JPH06327872A - Yarn tension control device for sewing machine - Google Patents

Abstract

PURPOSE:To provide a yarn tension control device which can prevent occurrence of puckering during high speed sewing, and which can form satisfactory balloon stitch. CONSTITUTION:Between an oval thread take-up 6 and a sewing part (a looper 10 and an upper needle), a yarn pay-out motor 7 is provided which is controlled to start its rotation so as to forcibly pay out the stretched yarn 9 toward the sewing part just before stretching of a yarn (the upper shaft is turned from an angle of zero deg. to an angle of 80 deg.) under the pick-up operation of the yarn 9 by the thread take-up 6 or the moving operation of a cloth to be sewn, but to stop its rotation when the yarn 9 is not stretched (the upper shaft is turned exceeding an angle of 80 deg.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread tension controller for a sewing machine.

[0002]

2. Description of the Related Art Conventionally, in this type of sewing machine, a thread hook, a thread tension adjusting device (adjusting dish), a balance, etc. are provided in a thread supplying path from a thread supplying source (thread winding) to a sewing portion (needle, looper). It is arranged. And by the vertical movement of the balance,
The yarn is fed from the yarn supply source, and the yarn tension at that time is adjusted by the yarn tension adjusting device. As shown in FIGS. 2 and 3, this thread tension adjusting device has two adjusting dishes 12a, 12
A thread 9 is passed between b, one adjusting plate 12a is in contact with the sewing machine main body, and a spring 13 whose elastic force can be changed by an adjusting screw 14 acts on the other adjusting plate 12b. The spring 13 is compressed by tightening, and the other adjusting plate 12b is pressed against the one adjusting plate 12a, whereby the frictional force between the yarn 9 and the adjusting plate 12 increases, and the tension of the yarn 9 increases. Is.

[0003]

However, such a yarn tension adjusting device has a drawback that the tension of the yarn increases as the number of revolutions of the sewing machine increases and the tightness of the yarn 9 increases. Also, the tension of the thread that is too large causes puckering (shrinkage), and in particular, with the lower thread of the double chain stitch, loose stitches called balloon stitches are preferred so that the stitches can easily stretch. There was a problem that loose seams could not be obtained due to the increased tightening condition.

The present invention has been made to solve the above-mentioned problems, and a thread tension control device capable of preventing the occurrence of puckering during high-speed sewing and forming a good balloon stitch. Is intended to provide.

[0005]

In order to achieve this object, a thread tension control device of the present invention has a function of picking up a thread by the balance and a suture cloth at the sewn portion between the balance and the sewn portion. When the thread is tense due to the action of
A thread feeding means for forcibly feeding the thread toward the sewing portion is provided.

[0006]

In the thread tension control device of the present invention having the above-described structure, the thread feeding means provided between the balance and the sewn portion performs the thread picking action by the balance and the movement of the suture cloth at the sewn portion. When the thread is tensioned due to the action, the thread is forcibly delivered toward the sewing portion.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The present embodiment is embodied in a sewing machine that performs double chain stitching. The sewing machine is a double chain machine in which an upper thread and a lower thread are entangled by relative movement of an upper needle (not shown) and a looper. The seams (not shown) are configured. The same names and reference numerals are used for the same parts as those of the conventional technique.

FIG. 1 is a perspective view of a bobbin thread feeding device of a sewing machine for feeding a thread 9 as a bobbin thread (looper thread). A pair of idler rollers 4a and 4b rotating around a lower thread introducing tube 2 and a support shaft 3, a thread tension adjusting device 5, a clam balance 6, a lower thread feeding motor 7, and the lower thread are provided in the lower thread supply path. A bobbin thread feeding motor / pulley 7A, a yarn path 8 and a looper 10 driven by the feeding motor 7 are provided.

The thread tension adjusting device 5 has the same construction as the conventional one, and applies a variable thread tension to the thread 9 in order to obtain a stitch having a good stitching condition. Further, the clam balance adjusts the amount of bobbin thread (loose amount) picked up in connection with sewing.

