping the sewing machine has been delayed.
Further, since the amount of thread consumption is large in chain stitches that are sewn with a single thread, skipping can be detected simply by providing a detection spring in the lifting path of the balance. However, in the case of lock stitching, the consumption of the upper thread is the same as the feed pitch, and therefore the accuracy of stitch skip detection cannot be obtained with the same method.

  An object of the present invention is to detect a skip quickly with an inexpensive apparatus without the need for adjusting the sensitivity of a sensor or the like even if the thickness or type of the thread changes, without being affected by dust or the like.

In order to solve the above problems, the invention described in claim 1
A needle bar connected to the upper shaft of the sewing machine and moving up and down;
A shuttle that rotates in conjunction with the upper shaft of the sewing machine and cooperates with the needle to form a seam;
A thread tensioner that is arranged on the path from the spool to the balance and applies tension to the upper thread;
In a sewing machine provided with the thread tensioner, swinging between an initial position and an operating position in response to an upper thread tension, and a thread take-up spring having a thread hook portion,
Detecting means for detecting whether or not the thread take-up spring is located at an initial position;
Control means for detecting stitch skipping based on detection of the behavior of the thread take-up spring by the detection means.

The invention according to claim 2 is the stitch skip detection device of the sewing machine according to claim 1,
A sewing machine motor that drives the upper shaft of the sewing machine;
A balance that moves up and down in conjunction with the sewing machine upper shaft;
A rotation angle detecting means for detecting a rotation angle of the sewing machine motor;
The control means detects whether or not the thread take-up spring is located at an initial position within a range of a predetermined upper shaft angle from a bottom dead center of the balance, and determines skipping of the thread.

The invention according to claim 3 is the device for detecting skipping of a sewing machine according to claim 1 or 2,
The detection means includes
Having a detection plate fixed to the sewing machine frame via an insulating member;
The control means includes
The potential of the detection plate is detected to detect the behavior of the thread take-up spring.

The invention according to claim 4 is the sewing machine skip detection device according to claim 3,
The detection plate is
A base fixed to the sewing machine frame;
It is characterized by comprising a detector that is formed to project from the base and is bent toward the swinging locus of the thread take-up spring.

The invention according to claim 5 is the stitch skip detection device of the sewing machine according to claim 1 or 2,
The detection means includes
It is characterized by having a sensor supported on the sewing machine frame in an adjustable manner.

The invention according to claim 6 is the stitch skip detection device for a sewing machine according to any one of claims 1 to 5,
The control means includes
When it is determined that the yarn is skipped, a warning signal is output or the driving of the sewing machine is stopped.

  According to the first aspect of the present invention, it is only necessary to detect the behavior of the thread take-up spring conventionally attached to the thread tensioner of the main-stitch sewing machine, particularly the operation of whether or not the thread take-up spring is positioned at the initial position. Can determine skipping. For this reason, it is not necessary to adjust the sensitivity of the sensor or the like even if the thickness or type of the thread changes, and the skip can be detected quickly with an inexpensive device without being affected by dust or the like.

  Further, according to the inventions of claims 2 to 5, the control means detects whether or not the thread take-up spring is located at the initial position within a range of a predetermined upper shaft angle from the bottom dead center of the balance. It is possible to reliably determine the skipping of the yarn.

It is a front view which shows the structure of one Embodiment of the sewing machine to which this invention is applied. It is a side view of a sewing machine. It is the perspective view which expanded the thread tension device, the thread take-up spring, and the detection means part. It is a front view explaining the detection operation | movement of the thread take-up spring of FIG. 3, and a detection means. b It is a graph showing the relationship of a balance and the action | operation of a thread take-up spring. It is a block block diagram of a skipping detection. It is a flowchart of a skipping detection. It is another flowchart of skipping detection. FIG. 10 is a block diagram illustrating skip detection according to a second embodiment. FIG. 10 is a block diagram illustrating skip detection according to a third embodiment. FIG. 10 is a block diagram illustrating skip detection according to a fourth embodiment. Embodiment 5 is shown. It is a graph showing the relationship of a balance and the action | operation of a thread take-up spring.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
1 and 2 show the configuration of an embodiment of a sewing machine to which the present invention is applied. 1 is a thread guide rod, 2 is a first thread tensioner, 3 is a first thread guide, and 4 is a first thread guide. 2 thread tensioner, 5 thread take-up spring, 6 thread handler, 7 balance, 8 second thread guide, 11 needle bar, 12 thread hook, 13 thread guide, 14 sewing needle ( Needle). The needle bar 11 is connected to a sewing machine upper shaft (not shown) and moves up and down. Further, the shuttle disposed on the sewing machine bed (not shown) rotates in conjunction with the upper shaft of the sewing machine, and forms a seam in cooperation with the needle 14 supported by the needle bar.

