JPH11221392A - Device for detecting needle break in sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To instantaneously stop a sewing machine after detection by surely detecting a needle break which occurs during sewing in the machine. SOLUTION: Presence or absence of a needle tip 10a which reaches a lower dead point is detected by a detecting equipment 11 during the vertical operation of a needle 10 between an upper dead point and the lower dead point during sewing in the sewing machine, it is decided whether a detection cycle(detection pulse) from the detecting equipment 11 is a fixed value or not by a cycle judging circuit 13, the needle break is decided when the proportion of the detection cycle becomes longer than the fixed value in comparison with the pulse signal of the sewing machine and the needle break judging signal is outputted to a needle break deciding circuit 14. Thus, the sewing machine is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine for detecting a broken needle of a sewing machine which detects a broken needle generated during sewing of the sewing machine and stops the sewing machine based on the detection signal.

[0002]

2. Description of the Related Art Conventionally, various devices have been conventionally known as devices which detect a sewing defect such as a skip or a thread break which occurs during sewing of a sewing machine and stop the sewing machine by the detection.

[0003]

By the way, in a sewing machine, there are many situations in which a needle breaks during sewing and it becomes impossible to continue sewing further.

[0004] However, in the past, there was no effective detection means even if a needle break occurred during sewing. Therefore, in the case of an automatic sewing machine or the like, even if a needle breaks, the sewing operation is continued for a while, and therefore, Not only does the broken needle damage the sewing product, it also affects the sewing parts of the sewing machine such as the needle plate and the shuttle, and there is a problem that the safety against the broken needle is extremely dangerous. .

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a sewing machine needle breakage detecting device capable of reliably detecting a needle breakage occurring during sewing of a sewing machine. I do.

Another object of the present invention is to provide a sewing machine needle breakage detecting device that stops sewing and immediately stops sewing when a broken needle is detected.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is a sewing machine needle breakage detecting device for detecting a needle breakage occurring during sewing of a sewing machine. When the needle reaches the bottom dead center for the needle that moves up and down between the top dead center and the bottom dead center according to the sewing operation of
A needle detecting means arranged close to the vicinity of the bottom dead center of the needle so as to detect the presence or absence of the needle, and a cycle determining means for determining whether a detection cycle output from the needle detecting means is a fixed value or not. And when the ratio of the detection cycle from the needle detecting means becomes longer than a predetermined value, the cycle determining means determines that the needle is broken.

A second aspect of the present invention adopts a configuration according to the first aspect of the present invention, wherein when the cycle determining means determines that the needle is broken, the sewing machine is stopped via the broken needle determining means. It is.

[0009]

According to the present invention, at the time of vertical movement between the top dead center and the bottom dead center of the needle during sewing of the sewing machine, the presence or absence of the needle (point) reaching the bottom dead center is constantly monitored, and Since the needle breakage of the sewing machine is detected by detecting an abnormality such as breakage of the needle tip caused by the needle breakage, it is possible to reliably detect the needle breakage during sewing. When a broken needle during sewing is detected, the sewing machine is stopped, and the sewing operation is immediately interrupted.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a needle breakage detecting device for a sewing machine according to the present invention. In the drawing, reference numeral 10 denotes a needle which has reached a bottom dead center of a sewing machine (not shown); A detector 11 is arranged at a position near the needle tip 10a of the needle 10 that has reached the bottom dead center.

Most of the needle breakage accidents that occur during sewing of the sewing machine are broken at the needle hole 10b as shown in FIG. 1, and the needle tip 10a (dotted line portion) at the tip is broken. Therefore, in the case of a normal needle 10 having no breakage, the detector 11 detects the needle tip 10a of the needle 10 located at the bottom dead center of the sewing machine. However, if the needle tip 10a is broken, it is not detected.

The detector 11 uses, for example, a proximity sensor, and outputs a detection signal to a cycle determination circuit 13 via a detection circuit 12. That is, the detector 11 and the detection circuit 12
And a resonance circuit that oscillates a resonance frequency, and the presence or absence of the needle 10 is detected based on the strength (high or low) of the oscillation intensity. And the value Q of this oscillation intensity (see FIG. 2)
When the needle 10 is not nearby, the value Q is high (needle absence detection), and when the needle 10 approaches, the value Q decreases (needle presence detection).

The period at which the needle 10 is detected by the detector 11 (the detection pulse of the needle 10) is the same as the rotation period of the sewing machine (the rotation pulse per rotation of the sewing machine), and the operating rotation speed of the sewing machine is a constant value. In the above case, the period becomes equal to or less than a fixed value. Therefore, it can be determined that a needle break has occurred when this detection period becomes longer than a certain value.
That is, it is determined whether or not a detection pulse of the needle 10 detected by the detector 11 has been input within one cycle of the rotation pulse of the sewing machine to determine whether the needle is broken. It is the role of the cycle determination circuit 13 to make this determination.

For this reason, the period judgment circuit 13 has the configuration shown in FIG.
As shown in FIG. 5, a detection pulse signal of the needle 10 detected by the detector 11 and a rotation pulse signal from the sewing machine are respectively input. When the sewing machine is in operation, both pulse signals are input. If it is normal,
On the other hand, when the detection pulse signal of the needle 10 is interrupted, it is determined that the needle is broken. The sewing machine is immediately stopped by outputting the needle break determination signal to the needle break determination circuit 14 and outputting a stop output signal from the needle break determination circuit 14 to the sewing machine.

