JPS609837B2 - How to prevent poor thread tightening in sewing machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting loosening of needle thread tension at the time of stopping and starting a sewing machine, and preventing poor thread tightening.

Taking the conventional manufacturing of fasteners as an example, Fig. 3 shows a state in which left and right fastener stringers are combined. and is sewn together with the bobbin thread 5. FIG. 4 shows a cross section along the seams during these sewing operations. At C, where the upper thread 4 and the lower thread 5 are in a steady sewing state, the tensions of the upper thread 4 and the lower thread 5 are not balanced. Although the thread is loose and sewing is being carried out at a constant rate, when the sewing machine is stopped, the motor continues to rotate due to inertia and the number of rotations gradually decreases, so the tension on the needle thread 4 gradually weakens.
As shown in part A, the tension between the upper thread 4 and the lower thread 5 deteriorates, and the loop formed by the upper thread 4 gradually becomes larger. In particular, when a monofilament thread is used as the needle thread 4, this phenomenon is severe because of its high rigidity. At the time of restart, the rotational speed of the motor gradually increases, so that before the steady state C is reached, a portion with poor yarn wadding occurs, as shown in section B. FIG. 5 is an easy-to-understand diagram of the above, and shows that the tension of the needle thread attenuates and increases in proportion to the number of rotations of the motor. Above A,
Since part B is the part where the combination of fastener stringers is defective, these parts must be cut and removed if it is to be made into a product.

This was a cause of poor product yield. The present invention aims to improve such conventional drawbacks by applying a predetermined pressing force to the upper thread between a thread presser tension device and a needle that is moved up and down by a motor, and stopping the upper thread from falling. A needle thread pressing mechanism equipped with means is provided, and from the end of sewing to the time when the motor stops rotating, the pressing force on the needle thread of the pressing mechanism is controlled by a device that responds to changes in the rotational speed of the motor. The pressing force of the pressing mechanism is applied to the upper thread and the upper thread is clamped from the start of general work until the motor reaches a steady state of rotation. A method for preventing yarn sagging in a sewing machine, which is characterized in that the applied pressing force is gradually reduced as the rotational speed of the motor increases from a stopped state, and the pressing force on the upper thread is released. This is a summary.

In the above, the pressing mechanism may be a cylinder mechanism such as a hydraulic type or an electric type, but an air cylinder mechanism is most suitable for handling.

Further, a solenoid valve can be used as a device for varying the pressure of the pressing mechanism in response to changes in the rotational speed of the motor. To explain an embodiment with reference to the drawings, FIG. 1 is a front view of a device in which the present invention has been carried out, and an upper thread 4 is supplied from a bobbin B mounted under the frame, and this upper thread 4 is connected to a tension disc-like device. It is inserted through the thread presser tension device T and the thread guide 6 into the needle hole at the tip of the needle 7. Reference numeral 8 denotes a motor, which is inputted by a switch 9 and rotates a belt 10, rotates a crank 11, moves a lever 12 up and down about a shaft 13, and moves the needle 7 up and down via a link 14 to perform sewing. It is something to do.

A air cylinder 15 is disposed above the intermediate position between the thread presser tension device T and the thread guide 6, and the presser body 16 at the lower end of the piston rod is used to support the upper thread 4.

A bearing plate 1 is located at a position opposite to the pressing body 16 across the needle thread 4.
7 is provided. 18 is a solenoid valve that selectively operates the air cylinder 15.

This solenoid valve 18 is adapted to operate depending on the operating status of the motor 8. That is, when the operation of the motor gradually decreases, the pressing force of the pressing body is gradually increased, and in the opposite case, the pressing force is gradually weakened. FIG. 1 shows the case where the rotation of the motor 8 is in a steady state, and the pressing body 16 and the upper thread 4
do not come into contact with.