  As shown in the figure, the yarn drawn from a bobbin (not shown) is passed through a thread guide rod 1, a first thread tensioner 2, and a second thread tensioner 4, and is hung on a thread hooking portion 5a of the thread take-up spring 5. . Then, the balance 7 is passed through the thread hook 6 and the first thread guide 3, the thread hook 12 and the thread guide 13 of the needle bar 11 are passed through the second thread guide 8, and the needle hole of the sewing needle 14 is passed. Has been passed.

In the embodiment, a detecting means is provided in the portion of the thread take-up spring 5 of the second thread tensioner 4 to detect the behavior of the thread take-up spring 5.
In particular, the balance 7 detects the presence or absence of skipping by detecting the operation timing of the thread take-up spring 5 during a predetermined interval from the bottom dead center of the balance.

FIG. 3 shows an enlarged view of the second thread tensioner 4 and the thread take-up spring 5, and 21 is a detection plate (detection means) for detecting the behavior of the thread take-up spring 5.
The second thread tensioner (thread tensioner) 4 includes a main body portion 4a, a thread take-up spring 5 attached to the outer periphery of the main body portion 4a, a pair of thread tension plates 4c, a spring 4d, and a dial 4e. ing. The main body 4a has a cylindrical shape and is fixed to the sewing machine frame. An arc-shaped through groove 4b is formed on the side surface of the main body 4a. Further, the pair of thread tension plates 4c is biased by the spring 4d and applies tension to the upper thread inserted between the thread tension plates 4c. The biasing force of the spring 4d is adjusted by the amount of rotation of the dial 4e.

The thread take-up spring 5 has a linear shape and is rotatably supported by a central axis of the main body 4a or a support shaft (not shown) fixed to the sewing machine frame. On the tip end side of the thread take-up spring 5, a thread hook portion 5a bent in an arc shape is provided.
The thread take-up spring 5 is disposed so as to protrude from the through groove 4b, and the upper thread is hung on the thread hook 5a. The thread take-up spring 5 is urged clockwise by a winding spring (not shown), but abuts on the upper end of the through groove 4b and stops at an initial position B indicated by a two-dot chain line in FIG. When tension is applied to the upper thread, the thread take-up spring 5 rotates counterclockwise, but abuts against the lower end of the through groove 4b and stops at the operating position A shown by the solid line in FIG. The thread take-up spring 5 swings between the initial position B and the operating position A in response to the upper thread tension.

The detection plate 21 is a conductive metal material and is fixed to the sewing machine frame via an insulating plastic (insulating member). The detection plate 21 includes a base portion 21a and a detection portion 21b. The base portion 21a is disposed in the vicinity of the second thread tensioner 4, and is fixed to the sewing machine frame with screws 31 via an insulating plastic (insulating member). The base 21 a does not contact the main body 4 a of the second thread tensioner 4. The detection part 21b is formed so as to protrude from the base part 21a, and is bent so as to be arranged on the swing locus of the thread take-up spring 5.
The detection plate 21 is connected to one end side of a conducting wire 30 from the input side of the sewing machine control box 22 (control means). The sewing machine control box 22 applies a potential of +12 V to the detection plate 21 via the lead wire 30. For this reason, when the thread take-up spring 5 is in the operating position A, the thread take-up spring 5 does not come into contact with the detection portion 21b of the detection plate 21, so that the potential of the detection plate is + 12V. When the thread take-up spring 5 is at the initial position B, the thread take-up spring 5 comes into contact with the detection portion 21b of the detection plate 21 and is connected to the sewing machine frame (GND) through the thread take-up spring 5 and becomes 0V. The sewing machine control box 22 (control means) detects the potential of the detection plate 21 and detects the behavior of the thread take-up spring 5.

FIG. 4 illustrates the detection operation of the thread take-up spring 5 and the detection plate 21 (detection means). The detection plate 21 is energized when the thread take-up spring 5 contacts from the operating position A to the initial position B as shown in the figure. When the thread take-up spring 5 moves to the operating position A, it is not energized.
If the thread take-up spring 5 is at the initial position B between the bottom dead center of the balance 7 and a predetermined upper shaft angle, the stitch is skipped.