Reference numeral 15 denotes a detection gate circuit.
The detection gate circuit 15 masks the needle break during the time from the input of the running signal of the sewing machine (the control signal for turning the sewing machine) to the time when the rotation speed of the sewing machine reaches a certain value (the rising time of the sewing machine). When the signal is removed, the detection is immediately inhibited.

Next, the operation of the device configured as described above will be described.

In FIG. 2, reference numeral 20 denotes a periodic waveform of the needle 10 for each needle (one cycle) in which the needle 10 moves up and down between the top dead center and the bottom dead center. Corresponds to one rotation of the sewing machine.

Reference numeral 21 denotes a periodic waveform that indicates the magnitude (high or low) of the oscillation intensity value Q oscillated from the detector 11 when the presence or absence of the needle 10 that moves up and down is detected by the detector 11. One cycle of the periodic waveform 21 naturally corresponds to one rotation of the sewing machine.

As can be seen from the periodic waveform 21 shown in FIG. 2, the value of the oscillation intensity when the needle 10 reaches the bottom dead center and the needle tip 10a is detected by the detector 11 (detection of the presence of the needle). Q becomes the lowest value, and conversely, as the needle 10 rises from bottom dead center to top dead center (needle-less detection), its value Q
Is getting higher.

As described above, the oscillation intensity value Q of the needle detector 11 becomes the lowest value when the presence of the needle is detected, and
When the value Q is not near, the detection pulse signal 22 is output from the detector 11 via the detection circuit 12 to the period determination circuit 13 when the value Q is the lowest. Has become.

That is, the level of the value Q of the periodic waveform 21 during normal normal sewing means that the detection cycle of a constant value is regularly repeated every rotation of the sewing machine, and the detection pulse signal 22 is also transmitted to the sewing machine. Is output to the cycle determination circuit 13 at every one rotation of. A rotation pulse signal 23 from the sewing machine is input to the cycle determination circuit 13 for each rotation of the sewing machine. As a result, both the former detection pulse signal 22 and the latter rotation pulse signal 23 are constant. If the value is input to the cycle determination circuit 13 at the cycle of the value, the cycle determination circuit 13 determines that the sewing machine is in a normal state without a broken needle, and the sewing of the sewing machine is continuously performed.

Assuming that the needle is broken (point A in FIG. 2) from the above normal state, the needle tip 10a is broken (FIG. 1) even if the needle 10 reaches the bottom dead center. As a result, detection of the needle 10 by the detector 11 (detection of the presence of the needle) is not performed.

As described above, if the needle 10 is not detected even when the needle 10 reaches the bottom dead center, the periodic waveform 21 indicating the oscillation intensity value Q is greatly disturbed as shown in FIG. And the low value indicating the needle presence detection disappears (the ratio of the detection cycle becomes longer than a certain value),
The detection pulse signal 2 from the detector 11 that has continued until then
2 also disappears and is no longer output to the period determination circuit 13. In this state, that is, when the detection pulse signal 22 is no longer output to the cycle determination circuit 13, the cycle determination circuit 13 determines that a needle break has occurred, and sends this needle break determination signal to the needle break determination circuit 14. A stop output signal is issued to the sewing machine from the needle breakage determination circuit 14 so that the sewing operation of the sewing machine is immediately interrupted.

In the above-described embodiment, the rotation pulse signal of the sewing machine is input to the cycle determination circuit 13. However, instead of this rotation pulse signal, a time period preset by a timer or the like is used as a pulse signal. Judgment circuit 1
3 may be input.

[0026]

As described above, the needle break detecting device of the present invention constantly monitors the vertical movement of the needle during sewing of the sewing machine, and detects an abnormality such as breakage of the needle tip due to the broken needle during sewing. Thus, it is possible to reliably detect broken needles during sewing.

When a broken needle is detected during sewing, an emergency stop is applied to the sewing machine to immediately stop the sewing operation, so that the sewing machine may be damaged by the broken needle or the needle may be damaged. This is a useful invention in terms of safety because it can prevent the sewing machine such as a plate and a shuttle from being damaged, and can easily find and recover a broken needle tip.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a device of the present invention.

FIG. 2 is a waveform diagram illustrating a detection operation of the device of the present invention.

[Explanation of symbols]

 10 Needle 11 Detector 12 Detection Circuit 13 Period Judgment Circuit 14 Needle Break Judgment Circuit 15 Detection Gate Circuit

Claims (2)

[Claims] 1. A sewing machine needle breakage detecting device for detecting a needle breakage occurring during sewing of a sewing machine, comprising: a needle that moves up and down between a top dead center and a bottom dead center in accordance with a sewing operation of the sewing machine; When the needle reaches the bottom dead center, the needle detection means arranged close to the bottom dead center of the needle so as to detect the presence or absence of the needle, and the detection cycle output from the needle detection means is constant. Cycle determining means for determining whether or not the value is a value, wherein the cycle determining means determines that the needle is broken when the ratio of the detection cycle from the needle detecting means is longer than a predetermined value. Characteristic needle break detector for sewing machine. 2. The machine according to claim 1, wherein when the cycle determining means determines that the needle is broken, the sewing machine is stopped via the needle breaking determining means.