JPS588874B2 - Method and device for detecting the amount of bobbin thread remaining on a sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and device for detecting the amount of bobbin thread remaining in a sewing machine.

Conventionally, this type of device has been provided which detects that the bobbin thread is completely consumed and activates an alarm such as a buzzer or lamp based on this detection.

However, when a sewing machine equipped with such a device sews a certain number of consecutive stitches, the bobbin thread is consumed during the sewing process, an alarm is activated, and the sewing machine is stopped after a while.

This is because even if the sewing machine is automatically stopped upon detection of bobbin thread consumption, there will be a delay in operation.

For this reason, several stitches will be stitched blankly, and when replenishing the bobbin thread and resewing, the position of the workpiece cloth must be corrected by that amount (the needle thread is usually cut once) to ensure accuracy. It must be ensured that a new seam is formed following the previous seam.

This is extremely troublesome and causes a decrease in work efficiency, and the threads are unsightly exposed on the fabric at the joint between the previous and subsequent stitches, reducing the commercial value of the finished product. It was intended to reduce the

In view of these circumstances, the present invention is designed to eliminate these defects at once by detecting the bobbin thread that is longer than the length required for continuous zigzag sewing of a certain number of stitches. be.

To explain one embodiment below, in the figure, 1 is a throat plate, 2 is a needle, 3 is a thread ring catcher for forming a lock stitch in cooperation with the needle 2, and an outer hook 4 and an inner hook are connected to each other. It consists of a pot 5.

A bobbin case 7, in which a bobbin 6 is rotatably supported, is removably inserted into the inner hook 5.

Further, on one side of the bobbin 6 facing the front opening 8 of the bobbin case I, eight light reflecting portions 9 are annularly provided at equal intervals as shown in FIG.

Reference numeral 10 denotes a mounting body fixed to the lower surface of the needle plate 1, on which a light projector 11 and a light receiver 12 that cooperate with the light reflection section 9 are mounted.

The light emitted by the light projector 11 is reflected by the light reflecting section 9 and enters the light receiver 12.

Furthermore, FIG. 3 shows the state in which the bobbin thread 13 is wound around the bobbin 6, and is shown in the unfolded state for ease of understanding. Required slack portions 13b are provided at positions separated by a length A or more required for continuous sewing.

The length of the bobbin thread required for this slack portion will be described later.

In order to wind the bobbin thread in this manner, it is sufficient to first wind the bobbin by length A, then provide the required slack portion 13b, and then wind the bobbin thread again.

This slack portion 13b can be created by a worker's hands or by a dedicated machine.

When using a machine, for example, a bobbin thread 13 of a length necessary for sewing a certain number of stitches is wound around the bobbin 6, and then a rod-shaped finger piece or the like is inserted around the wound thread and the finger piece is also wound. This can be done by winding it up a little in this way and then pulling out the fingers.

After that, you can continue to wrap the bobbin thread over it.

FIG. 4 shows a circuit for detecting the remaining amount of bobbin thread in cooperation with the above configuration, in which the signal from the light receiver 12 is applied as an input to the flip-flop 15 via the waveform shaping circuit 14. The output is applied as a reset signal to counters 16 and 17, which are formed by four flip-flops connected in cascade.

18 is a detector that generates one pulse every time the main shaft of the sewing machine rotates once, and the pulse signal is sent to the waveform shaping circuit 19.
The signal is added as an input signal to the counters 16 and 17 via the counters 16 and 17.

Reference numeral 20.21 denotes an AND circuit which receives the signal from the output terminal of the second flip-flop and the signal from the output terminal of the third flip-flop of the counter 16, 17, respectively, and 22 denotes an AND circuit 20.21. 21
The output terminal is connected to the gate of a silicon-controlled rectifier 24 connected in series to an alarm 23 such as a buzzer or lamp.

25 is a normally closed reset switch connected in series to the cathode of the silicon-controlled rectifier 24 to deactivate the alarm 23.

Next, the effect will be explained.

The bobbin 6 with the bobbin thread 13 wound thereon as described above is inserted into the thread ring catcher 3, and continuous sewing of a fixed number of stitches is started.

Normally, the bobbin 6 is rotated by letting out the bobbin thread 13, and the light from the emitter 11 is intermittently applied to the receiver 12 depending on the presence or absence of a light reflecting part on the side surface of the bobbin 6. Each time, the flip-flop 15 is reversed and its output is counter 16 by
．． A reset signal is alternately sent to the terminals 17 and 17.

During this time, the main shaft of the sewing machine rotates once (
That is, every time one stitch is sewn, the pulse signal from the detector 18 is sent to the counter 16. 17 (ie, the side to which the reset signal is not applied from flip-flop 15) starts counting, but that counter is reset before producing an output from its second and third flip-flops.