FIG. 5 is a graph showing the relationship between the operation of the balance 7 and the thread take-up spring 5. This graph is a curve for sewing thick products such as leather products and seat belts. The vertical axis in the figure is the upper shaft rotation angle indicating 0 to 360 degrees, and the horizontal axis is the thread take-up spring stroke. The thread take-up spring 5 is located at the initial position B at the stroke 0, and is located at the operating position A at the stroke 7 mm.
A curve S in FIG. 5 is a balance curve, which matches the upper thread supply amount of the balance 7. A curve T shows an operation curve of the thread take-up spring 5 per one rotation of the upper shaft, t1 is an operation curve when no skipping occurs, and t2 is an operation curve when a skipping occurs.
The thread take-up spring 5 normally starts to operate after the bottom dead center of the balance 7, but when the skip occurs, the hook does not draw the thread below the needle plate, so that the thread does not stretch and the thread It remains between the sewing needles 14. Then, the thread take-up spring 5 starts to move from about the top dead center of the needle bar (around the upper shaft rotation angle of 350 degrees shown in FIG. 5). Therefore, when the stitches are skipped, the operation timing change as shown in the drawing occurs in the thread take-up spring 5.
The bottom dead center of the balance 7 shown in FIG. 5 has an upper shaft rotation angle of about 290 degrees. When the stitch skip does not occur, the upper shaft rotation angle at which the thread take-up spring 5 is separated from the initial position B is about 300 degrees. When the stitch skip occurs, the upper shaft rotation angle at which the thread take-up spring 5 is separated from the initial position B is about 350 degrees.

Next, FIG. 6 shows a block configuration of the skip detection, and the sewing machine control box (control means) 22 detects the potential of the detection plate 21 and judges the behavior of the thread take-up spring 5.
The sewing machine control box 22 drives the sewing machine motor 23.
A motor encoder (rotation angle detection means) 24 is attached to the sewing machine motor 23. The motor encoder 24 outputs the angle of the sewing machine motor shaft as a signal to the sewing machine control box 22. The motor encoder 24 functions as a rotation angle detection unit that detects the rotation angle of the sewing machine motor 23.
An operation indicator 25 is connected to the sewing machine control box 22.
The sewing machine motor 23 is connected to the sewing machine upper shaft.
A balance 7 is connected to the sewing machine upper shaft. The balance 7 moves up and down in conjunction with the upper shaft of the sewing machine and raises the upper thread.

The operation of the skipping detection apparatus configured as described above will be described with reference to FIG.
Here, if no skipping occurs, the thread take-up spring movement expected start angle is about 300 degrees from the thread take-up spring operation curve t1 shown in FIG. 5, and the thread take-up spring 5 operates from the initial position B in FIG. This is the angle at which the movement starts toward the position A.
Further, the expected end angle of the thread take-up spring movement is an upper shaft angle of about 330 degrees, which is the angle moved to the operating position A in FIG.

  Since the sewing machine motor 23 is connected to the upper shaft, the sewing machine control box 22 can recognize the expected thread take-up spring movement start angle and the expected thread take-up spring movement end angle based on the motor shaft angle output from the motor encoder 24.

FIG. 7 is a flowchart for detecting the skipping. The sewing machine control box 22 determines whether or not the thread take-up spring movement scheduled start angle (upper shaft angle 300 °) is determined in step S1, as shown in the figure. If there is, the process proceeds to step S2.
In step S2, it is determined whether or not the thread take-up spring movement scheduled end angle (upper shaft angle 330 °) is reached, and if it is the thread take-up spring movement planned end angle, the process proceeds to step S3.
In step S3, the sewing machine control box 22 detects whether the thread take-up spring 5 is located at the initial position B from the potential of the detection plate 21, and if the thread take-up spring 5 is located at the initial position B, the occurrence of stitch skipping is detected. Determination is made and the process proceeds to step S4.
In step S4, a warning signal is output from the sewing machine control box 22 to the operation indicator 25 to warn the operator.

