JPS5913238B2 - How to cut thread on a sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thread cutting method for a sewing machine having a thread cutting device.

If the feed rate of the sewn cloth is increased, long threads remain on the back side of the cloth and spoil the aesthetic appearance, so it is necessary to remove them again using hand scissors or the like.

This invention was made to save such labor.
During the thread cutting cycle from the lower position of the needle to the upper position, the fabric feed is reversed to shorten the thread end remaining on the back side of the fabric.

One embodiment of the present invention will be described below. In the figure, 1
is a sewing machine arm, and inside this sewing machine arm 1, a main drive shaft 1 of the sewing machine is connected via a pulley 3 driven by a belt etc. by the rotation of a motor 2 equipped with a needle positioner device.
7 by a crank mechanism or the like. A hook 5, which reciprocates up and down to form stitches in cooperation with the needle 4, is housed in the bed 6 from the main drive shaft 17 of the sewing machine by means of a gear mechanism or the like.

1 is a detector that detects the lower and upper positions of the needle 4. After sewing the work cloth to a predetermined position, when the operator kicks back the pedal 8 to cut the sewing thread, the sewing machine moves from the lower position to the upper position of the needle. The thread trimming electromagnet 9, which is driven at a low speed and housed in the bed 6, is energized, and the energization of the electromagnet 9 causes the thread trimming knife 12 to cut the sewing thread at a position close to the needle hole 11 of the throat plate 10. This is a sewing machine equipped with a known thread cutting device.

In such a sewing machine, the feed dog 13 is connected to the throat plate 109 and the feed groove 1.
4, the cloth is fed by performing a movement in the direction of the arrow shown in FIG. 3 (the vertical axis shows the vertical feed amount and the horizontal axis shows the horizontal feed amount).

In a normal sewing machine with a thread trimming device, the top dead center of the needle is the angle O0 of the sewing machine's main drive shaft 17, and if this is taken as a reference, the lower position of the needle will be due to rotation of the fabric, etc., and skipped stitches will occur due to rotation of the fabric, etc. In order to prevent this, the angle of the main drive shaft 17 of the sewing machine is selected to be around 2300 degrees, and the upper position of the needle is set at the top dead center of the thread take-up to prevent the needle thread from coming out from the needle when cutting the thread and making it impossible to sew next time. The main drive shaft 17 angle of around 70° is selected.

For the above-mentioned reason, the knife mechanism cuts the sewing thread at a point near the 70° angle of the main driving shaft 17 of the sewing machine.

In other words, the cloth is fed by the feed dog 4 by a cloth feed amount P' which is approximately the same as the normal cloth feed amount P from the lower position of the needle during the thread cutting cycle to the sewing thread cutting point.

When the thread cutting operation is performed in this manner, a long thread remains on the back side of the cloth 24 as shown in FIG.

That is, the cutting point where the sewing thread is cut by the knife 12 is the needle plate 10.
Since the remaining end of the lower thread 15 remains (p + p') and the remaining end of the upper thread 16 remains on the back side of the cloth 24, the amount of cloth feed is large. 1 end of bobbin thread remaining
5. The needle thread remaining end 16 becomes large, resulting in an unsightly appearance of the sewn product, and requires labor, such as re-handling with a pair of scissors, which is disadvantageous in its lack of practicality.

This invention was made in order to eliminate the above-mentioned drawbacks.The sewing thread is cut during the thread trimming cycle from the lower position of the needle to the upper position of the needle, and the fabric feed is not controlled during this thread trimming cycle. This relates to a sewing machine thread cutting method that feeds thread in the opposite direction to the sewing cycle.

A specific configuration for implementing this method will be described below.

In FIG. 4, the feed adjustment cam 18 is connected to the feed adjustment screw 19.
The sewing machine arm 1 has a horizontal fabric feed adjustment device for general sewing machines in which the inclination of the sewing machine arm 1 changes with the movement of the sewing machine arm 1 as a fulcrum, and the horizontal feed amount of the feed dog 13 changes depending on the inclination. An electromagnet 21 is attached to the , and when the single magnet 21 is energized, the plunger 22 inside the electromagnet 21 is attracted and the feed adjustment cam 18 is rotated clockwise through the link 23 with the pin 20 as a fulcrum. The feed adjustment cam 18 changes its inclination, and the horizontal feed of the feed dog 13 is reversed to feed the cloth.

The electromagnet 21 is configured to be excited and demagnetized in synchronization with the thread cutting electromagnet 9.

When the petal 8 is kicked back after sewing the force fit cloth 24 to a predetermined position, the thread trimming electromagnet 9 is energized as described above.
The sewing thread is cut during the thread cutting cycle in which the thread cutting knife 12G operatively connected thereto and the twisting needle 4 are driven from the lower position to the upper position.

During this thread trimming cycle, the electromagnet 21 is energized, and the feed dog 1
The horizontal cloth feeding in step 3 is reversed to carry out cloth feeding.

Thus, when the thread trimming knife 12 is operated, the reverse cloth feed amount P' is increased in FIG. 5, and as a result, as is clear from FIG. '),
The needle thread remaining end 16 becomes P'.

P′=! As shown, the attraction of the electromagnet 21 causes the cloth 24 to
・ When feeding, the remaining ends 15 and 16 of the bobbin thread and upper thread become i each, and the remaining ends of the bobbin thread and upper thread are shorter than the conventional one shown in Fig. 2. Therefore, the aesthetic appearance of the fabric is improved and the practicality is improved. It has a rich effect.

As described above, according to the method of the present invention, the thread ends remaining on the back side of the sewn product are shortened, and even when the feed is increased to increase the amount of stitches, the appearance of the sewn product does not deteriorate compared to the conventional method. This eliminates the need for reprocessing using scissors or the like.

[Brief explanation of drawings]

Fig. 1 is a front view showing a sewing machine with a thread trimming device and a motor with a needle positioner, Fig. 2 is an enlarged sectional view of the thread cutting section using the conventional method, Fig. 3 is a motion diagram of the feed dog, and Fig. 4 is a horizontal feed. A sectional view showing the mechanism, and FIG. 5 is an enlarged sectional view of the thread cutting section according to the method of the present invention. In the figure, 1 is a sewing machine arm, 4 is a needle, 5 is a hook, 12 is a thread trimmer, 13 is a feed dog, 15 is a remaining end of a lower thread, and 16 is a remaining end of an upper thread. Note that the numerals in the middle of the figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a sewing machine equipped with a needle that moves up and down, a hook that works with the needle to form a stitch, and a cloth feed mechanism, the cloth feed is not performed during the thread trimming cycle from the lower position of the needle until it reaches the upper position. A thread for a sewing machine characterized in that the sewing thread is cut in the opposite direction to the cloth feed during the sewing cycle, so that when the forward feed amount of the cloth is P1 and the reverse feed amount of the cloth is P', it becomes P' middle ヱ. How to cut.