JPS6112055Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a looper thread loosening mechanism for a double chainstitch sewing machine equipped with a thread cutting device. In this type of sewing machine, the length from the looper thread hole to the cut end must be longer than the bobbin thread on a lockstitch sewing machine to prevent the looper thread from falling out of the looper thread hole when starting the next stitch. Therefore, when the movable blade moves forward to capture the looper thread, in order to prevent excessive tension from acting on the looper thread and cutting it when carrying the looper thread captured by the movable blade to the fixed blade. It is equipped with a thread loosening mechanism that lets out the necessary amount of looper thread from the supply source in advance. However, the conventional thread loosening mechanism, as disclosed in Japanese Patent Publication No. 54-24334, is located far from the thread cutting device, and the looper thread reaches the looper through a path bent by several thread guides. Even if the necessary amount of looper thread is paid out from the supply source in advance during operation, the resistance of each thread guide is accumulated and acts on the looper thread when the movable blade moves toward the fixed blade, so the movable blade cannot be moved at high speed. If the looper thread is loosened, the looper thread becomes excessively tense and easy to break in the middle, and the structure of the thread loosening mechanism is
As shown in the figure, once the looper thread T comes off from between the guide shaft 1 and the enclosure 2, it will be located below the block 3 and will not be able to return to its original state. Skipping stitches may occur during sewing,
During thread trimming, excessive tension is applied to the looper thread during the thread cutting process, causing it to break and the remaining thread from the looper becomes short, causing the looper thread to fall out of the looper thread hole at the beginning of the next stitch, making it impossible to continue sewing. There were some drawbacks such as:

An embodiment of this invention will be explained below with reference to the drawings.The sewing machine of this embodiment has a fixed blade 4 fixed to the machine frame away from the range of motion of a reciprocating looper (not shown), and a fixed blade 4 that captures the looper thread T and reciprocates. This is a double chainstitch sewing machine equipped with a thread cutting device consisting of a movable blade 5, and when the movable rod 7 moves to the right in FIG. , rod 10, crank 1
1, the movable blade 5 moves to the right, and then when the solenoid 6 is demagnetized, these members are moved by the spring 8.
At this time, the looper thread T is captured by the movable blade 5 and fed out from the thread hole of the looper, and then cut by the cooperation of the movable blade 5 and the fixed blade 4. It is something.

Reference numeral 12 denotes a thread loosening lever that can swing around a shaft 21, and is connected to a link 13 and a rod 14 so that it rotates clockwise when the solenoid 6 is energized and counterclockwise when the solenoid 6 is demagnetized. It is linked to the rod 10 via.

In Fig. 2, the looper thread T between the thread guides 15, 16, and 17 is controlled by the outer peripheral surface of a plate-shaped thread control cam (not shown) that rotates around a fixed shaft in synchronization with the movement of the looper. FIG. 2 is a perspective view of a thread loosening mechanism disposed adjacent to the looper thread control mechanism described in Japanese Patent Publication No. 54-43416 for bending and picking up the thread and releasing the bend and loosening the thread. That is, this thread loosening mechanism is a thread guide in which the free end, in which the thread hole 18 is formed opposite to the thread hole (not shown) of the thread guide 15, is spaced parallel to the thread guide 15, and the base part is fixed to the thread guide 15. 1
9 and the thread loosening lever 12 mentioned above. The thread loosening lever 12 consists of a trunk 12a, a thread hooking part 12b at its upper end, and an extending part 12c bent downward from the upper end of the trunk 12a. 2 from the solid line to the position indicated by the two-dot chain line in Figure 2, and solenoid 6.
When demagnetized, it returns to the solid line position again.

The guide bodies 15, 16, 17, and 19 are always locked in the state shown in the figure, and can stand approximately vertically about the shaft 20 when setting the looper thread T.

