JPS63270092A - Yarn breakage detector of sewing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention detects thread breakage of the needle thread of a sewing machine by outputting it from needle thread detection means installed opposite to the needle thread running path between the thread take-up thread and the sewing needle. The present invention relates to a thread breakage detection device for a sewing machine that is determined and detected by a control means based on an upper thread detection signal.

<Prior Art> When sewing with an automatic sewing machine, when a thread breaks, it is necessary to detect this and control the sewing machine motor to stop.

Therefore, according to Japanese Patent Publication No. 61-27073,
A thread breakage detector for detecting thread breakage of the needle thread has been proposed, and this thread breakage detector is equipped with a thread guide mechanism that guides the needle thread in a narrow path in the thread travel path between the thread take-up thread take-up and the sewing needle. A photoelectric detector is installed within the thread guide mechanism, and is configured to detect thread breakage while running the upper thread through narrow holes and grooves to prevent sagging.

<Problems to be Solved by the Invention> However, when this type of thread guide mechanism is installed, when setting the needle thread, the needle thread must be passed through a narrow hole or groove in the mechanism, and the thread This mechanism has the problem of bending the passage and making it difficult to thread the thread.

For this reason, it was considered to install a photoelectric detector opposite the needle thread running path without restraining the needle thread at all to detect thread breakage of the needle thread, but the thread take-up of the needle thread in the sewing machine was When the thread goes up, it is pulled, and when the thread take-up goes down, the tension loosens, causing the thread to swing out of the fixed upper thread travel path, that is, the detection range of the photoelectric detector, causing false detection and thread breakage. A problem was expected that would cause the sewing machine to stop even though it did not occur.

The present invention has been made in order to solve the above-mentioned problems, and provides a thread breakage detection device that can accurately detect thread breakage of the upper thread of a sewing machine, and is configured as follows.

<Means for solving the problem> That is, as shown in FIG. 1, the thread breakage detection device of the sewing machine of the present invention is installed opposite to the needle thread running path between the thread take-up lever and the sewing needle, Upper thread detection means A detects, timing detection means B detects the timing when the thread take-up goes up and the upper thread is in tension, and when timing detection means B detects the timing when the upper thread is pulled, the upper thread is detected. The control means C takes in the upper thread detection signal output from the means A.

<Function> In the thread breakage detection device having such a configuration, the control means C takes in the needle thread detection signal from the needle thread detection means A at the timing when the thread take-up is raised and the needle thread is in tension, so that the needle thread is not loosened. The control means determines whether or not the thread has broken only when it is properly positioned on the upper thread running path under tension, rather than in a state in which the upper thread is swung, thereby preventing erroneous detection of thread breakage due to swaying of the upper thread. , thread breakage can be detected accurately.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a partial front view of the sewing machine arm 2 of an industrial sewing machine, and FIG. 3 shows a left side view thereof.

To give an overview of the upper thread guide and pull-out mechanism provided along the running path of the upper thread 1, reference numeral 3 is a side thread tension device provided at the upper part of the sewing machine arm 2, and the upper thread drawn out from the spool is 1, pass it through, and send it downward while applying an appropriate amount of frictional force. The raw thread tension device 4 is provided below the side thread tension device 3, and the needle thread 1 sent from the side thread tension device 3 is hung therethrough.
The upper thread 1 is fed out while applying an appropriate frictional force to the upper thread 1.

A piece-shaped thread guide 5 is provided on the left side of the main thread tension device 4 so as to be movable up and down, and another thread guide 6 is fixed above the raw silk tension device 4. The heaven f! 7 is provided to be movable up and down. The balance 7 is linked to a crank mechanism connected to the left end of an upper shaft horizontally disposed within the sewing machine arm 2, and the operation of the crank mechanism causes the balance 7 to move up and down at a predetermined timing.

The upper thread 1 passes from the side thread tension device 3 to the main thread tension device 4, from the thread guide 5 on the left side to the thread guide 6 slightly above the right, and then to the thread take-up lever 7.
The thread is passed through the threading hole and moves downward. To the left of the thread guide 6 is a thread guide 8 for guiding the needle thread 1 moving downward from the thread take-up 7.
is attached, and further, another thread guide 9 is attached below the thread guide 8, and the upper thread 1 extending downward from the thread take-up lever 7 is
The thread is guided to a sewing needle 10 through two thread guides 8 and 9.

