JPH03295590A - Needle thread supply device for sewing machine - Google Patents

Abstract

PURPOSE:To prevent the excessive or insufficient supply of needle thread occurring by supplying a prescribed amount of needle thread via a thread delivery mechanism by controlling first and second thread pressers. CONSTITUTION:The needle thread is introduced from a thread supply source 10 to a first thread presser solenoid 14 via thread guides 12, 13, and furthermore, is introduced to a second thread presser solenoid 16 arranged at the rearward via a thread delivery roller 15. The thread delivery roller 15 is rotated by a motor 17 rotating at constant speed simultaneously with the application of a power source to a sewing machine, and the prescribed amount of needle thread 11 can be delivered. The amount of delivery of the thread can be detected by detecting the amount of rotation of the motor 17 by the slit plate of an encoder 18, etc. In such a way, it is possible to prevent the excessive or insufficient supply of the needle thread 11 occurring due to the deviation of a release timing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a needle thread supply device for a sewing machine, and more specifically, a thread feeding mechanism for feeding needle thread supplied from a needle thread supply source, and a thread feeding mechanism disposed before and after the thread feeding mechanism. Relating to a needle thread supplying device for a sewing machine, which has a first and second thread presser device, and supplies a predetermined amount of needle thread through a thread payout mechanism by controlling the first and second thread presser devices. .

[Prior Art] A needle thread supply device of a conventional sewing machine includes a thread feed roller that constantly rotates at a constant speed to feed the needle thread supplied from a thread supply source, and a thread presser solenoid and a thread presser solenoid arranged before and after the thread feed roller. It is supplied to the sewing machine needle through. In this case, by turning off (releasing) the first thread presser solenoid located on the thread supply source side, the upper thread is fed to the second thread presser solenoid via the thread payout roller, and after a predetermined amount of thread has been supplied, the upper thread is fed to the second thread presser solenoid. Turn on the thread presser solenoid, and then turn on the second term when the thread take-up approaches the top dead center.
The second thread presser solenoid is turned off to release the thread that has been supplied to the second thread presser solenoid and to supply it to the sewing machine needle. In this way, the first and second thread presser solenoids are turned on and off to supply a predetermined amount of upper thread each time the sewing machine rotates.

In such sewing machine devices, when the sewing machine finishes sewing or when the operator stops the sewing machine by stepping on the pedal, the upper thread and lower thread are cut by the cooperation of a moving knife and a fixed knife arranged adjacent to the hook. be done. At this time, the moving knife reciprocates and moves the captured upper thread to the fixed knife, so normally when cutting the thread, the necessary amount of thread is supplied by taking into account the amount of movement of the moving knife, and when cutting This prevents the upper thread from coming off the sewing machine needle.

At the time of thread trimming, in addition to the above-mentioned required amount of thread, it is also important to consider at what timing the needle thread is supplied. FIG. 6 shows a curve A showing the amount of thread drawn in by the hook, a curve B showing the amount of thread loosening by the thread take-up, and a thread trimming curve C corresponding to the rotation angle of the main shaft. As mentioned above, when the angle is 0 degrees or more, a predetermined amount of upper thread is required for thread trimming, and if the amount exceeds 0 degrees and the supply amount is insufficient, the thread will fall out. Therefore, it is necessary to supply a predetermined needle thread amount before 0 degrees.

[Problem to be solved by the invention] In the conventional device, the amount of thread drawn into the hook reaches the maximum at 330
Since the second thread presser is turned off in synchronization with the thread trimming signal before the end of the thread, the upper thread is released and supplied.
There is a problem in that excessive needle thread is supplied, and the excess thread accumulates around the hook, gets caught on the feed dog, or becomes tangled with the tip of the hook, preventing normal stitches from being formed. In order to prevent this, the second thread presser solenoid should be turned off in synchronization with the thread trimming signal. A device has been proposed that prevents the above-mentioned excessive needle thread supply amount by turning off the thread presser solenoid.

