JPH0333339Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is provided separately from the tension device that applies tension to the thread, and opens and closes the tension plate in conjunction with the rotation of the upper shaft, thereby tightening the thread in the bobbin winder. Regarding the auxiliary tension of the sewing machine that controls the supply of.

Note that in this specification, when the tension plate is closed, it refers to a state in which spring pressure acts on the tension plate, and when it is opened, it refers to a state in which the action of the spring pressure is released.

BACKGROUND OF THE INVENTION As sewing machines become faster, there is a tendency for a phenomenon called run-in, in which more thread is supplied from the spool through the tension device than is needed to form the stitches, to occur. This oversupply of thread makes the needle thread loops insufficiently absorbed by the thread take-up action of the thread thread take-up, resulting in slack remaining at the seam even after thread take-up, and sometimes the remaining needle thread loops are caught by the tip of the knife and the thread breaks. may cause It is not desirable to increase the presser pressure of the tension device in order to prevent overfeeding of yarn. This is because the original function of the tension device, which is performed when forming seams, will be impaired. Therefore, in high-speed sewing machines, as shown in Fig. 4, in addition to the tension device a, an auxiliary tension e is used which engages with a cam c fixed to the upper shaft b to open and close the space between the plates d in conjunction with the upper shaft. Set up, balance f
The gap between the trays was closed at an appropriate interval between the descent and rise of the yarn to prevent overfeeding of the yarn. However, with conventional auxiliary tensioners, the amount of yarn supplied is small, for example, for yarns with high elasticity because the yarn stretches and only a small apparent amount of yarn is supplied, and for yarns with low elasticity, it is large, and the amount of yarn supplied is small. It is not possible to deal with different yarns and supply the necessary amount of yarn. The amount of thread supplied also varies depending not only on threads with different degrees of elasticity, but also on the type of thread such as thread thickness, the sewing speed of the sewing machine, the type of fabric to be sewn, etc.

Problems that the invention aims to solve The purpose of this invention is to make it possible to feed the necessary amount of thread in accordance with the type of thread or cloth, the sewing speed of the sewing machine, etc.

Means for Solving the Problems According to the present invention, the above purpose is to change the mounting angle of the cam with respect to the upper shaft that controls the opening and closing between the plates as shown in Fig. 4, thereby adjusting the opening and closing timing between the plates. This is achieved by making it possible.

Here, instead of being attached directly to the upper shaft, the cam can also be attached to a rotating shaft or a swinging shaft that interlocks with the upper shaft.

Example As shown in Figure 2, under the top plate of the sewing machine,
An auxiliary tension B that opens and closes between the tension discs 2 in conjunction with the upper shaft 1 on the thread feeding side of the tension device A;
Prior to supplying the yarn, a yarn loosening lever 3 is arranged which cooperates with an auxiliary tension B to pull out the required amount of yarn from the spool in advance, and these auxiliary tension B and the yarn loosening lever 3 have a structure as shown in FIG. have. That is, a first eccentric cam 5 is fixed on the upper shaft 1 with a set screw 6 so that its mounting angle can be adjusted, and a second eccentric cam is attached to the upper shaft 1 at an appropriate distance from the cam 5 in the axial direction. A first fork 9 and a second fork 10, which are rotatably supported by a fixed shaft 8 fixed to the machine frame, are connected to the first eccentric cam (5) and the second fork. They fit into the eccentric cams 7, respectively, and are designed to individually swing vertically about the fixed shaft 8 as the upper shaft 1 rotates. The thread loosening lever 3 is shaped like a bell crank, and its middle part is pivoted to the machine frame, and its one end is shaped like a hook, and the other end is connected to the second fork 10 by a pitman 11. Forked 1
0, the hook-shaped part at the tip moves up and down between the thread guides 12, and both thread guides 12
The required amount of thread is pulled out from a bobbin winder (not shown) with the tension plate of the auxiliary tension B closed.

On the other hand, a bell crank lever 4 whose intermediate portion is pivoted to the machine frame is connected to the first fork 9 by a wire spring 15, and the bell crank lever 14 is slidably supported on a support shaft 16 at one end surface. The bracket 17 is always biased to the left in FIG. 2 by the coil spring 21 interposed between the collar 19 fixed to the support shaft 16, and A pair of tone plates 2, which are slidably supported by the guide plate 22, are pressed against the guide plate 22 to close the gap between the tone plates, and the fork 9 swings downward.
When the bell crank lever 14 swings counterclockwise in FIG. 1, the bracket 7 slides to the right in FIG. 2 against the action of the coil spring 21, releasing the pressure on the tone plate 2 and releasing the tone plate. There will be time allowed. . In the figure, 24 is a balance.

This device is constructed as described above, and in the thread take-up curve shown in FIG. 3, the tension plate of the auxiliary tension B is closed at point o on the way when the thread take-up 24 descends and the thread is let out, and then the thread loosening lever is 3 descends to push down the thread between both thread guides 12, and pull out the thread for one stitch from the bobbin winder in advance. When the thread take-up 24 rises after reaching the bottom dead center and absorbs the needle thread loop that has passed through the hook, the spring pressure acting on the tension plate is released at point p. Subsequently, as the thread take-up continues to rise further, the stitches are tightened and at the same time, the thread previously drawn out from the bobbin winder is fed through the tension device A and the auxiliary tension B as described above.
Here, the o and p points can be adjusted along the balance curve by loosening the set screw 6, changing the mounting angle of the first eccentric cam 5 with respect to the upper shaft 1, and changing the phase. As a result, for example, when using a thread that has a high degree of elasticity and is easy to stretch, change the mounting angle of the first eccentric cam 5 with respect to the upper shaft, move point P to point _P1 , and open the tension plate of the auxiliary tension. Increase the timing to ensure that the necessary amount of yarn is supplied, and conversely, if you use standard yarn that does not stretch, increase the
Return to the point to prevent the thread from flowing in.

In the above embodiment, the thread loosening lever is provided together with the auxiliary tension, but the thread loosening lever may be omitted and the auxiliary tension may be provided alone.

Effects of the invention As described above, the auxiliary tensioner of this invention is able to adjust the timing of opening and closing between the tension discs, thereby controlling the supply of thread from the bobbin winder, and adjusting the thread and fabric type and the sewing machine's sewing speed. It is possible to supply the required amount of yarn depending on the speed, etc.

Moreover, the cam in the conventional auxiliary tensioner is simply made to have an adjustable mounting angle.
The above effects can be obtained by only slightly changing the structure of the conventional auxiliary tension.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an auxiliary tension and thread loosening lever, FIG. 2 is a perspective view of the main parts inside the sewing machine, FIG. 3 is a thread take-up curve, and FIG. 4 is a perspective view of the main parts of a conventional sewing machine. 1... Upper shaft, 2... Tension disc, 3... Thread loosening lever, 5... Eccentric cam, 6... Set screw, 9... Bifurcated, 14... Bell crank lever, 16... Support shaft , 17...Bracket, 21...Coil spring,
24... Balance, A... Tension device, B... Auxiliary tension.

Claims (1)

[Scope of utility model registration request] In the auxiliary tension of a sewing machine, which is configured so that the tension disks are opened and closed by a cam that is linked to the rotation of the upper shaft, and which is provided to control the supply of thread from the bobbin spool separately from the tension device that applies tension to the thread. The above cam is attached to the shaft on which the cam is attached.
An auxiliary tensioner that is fastened so that the mounting angle can be adjusted.