The sewing needle 10 is attached to the lower end of a needle bar 11 that moves up and down, and is moved up and down by a crank mechanism provided at the left end of an upper shaft (not shown), and the lower part of the needle bar 11 is slidably supported by a needle bar bearing 12. A thread guide 13 is provided on the outside of this needle bar bearing 12.
is attached, and a thread guide 14 with a thread passing hole is also provided at the lower end of the needle bar 11, and the upper thread 1 extending downward from the thread guide 9 is inserted into the hole of the sewing needle 10 through the thread guides 13 and 14. be done.

A tip 21 of the needle thread detector is mounted by a mounting bracket 22 opposite the needle thread travel paths of the thread guides 8 and 9. This upper thread detector is located at the tip 21. It is composed of an optical fiber 23, and a needle thread detection section 20 including a light emitter 26 and a light receiver 27, and emits light emitted from the light emitter (e.g., a light emitting diode) 26 from the tip section 21 directly to the side of the needle thread 1. It has a structure in which a light receiver (for example, a phototransistor) 27 receives reflected light from the thread, and outputs the received light signal as an upper thread detection signal.

The tip 21 that emits and receives light is as shown in FIG. 4A.
It is a coaxial type in which a light emitting part 21a is arranged in the center and a light receiving part 21b is arranged on the outer periphery. connected to. Incidentally, the tip may be a biaxial type in which a light projecting part 21c and a light receiving part 21d are arranged side by side as shown in FIG. 4B. The tip portion 21 is disposed horizontally facing the needle thread 1 so as to irradiate the projected light directly to the side of the needle thread 1 and receive reflected light therefrom. In this case, the light projector 2
Since the light emitted from the sewing machine arm 1a is emitted parallel to the front surface of the sewing machine arm 2 with a certain degree of spread, the light emitted from the emitted light hits the front surface of the sewing machine arm 2, and the reflected light enters the light receiving section 21b, causing false detection. Because it is easy, the front of the tip 21,
That is, a semi-cylindrical recess 19 is provided on the left front surface thereof. Furthermore, a black shielding plate 18 is fixed to the left end of the recess 19 in order to prevent disturbance light from the light receiving section 21b from entering.

Floodlight 26. The upper thread detection unit 20 with a built-in light receiver 27 is attached to the back side of the sewing machine arm 2, and includes a drive circuit for projecting light, an amplifier for amplifying the received light signal, a circuit for shaping the signal waveform, and upper thread detection. It has a built-in comparison circuit for generating signals.

On the other hand, there is a timing signal generator 2 in the sewing machine arm 2 that outputs a timing signal of one pulse per rotation of the upper shaft.
5 is provided opposite to the pulse generating wheel mounted on the upper shaft. The timing signal generator 25 can be a well-known photoelectric switch, a hose element, an electromagnetic coil type pickup, etc., and the pulse generation wheel can be equipped with a slit or a slit accordingly.
A metal protrusion or the like may be provided.

FIG. 5 shows a schematic block diagram of the control device of the sewing machine. This control device includes a CPU 30. ROM31. RAM
The main part is a microcomputer such as 32, etc., and the CPU 30 controls the rotation of the sewing machine motor 35 and performs thread breakage detection processing, which will be described later, based on program data stored in the ROM 31 in advance. Input/output circuit 3
3 is a timing signal generator 25. The signal sent from the upper thread detection section 20 etc. is manually sent to the CPU 30, or the
It inputs and outputs signals, such as outputting control signals based on commands from U30. The sewing machine motor control circuit 34 is a circuit that controls the electric power etc. supplied to the sewing machine motor 35 to control the rotational speed of the motor and performs stop control. circuit 3
3 manually inputs a speed command signal to control the power supplied to the sewing machine motor 35, etc.

A rotary encoder 36 is attached to the rotating shaft of the sewing machine motor 35.
is connected, and while the motor drives the upper shaft one rotation, the rotary encoder 36 outputs, for example, t according to the rotation angle.
ooo pulses are output. A pulse signal from the rotary encoder 36 indicating the rotation angle of the upper glaze is sent from the input/output circuit 33 to the CPU 30 and counted.

Next, the needle thread breakage detection operation will be explained based on the flowchart of FIG.