As the sewing progresses (the suture cloth 1 moves in the direction of the arrow X), the thread 9 supplied from the thread winding (not shown) constituting the thread supply source passes through the lower thread introducing tube 2 and then, The thread tension adjusting device 5 is passed through one idle roller 4a which can be rotated around the support shaft 3 and is given a proper tension there, and then is passed through the other idle roller 4b and the clam balance 6 Leading to. Here, the yarn is picked up, an appropriate amount of yarn is secured, and then the bobbin thread delivering motor 7 is reached.

This bobbin thread feeding motor 7 has the function of pulling the thread 9 in the direction of the arrow Y as the suture cloth 1 moves in the direction of the arrow X, and when the thread balance 9 picks up the thread 9, the thread 9 moves in the direction of the arrow Z. A little before the time when tension is applied to the thread 9 between the balance 6 and the sewing portion by the action of being pulled in the direction (generally, in such a sewing machine, the upper shaft is from 0 degree (the needle bar uppermost position) to 80 degrees). The rotation is controlled to start in the direction of the arrow W at a proper speed and stop when the tension is not applied to the yarn 9 (upper axis is 80 degrees or more). Next, it is guided by the yarn path 8 and reaches the looper 10. here,
By the relative movement between the looper 10 and the upper needle (not shown),
The upper thread and the lower thread are intertwined with each other to form a double chain stitch (not shown).

Next, the operation of the thread tension control device of the sewing machine will be described.

When the sewing machine is driven, the suture cloth 1 moves in the direction of the arrow X.
Tension is applied to the yarn 9 by the action of pulling the yarn 9 in the direction of the arrow Y by moving in the direction, and the action of pulling the yarn 9 in the direction of the arrow Z when the yarn 9 is picked up by the balance 6. Shortly before this tension is applied, the yarn feeding motor 7
The yarn 9 slides on the surface of the yarn feeding motor / pulley 7A while the tension of the yarn 9 is small, but when the tension is large, the yarn 9 is strongly pressed against the surface of the yarn feeding motor / pulley 7A. The thread 9 and the thread feeding motor
The frictional force between the pulleys 7A becomes large. Due to this frictional force, the thread 9 is forcibly delivered toward the sewn portion.
Then, when tension is no longer applied to the yarn 9, the yarn feeding motor 7 stops rotating.

In this way, the bobbin thread delivering motor 7 starts rotating the bobbin thread delivering motor / pulley 7A just before the thread 9 is tensioned, and the thread 9 is forcibly delivered as the tension increases. The yarn 9 before the feeding motor 7, that is, the rotating yarn feeding motor from the yarn supply source
The increase in tension due to the inertial force and frictional force due to the inertia of the yarn 9 up to the pulley 7A and the increase in tension due to the yarn pick-up by the thread take-up 6 are absorbed by the bobbin thread feeding motor / pulley 7A. The tension between 7A and the sewn portion is kept substantially constant, and it is possible to prevent excessive tension of the thread. This also ensures that a good double chain stitch is always formed.

Although the above embodiment is applied to the lower thread of the double chain stitch sewing machine, the invention is not limited to this, and the upper thread of the double chain stitch sewing machine and the lock stitch sewing machine are also The same effect can be obtained by providing a roller portion similar to that of this embodiment at a predetermined position of the supply path.

[0016]

As is apparent from the above description, the yarn tension control device of the present invention is provided with the yarn feeding means for forcibly feeding the yarn, so that the yarn tension control device has a simple structure and is used for high-speed sewing. It is possible to prevent the occurrence of puckering due to excessive tension.

[Brief description of drawings]

FIG. 1 is a perspective view of a bobbin thread feeding device of a sewing machine of the present invention.

FIG. 2 is a front view of a conventional bobbin thread tension adjusting device.

3 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 1 Suture Cloth 6 Clam Balance 7 Lower Thread Feeding Motor 7A Lower Thread Feeding Motor / Pulley 9 Lower Thread 10 Looper

Claims (1)

[Claims] 1. A sewing machine configured such that, when a sewing machine motor is started, a thread delivered from a thread supply source is guided to a sewing portion via a balance provided in a thread supply path. A thread feeding means for forcibly feeding the thread toward the sewn portion at the time of tension of the thread due to the action of picking up the thread by the balance and the action of the movement of the suture cloth at the sewn portion. A thread tension control device for a sewing machine characterized by the above.