JPH0144355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a bobbin thread shortage detection device for a light reflection type sewing machine.

[Prior art]

Conventionally, this type of device was
As described in Publication No. 43796, a through hole is formed in the flange of the bobbin, and a flange ring consisting of first and second light reflecting surfaces having different light reflectances can be rotated around the bobbin winding shaft. Using a bobbin that is installed so that the first light-reflecting surface always faces the through-hole due to the spring, when the bobbin thread is insufficient, the first light-reflecting surface faces the through-hole, and a lamp is installed. A type of detector is known in which the intensity of the reflected light of the detection light projected by the detector is detected by a photoelectric element.

[Problem that the invention seeks to solve]

Conventionally, as mentioned above, the strength of reflected light is detected by a photoelectric element, and the detection sensitivity has been a problem.

That is, it is known that in order to increase the detection sensitivity, it is generally necessary to increase the light receiving sensitivity of the photoelectric element itself or to intensify the detection light projected onto the detection position. However, in this method, the photoelectric element detects disturbance light such as reflected light from a portion other than the detection position or light leaked from the outside, causing malfunction. Therefore, in order to eliminate the influence of this disturbance light, measures have been taken such as lowering the sensitivity of the photoelectric element or weakening the detection light. Therefore, it is necessary to delicately adjust the sensitivity of the photoelectric element, and there is a drawback that readjustment is often required even if the usage conditions differ.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a bobbin thread shortage detection device for a sewing machine that is less affected by the above-mentioned disturbance light and has high detection accuracy.

[Means for solving problems]

In the present invention, light is projected toward the bobbin thread wound around the bobbin by operating the light emitting means in response to the light emitting signal repeatedly generated by the light emitting signal generating means. At the same time, the time setting means sets a predetermined length of time in synchronization with each of the light emission signals. On the other hand, the light receiving means receives the light reflected by the bobbin thread and generates a light receiving signal, and the abnormal signal generating means generates an abnormal signal when the light receiving signal is not generated within the set time. , the display means displays the shortage of the bobbin thread when this abnormal signal occurs.

[Effect]

The effects of the present invention are as follows. When the bobbin thread is present at a position onto which light is projected by the light emitting means, a light reception signal is generated within the time set by the time setting means. However, when there is a shortage of bobbin thread, the light reception signal is not generated within the set time, and the abnormality signal is generated to indicate the lack of bobbin thread.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of an embodiment of the present invention will be explained below with reference to the drawings.

In FIGS. 2 and 3, a hook shaft 2 is located in a bed 1 serving as a machine frame of the sewing machine, as a main shaft (not shown).
The outer hook 3 is fixed to the hook shaft 2. An inner hook 4 is supported on the outer hook 3, and a bobbin case 6 containing a bobbin 5 is removably attached to the inner hook 4.

The bobbin case 6 is provided with a notch 61 that allows the needle 13 to fall, and when the bobbin 5 is housed in the bobbin case 6, the bobbin 5
The flange portion 51 is directly visible through the notch 61. Further, the bobbin 5 is integrally formed of a synthetic resin material that is transparent to light and does not particularly reflect infrared rays, and is generally available as a commercially available product.

An opening 7 is formed in a portion of the bed 1 facing the end surface of the bobbin case 6, and an opening/closing cover 8 that can open and close the opening 7 is screwed onto the bed 1. A light emitting diode 9 and a phototransistor 1 as light emitting elements are provided on the inner surface of the opening/closing cover 8 and in a portion facing the notch 61.
A sensor 11 consisting of 0 and 0 is fixed.

The light emitting diode 9 is capable of projecting infrared rays through the collar portion 51 toward a lower thread existing at a predetermined position within the region where the notch 61 is formed, among the lower threads wound around the bobbin 5. be. On the other hand, the phototransistor 10 receives the infrared rays reflected by the bobbin thread and transmitted through the collar portion 51, and generates a signal SS.

Incidentally, a throat plate 12 is installed on the upper surface of the bed 1, and a needle 13 and a presser foot 14 are suspended from above the throat plate 12. Further, within the bed 1, a feeding device 15 is installed which performs a known feeding movement in conjunction with the lower shaft.

