JP2683424B2 - Needle breakage detector for sewing machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine needle breakage detecting device, and more particularly to a sewing machine needle breakage detecting device for detecting needle breakage occurring during sewing of a sewing machine.

[Prior Art] Conventionally, there is known a device that detects a sewing failure (for example, stitch skipping, slipping out, thread breakage, etc.) that occurs during sewing of a sewing machine and, in some cases, stops the sewing machine in an emergency. In addition, the needle may be broken during sewing and the sewing may not be continued any more.

[Problems to be Solved by the Invention] In the past, even if a needle break occurred during sewing, there was no effective detection means. Therefore, in an automatic machine such as a cycle sewing machine, even if the needle is broken, the sewing operation continues as it is. Not only does it damage the sewn item due to the broken needle remaining on the needle bar and make it impossible to re-sew it (defective product),
There was a problem that it also affects the equipment such as the tip of the hook and is very dangerous in terms of safety.

Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a needle breakage detecting device for a sewing machine, which can reliably detect a needle break during sewing.

[Means for Solving the Problems] In the present invention, in order to solve the above-mentioned problems, in a needle breakage detecting device for a sewing machine that detects a breakage of a needle that occurs during sewing of a sewing machine, a sewing operation according to the sewing operation during sewing of the sewing machine is performed. A reciprocating member that reciprocates from a first position to a second position;
Means for measuring the time during which the reciprocating member is moving to the second position, and means for calculating the ratio of the time during which the reciprocating member is moving to the second position for each sewing cycle are provided. A configuration is adopted in which needle breakage is detected when the ratio of the time becomes smaller than a predetermined value.

[Working] With such a configuration, the sewing operation during sewing, especially the thread take-up operation is constantly monitored (sampled), abnormalities in the thread take-up operation due to needle breakage during sewing are detected, and needle breakage of the sewing machine is detected. Therefore, the needle breakage can be reliably detected during sewing. If needle breakage during sewing is detected,
An emergency stop is applied to the sewing machine and the sewing operation is interrupted.

EXAMPLES Hereinafter, the details of the present invention will be described based on examples shown in the drawings.

FIG. 1 is a block diagram of a needle breakage detecting device for a sewing machine according to an embodiment of the present invention. In block 1, a signal from a detection plate for detecting needle breakage is generated. Abnormalities in the sewing operation due to the needle breakage are detected by attaching the detection plate 10 to the second thread tension portion of the head of the sewing machine as shown in FIGS. 2 and 3.

A thread take-up spring 13 is attached to the thread tension portion 11 as is well known, and the thread sent from the balance side is
14 is supplied to the needle bar side via this thread take-up spring. As shown in FIG. 3, the thread take-up spring 13 reciprocates in the range between the first and second positions indicated by A and B for each one rotation of the sewing machine, that is, for each stitch according to the sewing operation. It is a reciprocating member, and a signal is obtained from the detection plate 10 according to the reciprocating member. In this case, the detection plate + 12V, the head including the thread take-up spring is ground (GND)
The reciprocating movement of the thread take-up spring 13 during sewing is converted into an electric signal. The thread take-up spring 13 is AB for each stitch during sewing.
Since it makes one round trip in the section (1), the electric potential of the detection plate 10 is 12V electrically until the point A and the points A to B are reached, and becomes 0V when the point B is reached.

The signal from the detection plate 10 is input to the sample and hold circuit 2 shown in FIG.
The number of times the detection plate 10 and thread take-up spring 13 are turned on,
As will be described later, the number of times the point B is reached and becomes 0V is counted. The signal from the counter 3 is input to the arithmetic processing unit 4, and moves to the time when the thread take-up spring is in contact with the detection plate for each stitch (each sewing cycle of the sewing machine), that is, point B, according to the number of times of ON and the sampling time. The operating time, the ratio, and the average value of the ratio are calculated. That is, the sample / hold circuit 2 and the counter 3 constitute means for measuring the time during which the thread take-up spring 13, which is the reciprocating member, is moving to point B for each needle, and the arithmetic processing section 4 is for the one needle. It is a means for calculating the ratio of the time moving to point B for each time and the average value of the ratio. The discrimination processing unit 5 is connected after the arithmetic processing unit 4. In this discrimination processing unit, the average value is compared with a predetermined value, and if it is determined that the average value is smaller than the predetermined value, needle breakage is detected. When this needle break is detected, the emergency stop interrupt signal generator 6 causes the sewing machine 7 to make an emergency stop.

 The operation of the thus configured device will be described.

In step S1 of FIG. 4, it is determined whether or not the needle break detection mode has been entered by interrupt processing, and if the detection mode has been entered, the detection plate is entered in step S2.
The signal from 10 is read. This reading is performed in the sample and hold circuit 2 by sampling the signal of the sewing plate during sewing at a constant interval by a soft timer. As described above, the signal from the detection plate 10 is + 12V when the thread take-up spring 13 is located at the point A and between A and B, and is off when it is located at the point B, and 0V when it is located at the point B. , The counter 3, the sampling plate 10 and the thread take-up spring 13 during the sampling period.
The number of turns on is counted (step S3).