As described above, when the thread take-up spring movement is scheduled to end (upper shaft angle 330 °), the behavior of the thread take-up spring, that is, whether or not the thread take-up spring 5 is located at the initial position B is monitored. The sewing machine control means determines that the thread is skipped.
In the above-described embodiment, the behavior of the thread take-up spring 5 is detected at the expected end angle of the thread take-up spring movement (upper axis angle 330 °) after the bottom dead center of the balance (upper axis 290 °). Instead, in consideration of the upper shaft rotation angle (350 °) at which the thread take-up spring 5 is separated from the initial position B when skipping occurs, the thread take-up is performed between the upper shaft angle 330 ° and the upper shaft angle 350 °. It is easy to detect the behavior of the spring.
Furthermore, the bottom dead center of the balance varies depending on the type of sewing machine, but various sewing machines can be used in a predetermined section V1 from (balance bottom dead center + 40 °) to (balance bottom dead center + 60 °) after the balance bottom dead center. The attached thread take-up spring 5 behaves in the same manner. For this reason, in the predetermined section V1, the sewing machine control box 22 detects the behavior of the thread take-up spring 5, determines the skipping of the thread, outputs a warning signal to the operation indicator 25, or stops driving the sewing machine. Is also easily considered.

FIG. 8 is another flowchart for detecting the skipping. The sewing machine control box 22 determines whether or not the thread take-up spring movement start scheduled angle (upper shaft angle 300 °) is determined in step S11 as shown in FIG. If it is an angle (upper shaft angle 300 °), the process proceeds to step S12.
In step S12, the sewing machine control box 22 detects whether or not the thread take-up spring 5 is located at the initial position B from the potential of the detection plate 21. Determination is made and the process proceeds to step S13.
When the thread take-up spring 5 is not located at the initial position B, the process proceeds to step S11.
In step S13, it is determined whether or not the maximum thread take-up spring movement scheduled end angle (upper shaft angle 350 °) is reached, and if it is the maximum thread take-up spring movement planned end angle, the process proceeds to step S14.
If the maximum thread take-up spring movement end scheduled angle is not reached, the process proceeds to step S12.
In step S14, a warning signal is output from the sewing machine control box 22 to the operation display 25 to warn the operator or stop the driving of the sewing machine.

  In this way, it is controlled whether or not the thread take-up spring 5 is positioned at the initial position B between the yarn take-up spring movement start scheduled angle (upper shaft angle 300 °) and the maximum thread take-up spring move end planned angle (upper shaft angle 350 °). When the means is monitored and located at the initial position B, the sewing machine control means determines that the yarn is skipped from the potential of the detection plate 21. Since the bottom dead center of the balance has an upper shaft angle of 290 °, the behavior of the thread take-up spring is monitored between (balance bottom dead center + 10 °) and (balance bottom dead center + 60 °).

FIG. 13 is a graph showing the relationship between the operation of the balance 7 and the thread take-up spring 5 when sewing a thin material such as a Y-shirt. The horizontal axis in the figure is the upper shaft rotation angle, and represents the relationship between the displacement amount of the thread take-up spring 5 when the thread tension is strong, medium and weak with respect to the rotational phase of the upper shaft.
A curve SA in FIG. 13 is a balance curve. TA1 is a displacement curve of the thread take-up spring when the set thread tension is strong, TA2 is a medium set thread tension, and TA3 is a weak set thread tension. UA is a hook upper thread required amount curve.
From the graph of FIG. 13, the thread take-up spring moves from the initial position to the operating position at least after the bottom dead center θ1 of the balance, regardless of the strength of the thread tension, when the thread skip does not occur. At the hook crossing phase θ2, the displacement amounts of the thread take-up spring are h1, h2, and h3.
Although the thread take-up spring displacement curve when thread skipping is not shown in FIG. 13, the thread take-up spring is moved from the origin position from about (balance bottom dead center θ1 + 60 °) in the same manner as the thick sewing in FIG. Start moving to the working position.
From the above description of FIGS. 5 and 13, even if the thickness of the sewing product and the strength of the set thread tension are changed, the distance between the bottom dead center of the balance and the predetermined upper shaft angle (balance bottom dead center + 60 °) (predetermined section) V2) By monitoring the behavior of the thread take-up spring and whether or not the thread take-up spring 5 is positioned at the initial position, it is possible to detect thread skipping.

  Further, the bottom dead center of the balance varies depending on the type of the sewing machine, but the thread take-up spring 5 attached to various sewing machines after the bottom dead center of the balance behaves in the same manner. For this reason, in various types of sewing machines, when the behavior of the thread take-up spring and whether the thread take-up spring 5 is located at the initial position are monitored from the bottom dead center of the balance to a predetermined upper shaft angle (balance bottom dead center + 60 °), Can be detected.