Next, the electrical configuration will be explained.

In FIG. 1, a first oscillator 20 generates at least one pulse-like light emission signal CP1 during one rotation of the outer hook 3 when the sewing machine is started;
The light emission signal CP1 is used as the first time setting means.
The light is supplied to the light emitting diode 9 whose cathode is grounded via a one-shot multivibrator 21 (hereinafter referred to as a first one-shot) and a resistor 22.

This first one shot 21 emits the light emission signal.
In response to the rising edge of CP1, one pulse having a constant minute time width is generated as a reference signal CL, and the signal CL is transmitted to the third one-shot multivibrator 31 (hereinafter referred to as the third one-shot) and described later. It is configured to be supplied to the clock terminal CK2 of the second D-type flip-flop 30.

The third one shot 31 is the reference signal CL.
The circuit is configured to supply one pulse having a time width shorter than that of the reference signal CL as the clear signal P1 to the clear terminal CLR of the D-type first flip-flop 25 in response to the rise of the reference signal CL. There is.

Further, the light emitting diode 9 receives the light emitting signal.
It is configured to project infrared rays upon the occurrence of CP1.

The phototransistor 10 has an emitter terminal grounded, and a collector terminal connected via a resistor 23 to a positive power supply Vs and an input terminal of a second one-shot multivibrator 24 (hereinafter referred to as a second one-shot). It generates a signal SS by receiving infrared light. This second one-shot 24 generates one pulse as the light reception signal CP2 in response to the fall of the signal SS,
The circuit is configured to supply the signal CP2 to the clock terminal CK1 of the first D-type flip-flop 25. This D-type first flip-flop 25 and the phototransistor 10 constitute a light receiving means.

Here, the time width of the light reception signal CP2 is narrower than the time width of the reference signal CL, and the time width of the clear signal P1
The time width is set to be wider than the time range of . Furthermore, when the bobbin thread is present at the infrared projection position, the time width of the reference signal CL is set so that the fall of the light reception signal CP2 occurs during the generation period of the reference signal CL.

The D-type first flip-flop 25 is of the type that is automatically cleared when the power is turned on, and its data terminal D1 is connected to the positive power supply Vs.
An inverting output terminal Q1 is connected to a data terminal D2 of a second flip-flop 30 of type D. The D-type first flip-flop 25 holds the high level signal supplied to the data terminal D1 and inverts the signal in response to the fall of the light reception signal CP2 supplied to the clock terminal CK1. The resulting low level signal is generated at the inverting output terminal Q1 as a data signal SP1. On the other hand, when the clear signal P1 is supplied to the clear terminal CLR, the flip-flop 25 generates a high level signal at the inverting output terminal Q1 as the data signal SP1. D-type second flip-flop 3
0 is an auto-clear type, whose output terminal Q2 is connected to the reset terminal RT of the second oscillator 27, and holds the data signal SP1 in response to the fall of the reference signal CL; The configuration is such that the signal is generated as a control signal CS at the output terminal Q2. Output terminal Q2 at this time
A high-level signal generated during this period is considered an abnormal signal. The D-type second flip-flop 30, the third one-shot 31, and the D-type first flip-flop 25 constitute abnormal signal generating means.

The second oscillator 27 is connected to a light emitting diode 29 whose cathode is grounded via a resistor 28.
This second oscillator is activated when a high level control signal CS is supplied to the reset terminal RT, and supplies an oscillation pulse of a constant frequency to the light emitting diode 29, causing it to blink. On the other hand, when a low level control signal CS is supplied to the reset terminal RT, its operation is stopped and the supply of oscillation pulses is stopped. This second oscillator 27, resistor 28 and light emitting diode 2
9 constitutes a display means.

Next, its effect will be explained.

First, in order to start sewing work, the sewing machine user winds the bobbin thread onto the bobbin 5, and then
is housed in a bobbin case 6, and the bobbin case 6 is attached to the inner hook 4. Next, the opening/closing cover 8 is operated to close the opening 7, the work cloth is set, and the power is turned on.

At this time, the electrical circuit is enabled and the D-type first flip-flop 25 receives a high level data signal.
SP1 is supplied to the data terminal D2 of a second D-type flip-flop 30, which supplies a low-level control signal CS to the reset terminal RT of the second oscillator 27. Therefore, the second oscillator 27 is in a deactivated state.

