JPH0728974B2 - Skipper detection device for sewing machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a stitch skipping detection device for a sewing machine, which detects stitch skipping by measuring the needle feed length of each needle by a contact sound.

[Prior Art] Conventionally, as a means for detecting skipped stitches, a differential space filter in which one comb-shaped slit is inserted between one comb-shaped slit is configured, and this differential space filter is used. An apparatus has been proposed in which the upper thread is detected through a photodetector through the needle (see Japanese Patent Laid-Open No. 63-37082).

In this device, when the upper yarn is supplied, the shadow of the upper yarn is detected by the differential space filter, and the traveling yarn length is detected by the movement of the shadow.

As another stitch skipping detecting device, a device for detecting the tension of the upper thread by a strain gauge has been proposed (Japanese Patent Laid-Open No. 55-
22115 gazette).

[Problems to be Solved by the Invention] However, in the former device, since the measurement is performed by the shadow of the upper thread projected on the differential space filter, it is very difficult to detect depending on the thickness and type of the thread, and There is a drawback that cotton dust easily adheres to the differential space filter, which causes malfunction.

Further, in the latter device, there is a problem that it is difficult to accurately detect skipped stitches because the needle thread tension fluctuates greatly even in a normal state.

According to the present invention, the upper thread is brought into contact with the sound detection sensor to detect the length of the friction sound generated when the upper thread travels every rotation of the sewing machine. It is an object of the present invention to provide a stitch skipping detection device for a sewing machine capable of detecting a stitch.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention makes the needle thread of a sewing machine contact a sound detection sensor, and the needle feed length of each needle of the needle thread is adjusted when the needle thread is running. The contact sound is detected, and the skipped stitch is detected from the change in the contact sound.

Further, the upper thread of the sewing machine is brought into contact with the sound detecting sensor, and the length of the upper thread of each needle of the upper thread is detected by the generation time of the contact sound when the upper thread travels per revolution of the sewing machine. Is compared with the generation time of the contact sound measured before that, and skipped stitches are detected from the difference in the generation time of the contact sound.

Further, the upper thread of the sewing machine is brought into contact with the sound detecting sensor, and the yarn feed length for each stitch of the upper thread is detected by the generation time of the contact sound when the upper thread is running for each revolution of the sewing machine. Is compared with the contact sound generation time measured before, and the difference in the contact sound generation time is compared with the change in the rotational speed of the sewing machine to detect skipped stitches.

[Operation] According to the present invention, when a sound detecting sensor is attached to the needle thread path of the sewing machine and the needle thread is brought into contact with the sound detecting sensor to drive the sewing machine, when the needle thread is fed for each stitch, Friction noise is generated by the movement of the upper thread. This friction noise is detected by a sound detection sensor, and this detection signal is output as a signal in the frequency range required by the bandpass filter, and this signal is waveform-shaped. This waveform-shaped signal is time-measured in the time-measuring circuit by the clock from the timing generating circuit by the signal from the rotation speed sensor, and the time-measured data is stored in the temporary storage device. Then, the difference between the time-measured data of the detection signal due to the next frictional sound detected in the same manner and the time-measured data of the stored detection signal is calculated by the calculation circuit and output to the error detection comparison circuit. On the other hand, the rotation speed sensor outputs a rotation speed signal in response to a signal from the rotation detection sensor, and the rotation speed signal is temporarily stored in a temporary storage device. And
When the next rotation speed signal is output from the rotation speed detector, it is compared with the temporarily stored rotation speed signal, and if there is a difference, error data due to variations in this rotation speed is stored in the ROM. This error data is read from the ROM and input to the error detection / comparison circuit, and is compared with the difference data of the detection signal due to the friction noise in the comparison circuit to output the skipped signal.