That is, in such a device, the second thread presser is turned off after a predetermined time (approximately 164 m5ec) has elapsed from the beginning of the sewing machine needle down detection after the thread trimming signal is input, and the necessary amount of thread is supplied. However, due to the characteristics of the sewing machine's drive motor, such as inertia, stopping accuracy, and braking characteristics, the thread trimming speed (approximately 160 seconds)
It is difficult to stably obtain a low-speed rotation of pm (low-speed rotation of pm), and therefore, thread cutting at high speeds may be performed at a thread cutting speed of 300 to 150 spm, unlike thread cutting after stopping the -H sewing machine. There is. For example, if the needle thread supply amount is determined assuming that the sewing machine rotates at 160 spm, as mentioned above, even if the sewing machine rotates at 240 spm, the needle thread will be supplied in the same amount of time, and the needle thread supply will be delayed by 240/160 times. When the knife cuts the needle thread that has been captured, a situation occurs in which the necessary amount of needle thread is not supplied, and as a result, the needle thread comes off from the sewing machine needle when the thread trimming is completed, and the needle thread cannot be transferred to the needle that starts the next sewing. There was a problem that I had to pass.

Therefore, the present invention has been made to solve these problems, and an object of the present invention is to provide a needle thread supply device for a sewing machine that can supply the required amount of thread at the time of thread trimming regardless of fluctuations in thread trimming speed. SUMMARY OF THE INVENTION In order to solve these problems, the present invention has a thread unwinding mechanism that unwinds the upper thread supplied from an upper thread supply source, and first and second thread pressing devices disposed before and after the thread unwinding mechanism. In a needle thread supply device of a sewing machine that supplies a predetermined amount of needle thread through a thread payout mechanism by controlling the first and second thread presser devices, means for generating a thread trimming signal after the sewing machine finishes sewing. and a means for detecting the rotation amount of the sewing machine in synchronization with the sewing machine needle down detection signal after generation of the thread trimming signal, and turning off the first thread presser when the detection of the rotation amount of the sewing machine starts. The upper thread is fed out to a second thread holding device via a thread feeding mechanism, and when a predetermined amount of rotation of the sewing machine is detected, the second thread holding device is turned off and the needle thread is fed out to the second thread holding device. We adopted a structure that releases and releases the upper thread.

[Function] In this configuration, a thread trimming signal is generated when the needle down detection signal rises after the sewing machine finishes sewing, and the rotation amount of the sewing machine is detected in synchronization with the falling needle down detection signal. The amount of rotation of the sewing machine is detected, for example, by counting pulses obtained from a tacho generator that measures the speed of the sewing machine. When a predetermined number of pulses are counted, that is, after the sewing machine enters a thread cutting operation and rotates by a predetermined angle, the second thread presser is turned off, and the second thread presser is fed out to release the loose upper thread. With such a configuration, even if the thread trimming speed fluctuates, the required amount of thread will be released at a predetermined rotation angle of the sewing machine (preferably set to around 0 degrees), and excessive thread will be released due to deviations in release timing. This makes it possible to prevent excessive needle thread supply or insufficient supply.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

In FIGS. 1 and 2, the reference numeral IO indicates a yarn supply source, and the needle thread 11 is supplied from this yarn supply source IO to the thread guide 12.
．． 13 to the first thread presser solenoid 14. The thread presser solenoid 14 is turned on and off to hold or release the upper thread 11, as will be described later. The upper thread 11 is further guided from the first thread presser solenoid 14 via a thread payout roller 15 to a second thread presser solenoid 16 arranged at the rear.

