JPH06319885A - Controller for thread tension of sewing machine - Google Patents

Abstract

PURPOSE:To provide the controller for thread tension capable of preventing the generation of packering at the time of high-speed sewing and forming a good baloon stitch. CONSTITUTION:A motor 3 controlled to rotate at the proper speed in synchronism with the sewing machine motor and a thread feeding motor pulley 3A are provided on a thread supply route located between the thread supply source and an oval ballance 7.

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 tray), 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
The thread 9 passes between b, one adjusting dish 12a is in contact with the sewing machine body 17, and the other adjusting dish 12b has a spring 13 whose elastic force can be changed by an adjusting screw 14. By tightening the adjusting screw 14, the spring 13
Is compressed, and the other adjusting pan 12b is replaced with the other adjusting pan 12a.
The thread 9 and the adjusting tray 12 have a large frictional force, and the tension of the thread 9 increases.

[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 in that loose seams could not be obtained due to the increased tightening condition.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to prevent the occurrence of puckering during high-speed sewing and to form a good balloon stitch. The purpose is to provide a control device.

[0005]

In order to achieve this object, a yarn tension control device of the present invention forcibly delivers a yarn between a yarn supply source and a balance in relation to rotation of a sewing machine motor. The yarn feeding means is provided.

[0006]

In the yarn tension control device of the present invention having the above-mentioned structure, the yarn feeding means provided between the yarn supply source and the thread take-up forcibly delivers the yarn in association with the rotation of the sewing machine motor. Prevents thread tension.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. This embodiment is embodied in a sewing machine that performs double chain stitching. The sewing machine is a double chain stitching machine in which an upper thread and a lower thread are entangled by relative movement of an upper needle (not shown) and a looper. It constitutes an eye (not shown).
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). In the lower thread supply path, the lower thread introducing pipe 2, the lower thread feeding motor 3,
A bobbin thread delivering motor / pulley 3A driven by the bobbin thread delivering motor 3, a pair of idle rollers 5a and 5b rotating about a support shaft 4, a thread tension adjusting device 6, a clam balance 7, a fixed shaft 8, and a thread. A road 10 and a looper 11 are provided.

The lower thread feeding motor 3 is controlled to rotate at an appropriate speed in synchronization with a sewing machine motor (not shown), and the lower thread feeding motor / pulley 3A is fixed to the motor shaft thereof. ing. The bobbin thread delivering motor 3 and the bobbin thread delivering motor / pulley 3A constitute a thread delivering means. The thread tension adjusting device 6 has the same configuration as the conventional one, and in order to obtain a stitch with a good stitching tone,
A variable thread tension is applied to the thread 9. Further, the clam balance 7 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 lower thread. It reaches the yarn feeding motor / pulley 3A. Then, the thread tension adjusting device 6 is passed through one idle roller 5a which can be rotated around the support shaft 4, and the thread tension adjusting device 6 is provided with an appropriate tension. Then, the thread tension adjusting device 6 is passed through the other idle roller 5b and the clam balance. To 7. The yarn is picked up here to ensure the proper amount of yarn. Then, passing through the fixed shaft 8 and guided by the yarn path 10,
Reach Looper 11. Here, the upper thread and the lower thread are entangled by the relative movement of the looper 11 and the upper needle (not shown),
A double chain stitch (not shown) is formed so that the thread 9 is consumed in the arrow Y direction.

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

When the sewing machine motor is driven, the bobbin thread feeding motor 3 starts rotating in synchronization with it. Tension is applied to the thread 9 only when the thread 9 is consumed in the direction of the arrow Y in FIG. 1 (generally, in the case of this kind of sewing machine, the upper axis is 0 degrees (the uppermost position of the needle bar) to 80 degrees). A frictional force acts between the bobbin thread delivering motor / pulley 3A and the thread 9 rotating at various speeds, and the thread 9 is forcibly delivered.

In this way, when tension is applied to the thread 9 (that is, the timing of thread tightening), the bobbin thread delivering motor / pulley 3
Since the yarn 9 is forcibly delivered by A, the yarn 9 before the bobbin yarn delivering motor / pulley 3A, that is, the inertial force due to the inertia of the yarn 9 between the bobbin winding and the yarn delivering motor / pulley 3A is Feeding motor / pulley 3
Since it is absorbed by A, it is possible to prevent the tension of the yarn 9 from increasing due to this inertial force.

The following theoretical formula (1) shows the tension T of the thread of the sewing machine.

T = a × w × n ² + b × p × v −−−−−−−−−− (1) T: tension of the yarn 9 a: proportional constant w: of the yarn before the pulley 3A of the motor 3 Inertial weight n: Rotational speed of sewing machine b: Proportional constant p: Pushing force of thread 9 against pulley 3A v: Relative sliding speed between thread 9 and pulley 3A a × w × n ² in this theoretical formula (1) is the sewing machine Indicates the inertial force depending on the rotation speed, and b × p × v indicates the frictional force. Although the inertial weight w of the thread itself is small, it is proportional to the square of the rotation speed, so the inertial force (a × w
× n ² ) becomes very large. It is understood that if the yarn feeding motor / pulley 3A absorbs this inertial force, the excessive tension of the yarn 9 at the time of high-speed sewing can be considerably prevented.

The above embodiment is an example of the lower thread of the double chain stitch sewing machine, but the present invention is not limited to this, and the upper thread of the double chain stitch sewing machine and the thread of the lockstitch sewing machine are also the same. The same effect can be obtained by providing the yarn feeding means similar to that of this embodiment at a predetermined position of the supply path.

[0017]

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

[Brief description of drawings]

FIG. 1 is a perspective view of a bobbin thread feeding device of a sewing machine according to a first embodiment.

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]

 3 Bobbin thread feeding motor 3A Bobbin thread feeding motor / pulley 4 Clam balance 9 Thread 11 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 tension control device for a sewing machine, characterized in that a thread feeding means for forcibly feeding the thread in relation to the rotation of the sewing machine motor is provided between a supply source and the balance.