JPH0632739B2 - Lower thread loosening mechanism of zigzag sewing machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a zigzag sewing machine, which bends a zigzag sewing machine by engaging a lower thread between a bobbin and a seam when the needle drop is either left or right. Accordingly, the present invention relates to a lower thread loosening mechanism for drawing a required amount of lower thread from a bobbin, and particularly to a lower thread loosening mechanism suitable for use in a tilt rotary hook type full rotary hook.

2. Description of the Related Art In a zigzag stitch formed by a zigzag sewing machine, the positions of the upper and lower threaded knots are different when the needle drop is on the left side and on the right side, and one of them tends to be exposed from the cloth. The reason for this will be described with reference to FIGS. FIGS. 5A to 5D show the stitch forming process when the needle drop is on the left side and FIGS. 6A to D are on the right side. The needle thread loop b captured by the sword tip a is shown in FIG. 6A) The bobbin is pulled by the rotation of the sword tip to pass through the bobbin c (Figs. 5B and 6B). After passing through the bobbin c, the thread is taken up by the thread take-up action of the balance (Figs. 5C and 6C). The lower thread d is caught and pulled to the lower side of the cloth (5th
D, 6D). Subsequently, the cloth for the first stitch is fed, and the cloth feeding operation and the thread picking-up operation by the balance tighten the seam to pull in the repulsive knot of the upper thread and the lower thread (5E, 6E). In the figure, the length of the lower thread from the bobbin c to the seam is shorter because the length l ₁ to the left knot is shorter than the length l ₂ to the right knot. The bobbin thread must be pulled out from the bobbin c by an additional amount when forming the seam at the right needle drop position, as compared with the case at the left needle drop position. This will be explained in more detail with reference to FIG. 7. When the seam is formed at the left needle drop position, the bobbin thread between the eggs is manually carried up by the needle thread loop and knotted at the left needle drop position g, and the necessary shortage thread is required. While the amount is pulled out from the bobbin, the bobbin thread between ef is knotted at the right needle drop position f at the right needle drop position, and the necessary shortage of thread is pulled out from the bobbin. The length l _{1 of} is shorter than the length l _{2 of the} bobbin thread between ef, and the bobbin thread is added to the bobbin more when forming the seam at the right needle drop position than when forming the seam at the left needle drop position. I have to pull it out.

Spring pressure acts on the lower thread pulled out from the bobbin,
To draw more bobbin thread than the bobbin requires a larger drawing force. However, since the drawing force does not change regardless of the needle drop position, the needle thread at the right needle drop position cannot draw in the bobbin thread sufficiently in the illustrated one,
The repulsive knot points of both threads are exposed on the lower surface of the cloth, and as shown in FIG. 8, the upper thread remains on the lower side of the cloth.

Problems to be Solved by the Invention In the present invention, the positions of the knot points of the upper thread and the lower thread are aligned regardless of the needle drop position so that the upper thread or the lower thread does not remain on the opposite surface. Is.

Means for Solving the Problems The present invention therefore provides a thread hooking member that reciprocates in conjunction with a main shaft, and the member has a stitch on the bobbin when the needle drop at the time of forward movement is far from the thread drawing port of the bobbin. To engage the lower thread and bend the thread, thereby pulling out the required amount of the lower thread from the bobbin to make the length of the lower thread to the seam the same regardless of the left and right positions of needle drop, It is separated from the bobbin thread during the backward movement so as not to hinder pulling up of the needle thread loop.

The thread hooking member can be configured to operate only when the needle swings to one side in conjunction with the zigzag mechanism, but is preferably configured to interlock with the lower shaft and reciprocate each time the lower shaft rotates. It is desirable that the structure be simplified. In the latter case, the thread hooking member is normally set to catch and engage the bobbin thread only when it is located on either one of the left and right sides, but it may be engaged with the bobbin thread at any position.

The yarn hooking member of the present invention can be applied to a horizontal rotary hook, a vertical rotary hook type full rotary rotary hook or a half rotary rotary hook, but is most preferably applied to an inclined rotary hook type full rotary rotary hook.
It is possible to provide a bobbin for the bobbin thread on the hook itself in the vertical hook or in the half rotary hook by the feed table in the horizontal hook, and the same effect as the present invention can be obtained by means other than the means according to the present invention. On the other hand, it is difficult to provide the above-mentioned means in terms of space in the inclined rotary type rotary rotary hook.

