JPS5921739Y2 - Sewing machine second thread tension device - Google Patents

Description

[Detailed description of the invention] This invention consists of a thread cutting device that operates to cut the needle thread connected to the workpiece below the throat plate while feeding it out from the supply source side, and In a sewing machine equipped with a first tension device associated with the needle thread to apply tension suitable for forming the needle thread and to release said tension on the needle thread in conjunction with the operation of the thread cutting device, the first tension tension device is applied to the needle thread. This invention relates to a second thread tension device that constantly applies a cooling force that is weaker than the tension generated by the device.

In a sewing machine equipped with this type of thread trimming device, when the needle thread is fed out by the thread trimming device, the needle thread may be stretched strongly and cut, or the needle thread may be fed out for a long time from its supply source, and this may cause the needle to make a hole in the needle. In order to prevent the length from the needle thread to the cut end of the needle thread to be too long or short, a second thread tension device is provided which always applies a tension to the needle thread that is weaker than the tension provided by the first tension tension device. It is known to release the tension caused by the first tensioner when thread trimming.

However, the conventional second thread tension device is provided at the center of the pressing body 54 with respect to the support shaft 53 whose free end faces the face plate 52 and whose base end is fixed to the thread guide body 51 as shown in FIG. Since the hole 55 of the pressing body 54 is configured to have a loose fit, the upper surface a of the hole 55 of the pressing body 54 always comes into contact with the support shaft 53 due to its own weight (solid line in the figure), but the lower surface of the hole 55 is in contact with the support shaft 53. 53, the upper surface a of the hole 55 is less likely to slip than the lower surface due to friction with the support shaft 53, and due to the elastic force of the coil spring 57 compressed between the pressing body 54 and the spring receiver 56, When pressed to the right, the pressing body 54 tilts as shown by the two-dot chain line in the same figure.In particular, since the elastic force of the coil spring 57 is significantly weaker than that of the first system tensioner, the pressing body 54 tilts as shown by the two-dot chain line in the figure. Sometimes it stopped midway due to the auction with the support shaft 53.

Therefore, the elastic acting force of the coil spring 57 is not reliably transmitted to the needle thread T, and since the pressing body 54 is tilted so that the upper part is separated from the thread guide body 51, the needle thread T is caused by thread twisting and vibration. There were drawbacks such as the thread protruding upward from between the thread guide member 51 and the thread guide member 51.

The purpose of this invention is to simplify the structure and to eliminate the above-mentioned conventional drawbacks.

Examples of this invention will be described below with reference to the drawings.

The sewing machine of this embodiment is a known sewing machine equipped with a thread cutting device (not shown) that cuts needle thread T while feeding it out from a supply source below the throat plate, and includes a face plate cover 1 that covers the face part. A face plate 3 is fixed to the end face of the arm 2, which is detachably supported or openable and closable by a hinge provided at the rear part, with an appropriate gap S formed in the upper part thereof.
This face plate 3 has a cylindrical groove 4 with a flat bottom and a rectangular hole 5 formed therein.

Between the face plate 3 and the end face of the arm 2 (within the gap S), the thread guide 6 maintains the gap S between the face plate 3 and the locking part 7 at one end.
is loosely fitted into the hole 5 of the face plate 3, and the other end is fixed to the face plate 3 with a screw 8.

This thread guide body 6 has a thread hooking section 11 that bends the path of the needle thread T paid out from the bobbin winder (needle thread supply source) 9 and guides it toward a first system tensioner 10 provided inside the arm 2. and face plate 3
An introduction section 13 has a lower surface 12 that protrudes upward from the upper surface 3a and intersects the upper surface 3a of the face plate 3 toward the thread hooking section 11; A guide surface 14 is formed on the path, facing the groove 4 of the face plate 3 and parallel to the bottom surface thereof.

A cylindrical pressing body 16 having a hollow portion 15 with one end closed faces the guide surface 14 of the thread guide 6 with the end surface where the hollow portion 15 is closed, and the end surface is in contact with the guide surface 14. The other end is loosely fitted into the groove 4 of the face plate 3 so that it can be moved in the direction of separation.

Further, a coil spring 17 having an elastic force that applies a tension weaker than the tension exerted by the first system tension device 10 to the needle thread is compressed and disposed between the hollow portion 15 of the pressing body 16 and the groove 4 of the face plate 3. .

