JPS5949034B2 - Sewing machine skipped stitch detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stitch skip detection device for a sewing machine that uses a magnetic recording medium to detect stitch skips that occur during sewing operations.

In general, sewing machines have a problem in that a stitch is not partially formed during a sewing operation, that is, so-called skipped stitches occur.

There are various possible causes for this skipped stitch, but in the case of double chain stitching, the needle thread is charged with static electricity due to friction with the fabric being sewn, and the needle thread adheres to the sewing machine needle, causing the needle thread to loop. This is thought to be because the louver does not form a loop, and therefore the louver cannot scoop up the loop, or conversely, the needle thread does not scoop up the loop formed by the louver thread.

In any case, if skipped stitches occur, the sewing product will be defective, so if skipped stitches occur, it can be immediately detected, displayed or notified, or the sewing operation can be automatically stopped. It is hoped that this will be done.

In particular, there is a strong desire for this in garment factories that use industrial sewing machines, as they are moving toward unmanned sewing machines that operate automatically.

The present invention has been made to meet such needs, and provides a stitch skip detection device for a sewing machine that can quickly and reliably detect stitch skips during sewing operations.

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

Needle thread 2 is supplied to a sewing machine needle 1 through a pair of thread tension devices 3 and 4.

A magnetic disk 5 as a magnetic recording medium is rotatably disposed between the thread tension devices 3 and 4, and the needle thread 2 is wound once around the outer peripheral surface of the magnetic disk 5.

Incidentally, a groove into which the needle thread 2 enters is formed on the outer circumferential surface of the magnetic disk 5 to prevent the needle thread 2 from coming off.

A write head 7, a read head 8, and an erase head 9 are arranged close to the magnetic surface 6 of the magnetic disk 5 in the direction of rotation of the magnetic disk 5.

Note that a predetermined interval, which will be described later, is provided between the write head 7 and the read head 8, and an appropriate interval is provided between the read head 8 and the erase head 9.

On the other hand, a synchronization signal generator 1 generates a synchronization signal (pulse) periodically in response to one cycle of sewing operation of the sewing machine, for example, in synchronization with the rotation of a rotary pulley 10 in the sewing machine.
1 is provided, and the synchronization signal generated by the synchronization signal generator 11 is written onto the magnetic disk 5 via the write head 7.

Further, the synchronization signal written on the magnetic disk 5 is read by a read head 8, and erased by an erase head 9 supplied with an erase signal from an erase signal generator 12.

Then, the synchronization signal generated by the synchronization signal generator 11,
The read synchronization signal read by the reading head 8 is input to the discrimination circuit 13, and the discrimination circuit 13 outputs the synchronization signal generation circuit 1.
Based on the synchronization signal generated by 1, it is determined whether or not the read head 8 has read the synchronization signal from the magnetic disk 5 every l cycle of sewing operation, and if the read head 8 has not read the synchronization signal, the determination circuit 13 detects skipped stitches. The discrimination circuit 13 has a logical configuration so as to generate a signal.

Note that the synchronization signal read by the read head 8 is transmitted to the amplifier circuit 1.
4 to match the level with the synchronizing signal from the synchronizing signal generating circuit 11.

Incidentally, in this embodiment, the distance between the write head 7 and the read head 8 is defined as the interval of synchronization signal generation in the synchronization signal generator 11, that is, the distance between the magnetic disk 5 and the needle thread 2 in one direction of the sewing machine needle in one cycle of sewing operation. The rotation angle is made slightly smaller than the rotation angle when the magnetic disk 5 is rotated normally, so that the read head 8 can read the synchronization signal during one cycle of sewing operation if the magnetic disk 5 is rotated normally.

With this configuration, assuming that normal sewing operation without skipped stitches is being performed, the needle thread 2 is consumed by traveling a predetermined length in one direction of the sewing machine needle for each cycle of sewing operation. Ru.

Therefore, the magnetic disk 5 is also driven by the needle thread 2 and
It rotates intermittently in the direction of the arrow by a predetermined angle for each sewing operation of the cycle.