Next, when the sewing machine is started, the sewing work begins, and the first oscillator 20 repeatedly generates the light emission signal CP1, and in response to the rise of the signal CP1, the first one shot 21 has a minute time width. One reference signal CL is supplied to the third one-shot 31 and the second D-type flip-flop 30. In response to the rise of the reference signal CL, the third one shot 31 supplies a clear signal P1 having a shorter time width than the reference signal CL to the clear terminal CLR of the D-type first flip-flop 25.

On the other hand, the light emitting diode 9 projects infrared rays through the collar portion 51 onto the bobbin thread wound at a predetermined position on the bobbin 5 in response to the light emission signal CP1. The phototransistor 10 receives the infrared rays reflected by the lower thread and transmitted through the collar portion 51, and generates a signal SS. Second one shot 24
generates one light reception signal CP2 in response to the fall of the signal SS, and sends this signal CP2 to the clock terminal CK1 of the first D-type flip-flop 25.
supply to.

Here, a case where the bobbin thread is present at the position where the infrared rays are projected will be described with reference to FIGS. 4A to 4F. In this case, the D-type first flip-flop 2 is cleared by the clear signal P1.
5 generates a high-level data signal SP1, and this data signal SP1 changes to a low level as shown in FIG. 4E when the light reception signal CP2 falls. After this, the D-type second flip-flop 3
0 holds the data signal SP1 at a low level in response to the fall of the reference signal CL, and sends this signal SP1 to the reset terminal RT of the second oscillator 27 as a control signal.
Supplied as CS. As a result, the operation of the second oscillator 27 is stopped.

A case in which the infrared rays are not reflected and not received by the phototransistor 10 because there is no bobbin thread at the position where the infrared rays are projected will be described with reference to FIGS. 5A to 5F. In this case, the light reception signal CP2 is no longer generated, and as shown in FIG. 5E, the data signal SP1, which has been set to high level by the clear signal P1, is not set to low level but is maintained as it is. Therefore, the D-type second flip-flop 30 holds the high level data signal SP1 in response to the fall of the reference signal CL.
As shown in Figure 5F, the high level control signal CS
is supplied to the second oscillator 27 to activate it,
The light emitting diode 29 is made to blink.

FIGS. 6A to 6F show cases in which when there is no bobbin thread at the position where the infrared rays are projected, the infrared rays are reflected at another location inside the hook other than the bobbin thread and are received by the phototransistor 10. Explain with reference to. In this case, the infrared rays pass through the projection position and are reflected by the inner surface of the bobbin case 6, resulting in a very long optical path. Therefore, the time from when the infrared rays are projected to when the infrared rays are received by the phototransistor 10 becomes longer, and the light reception signal CP2 is generated after the generation of the reference signal CL is completed. In other words, the clear signal P1 generated in response to the rise of the reference signal CL causes the data signal SP1 to go high, and the D-type second flip-flop 3
0 supplies a high-level control signal CS to the second oscillator 27 in response to the fall of the reference signal CL to activate it and cause the light emitting diode 29 to blink.

In this embodiment, the above-mentioned series of operations is performed at least once per rotation of the main shaft, and the user of the sewing machine can be aware of the shortage of bobbin thread during sewing work. Can be done.

Furthermore, even when there is no bobbin thread at the infrared ray projection position, when the phototransistor 10 does not receive reflected light, and even when it receives reflected light from the bobbin case 6, etc., it does not malfunction.
It is possible to accurately detect and display the lack of bobbin thread. That is, in this embodiment, instead of detecting the lack of bobbin thread based on the amount of light received by the phototransistor 10, the fall of the light reception signal CP2 is detected within the time set by the reference signal CL from the first one shot 21. Depending on whether it occurs or not,
Since the lack of bobbin thread is detected, the detection state of the bobbin thread is completely unaffected by the strength of the infrared rays projected from the light emitting diode 9, the light receiving sensitivity of the phototransistor 10, and is not affected by external light leakage into the bobbin case 6. It is extremely unlikely to be affected.