Embodiments FIGS. 1 to 3 show an example in which the lower thread slackening mechanism according to the present invention is provided in a tilt rotary hook type full rotary hook. An end face cam 2 fixed to a lower shaft 1 has a middle portion in a frame. The pin 4 of the lever 3 axially attached is elastically contacted by the action of the spring 5, so that the lever 3 swings in the horizontal direction by the rotation of the end face cam 2, and the hook-shaped lever 6 is attached to the tip of the lever 3. The hook-shaped lever 6 is pivotally mounted and guided by a support member 7 to perform a reciprocating linear motion in the horizontal direction by the swinging of the lever 3. A hook portion 9 protruding toward the needle 8 is provided at the tip of the hook. In the illustrated embodiment, the hook-shaped lever is made of sheet metal, but it is also possible to bend the wire to form the hook. In this case, there are advantages that the manufacturing cost is low and the yarn slippage is good. In the figure, 11 is a hook, 12 is a bobbin case,
13 is a bobbin and 14 is a needle plate.

Next, the function of the hook-shaped lever of this embodiment when forming a seam will be described with reference to FIGS.

This figure corresponds to FIGS. 5A to 5E when the needle drop is on the right side, in which the needle 8 rises from the bottom dead center and the needle thread loop 15 is put into the hook 13
When it is caught by the tip of the sword, the hook-shaped lever 6 moves forward, and the hook portion 9 catches and engages the lower thread 16 extending from the bobbin 13 to the seam and bends it in the direction of advance (FIG. 4A). The hook portion 9 keeps going forward until the needle thread loop 15 caught and pulled by the sword tip passes through the bobbin 13 to bend the lower thread (Fig. 4B).
After the upper thread loop has passed through the bobbin, the needle thread loops back and separates from the lower thread so that there is no hindrance to pulling up the upper thread loop by the balance (Fig. 4C).

The bobbin thread is pulled up to the lower surface of the cloth by the thread take-up operation of the thread balance (Fig. 4D), and the thread is tightened by the feeding operation by the cloth feed for the first stitch and the thread take-up operation of the thread balance. Nodal points are pulled into the cloth (4E
Figure).

The seam when the needle drop is on the left is also formed in the same manner as in FIGS. 6A to 6E. At this time, the hook portion of the hook-shaped lever does not engage with the bobbin thread even when it reaches the most advanced position during forward movement.

According to the bobbin thread loosening mechanism of the present invention, as described above, the bobbin thread length from the bobbin to the seam is substantially the same regardless of the needle drop position, and therefore the upper thread Also, the positions of the knot points of the bobbin thread and the bobbin thread can be aligned, and the upper thread and the bobbin thread can be prevented from remaining on the surface on the opposite side, and a clean zigzag stitch can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view of a lower thread loosening mechanism provided in a tilt rotary type gold rotary hook, FIG. 2 is a front view of the same, FIG. 3 is a right side view of the same, and FIGS. The figure which shows the formation process of the seam by the device which employs the thread loosening mechanism, the figure 5A-E is the figure which shows the formation process of the seam by the former example, the figure 6A-E shows the formation of the seam when needle drop differs FIG. 7 is a diagram showing a process, FIG. 7 is an explanatory diagram, and FIG. 8 is a diagram showing a conventional zigzag stitch as seen from the lower side of the cloth. 1 ... Lower shaft, 2 ... End surface cam, 3 ... Lever 6 ... Hook-shaped lever, 7 ... Support member 8 ... Needle, 9 ... Hook part, 11 ... Hook 13 ... Bobbin

Claims (1)

[Claims] 1. A thread hooking member which horizontally reciprocates in conjunction with a main shaft under a needle plate, wherein the needle drop at a zigzag stitch at the time of forward movement is located at a position far from a thread discharge port of a bobbin. At a certain time, the lower thread between the bobbin and the seam is engaged to bend the thread, thereby pulling out the required amount of the lower thread from the bobbin, and the needle drop during zigzag sewing is closer to the bobbin thread outlet. The lower thread loosening mechanism of the zigzag sewing machine does not reach the lower thread between the bobbin and the seam and does not engage with the lower thread.