This invention has the above structure, and when the thread cutting operation is performed by an appropriate means, the solenoid 6 is energized for a certain period of time and then demagnetized. When the solenoid 6 is energized, the movable blade 5 moves to the right in FIG. 1, and at the same time, the thread loosening lever 12 rotates around the shaft 11 to the position indicated by the two-dot chain line in FIG. 2 (FIG. 3 b). . As a result, the looper thread T is bent upward from the thread holes of the thread guides 15 and 19, and as the looper thread T is bent deeper, a considerable amount of the looper thread is let out from the supply source.

Next, when the solenoid 6 is demagnetized, the movable blade 4 captures the looper thread T and returns to the left in Fig. 1. At the same time, the thread loosening lever 12 returns to the solid line position in Fig. 2, thereby allowing the thread to be fed forward. Release the looper thread T.

Therefore, for example, if you operate the thread trimming device by mistake at the beginning of sewing, and then operate the thread trimming device again, the thread guides 15, 19 may be damaged by the initial thread trimming.
Because the looper thread T is paid out and loosened in between,
The looper thread T moves freely around the thread holes 18 of the guides 15 and 19, and even if the thread loosening lever 12 moves clockwise during the second thread trimming, the looper thread T remains in the thread hook 1.
2b, the swinging end (extending portion 12c) of the thread loosening lever 12 is larger than the circle drawn when the bent top of the previously loosened looper thread T pivots around the thread hole 18. Since it is always located on the outside, even if the looper thread T moves to go around below the thread loosening lever 12, it is blocked by the extending portion 12c.

As mentioned above, in this invention, the swinging tip of the thread loosening lever is always placed outside the circle drawn when the bent top of the looper thread, which is bent by the forward movement of the thread loosening lever, turns around the thread hole in the thread guide. Even if the thread trimming device is operated twice in a row by mistake at the beginning of sewing, the looper thread loosened by the first thread trimming operation will be loosened by the second thread trimming operation. The thread does not go around to the side opposite to the thread hooking part of the lever, so stable stitches without skipped stitches can always be obtained when sewing, and when thread trimming, a constant amount of looper thread is fed out from the supply source to ensure cutting. I can do it,
It has excellent effects such as preventing the thread from coming off at the beginning of the next stitch.

In addition, in the present invention, the extending portion 12 of the thread loosening lever 12
Although c is shown bent in one swing direction with respect to the trunk 12a, both may be formed in a straight line.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the interlocking relationship between the thread cutting device and the thread loosening mechanism, Fig. 2 is a partially enlarged perspective view of the thread loosening mechanism, Fig. 3 is an explanatory diagram of the operation, and Fig. 4 shows a conventional example. FIG.

Claims (1)

[Scope of Claim for Utility Model Registration] A fixed blade 4 fixedly arranged at a position away from the movement path of the looper, a solenoid 6 that operates in response to a thread trimming command, and a movable blade 5 that reciprocates in conjunction with the operation of the solenoid. In a chainstitch sewing machine equipped with a thread cutting device that feeds out the required amount of looper thread between the stitches and the looper from the supply source side and then cuts it when the movable blade moves back toward the fixed blade, the looper thread is supplied more quickly than the looper. It has thread guides 15 and 19 which are fixedly disposed at the front in the direction and have a pair of spaced apart opposing thread holes, and a thread hooking part 12b having a U-shaped wall in the middle, and which is linked to the operation of the solenoid. It swings back and forth around the end, and when the movable blade moves forward, the looper thread between both thread holes of the thread guide is caught in the thread hook part and bent, and is fed out from the supply source, and when the movable blade moves back, the looper thread is released. and a thread loosening lever 12 for loosening the looper thread, and the bent top of the looper thread, which is bent by the forward movement of the thread loosening lever, is always the free end of the thread loosening lever ahead of the thread hooking part. A thread loosening mechanism for a chainstitch sewing machine characterized by being formed so as to be located outside the circle drawn when turning around a hole.