As shown in FIG. 3, the thread pay-out roller 15 is rotated by a motor 17 that rotates at a constant speed at the same time as the sewing machine is powered on, and is configured to pay out a predetermined amount of the upper thread 11. The amount of rotation of the motor 17 is detected by a slit plate of an encoder 18, etc., so that the amount of yarn let out can be detected. A lever 20 of the thread feeding roller 15 rotates clockwise with one end 20a as a fulcrum, thereby lifting the auxiliary roller 19 upward. Further, by the downward biasing of the solenoid 21, the lever 20 rotates counterclockwise about the shaft 20a and comes into contact with the auxiliary roller 19, thereby ensuring thread payout. The solenoid 21 is configured to be energized only when energized to self-maintain its position.

The upper thread 11 released from the second thread presser solenoid 16 is guided to the thread take-up lever 24 via the thread guide 23, and further to the thread guide 25.
It is supplied to the sewing machine needle 26 via. Due to the knot with the bobbin thread fed from the hook 27 as the needle 26 moves up and down,
Sewing is performed on the cloth 30 on the throat plate 29.

As shown in detail in FIG. 2, a fixed knife 32 is arranged adjacent to the pot 27.

A movable knife 31 is arranged to reciprocate with respect to the fixed knife 32. At the end of sewing or when the operator performs a thread cutting operation, the movable knife 31 captures the thread, and then moves to the fixed knife 32 to cut the upper and lower threads.

FIG. 4 shows a block diagram of the control system in this embodiment, and the reference numeral 40 in the figure is a CPU (controller) that performs overall control. This CP
A memory device 41 such as ROM or RAM is connected to U40, and the sewing machine is controlled by a predetermined sequence program stored in this memory device, various data are stored, and predetermined control is performed. It is configured. A device 46 that generates a thread trimming signal at the end of sewing or when the operator operates a pedal is connected to this CPU 40, and the thread trimming signal is input to the CPU 40 (2). A needle lowering signal is input from the device 47, and a pulse indicating the speed of the sewing machine, that is, the rotation angle of the sewing machine is input from the tacho generator 48, which detects the speed of the sewing machine.Furthermore, the CPU 40 measures the amount of rotation of the motor 17. Pulses from encoder 18 are manually input.

Furthermore, the CPU 40 includes a first solenoid drive circuit 43,
A second solenoid drive circuit 44 is connected to the first thread presser solenoid 14 .
The second thread presser solenoid 16 is driven. Also CPU4
0 is connected to a thread pay-out motor drive circuit 45,
The motor 17 is thereby driven.

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

First, in the normal sewing operation of the sewing machine, the upper thread is supplied as follows. That is, by releasing the first thread presser solenoid 14, the needle thread 11 is drawn out from the thread supply source via the thread feeding roller 15, which is constantly rotating after the sewing machine is powered on. At this time, the second thread presser solenoid 16 is turned on and presses the thread.

In the CPU 40, a target value of the feed amount is calculated according to the sewing pitch. At this time, since the rotation amount of the motor 17 is measured by the encoder 18, when a pulse corresponding to the target value of the above-mentioned feeding amount is output from the encoder 18, the CPU 40 controls the first solenoid drive circuit 4.
3, the first thread presser solenoid 14 is activated to hold the thread and cut off the supply of the upper thread. On the other hand, when the balance 24 reaches near the top dead center, the second solenoid drive circuit 44
The second thread presser solenoid 16 is turned off via the switch. As a result, the upper thread that has been let out in accordance with the above-mentioned target value is transferred to the thread take-up lever 2 via the released second thread presser solenoid 16.
4 and the sewing machine needle 26. In this manner, during normal operation, the needle thread is let out by a predetermined amount under the above-described control to sequentially form stitches and perform sewing.

When the sewing operation of the sewing machine is finished, or when the operator depresses the pedal to cut the thread of the sewing machine, a thread trimming signal C is generated at the rising edge of the needle down detection as shown in FIG. PI is at the rising edge and P2 is at the falling edge. At this falling point, the tacho generator (TG) is activated at P2.
Start counting pulses T from . This starting point is near about 250 degrees.