On the other hand, the user who recognizes that the bobbin thread has been consumed stops the sewing machine and operates the opening/closing cover 8 to open the opening 7.
, and replace the bobbin 5. Here, since the sensor 11 is installed on the inner surface of the opening/closing cover 8, it does not interfere with replacing the bobbin 5.

It should be noted that the present invention is not limited to the above-described embodiments, and instead of using the first one shot 21 as a time setting means, the time may be set by counting a predetermined number of signals having a frequency sufficiently higher than the light emission signal CP1. A counter may also be used.

〔Effect of the invention〕

The present invention provides a time setting means for setting a predetermined length of time in synchronization with a light emission signal that activates the light emission means, and an abnormality when a light reception signal from the light reception means is not generated within the set time. Since the system is configured to include an abnormality signal generation means that generates a signal, and to indicate the lack of bobbin thread when the abnormal signal is generated, it is not affected at all by the strength of the projected light from the light emitting means and the light receiving sensitivity of the light receiving means. Also, the influence of ambient light is extremely reduced, making it possible to accurately detect the lack of bobbin thread.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the electrical configuration of one embodiment of the present invention, Figure 2 is a front view showing the mechanical configuration of this embodiment, and Figure 3 is the same as in Figure 2 with the top surface of the sewing machine bed removed. a top view showing the mechanical configuration;
Fig. 4A to Fig. 4F show the states of each signal when the bobbin thread is present at a predetermined position where infrared rays are projected, Fig. 4A is a time chart showing the light emission signal, and Fig. 4B is a time chart showing the reference signal,
Fig. 4C is a time chart showing the clear signal, Fig. 4D is a time chart showing the light reception signal, Fig. 4E is a time chart showing the data signal, Fig. 4F
are time charts showing control signals, and FIGS. 5A to 5F show the signal states when the bobbin thread is not present at the predetermined position and the infrared rays are not received by the phototransistor, Fig. 5A is a drawing corresponding to Fig. 4A, Fig. 5B is a drawing corresponding to Fig. 4B, Fig. 5C is a drawing corresponding to Fig. 4C, Fig. 5D is a drawing corresponding to Fig. 4 FIG. 5E is a drawing corresponding to FIG. 4E, FIG. 5F is a drawing corresponding to FIG. 4F, and FIGS. 6A to 6F.
shows the state of each signal when infrared rays are received by the phototransistor even though it is not present at a predetermined position, and FIG. 6A corresponds to FIG. 4A, and FIG. 6B is a drawing corresponding to Fig. 4B, Fig. 6C is a drawing corresponding to Fig. 4C, Fig. 6D is a drawing corresponding to Fig. 4D, and Fig. 6E is a drawing corresponding to Fig. 4E. The drawing, FIG. 6F, is a drawing corresponding to FIG. 4F. 1 is a bed, 5 is a bobbin, 51 is a flange, 7 is an opening, 8 is an opening/closing cover, 9 is a light emitting diode, 10
is a phototransistor, 20 is a first oscillator, 2
1 is the first one-shot multivibrator, 2
4 is the second one-shot multivibrator, 2
5 is a D-type first flip-flop, 27 is a second flip-flop.
30 is a D-type second flip-flop, 31 is a third one-shot multivibrator, CP1 is a light emission signal, CP2 is a light reception signal, CL is a reference signal, and CS is an abnormal signal.

Claims (1)

[Scope of Claims] 1. A light emitting means operable to project light toward a bobbin thread wound around a bobbin disposed within the frame of a sewing machine, and a light emitting signal for activating the light emitting means. a light-emitting signal generating means that repeatedly generates a light-emitting signal, a light-receiving means that receives light reflected by the bobbin thread and generates a light-receiving signal, and a predetermined length of time in synchronization with each of the light-emitting signals. an abnormality signal emitting means for generating an abnormal signal when the light reception signal is not generated within the set time; and a display means for displaying the shortage of the bobbin thread when the abnormal signal is generated. A bobbin thread shortage detection device for a sewing machine. 2. The bobbin thread shortage detection device for a sewing machine according to claim 1, wherein the light emitting signal generating means generates the light emitting signal at least once during one revolution of the main shaft of the sewing machine.