On the other hand, a synchronizing signal generator 11 generates a synchronizing signal, and the synchronizing signal is sequentially written to the magnetic disk 5 via the write head 7 and is input to the discrimination circuit 13.

Further, the read head 8 reads the previously written synchronization signal at the timing when a new synchronization signal is being written by the write head 7, that is, at the timing when the synchronization signal is input to the comparator circuit 13. A synchronizing signal is input to the comparison circuit 13 via the amplifier 14.

Therefore, when the normal sewing operation is repeated, the needle thread 2 advances normally, and the magnetic disk 5 rotates normally, the synchronization signal generator 11 is generated to the discrimination circuit 13. Since the synchronization signal and the read synchronization signal from the read head 8 are always input at the same timing as shown in FIG. 3, the discrimination circuit 13 does not generate a skipped stitch signal.

However, when skipped stitches occur during the sewing operation, the needle thread 2 is not consumed normally, so the needle thread 2 does not travel and the magnetic disk 5 does not rotate.

Therefore, even if a synchronization signal is input from the synchronization signal generator 11 to the discrimination circuit 13, the read head 8 cannot read the synchronization signal from the magnetic disk 5 at that timing, and as a result, the discrimination circuit 13 receives the read synchronization signal. Since there is no input,
The determination circuit 13 logically determines that skipped stitches have occurred and generates a skipped stitch detection signal.

Therefore, the desired purpose can be achieved by operating a skipped stitch indicator or a skipped stitch alarm or by stopping the sewing operation in the sewing machine using the skipped stitch detection signal.

In this embodiment, a magnetic disk is used as the magnetic recording medium, but it goes without saying that magnetic drums, endless magnetic tape, etc. can also be used.

Further, although the magnetic disk is driven directly by the needle thread, it may be driven indirectly, and in short, it is sufficient if the magnetic disk is rotated in synchronization with the traveling of the sewing machine needle thread.

Furthermore, in the above embodiment, if the synchronization signal generated by the synchronization signal generator and the synchronization signal read by the reading head are input to the discrimination circuit at the same timing, it is determined that there is no skipped stitches. 1 even if the input phases of both signals are shifted
If both signals are input during the sewing operation of the cycle, for example, the counter counts the synchronization signal from the synchronization signal generator, and the counter is not reset by the synchronization signal read by the read head, but the synchronization signal is continuously counted. By using the output of the counter as a skipped stitch detection signal, it is possible to determine whether or not the read head has read the synchronization signal from the magnetic recording medium during one cycle of the sewing operation. Therefore, it is not necessary for the synchronization signal to be input from the synchronization signal generator and the read head at the same timing.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a perspective view showing the relationship between the magnetic recording medium section and the sewing machine needle thread section, and Fig. 2 shows the discrimination circuit section for obtaining a skipped stitch detection signal. The block diagram shown in FIG. 3 is a waveform diagram showing a write signal to a magnetic recording medium, a read signal from the magnetic recording medium, and the logical relationship between these signals and a skipping signal. 1... Sewing machine needle, 2... Sewing machine needle thread,
3, 4...Thread tension regulator, 5...Magnetic recording medium, 7...Writing head, 8...Reading head, 11...・Synchronization signal generator, 13・
...Comparison circuit.

Claims (1)

[Claims] 1. A magnetic recording medium that rotates in synchronization with the running of the needle thread supplied to the sewing machine needle, a synchronization signal generator that generates a synchronization signal in response to one cycle of sewing operation of the sewing machine, and this generator a write head for writing a synchronization signal to the magnetic recording medium; a read head provided to read the synchronization signal written to the magnetic recording medium by the write head for each cycle of sewing operation; A determination circuit that determines whether or not the read head has read the synchronization signal for each cycle of sewing operation and generates a skipped stitch detection signal if the read head has not read the synchronization signal; A skipped stitch detection device for a sewing machine, comprising an erasing head that erases data each time the reading head reads.