[Embodiment] Referring to FIG. 1, in a stitch skipping detection device according to an embodiment of the present invention, a sound detecting sensor 1 for detecting a friction sound of an upper thread.
For example, as shown in FIG. 2, the upper thread 4 is configured to pass through the groove 3 provided on one surface of the piezoelectric element 2. When the upper thread 4 is pulled during yarn feeding, Friction noise is generated by rubbing against the element 2, and the friction noise is detected by the piezoelectric element 2. The frictional sound signal detected by the sound detection sensor 1 in this way is amplified by the amplifier 5, and only the necessary frequency of the frictional sound signal passes through the bandpass filter 6, and the waveform shaping circuit 7 can measure the time. The signal having such a waveform is shaped (see FIG. 2 (c)). Further, a clock signal is generated from the timing generation circuit 9 according to the timing from the rotation detection sensor 8 (see FIG. 2A) {see FIG. 2B}, and is input to the time measurement circuit 10. The clock signal input to the time measuring circuit 10 is passed only between the signals sent from the waveform shaping circuit 7, and the number of the passed clock signals {see FIG. 2 (d)} is data as yarn feeding data. It is stored in the temporary storage device 11. Similarly, the next yarn feeding data sent from the time measuring circuit 10 and the yarn feeding data read from the data temporary storage device 11 are input to the arithmetic circuit 12, and the difference between them is calculated. If the upper thread 4 is normally fed when the sewing machine is rotating at a constant speed, the difference between the yarn feeding data that is input one after another is zero and the skipped stitch signal is not output. Here, when the difference between the next signal and the next signal is large, a skip signal is issued.

The mechanical speed of the sewing machine causes variations in the number of rotations. This variation in the number of revolutions is 1 in the number of revolutions detector 13 by the timing signal from the revolution detection sensor 8.
The number of revolutions per minute (rpm) is detected, this revolution number signal is temporarily stored in the revolution number temporary storage device 14, and then the revolution number detector 13
The arithmetic circuit 15 calculates the difference between the rotational speed signal detected in step 1 and the rotational speed signal read from the rotational speed temporary storage device 14, and stores it in the ROM 16 in advance as error data. And ROM
The error signal read from 16 is input to the error detection / comparison circuit 17, and this error signal is compared with the signal of the difference in the yarn feeding data output from the arithmetic circuit 2. When the ratio is large, the stitch skip signal is generated. As a result, the error detection comparison circuit 17 outputs an error signal.

In this embodiment, the frictional noise at the time of supplying the upper thread is thus detected,
Since the signals due to the frictional noises sent one after another are compared and a skipped signal is output when the difference is large, and this skipped signal can be discriminated by the change in the number of revolutions,
Accurate skipping can be easily detected.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, the running of the upper thread at the time of supply is detected by the friction noise, the timing at which the friction noise is generated is detected for each rotation of the sewing machine, and the sewing machine Since it is possible to correct the deviation of the generation of the friction noise during acceleration or deceleration, there is an advantage that skipped stitches can be accurately and easily detected.

[Brief description of drawings]

FIG. 1 is a block diagram of a skipped stitch detecting device according to one embodiment of the present invention, FIG. 2 is a perspective view of a piezoelectric element used as a sound detecting sensor in FIG. 1, and FIG. 3 is a waveform of each part of FIG. It is a figure. 1 ... Sound detection sensor, 2 ... Piezoelectric element, 3 ... Groove, 4 ... Upper thread,
5 ... Amplifier, 6 ... Band pass filter, 7 ... Waveform shaping circuit, 8 ... Rotation detection sensor, 9 ... Timing generation circuit, 10
... Time measuring circuit, 11 ... Data temporary storage device, 12 ... Operation circuit, 13 ... Revolution speed detector, 14 ... Revolution speed temporary storage device, 15 ...
Operation circuit, 16 ... ROM, 17 ... Error detection comparison circuit.

Claims (3)

[Claims] 1. A needle thread of a sewing machine is brought into contact with a sound detecting sensor,
A stitch skipping detection device for a sewing machine, which detects a yarn feed length of each needle of the upper yarn by a contact sound when the upper yarn is running, and detects a stitch skip based on a change in the contact sound. 2. A needle thread of a sewing machine is brought into contact with a sound detecting sensor,
The length of feed of each needle of the upper thread is detected by the generation time of the contact sound when the upper thread travels per revolution of the sewing machine, and the generation time of the contact sound is the contact sound generation time measured before that time. A stitch skipping detection device for a sewing machine, which detects stitch skipping based on a difference in generation time of contact sound, compared with. 3. A needle thread of a sewing machine is brought into contact with a sound detecting sensor,
The length of feed of each needle of the upper thread is detected by the generation time of the contact sound when the upper thread travels per revolution of the sewing machine, and the generation time of the contact sound is the contact sound generation time measured before that time. And a stitch skipping detection device for a sewing machine, wherein the stitch skipping is detected by comparing the difference in the generation time of the contact sound with the change in the rotation speed of the sewing machine.