After one TG pulse, the first thread presser solenoid 14 is released (turned off) (Sl). As a result, the upper thread 11
The yarn is fed from the yarn supply source lO via the yarn feeding roller 15 to the second yarn presser solenoid 16 which is turned on. The off time of the first thread presser solenoid 14 is set to the required amount of thread in consideration of the next sewing operation. This required amount of thread is detected by the encoder 18, and the thread presser solenoid 1 of the rear cylinder 1
4 is turned on (S2), and further thread feeding is interrupted.

In the present invention, the second thread presser solenoid 16 is turned on at 60 degrees to cut off the thread supply, and in this invention, TG pulses are counted from the time when the needle down detection is off, thereby controlling the on/off timing of the thread presser solenoid. By doing so, it becomes possible to supply the required amount of needle thread for thread cutting corresponding to the rotation angle of the sewing machine. In the 1-motion diagram in Fig. 5, the thread pull-in amount (A) of the hook
The difference between the thread loosening amount (B) and the thread take-up thread take-up amount (B) is the thread allowance, but when the movement of the moving knife during thread trimming is added as an element, there will be a time when there is no thread allowance in the motion diagram (
For example, the area of Ao).

In the present invention, the thread presser solenoid 1
4. When the corresponding count value is reached to control the on/off of 16 (S3), the second thread presser solenoid 16
is turned off to release the upper thread that had been intended to be fed out to the second thread presser solenoid 16 and released. After that, the rotation angle of the sewing machine is reduced.

[Effects of the Invention] As described above, the present invention includes a means for generating a thread trimming signal after the sewing machine finishes sewing, and a means for controlling the rotation amount of the sewing machine in synchronization with a sewing machine needle down detection signal after the thread trimming signal is generated. When the rotation amount of the sewing machine starts to be detected, the first thread presser is turned off, the upper thread is fed out to the second thread presser via the thread payout mechanism, and the rotation of the sewing machine is adjusted to a predetermined rotation level. When the amount is detected, the second thread presser is turned off and the second
Since the needle thread that has been paid out to the thread presser is released and supplied, even if the thread trimming speed fluctuates, the required amount of thread will be released at the specified rotation angle of the sewing machine.
Excessive supply or insufficient supply of needle thread due to deviations in discharge timing is prevented, stable feeding is possible, and the reliability of the sewing machine is improved.

[Brief explanation of the drawing]

Fig. 1 is an external view showing the overall appearance of a sewing machine equipped with the device of the present invention, Fig. 2 is a layout drawing showing the configuration of the needle thread supply device,
Fig. 3 is a perspective view showing the thread pay-out roller, Fig. 4 is a block diagram showing the configuration of the control circuit, Fig. 5 is a motion diagram showing the control flow of the sewing machine, and Fig. 6 is a thread cutting curve. 21 is a motion diagram diagram shown in FIG.
0--System supply source 11-- Upper thread 14.16...
・Thread presser solenoid 15-- system feeding roller

Claims (1)

[Scope of Claims] 1) A thread unwinding mechanism that unwinds the upper thread supplied from an upper thread supply source, and first and second thread holding devices arranged before and after the upper thread, and the first and second thread A needle thread supply device of a sewing machine that supplies a predetermined amount of needle thread via a thread payout mechanism by controlling a presser foot device, comprising means for generating a thread trimming signal after the sewing machine finishes sewing, and after generating the thread trimming signal. means for detecting the rotation amount of the sewing machine in synchronization with the sewing machine needle lower detection signal, and when the detection of the rotation amount of the sewing machine starts, the first thread presser is turned off and the upper thread is passed through the thread pay-out mechanism. When a predetermined amount of rotation of the sewing machine is detected, the second thread presser is turned off to release and release the upper thread fed out to the second thread presser. Features: Needle thread supply device for sewing machines. 2) The needle thread supply device for a sewing machine according to claim 1, wherein the rotation amount of the sewing machine is determined by counting pulses obtained from a tacho generator that measures the speed of the sewing machine.