JPS5810115B2 - Upper thread non-adjustable sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a needle thread adjustmentless sewing machine that automatically performs proper thread alignment.

In a lockstitch sewing machine, the tension of the lower thread is set to a certain value, and the tension of the upper thread is adjusted according to changes in the fabric, thread, and stitch, and the upper and lower threads intersect at the center of the thickness of the fabric. It is recognized as the best stitch.

Conventionally, the tension of the upper thread is applied by the frictional resistance of the thread by sandwiching the upper thread between two tension discs and sliding it between the tension discs, and the tension is adjusted by the clamping pressure of both thread tension discs. This was done by changing the .

In this case, the operator performs trial sewing in advance, adjusts the clamping pressure based on the results, and then repeats the trial sewing, which is not only cumbersome, but also the frictional resistance tends to change with changes in sewing conditions. It is very difficult to accurately adjust the tension of the upper thread in response to changes in fabric, thread type, or sewing pattern.

The present invention detects the tension of the upper thread during sewing and uses changes in this tension to automatically adjust the thread appropriately.
To provide a needle thread non-adjustable sewing machine that does not require a worker to adjust needle thread tension.

FIG. 1 is an explanatory diagram of a process in which a sewing machine forms a stitch by crossing an upper thread and a lower thread.

In the figure, after the needle thread loop 2a of the needle thread 2 formed below the sewing cloth 1 scoops up the bobbin thread 3, the needle thread 2 is pulled up by the rise of the thread take-up, and the needle thread loop 2a shrinks and moves upward. The machine moves, pulls up the bobbin thread 3, threads the thread, and forms a stitch.

If the change in needle thread tension is examined by taking the lowest position P of the needle thread loop and the needle thread tension T on the vertical and horizontal axes, respectively, the tension curve shown in FIG. 2 is obtained.

That is, in the process of pulling up the needle thread 2, the needle thread tension T increases rapidly when the lowest point P of the needle thread loop 2a reaches the downward direction A of the sewing cloth 1, and then at the center B of the sewing cloth 1. After leveling off, at a point beyond the upper surface C of the sewing cloth 1, the tension T takes a value slightly larger than the value when the lowermost point P of the needle thread loop was initially below the sewing cloth 1.

The present invention utilizes this change in needle thread tension to release the needle thread when the needle thread pulls up the bobbin thread during the stitch formation process and crosses the upper and lower threads at the center of the sewing cloth, thereby increasing the tension of the needle thread. By eliminating this, the upper and lower threads are prevented from pulling up the lower thread any further, and the upper and lower threads intersect at the center of the fabric.

Examples will be described below based on the drawings.

In FIG. 3, a needle thread 2 is supplied from a thread spool, and is supplied from a thread guide 3 to a needle guide 7 from a thread take-up via an electromagnetic needle thread adjustment device 4 and a tension detection device 5.

The electromagnetic upper thread adjusting device 4 is attached to the sewing machine frame M as shown in FIG.
An electromagnet 9 fixed to an L-shaped frame 8, an armature 10 of the electromagnet 9, and a shaft 10 of the armature 10.
When the electromagnet 9 is not energized, the armature 10 is pressed by the spring 11 to a pressure contact plate 12 fixed to the rising portion 8a of the frame 8, and the upper thread 2 is connected to the pressure contact plate 12. 12 and the armature 10, and an appropriate thread tension is applied (FIG. 4A).

Further, the electromagnet 9 is energized by the operation of a sensing device 13 which will be described later, and the armature 10 is displaced in the direction of the electromagnet 9 due to the energization of the electromagnet 9, and the pressure contact between the pressure contact plate 12 and the armature 10 is released, and the upper thread 2 is released. (Figure 4B).

The tension detection device 5 includes a tension detection lever 1 having a magnet 14 fixed to one end and the other end bent at a right angle to form a thread hook 15.
6 and a detection spring 17.

The tension detection lever 16 is pivotally supported at its center by a shaft pin 18 on the machine frame M, and the detection spring 17 is inserted between the shaft pin 19 protruding from the machine frame M and the thread hook 15 side of the tension detection lever 16. It is stretched and urges the thread hook 15 downward.

In this embodiment, the spring constant of the detection spring 17 corresponds to the tension Tc at point B in FIG. The magnet 14 on the opposite side of the tension detection lever 16 faces the sensing device 13 when the tension detection lever 16 is turned.

The sensing device 13 has a Hall element, and the magnet 1
4 are opposed to each other, that is, when the needle thread tension reaches Tc, the electromagnet 9 of the electromagnetic needle thread adjusting device 4 is excited through a suitable circuit.