Subsequently, in step S4, it is determined whether or not one stitch is finished. If finished, the process proceeds to step S5 and the detection plate 10
The ratio x of the time when the thread take-up spring 13 is in contact with is calculated. This ratio x is the time during which the detection plate 10 and the thread take-up spring 13 are in contact during one rotation of the sewing machine (one needle), that is, the time when the detection signal becomes 0V, Ton, and the time when both members are separated, that is, the detection. It is expressed as a percentage of x = Ton / (Ton + Toff), where Toff is the time when the signal becomes + 12V. Ton and Toff are ON of the sampling period described above,
It can be calculated based on the number of times it has been turned off. In FIG. 5, the value of x is shown on the vertical axis, and the number of stitches is shown on the horizontal axis. The ratio x (%) of the number of times of turning on for each stitch (time to turn on) thus calculated is stored in the memory as data for each stitch. In the arithmetic processing unit 4, this data x
Besides, the average value of data for several stitches is calculated (step S6).

By the way, during normal sewing, during T,
As shown in FIG. 5, x is + -α with respect to the average value.
The data changes in the range of, but as shown by t,
When needle breakage occurs, the data x changes to abnormal values such as x1 and x2 (values below x-α).

Utilizing this, the variation width α of x with respect to the average value is calculated in step S7, and then the threshold value xref (x-α-β) is set for this average value in step S8. Data xk at the time of sewing in the discrimination processing unit 5
And xref are compared, and if needle breakage occurs at time t, xk is
Since it is less than xref, it is judged that the needle is broken at that time (step
S9), an emergency stop signal is sent to the sewing machine 7 via the emergency stop interrupt signal generator 6 (step S10) to stop the sewing operation.

In the above-described embodiment, the average value of x is calculated and this is compared with a predetermined threshold value.
The thread take-up spring is characterized in that the ratio of the time during which the thread take-up spring is moving to the position B is calculated for each sewing cycle, preferably for each stitch, and the above-mentioned ratio of time is directly calculated without necessarily obtaining the average value. The needle breakage may be detected by comparing with a predetermined value.

Further, in the above-described embodiment, it is premised that the thread (upper thread) is not broken when needle breakage occurs, and in this case, the time during which the detection plate 10 and the thread take-up spring 13 are in contact with each other as described above. Becomes shorter than the normal sewing, and x becomes an abnormal value. However, when the thread is cut, the detection plate and the thread take-up spring do not contact each other, and the value of Ton becomes 0. Needless to say, the method can detect needle breakage.

Further, even if a stitching defect or a phenomenon that affects the sewing such as stitch skipping, loose thread and needle thread coming out of the thread guide occurs, the above-mentioned value of x is different from the normal value. By properly setting these phenomena, it is possible to stop the sewing machine and take emergency measures depending on the case.

[Effects of the Invention] As described above, in the present invention, the sewing operation during sewing is constantly monitored, and the abnormality in the operation due to the needle breakage during sewing is detected. Break detection is possible. When needle breakage occurs during sewing in this way, it can be detected and an emergency stop can be used to stop the sewing machine, preventing machine damage and causing needle thread breakage after needle replacement. The same restart as in the case of an emergency stop is possible, and the defective rate of the sewn product can be reduced.

In addition, it is possible to detect a phenomenon such as a skipped stitch, a loose thread and a needle thread coming out of the thread guide, or a phenomenon that affects the sewing, and it is also possible to stop the operation. Can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the device of the present invention, FIG. 2 is a perspective view showing the structure of a detection plate, and FIG. 3 is an explanatory diagram explaining the detection operation by the thread take-up spring, and FIG.
FIG. 5 is a flow chart showing the flow of control, and FIG. 5 is an explanatory diagram showing calculated values of read data during sewing. 2 …… Sample hold circuit 3 …… Counter 4 …… Arithmetic processing unit 5 …… Judgment processing unit 6 …… Emergency stop interrupt signal generator 7 …… Sewing machine 10 …… Detection plate 13 …… Thread take-up spring

Claims (4)

(57) [Claims] 1. A needle breakage detecting device for a sewing machine, which detects a breakage of a needle occurring during sewing of a sewing machine, comprising: a reciprocating member that reciprocates from a first position to a second position according to a sewing operation during sewing of the sewing machine. Means for measuring the time during which the reciprocating member is moving to the second position, and means for calculating the ratio of the time during which the reciprocating member is moving for the second position for each sewing cycle of the sewing machine are provided. A needle breakage detecting device for a sewing machine, wherein the needle breakage is detected when a ratio of the time becomes smaller than a predetermined value. 2. A stitch breakage is detected when an average value of the ratios during a predetermined period during sewing is calculated and the average value becomes smaller than a predetermined threshold value.
A needle breakage detecting device for a sewing machine according to the item. 3. The needle breakage detecting device for a sewing machine according to claim 1, wherein the reciprocating member is a thread take-up spring provided in a thread tension portion. 4. The machine according to any one of claims 1 to 3, wherein an emergency stop is applied to the sewing machine when the needle break detection is detected.
The needle breakage detecting device for a sewing machine according to any one of items 1 to 10.