JPH03292993A - Needle thread feeder of sewing machine - Google Patents

Abstract

PURPOSE:To prevent uneven stitches even when a sewing machine is operated an any rotating speed or even when the rotating seed is sharply changed from a high speed to a low speed, by a method wherein a device is provided to detect the decrease amount of rotating speed of the sewing machine, and when the decrease amount exceeds a specified value, the feed rate of needle thread is corrected so as to reduce the feed rate of needle thread. CONSTITUTION:A CPU 40 takes in needle position signals 42 according to the sewing action of a sewing machine, and calculates the speed of the sewing machine by time measuring of needle position signals, and a needle thread feeder feeds needle thread corresponding to the calculated result. By comparing the present sewing machine speed with the speed one cycle before, it is judged whether or not the speed is sharply changed to a low speed. When it is not a sharp speed reduction, needle thread is fed at a normal rate, and when it is a sharp reduction, the needle thread feed rate is corrected. Thereby, in the case of a sharp speed reduction, the needle thread feed rate is corrected to a lower one, so that uneven stitches due to a sharp speed reduction are avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a needle thread supply device for a sewing machine, and more particularly to a needle thread supply device for a sewing machine that supplies needle thread from a needle thread supply source to a sewing machine needle. It is something.

[Prior Art] A needle thread supply device of a conventional sewing machine includes a thread pay-out roller that constantly rotates at a constant speed to feed the needle thread supplied from a thread supply source, and first and second thread presser solenoids arranged before and after the 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, then press the injection tube 2 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.

It is known that when a sewing machine rotates at high speed, the actual feed amount compared to the set feed amount of the sewing machine increases due to factors such as play in the feed mechanism that feeds the thread, elongation due to inertial force, and deflection. Since the yarn supply path is longer when rotating than when rotating at low speed, the amount of yarn supplied must be increased.6For example, as shown in Fig. 8, the L yarn 2 fed through the thread take-up is At low speeds, the thread follows the path shown by the solid line, but at high speeds, the inertial force of the thread increase increases and the thread supply path becomes longer, as shown by the dotted line. Therefore, the amount of yarn supplied must be larger at high speeds than at low speeds. For this reason, in conventional devices, as shown in Figure 9, the thread payout amount varies depending on the rotational speed of the sewing machine.
For example, the amount of feed is increased at high speed rotations than at low speeds, increasing by about 2% for every 11,000 sp, to compensate for the error caused by the inertial force described above.

[Problem to be Solved by the Invention] In such a conventional device, when the sewing machine changes slowly from high speed to low speed or from low speed to high speed,
Since the upper thread is properly supplied by the correction according to the sewing machine rotation speed as shown in FIG. 9, the bobbin thread 5 and sewing machine needle 8 supplied from the hook 3 as shown in FIG. Normal sewing is performed on the cloth 4 with the needle thread 2 supplied from the sewing machine. In this case, by the above-described correction, uniform stitches can be obtained regardless of the rotational speed of the sewing machine.

However, when the sewing machine rotates at high speed (for example, 3000 s)
pm) to a low speed (for example, 500 spm), mechanical elements such as the balance and hook cannot keep up with the inertia caused by the sudden deceleration. Therefore, for example, the ninth
300 at 500 spm as shown by number 6 in the figure.
Yarn corresponding to 0 spm is supplied, resulting in excessive supply. Therefore, as shown in FIG. 7(B), uneven stitching 7 occurs during low speed rotation. The uneven stitching caused by such excessive supply not only causes the thread to float up from the fabric 4, but also reduces the quality of the sewing product.
This results in the occurrence of fraying.

Therefore, the present invention was made to solve these problems, and no matter what the sewing machine rotation speed,
Another object of the present invention is to provide a needle thread supply device for a sewing machine that can perform high-quality sewing without causing uneven stitching even when the speed suddenly changes from high speed to low speed.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a needle thread supply device for a sewing machine that supplies needle thread from a needle thread supply source to a sewing machine needle by measuring the number of revolutions of the sewing machine. means for supplying the upper thread according to the rotational speed of the sewing machine; and means for detecting the amount of deceleration of the rotational speed of the sewing machine; A configuration has been adopted that reduces the amount of needle thread supplied by making corrections to the above.

[Function] In such a configuration, the number of rotations (speed) of the sewing machine is measured from the needle position signal of the sewing machine, and the upper thread is supplied from the upper thread supplying means in accordance with the rotational speed (speed) of the sewing machine.

The amount of needle thread supplied is normally such that when the sewing machine is rotating at high speed, the amount of thread being fed out is greater than when the sewing machine is rotating at low speed. Here, by comparing the speed of the sewing machine with the speed of one cycle, it is determined whether or not there has been a sudden deceleration in the rotation speed, and if there has been no sudden deceleration, normal thread unwinding is performed, or if there has been a sudden deceleration. In this case, the yarn payout amount is corrected. If this causes a sudden deceleration, the amount of needle thread supplied is corrected and the amount of needle thread supplied is reduced, so that uneven stitching caused by the sudden deceleration can be eliminated.

[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 1o indicates a thread supply source, and from this thread supply source 1o, the upper thread 11 is
．． 13 to the first presser solenoid 14. The original presser solenoid 4 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 original presser solenoid 14 via a thread pay-out roller 15 to a second original presser solenoid I6 provided 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. This yarn pay-out roller 15 is normally in contact with an auxiliary roller 19 that is rotatably supported at one end by a shaft 20a and rotatably supported at the other end by a protrusion of a lever 20 that is biased by a spring 22. . Then, as the solenoid 21 is biased in one direction, the lever 20 rotates clockwise about the shaft 20a and lifts the auxiliary roller 19 upward. In addition, the lever 20 rotates counterclockwise about the shaft 20a as a fulcrum by the downward biasing of the solenoid 21, and comes into contact with the auxiliary roller 19 to ensure thread payout. It is a mechanism that self-maintains its position by energizing it.

