JP2576713Y2 - Bottom thread breakage detection device of sewing machine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lower thread breakage detecting device for a sewing machine that processes a sheet-like body such as a cloth using an upper thread and a lower thread such as a sewing machine and an embroidery machine.

[0002]

2. Description of the Related Art Generally, a lower thread bobbin of a sewing machine such as a sewing machine or an embroidery machine is located under a work table, and it is difficult to grasp a remaining thread state. Often there was. However, since the distance from the bobbin to the cloth on the work table from the bobbin is short, the movement is intense, and the surrounding space is small, it is extremely difficult to add a detecting device to the lower thread.

Further, in the conventional yarn breakage detecting device, a dancer roll is applied to the yarn to know the tension of the yarn from the displacement of the roll, or the rotation of the roll in contact with the traveling yarn is detected by an encoder. , Both of which were in contact with the yarn.

[0004]

[Problems to be solved by the present invention] On the other hand, the present invention focuses on the fact that the upper thread stops when the lower thread runs out, and focuses on the shape and structure of the thread itself, leaving the narrow space under the work table as it is. It is an object of the present invention to provide a device for detecting a lower thread breakage in a non-contact manner without providing a contact object such as a dancer roll in a large space on a work table.

[0005]

According to the present invention, a lower thread breakage detecting device for a sewing machine is provided by an upper thread bobbin disposed above a worktable.
The upper thread unwound from the lower thread below the workbench
Thread breakage of sewing machines such as sewing machines, embroidery machines, etc.
A slit light source provided to irradiate slit light in a direction crossing the upper thread on one side of the upper thread path through which the upper thread passes, and an upper side on the other side sandwiching the upper thread path. A light receiving element provided to receive the projected image of the yarn, a selection circuit for extracting an alternating current component within a predetermined frequency range from the electric output signal of the light receiving element, and a detection signal when the alternating current component falls below a predetermined value be equipped with an output circuit which emits
It is characterized by that .

[0006]

The yarn has a wavy change in diameter due to twisting.
Therefore, the amount of light received by the light receiving element that receives the projected image periodically changes in accordance with the pitch of the yarn diameter change and the running speed. That is, the light reception output signal includes an AC component. A sorting circuit separates this AC component. When the lower thread runs out, the running of the upper thread stops, and the AC component becomes zero. In addition, the AC component becomes zero even when the upper thread disappears.

[0007]

FIG. 1 shows an embodiment of the present invention. A slit 2 having a width of, for example, 0.25 mm is provided on the front surface of the lamp 1.
The slit light 3 having a width of 0.25 mm irradiates the upper thread 4. The slit 2 is provided in a direction orthogonal to the running direction of the upper thread 4. On one side of the upper thread 4, a light receiving element 5 for receiving a projected image of the upper thread is provided. This light receiving element 5 has an elongated shape,
As shown in FIG. 4, the long side of the light receiving surface is sufficiently longer than the maximum diameter of the projected image of the upper thread 4.

The output electric signal of the light receiving element 5 is input to an AC amplifier 6 where the DC component is cut and only the AC component is amplified, and then input to a filter (filter) 7 having the following predetermined frequency characteristic. Usually, a low-pass filter or a band-pass filter is used as this filter. The AC amplifier 6 and the filter 7 constitute a sorting circuit.

The output of the filter 7 is a one-shot timer 8
Is input to the output of the one-shot timer 8 is compared with the comparison voltage E ₃ is input to the comparator 9, the detection signal according to the magnitude relation is output. The one-shot timer 8 and the comparator 9 constitute an output circuit. By the output of the comparator 9, for example, a notification buzzer sounds,
An action such as turning on an alarm lamp or stopping a motor that is a power source of the sewing machine is performed.