  As described above, in the flowchart of FIG. 7, the behavior of the V1 section thread take-up spring from (balance bottom dead center + 40 °) to a predetermined upper shaft angle (balance bottom dead center + 60 °) is monitored. The behavior of the V2 section thread take-up spring from the bottom dead center to a predetermined upper shaft angle (balance bottom dead center + 60 °) was monitored. Since the V1 section is included in the V2 section, the control means collectively refers to the control means that the thread take-up spring 5 is moved to the initial position B between the balance bottom dead center and a predetermined upper shaft angle (balance bottom dead center + 60 °). It is determined whether or not the yarn is skipped.

  In the above embodiment, the section to be detected is set to a predetermined upper axis angle from the bottom dead center of the balance (balance bottom dead center + 60 °). Instead of this, it is also preferable to use a balance bottom dead center + 10 ° to a predetermined upper axis angle (balance bottom dead center + 60 °), and a balance bottom dead center + 20 ° to a predetermined upper axis angle can be easily considered. Also, it is easily conceivable to set the predetermined upper axis angle to the balance bottom dead center + 50 ° or to the balance bottom dead center + 40 °.

  As described above, the section detected by the control means can be changed within the range from the bottom dead center of the balance to the predetermined upper axis angle (balance bottom dead center + 60 °). This is defined as a section in which the control means detects within a predetermined upper axis angle range from the bottom dead center of the balance.

In the above embodiment, the detection plate 21 is fixed to the sewing machine frame with the screw 31, and the thread take-up spring 5 at the initial position B is arranged so as to contact the detection plate 21. Instead of this, it is also conceivable to easily adjust the fixing position of the detection plate 21 by providing a long hole (not shown) in the detection plate 21 and inserting a screw 31 into the long hole.
The detection plate 21 is fixedly arranged so that the detection plate 21 comes into contact with the thread take-up spring 5 at a position moved from 0.1 mm to 0.5 mm from the initial position B toward the operation position A. It is preferable. That is, if the position to be detected is slightly shifted from the initial position B to the operating position A side, the yarn take-up spring 5 may move slightly despite the occurrence of skipping due to the yarn violence. Detection can be prevented. This detected position is defined as an initial position B including a position slightly shifted from the initial position B to the operating position A side.

  As described above, according to the skip detection device of the embodiment, since the operation of the thread take-up spring 5 is only detected by the detection plate 21, it is not necessary to adjust the sensitivity of the sensor or the like even if the thickness or type of the thread changes, It is not affected by garbage.

(Modification)
In the above embodiment, the operator is warned by the operation indicator 25, but the sewing machine motor 23 may be stopped simultaneously with the warning.
Further, for example, when the operation display 25 is not connected to the sewing machine control box 22, a warning may be given using a display or warning device built in the sewing machine control box 22.
Further, a warning device may be connected to the sewing machine control box 22 separately from the operation indicator 25, and the worker may be warned with the warning device.
In addition, it is needless to say that specific details such as the shape and configuration of the detection means can be appropriately changed.

(Embodiment 2)
FIG. 9 shows the second embodiment. In the first embodiment described above, the bottom dead center of the balance (upper shaft angle 290 °), the planned starting angle of thread take-up spring (upper shaft angle 300 °), and the expected end angle of thread take-up spring movement. (Upper shaft angle 330 °) is recognized by an output signal from the motor encoder 24. As shown in the figure, a sewing machine angle detector (rotation angle detecting means) 16 is attached to a wheel 15 mounted on the upper shaft of the sewing machine. In the type of sewing machine to which the sewing machine is attached, by using the angle signal from the sewing machine angle detector 16, the bottom dead center of the balance (upper shaft angle 290 °), the expected start angle of the thread take-up spring movement (upper shaft angle 300 °), and the end of the thread take-up spring movement end A predetermined angle (upper shaft angle 330 °) may be recognized.

(Embodiment 3)
FIG. 10 shows a third embodiment. As shown in the figure, in the sewing machine control box 22, a balance bottom dead center (upper shaft angle 290 °) is measured by a balance position detector (rotation angle detection means) 17 of the balance 7. The thread take-up spring movement scheduled start angle (upper shaft angle 300 °) and the thread take-up spring movement planned end angle (upper shaft angle 330 °) may be recognized.

(Embodiment 4)
FIG. 11 shows the fourth embodiment. In the third embodiment, the detection plate 21 and the balance position detector 17 are connected to the sewing machine control box 22, but as shown in the figure, a control box different from the sewing machine control box is shown. The detecting means 21 and the balance position detector 17 may be connected to 27.
In this case, the control box 27 can incorporate a display and a warning device.