The upper thread 11 released from the second main presser solenoid 16 is guided to the thread take-up thread 24 via the thread guide 23, and further to the thread guide 25.
It is supplied to the sewing machine needle 26 via. As the needle 26 moves up and down, the cloth 30 on the throat plate 29 is sewn by knotting with the bobbin thread 28 fed from the hook 27. In FIG. 2, reference numeral 31 indicates a cutting device for cutting the upper thread and lower thread at the end of sewing.

FIG. 4 shows a block diagram of the control system in this embodiment, and in the same figure, the reference numeral 40 is a CPU (controller) that performs overall control.
A memory device 41 such as ROM or RAM is connected to 40, and the sewing machine is controlled by a predetermined sequence program stored in this memo J device, and various data are stored and predetermined controls are performed. It is composed of A needle position signal 42 from a needle position detector attached to the main shaft (not shown) of the sewing machine is input to the CPU 40.
The rotational speed of the sewing machine is thereby measured. Also CP
Pulses from the encoder 18 that measure the amount of rotation of the motor 1'T are input manually to U40. Further, a first solenoid drive circuit 43 and a second solenoid drive circuit 44 are connected to the CPU 40, and the first original presser solenoid 14. The second main presser solenoid 16 is driven. Further, a thread payout motor drive circuit 45 is connected to the CPU 40, and the motor 17 is driven by this.

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

First, in accordance with the sewing operation of the sewing machine, the CPU 40 takes in the needle position signal 42, and calculates the speed of the sewing machine, that is, the number of rotations, by measuring the time of the needle position signal (steps SL and S2 in FIG. 5).

When the sewing machine is powered on, the motor 17 is driven, so the thread pay-out roller 15 is constantly rotating, and by releasing the first presser solenoid 14, the needle thread 11 is drawn out from the thread supply source. At this time, the second original presser solenoid 16 is turned on and presses the yarn.

In accordance with the speed measurement, the CPU 40 calculates a corrected target value for the payout amount according to the rotational speed as shown in FIG. 9, and the needle thread is paid out accordingly. 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 garlic 18, the CPU 40 causes the The main presser solenoid 14 of No. 1 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 main presser solenoid 1 is activated via the second solenoid drive circuit 44.
6 is turned off. As a result, the needle thread that has been let out in accordance with the above-mentioned target value is supplied to the thread take-up 24 and the sewing machine needle 26 via the released second main presser solenoid 16. 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. This state is shown in section T1 in FIG.

Here, as shown in step S3 in FIG. 5, it is determined whether or not there is a rapid deceleration mode. If it is not a sudden deceleration and it was determined in step S4 that the sewing machine was rotating at a low speed last time, normal feeding processing is performed in step S5, and the rapid deceleration mode flag is turned off in step s6. On the other hand, if it is determined that the rapid deceleration mode is in step S3 (for example, 50
If the measured speed is determined to be high in step S4 (for example, if it is rotating at 3000 spm as shown in FIG. 6), the previous speed is changed in step S7. and determines whether or not the vehicle is rapidly decelerating in step S8.
If there is a sudden deceleration state, a correction process is performed on the yarn payout amount in step S9, and if not, the process moves to step S5 and normal processing is performed. When the feed-out correction is performed, a flag indicating the rapid deceleration mode is turned on in step SIO.

The period during which this correction of the feeding amount is performed is indicated by T2 in FIG. Specifically, as shown in Fig. 9, in the case of sudden deceleration, oversupply occurs, so a negative correction is made as shown by the reference numeral 50 in Fig. 9 to offset the excess supply. 6 [Effect of the Invention J As is clear from the above description, according to the present invention, it is possible to detect whether or not the rotational speed of the sewing machine has decelerated by a predetermined amount or more, and to determine whether or not a sudden deceleration has occurred. In this case, the amount of needle thread supplied is corrected to reduce the amount of needle thread supplied, which eliminates uneven stitching and allows high-quality sewing to be performed.

[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 yarn pay-out roller, Fig. 4 is a block diagram showing the configuration of the control circuit, Fig. 5 is a flow chart showing the flow of control, and Fig. 6 is a rapid deceleration state in which the feed amount is corrected. 7 (A) and (B) are explanatory diagrams showing sewing conditions at high and low speeds, and FIG. 8 is a speed characteristic diagram showing the
FIG. 9 is an explanatory view of the movement of the take-up illustrating the movement of the take-up lever at high speed and low speed, and FIG. 9 is an explanatory view of correction showing the correction of the amount of yarn let out. lO... Thread supply source 11... Needle thread 14.16.
・・Material presser solenoid 15・-system feeding port 24・・Take-up lever 26・・・Sewing machine needle holder 1 p. 70. ,,Fig. 4 Shaoqingbian r [Fig. 5

Claims (1)

[Scope of Claims] 1) A needle thread supply device for a sewing machine that supplies needle thread from a needle thread supply source to a sewing machine needle, comprising means for measuring the number of rotations of the sewing machine, and supplying the needle thread in accordance with the number of rotations of the sewing machine. and a means for detecting the amount of deceleration of the rotational speed of the sewing machine, and when the amount of deceleration exceeds a predetermined value, the amount of needle thread supplied is corrected and the amount of needle thread supplied is reduced. Needle thread supply device for sewing machines.