When the motor 8 is stopped at the end of the workday, the rotation will gradually decrease due to inertia, and the solenoid valve 1 responds to the change in rotation speed.
8 is activated, the pressing body 16 at the lower end of the piston rod of the air cylinder 15 is gradually pushed down, and the upper thread 4 is brought into contact with the upper thread 4.
Add tension to. Then, at the same time as the motor 8 stops rotating, the upper thread is stopped between the pressing body 16 and the bearing plate 17. At the end of the working day, the pressing body 16 is raised to the top dead center, but at the start of the next working day, the upper thread 4 is raised again between the pressing body 16 and the support plate 17.
The motor 8 is started from this state. Then, the number of rotations of the motor 8 gradually increases, and in accordance with the increase, the pressing body 16 also rises while pressing the needle thread 4 due to the action of the solenoid valve 18. When the rotation of the motor 8 reaches a steady state, the pressing body Release the body 16 from the needle thread 4. The above is illustrated in an easy-to-understand diagram in FIG. 2, in which the upper thread 4 of the pressing body 16 is
By adjusting the pressing force on the upper thread, the needle thread tension is always kept constant.

Adjustment of the pressing force of the upper thread 4 is determined by the pressing depth of the pressing body 16, and at this time, the pressing depth of the pressing body 16 is adjusted so that the upper thread 4 is supplied with a constant tension from the thread presser tension device T. This is what determines the

Incidentally, when the sewing machine is stopped, the upper thread 4 is preferably held and fixed between the pushing body 16 and the bearing pressure plate 10 as shown in the embodiment.

In this way, the needle thread 4 remains stable when the sewing machine is stopped. FIG. 6 is for explaining another embodiment, in which parts with the same names as those in FIG. It is attached to a member separate from the main body.

In Fig. 6, a solenoid valve 18 that is linked to the rotation speed of the motor.
The illustration of is omitted. This thread presser tension device is called a gate tensor, and as shown in FIGS. 7 and 8, the upper thread 4 is sandwiched between a fixed plate 19 and a movable plate 20, and the movable plate 20' has a weight. 21 functions as a thread presser from which it was hanging. The present invention is as described above, and the tension applied to the needle thread during sewing is always constant regardless of whether it is started, stopped, or normal, and even when sewing long items, the loop created by the needle thread becomes large. There is no problem of poor thread tightness, and it is possible to manufacture a certain product in a timely manner.

[Brief explanation of the drawing]

FIG. 1 is a front view of a device suitable for implementing the present invention, FIG. 2 is a diagram showing the functions of the present invention, FIG. 3 is a sectional view of a combination of fastener stringers suitable for applying the present invention, and FIG. Figure 4 is a sectional view taken along the seam, Figure 5 is a diagram showing the relationship between the rotational speed of the motor and needle thread tension in the conventional example, and Figure 6 is a front view of the device explaining another embodiment. , FIG. 7 is a perspective view showing a specific example of the thread presser sewing machine device shown in FIG. 6, and FIG. 8 is an end view taken along line A--A in FIG. 7. 1... Tape, 2... Core string, 3... Element,
4... Upper thread, 5... Lower thread, 6... Thread guide, 7... Needle,
8...Motor, 9...Switch, 10...Belt, 11...Crank, 12...Lever, 13...Shaft, 14...Ring, 15.
... Air cylinder, 16 ... Pressing body, 17 ... Bearing plate 18 ... Solenoid valve, 19 ... Fixed plate, 20 ... Movable plate, 21 ... Weight, F ... Frame, T ...・Thread presser tension device, B...Bobbin. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8

Claims (1)

[Claims] 1. An upper thread presser groove is provided between the thread presser tension device and the needle that is moved up and down by a motor, which applies a predetermined pressing force to the upper thread and has means for clamping the upper thread.
From the end of sewing until the motor stops rotating,
Pressure force on the needle thread in the presser groove is gradually applied by a device that responds to changes in the rotational speed of the motor, and then the needle thread is clamped, so that the rotation of the motor is in a steady state from the start of sewing. By the time when A method for preventing poor thread tightening in a sewing machine, characterized by releasing a pressing force against the sewing machine.