Since this invention has the above-described configuration, the lower surface B of the circumference of the pressing body 16 is always aligned with the face plate 3 as shown in FIG. 4 due to its own weight.
, but the upper surface A of the circumference is separated from the side surface of the groove 4 .

Therefore, since the lower surface B is more difficult to slip than the upper surface A with respect to the groove 4, even if the pressing body 16 is pressed to the right by the coil spring 17 from the solid line in FIG. As shown by the two-dot chain line in FIG. 2, the upper part is inclined closer to the thread guide 6 than the lower part, and the needle thread is sandwiched between it and the guide surface 14 of the thread guide 6.

Further, since the diameter of the pressing body 16 is significantly larger than the tolerance with respect to the groove 4, the angle at which the pressing body 16 is inclined is very small, and the tension due to the elastic force of the coil spring 17 is reliably applied to the needle thread T. The tension also becomes approximately constant.

As described above, this invention consists of a cylindrical groove 4 that is open in one horizontal direction and provided in the machine frame, and a needle thread supply source that is placed on the needle thread path between the needle thread supply source and the first system tension device. and an introduction member having a thread hooking part 11 for bending and changing the direction of the needle thread path between the first system tension devices, and having a flat surface for slidingly guiding the middle part of the hooked needle thread to the thread hooking part. A thread guide 6 integrally formed with a flat guide surface 14 facing away from the open end of the section 13 and the groove 4, and a thread guide 6 that is loosely fitted and supported in the groove so as to be movable in the direction of separation between the machine frame and the thread guide. and a pressing body 16 provided with a hollow portion 15 that faces the guide surface of the thread guide at one end in the moving direction and opens at the other end.
and an elastic body 17 which is compressed and arranged between the hollow part of the pressing body and the groove of the machine frame and has an elastic force that applies a tension to the needle thread that is weaker than the tension applied by the first system tensioner, and is provided with Since the needle thread between the thread hooking part and the first tensioner is pinched between the surface and one end of the pressing body, the movement of the pressing body is smoother than in the conventional type, and the needle thread is not easily affected by the needle thread. The tension can be reliably applied, and since the upper part of the pressing body is slightly tilted so that it is closer to the guiding surface of the thread guide body than the lower part, the needle thread is removed from between the pressing body and the guiding surface during sewing. This has the effect of preventing the needle from jumping upward and making the length from the needle to the cut end constant after the needle thread is cut by the thread cutting device.

In addition, if you hook the middle part of the needle thread onto the thread hook part of the thread guide and then set it to the first thread tension while gently pulling the end of the thread, it will automatically set to the second thread tension. ,
It also has the effect of providing excellent threading operability.

[Brief explanation of drawings]

Figure 1 is a perspective view of the sewing machine head, Figure 2 is an exploded perspective view of the main parts, Figure 3 is a plan view of the main parts, and Figure 4 is IV-I of Figure 3.
A cross-sectional view along the V line, FIG. 5, is a conventional question diagram. In the figure, 4 is a groove, 6 is a thread guide, 10 is a first system tensioner, 1
6 is a pressing body, and 17 is a coil spring as an elastic body.

Claims (1)

[Scope of Claim for Utility Model Registration] A thread cutting device that cuts needle thread connected to a workpiece while being fed out from its supply source; In a sewing machine equipped with a first system tension device that applies tension suitable for stitch formation to the needle thread and releases the tension applied to the needle thread in conjunction with the operation of the thread trimming device, the needle thread is opened horizontally in one direction. A cylindrical groove 4 provided in the machine frame is arranged on the needle thread path between the needle thread supply source and the first system tension device, and bends and changes the needle thread path between the needle thread supply source and the first system tension device. A member for having a thread hooking part 11, which includes an introduction part 13 having a flat surface for slidingly guiding the middle part of the hooked needle thread to the thread hooking part, and a flat guide facing away from the open end of the groove 4. A thread guide body 6 having a surface 14 integrally formed therein; and a thread guide body 6 that is loosely fitted in a groove and supported so as to be movable between the machine frame and the thread guide body in the direction of separation thereof, and one end in the direction of movement faces the guide surface of the thread guide body. A pressing body 16 having a hollow part 15 open at the other end, and an elastic force compressed between the hollow part of the pressing body and the groove of the machine frame to apply a tension to the needle thread that is weaker than the tension by the first tension device. A second thread tension device for a sewing machine, comprising: an elastic body 17 having a thread guide body and one end of a pressing body to pinch the needle thread between a thread hooking portion and a first system tension device.