However, when the bobbin thread 13 is consumed up to its slack portion 13b, the bobbin 6 is temporarily no longer rotated due to the slack, the flip-flop 15 is temporarily set to one state, and the signal from the detector 18 is It is added to the counter 16 or 17 on the side that is not reset, and when that counter counts 6 stitches, in other words, when the output terminals from the second and third flip-flops of that counter generate an output, it becomes AND. It is applied to circuit 20 or 21, the output of which is applied to OR circuit 22, and the output from the OR circuit makes silicon controlled rectifier 24 conductive and activates alarm 23.

Therefore, the slack portion 13b of the bobbin thread needs to have a length of six stitches or more.

The activation of the alarm 23 notifies the operator that the remaining amount of bobbin thread is enough to carry out one continuous sewing operation with a certain number of stitches.

Therefore, even if the alarm 23 is activated, the continuous sewing of a certain number of stitches can be normally completed to the end, and the operator must remove the bobbin thread 13 after finishing the continuous sewing.
It is only necessary to take out the bobbin 6 that has been used up and insert a bobbin with a new bobbin thread wound thereon.

Thereby, there is no possibility that the bobbin thread 13 is consumed in the middle of sewing.

The operation of the alarm 23 is stopped by opening the reset switch 25 once, as the silicon-controlled rectifier 24 becomes non-conductive.

In the above description, the alarm 23 is activated when the bobbin 6 is temporarily not rotated during six stitches of sewing due to the slack portion 13b of the bobbin thread 13, but this is for the following reason.

In other words, since the tip of the bobbin thread 13 has been cut off by the thread trimmer at the end of the previous sewing, there is usually at least a few stitches of slack at the beginning of the bobbin thread, and this slack causes an alarm at the start of sewing. The device 23 is not activated.

In the above embodiment, the alarm 23 is activated when the bobbin is not rotated during six stitches of sewing, but this may be set as appropriate if necessary.

Further, the intervals between the light reflecting portions 9 must be set such that the counter 16 or 17 is reset before it counts six inclines of pulses.

Therefore, this interval is influenced by how many stitches of input pulses are received by the counter to activate the alarm 23 and by the stitch pitch, that is, the amount of bobbin thread consumed.

Further, although the above-mentioned device has been described for detecting the remaining amount of bobbin thread, it also works as a thread breakage detecting device for the upper thread and bobbin thread at the same time.

That is, even if either the upper thread or the lower thread breaks, the bobbin 6 will not rotate, and the alarm 23 will be activated in the same manner as described above.

Furthermore, the counters 16 and 17 may have any structure.

The present invention has the configuration as described in detail above, and the required slack portion is removed from the bobbin thread wound on the bobbin at a position separated from the winding start end by a distance longer than the length required for continuous sewing of a certain number of stitches. The system detects when the bobbin thread is consumed up to the slack part and the bobbin temporarily stops rotating due to the slack, so even after this detection, sewing continues normally until the end. Therefore, for example, as shown in the above embodiment, an alarm is activated based on the detection to notify the worker, and when the alarm is activated, the alarm is activated after the sewing is finished. If the bobbin is replaced, the lower thread will not be consumed in the middle of sewing as in the past.

Furthermore, since it detects when the bobbin temporarily stops rotating due to slack in the bobbin thread, by appropriately setting the position where the slack is formed, it is possible to sew a certain number of consecutive stitches regardless of the length. It has excellent effects such as adaptability.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the mechanical configuration, Figure 2 is a diagram showing a bobbin equipped with a light reflecting section, Figure 3 is an explanatory diagram showing how to wind the bobbin thread, and Figure 4 is a detection circuit. . In addition, in the figure, 1 is a throat plate, 3 is a thread ring catcher, 6 is a bobbin, 9 is a light reflection part, 11 is a light emitter, 12 is a light receiver, 13 is a bobbin thread,
13a is the winding start end, 13b is a slack portion, 15 is a flip-flop, 16 and 17 are counters, 18 is a detector,
20.21 is an AND circuit, 22 is an OR circuit, and 23 is an alarm.

Claims (1)

[Scope of Claims] 1. When winding the bobbin thread around the bobbin that is rotatably supported inside the thread loop catcher, a position separated from the winding start end by at least the length necessary for sewing a certain number of consecutive stitches. A method for detecting the amount of bobbin thread remaining in a sewing machine, wherein a required slack portion is provided in the sewing machine, and it is detected that the bobbin thread is consumed up to the slack portion and the bobbin is temporarily no longer rotated due to the slack. 2. A bobbin rotatably supported inside the thread ring catcher;
The bobbin thread wound on the bobbin must have the required slack at a position that is at least the distance required for a certain number of consecutive stitches from the winding start end, and the bobbin thread must be able to reach that slack part. A device for detecting a remaining amount of bobbin thread for a sewing machine, comprising: detecting means for detecting that the bobbin is temporarily no longer rotated due to consumption and slack of the bobbin.