Now, during sewing, the top post 6 is raised and the upper thread 2 is being threaded.
is pulled up and the lowest point P of the upper thread loop 2a reaches the center of the sewing cloth 1, that is, when the intersection of the upper and lower threads reaches the center of the sewing cloth 1, the upper thread tension becomes Te. Become.

When the needle thread tension reaches Tc, the thread hook 1 of the tension detection lever 16
5 is pulled up against the detection spring 11, and the magnet 14 on the opposite side is lowered to face the sensing device 13.

When the magnet 14 faces the sensing device 13, the sensing device 1
3 is activated, energizing the electromagnet 9, releasing the upper thread 2, and stopping the thread 2 from pulling up the lower thread 3 any further.

The above example utilizes the tension at point B on the tension curve in FIG. 2. Next, a second embodiment will be described in which the tension at point A, which is the rising portion of the tension curve, is utilized.

The second embodiment differs from the first embodiment only in the spring constant of the detection spring 17 and the provision of a delay circuit.

That is, the spring constant of the detection spring 17 corresponds to the tension when the lowest point P of the needle thread loop 2a reaches the lower surface of the sewing cloth 1, and the tension TL at the rise of point A in FIG. The magnet on the opposite side of the tension detection lever 16 faces the sensing device 13 when the tension of the upper thread 2 applied to the thread hook 15 of the detection lever 16 reaches TL.

FIG. 5 shows a block diagram of the second embodiment, and when the magnet 14 faces the sensing device 13, the sensing device 13
issues a signal to the delay circuit 20.

After receiving the signal from the sensing device 13, the delay circuit 20 delays the time required for the lowest point P of the upper thread loop 2a to reach the center point B of the sewing cloth 1 from the lower surface A of the sewing cloth 1, and then activates the electromagnetic upper thread adjustment device. 4, and its time is calculated from the rotation speed of the main shaft of the sewing machine and the thickness of the sewing cloth.

According to the second embodiment, in the process of raising the thread take-up lever 6 and threading, the upper thread 2 is pulled up and the lowermost point P of the upper thread loop 2a is pulled up.
hits the lower surface A of the sewing cloth 1, the needle thread tension increases and TL
becomes.

At this time, the thread hook 15 of the tension detection lever 16 is connected to the detection spring 17.
The magnet 14 is pulled up against the sensing device 13
, the sensing device 13 issues a signal to the delay circuit 20 .

The delay circuit 20 activates the electromagnetic upper thread adjusting device 4 after the required time to release the upper thread 2.

In addition, in both the first and second embodiments, when one yarn threading is completed, the excitation of the electromagnet 9 is released, and the upper thread 2 is moved again to the pressure contact plate 1.
2 and armature 10 and tension is applied, and then the next stitch is formed.

As explained above, according to the present invention, the needle thread is released at the same time as the upper and lower threads intersect at the center of the sewing cloth, so even if the thread take-up goes up thereafter, the needle thread can be simply pulled out from the thread spool to sew. Since the eyes are not tightened any further, the correct seam can always be formed.

In other words, it is possible to provide a needle thread non-adjustable sewing machine that does not require the operator to make troublesome adjustments to the needle thread tension.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of stitch formation on a sewing machine, Fig. 2 is a tension curve diagram of the needle thread, Fig. 3 is a configuration diagram of the present invention, Fig. 4 is a side view of the electromagnetic needle thread adjustment device, and Fig. 5 is a block diagram. 1... Sewing cloth, 2... Upper thread, 3... Lower thread, 4...
・Electromagnetic needle thread adjustment device, 5...Tension detection device, 9...
Electromagnet, 13... Sensing device, 14... Magnet,
16...Tension detection lever, 17...Detection spring, 20
...Delay circuit.

Claims (1)

[Scope of Claims] 1. A tension detection device that responds to needle thread tension in the process of stitch formation of a sewing machine, a sensing device that senses the operation of the tension detection device and operates a needle thread adjustment device, and a sensor that temporarily adjusts the needle thread. and the upper thread adjusting device that operates to release the upper thread to eliminate tension on the upper thread, and the upper thread adjusting device operates when the stitch formed by intersecting the upper thread and the lower thread reaches the center of the sewing cloth. A sewing machine with no upper thread adjustment that releases the upper thread. 2. The tension detection device operates in response to the needle thread tension when the stitch formed by crossing the upper thread and the bobbin thread reaches the center of the sewing cloth, and the sensing device 2. The sewing machine without needle thread adjustment according to claim 1, wherein the needle thread adjustment device is actuated to release the needle thread at the same time as the sensing is detected. 3. The tension detection device operates in response to the needle thread tension when the lowest point of the needle thread loop reaches the lower surface of the sewing cloth, and after a required period of time after the detection device senses the operation of the tension detection device. 2. The needle thread non-adjustable sewing machine according to claim 1, wherein the needle thread adjustment device is actuated to release the needle thread.