The CPU 30 executes thread breakage detection processing as shown in FIG. 6 as part of its main routine, and upon entering this routine processing, it first determines in step 100 whether or not a timing signal has been input. When the sewing machine motor 35 is rotationally driven and the upper shaft rotates, the timing signal generator 25 outputs a timing signal at the timing when the upper shaft rotates once.

When this timing signal is input to the input/output circuit 33,
Next, the process proceeds to step 110, and counting of the number of pulses of the rotation angle signal sent from the rotary encoder 36 is started.

Subsequently, the process proceeds to step 120, in which it is determined based on the count value of the rotation angle signal whether or not the balance 7 has reached a raised position slightly before the top dead center. The position of this take-up lever is where the upper thread 1 is always in tension, and since the rotation of the upper shaft always corresponds to the vertical movement of the take-up lever 7, when the count value of the rotation angle signal reaches a certain value, the take-up lever The CPU 30 determines that the number 7 has reached just before the top dead center during the ascent.

When it is determined that the thread take-up lever 7 has reached a position slightly before the top dead center, the process proceeds to step 130, where the upper thread detection signal sent from the upper thread detection section 20 is fetched from the input/output circuit 33h1. The upper thread detection signal output from the upper thread detection section 20 is, for example, at a high level when the upper thread is detected, and at a low level when the upper thread cannot be detected.

Therefore, in the next step 140, it is determined whether or not the thread has broken based on this upper thread detection signal, and when the upper thread detection signal is at a low level, it is determined that the upper thread 1 has broken, and then in step 1
50, a control signal for a deceleration command is sent to the sewing machine motor control circuit 34 to decelerate the sewing machine motor 35. When the sewing machine motor 35 is decelerated to a predetermined speed, stop control is performed to stop the motor, and the sewing machine stops. do.

On the other hand, in step 140, if the upper thread detection signal is at a high level indicating upper thread detection and it is not determined that thread breakage has occurred, this process is exited and the process proceeds to other sewing machine motor control processes.

In this way, each time the timing signal is input from the timing signal generator 25, the CPU 30 performs steps 100 to 1.
40, and when it is determined in step 140 that the needle thread has broken, the CPU operates to stop the sewing machine motor 35 in step 150.
30 takes in the needle thread detection signal sent from the needle thread detection section 20 at a position slightly before the top dead center of the thread take-up 7, that is, when the thread take-up 7 is raised and the needle thread is in tension. Therefore, when the upper thread 1 becomes loose or becomes tense due to the vertical movement of the thread take-up lever 7, the thread swings at the part where the tip 21 of the upper thread detector is installed, and especially when the upper thread becomes loose, The upper thread 1 is likely to fall out of the detection range of the upper thread detector, and a signal indicating a thread breakage may be output from the upper thread detector 20 even if no thread breakage occurs. Since the upper thread detection signal is taken in only when the sewing machine is in a tensioned state, the above-mentioned erroneous detection will not occur, and the sewing machine will not be stopped inadvertently due to erroneous detection of thread breakage.

Note that although a reflective photoelectric detector is used as the upper thread detector, a transmission type photoelectric detector may also be used.

<Effects of the Invention> As explained above, according to the thread breakage detection device for a sewing machine of the present invention, the control means detects the needle thread detection signal from the needle thread detection means at the timing when the thread take-up is raised and the needle thread is in tension. Therefore, the control means determines whether or not the thread has broken only when the upper thread is stretched and correctly positioned on the upper thread travel path, rather than when it is loose and easily swings. This prevents erroneous detection of thread breakage, and in particular prevents problems where the sewing machine stops due to erroneous detection.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the present invention, Figs. 2 to 5 show an embodiment thereof, Fig. 2 is a partial front view of the sewing machine, Fig. 3 is a left side view of the same, and Fig. 4 A and B are top views. FIG. 5 is a block diagram of the control device, and FIG. 6 is a flowchart of thread breakage detection processing. A... Upper thread detection means, B... Timing detection means, C... Control means. Figure 1: 9th mouth 3rd mouth

Claims (1)

[Scope of Claims] Needle thread detection means installed opposite to the needle thread travel path between the thread take-up lever and the sewing needle and detects the needle thread, and a timing for detecting the timing when the thread take-up lever rises and the needle thread becomes in tension. A thread breakage detection device for a sewing machine, comprising: a detection means; and a control means for capturing an upper thread detection signal output from the upper thread detection means when the timing detection means detects the timing of pulling the upper thread.