FIG. 2 shows the circuit side of the one-shot timer 8 and the comparator 9. Since the collector-emitter of the transistor T when the input voltage E ₁ applied to the base of the transistor T is small is off, the capacitor C is the resistance R ₁
Time constant for the DC power supply V through a R ₂ C (R ₁ + R
Charging proceeds with _2), the output voltage E ₂ increases with time. Transistor T input voltage E ₁ is increased from a predetermined value
Turns on, the electric charge of the capacitor C becomes the time constant CR ₁
Is discharged. If the resistance value R ₂ By setting sufficiently large as compared with the R _1, discharge proceeds rapidly, the output waveform is a triangular waveform.

The comparator 9 compares the output voltage E ₂ of the one-shot timer 8 with the comparison voltage E _{3. When} the output voltage E ₂ is lower, the comparator 9 is at L level, and when the output voltage E ₂ is higher, the output level is H. Outputs a level and a binary signal. FIG. 3 shows a positional relationship between the slit light 3 passing through the slit 2, the light receiving surface of the light receiving element 5 that receives the slit light 3, and the traveling upper thread 4. When the average value of the length of one twist of the yarn is about 1 mm and the traveling speed is 3 mm / sec, the output signal of the light receiving element 5 includes an AC component of about 3 Hz.

FIG. 4 shows voltage waveforms at various parts of the light receiving system circuit. Filter 7, for example, the output of the low pass filter becomes an AC waveform of the example 3Hz as shown in (A) FIG., Or the yarn is eliminated by suddenly at time t _1,
Alternatively, if stopped, the output of the filter 7 becomes 0. The one-shot timer 8 outputs a triangular waveform having a fundamental frequency of 3 Hz with respect to the above-described AC waveform of 3 Hz.
_{From 1} onward, the potential rises steadily with the time constant C (R ₁ + R ₂ ), and eventually exceeds the comparison voltage E ₃ of the comparator 9 at time t ₂ . At this time, the output of the comparator 9 is inverted from L level to H level.

FIG. 5 is an external view of an embodiment of the present invention. The detector case 11 includes a fixed portion 12 disposed near the upper thread bobbin 16 of the upper surface 15 of the sewing machine main body, and a movable portion 13 that opens and closes so as to sandwich the upper thread 4. Is formed. The lamp 1 and the slit 2 are housed in the movable part 13. Unwound from the upper thread bobbin 16
The upper thread passing through the detector case 11
It is designed to be entangled with a lower thread arranged below .

[0014]

According to the present invention, only the upper thread is provided on the upper surface of the sewing machine close to the upper thread, preferably near the upper thread bobbin, without changing the supply path of the upper thread and the lower thread and the mechanism of the sewing machine at all. Thus, it is possible to detect that the lower thread has been lost due to the non-contact.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the output circuit unit of FIG. 1;

FIG. 3 is an operation explanatory view of the optical system of the present invention.

FIG. 4 is an operation explanatory view of the electric circuit system of the present invention.

FIG. 5 is an external perspective view of the embodiment of the present invention in use.

[Explanation of symbols]

 1 ... lamp 2 ... slit 3 ... slit light 4 ... needle thread 5 ... light receiving element 6 ... AC amplifier 7 ... filter 8 ...・ One shot timer 9 ・ ・ ・ ・ Comparator

Claims (1)

(57) [Scope of request for utility model registration] An upper thread bobbin disposed above a work table.
The upper thread unwound from the lower thread below the workbench
Thread breakage of sewing machines such as sewing machines, embroidery machines, etc.
An apparatus, on one side sandwiching the yarn channel on passing the needle thread, a direction crossing the upper thread
A light source with a slit provided to irradiate the slit light to the other side, and a projected image of the upper thread is received on the other side sandwiching the upper thread path .
Including cormorants and light receiving element provided in the selection circuit for taking out an alternating current component of a predetermined frequency range of the electrical output signal of the light receiving element, and an output circuit that AC component that emits a detection signal when drops below a predetermined value, the A lower thread breakage detecting device for a sewing machine.