(Embodiment 5)
FIG. 12 shows the fifth embodiment.
The yarn drawn out from the thread winding (not shown) passes through a thread take-up spring 34 attached to the first thread tensioner 32, the second thread tensioner 33, and the second thread tensioner (thread tensioner) 33, and is not shown. Guided by a balance and a needle.
An optical sensor (detection means) 35 is fixed to the sewing machine arm (sewing machine frame). The optical sensor 35 has a main body part 35a and a detection part 35b. A long hole 35aa is formed in the main body portion 35b along the vertical direction. The optical sensor (detection means) 35 is adjustable along the vertical direction with the detection unit 35b on the upper side, and is fixed to the sewing machine arm with screws (not shown).

The thread take-up spring 34 has a light shielding plate 36 fixed to the sewing machine arm side. The thread take-up spring 34 swings between an upper initial position B and an operating position A below the initial position B. The optical sensor 35 is arranged so as to face the position of the light shielding plate 36 at the initial position B of the thread take-up spring swing locus. Then, it is detected whether or not the thread take-up spring 34 is located at the initial position.
The sewing machine control box (control means) to which the optical sensor 35 is connected has the thread take-up spring 5 at the initial position B within a range of a predetermined upper shaft angle U (balance bottom dead center + 60 °) from the balance bottom dead center. If the position is not detected, it is determined that the thread is skipped. When it is determined that the yarn is skipped, a warning signal is output or the sewing machine is stopped.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above-described embodiment, a non-contact optical sensor is used as the sensor, but it is also conceivable to use a non-contact magnetic sensor, a contact micro switch, or the like instead.
In the fifth embodiment, since the optical sensor 35 and the light shielding plate 36 are used, the sensor output value increases when starting to be separated from the initial position B. Therefore, when the predetermined detection amount is reached, it is determined that the initial position B is not reached. It is also easy to do.
In addition, as described with reference to FIG. 13, the thread take-up spring behaves in the same manner after the bottom dead center of the balance even when sewing a thin machine such as a sewing machine. Therefore, the present invention may be applied to a sewing machine that sews a thin machine or the like. Easy to think.
Further, in the above embodiment, the thread take-up spring 5 is urged clockwise, and when the tension is not applied to the upper thread, the thread take-up spring rotates in the clockwise direction and is set as the initial position B. When the present invention is applied to a thread tensioner in which the thread take-up spring is biased counterclockwise, the initial position B and the operating position A are switched.

4 Thread tensioner 5 Thread take-up spring 7 Balance 21 Detection plate (detection means)
22 Sewing machine control box (control means)
24 Motor encoder (rotation angle detection means)
27 Control box (control means)
35 sensors

Claims (6)

A needle bar connected to the upper shaft of the sewing machine and moving up and down;
A shuttle that rotates in conjunction with the upper shaft of the sewing machine and cooperates with the needle to form a seam;
A thread tensioner that is arranged on the path from the spool to the balance and applies tension to the upper thread;
In a sewing machine provided with the thread tensioner, swinging between an initial position and an operating position in response to an upper thread tension, and a thread take-up spring having a thread hook portion,
Detecting means for detecting whether or not the thread take-up spring is located at an initial position;
And a control unit that detects a skip of the yarn based on the detection of the behavior of the thread take-up spring by the detection unit. A sewing machine motor that drives the upper shaft of the sewing machine;
A balance that moves up and down in conjunction with the sewing machine upper shaft;
A rotation angle detecting means for detecting a rotation angle of the sewing machine motor;
The control means detects whether or not the thread take-off is detected by detecting whether or not the thread take-up spring is located at an initial position within a range of a predetermined upper shaft angle from a bottom dead center of the balance. The stitch skip detection device of the sewing machine described in 1. The detection means includes
Having a detection plate fixed to the sewing machine frame via an insulating member;
The control means includes
3. The stitch skip detection device according to claim 1, wherein a potential of the detection plate is detected to detect a behavior of the thread take-up spring. The detection plate is
A base fixed to the sewing machine frame;
4. The sewing machine skip detection device according to claim 3, further comprising a detection unit that protrudes from the base and is bent toward the swinging locus of the thread take-up spring. The detection means includes
3. The stitch skip detection device according to claim 1, further comprising a sensor that is adjustably supported by the sewing machine frame. The control means includes
6. The stitch skip detection device according to claim 1, wherein when it is determined that the yarn is skipped, a warning signal is output or the driving of the sewing machine is stopped.

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