JPH07289761A - Puckering prevention device for sewing machine - Google Patents

Abstract

PURPOSE:To provide a puckering prevention device possible to suppress generation of puckering on a sewing product and to obtain good sewing product quality. CONSTITUTION:With a sewing machine made to transfer cloth W laid on a needle plate 11 by feed teeth to perform 4 movements synchronizing with the vertical motion of a sewing needle N, a length at least the distance from the needle location hole to the rear end of the feed teeth inserting slot 11d in the feed teeth passing the needle location hole 11a on the needle plate and being on a line parallel to the cloth transfer direction X is set to a length shorter than a stitch pitch. Along with it, a distance da from the center of the needle location hole to the most rear end of the feed teeth is made to be smaller than the stitch pitch when the feed teeth protruding out of the feed teeth inserting hole, and a tip part 15b1 is set on the most rear position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of quality of sewing products by a sewing machine, and more particularly, to a puckering prevention device for preventing puckering from occurring around a stitch forming portion when a sewing operation is performed by the sewing machine. Regarding

[0002]

2. Description of the Related Art As is well known, in a lockstitch sewing machine, a sewing machine hook is rotated in synchronization with a vertical movement of a sewing needle.
The lower thread and the upper thread are knotted to perform the stitch forming operation. FIG. 7 is a diagram conceptually showing this stitch forming operation. When the sewing needle N passes through the cloth W and the needle drop hole 1a of the needle plate 1 to reach the bottom dead center and then rises slightly, the same figure (a)
As shown in FIG. 3, an upper thread loop IL is formed below the needle plate 1 by friction between the cloth W and the upper thread. This needle thread loop I
L is caught by the sword tip Ca of the sewing machine hook C and passes around the inner hook supporting the lower thread bobbin B, so that the lower thread bobbin B is substantially the upper thread loop as shown in FIG. After passing through the inside of the IL, the upper thread I1 and the lower thread I2 are knotted, as shown in FIG. When the balance T pulls up the upper thread I1 inserted through the sewing needle N, the knot points of the upper thread I1 and the lower thread I2 are held at approximately the middle of the cloth thickness due to the balance of the tensions generated in the upper thread I1 and the lower thread I2. The stitch forming operation is completed (see (d) in the figure), and the same operation is repeated thereafter.

On the other hand, when the ascending / descending operation of the sewing needle N is started, the feed dog 2 accommodated in the sewing machine bed is accordingly accompanied.
Performs the combined four movements of up, down, front and back, and the cloth W placed on the upper surface of the needle plate 1 is moved forward (X direction) by these four movements.
It is designed to be sent intermittently to. That is, when the sewing needle N is pulled out upward from the cloth W, the feed dog 2 is projected from the upper surface of the needle plate 1, and the saw tooth-shaped tooth portion 2a formed on the upper surface of the feed dog 2 is pressed by the cloth pressing member (see FIG. The cloth W is pressed against and engaged with the lower surface of the cloth W which is pressed downward by (not shown), and the cloth W is moved forward together with the feed dog 2 (see FIG. 7C).

When the sewing needle N penetrates the cloth W, the feed dog 2 is retracted below the needle plate 1 and is moved rearward while being separated from the lower surface of the cloth W. Therefore, the cloth W is intermittently conveyed forward together with the feed dog 2, and the stitches are sequentially formed at a pitch corresponding to each conveying distance. As shown in FIG. 8, a plurality of feed dogs 2 (here, four on the front, back, left, and right of the needle drop hole 1a) are arranged, and the feed dog insertion holes 1b, 1c formed on the needle plate 1 respectively. , 1d, 1e
It is supposed to appear from.

[0005]

As described above, in the conventional sewing machine using the feed dog 2, each tooth portion 2a of the feed tooth 2 is formed in a sawtooth shape, and each tooth portion 2a is formed on the lower surface of the cloth W. By making it bite, the shift of the cloth W and the feed dog 2 at the time of carrying the cloth can be prevented. However, the sawtooth shape of each tooth portion 2a is effective in obtaining an appropriate amount of conveyance, but on the other hand, it also causes wrinkles called puckering to be formed around the stitches of the finished cloth. Was there.

That is, when the cloth to be handled is a thin cloth or a soft cloth, the cloth W placed on the feed dog 2 falls between the top portions 2a1 of the adjacent tooth portions 2a as shown in FIG. There is a problem in that the wrinkles are wrinkled and are fixed by the seams as shown in FIG. 11 (a).

Further, the feed dog 2 located immediately before the needle drop hole 1a (the feed dog protruding from the feed dog insertion hole 1c) at the time of contact with the cloth W is sewn at present as shown in FIG. When the needle thread pulling operation of the balance T is performed in this state in many cases, the needle thread tension that is caused by the pulling operation is applied to the front stitch S2 that has already been formed. This has a problem in that it causes excessive tension in the seam and causes wrinkles near the needle drop point of the cloth (see FIG. 11B).

However, if the tension is set by a thread tension device or the like in consideration of the influence on the front stitches, it is possible to form all the stitches with an appropriate tension, but the setting work is performed. I had to rely on my experience and intuition, and it took a lot of time and effort to make the correct settings.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a puckering prevention device capable of suppressing the occurrence of puckering in a sewn product and obtaining a good sewn product quality. To do.

[0010]

[Means for Solving the Problems] In order to achieve the above object,
The present invention comprises the following means. That is, according to the present invention, a needle plate having a needle drop hole for penetrating a sewing needle and a plurality of feed dog insertion holes formed in front and rear of the needle drop hole in the cloth conveying direction is synchronized with the ascending / descending operation of the sewing needle. And four movements are performed, and a plurality of sawtooth-shaped tooth portions formed on the upper surface move the feed dogs into and out of the feed dog insertion holes and the cloth located on the needle plate downward at least around the needle drop holes. In a sewing machine having a pressing member for pressing,
(A) Among the feed dogs that pass through the needle drop hole and are arranged on a straight line parallel to the cloth conveyance direction, at least the distance interval from the needle drop hole to the rear end of the feed dog insertion hole is smaller than the stitch pitch. The length is set, and the top of the feed dog protruding from the feed dog insertion hole is located at the last position.

As another means for achieving the above object, (b) at least a portion of the feed dog located at the rear of the needle drop hole may be formed flat. ) The tooth portions of at least the portion of the feed dog located rearward of the needle drop hole may be formed with an adjacent interval smaller than the tooth portions at other positions.

[0012]

With the structure of (a) above, the top of the feed dog located at the rearmost position presses the seam currently formed from below in the vicinity of the front part of the needle drop hole, so that the balance is Even if the upper thread I1 is pulled up, the tension generated in both threads does not affect the already formed stitches, and the occurrence of puckering is greatly suppressed. Therefore, the tension of the thread need only be set considering the tension generated for each needle, and the setting operation can be simplified.

Further, in the one having the above-mentioned constitution (b), since the flat portion of the feed dog supports the cloth located at the rear of the needle drop hole from the lower surface, the supported cloth is supported. Bending and wrinkling do not occur, and the occurrence of puckering is suppressed here. Furthermore, above (C)
In the one having the configuration of, since the tooth portion formed with the adjacent distance smaller than the other portions in the feed dog supports the cloth from the lower surface, even if the cloth is thin, The bending of the cloth between the adjacent tooth portions hardly occurs, and the occurrence of puckering is suppressed.

[0014]

Embodiments of the present invention will be described below. 1 to 4 are views showing an embodiment of the present invention. In the figure, 11 is a needle plate detachably attached to the sewing machine bed with screws or the like. The needle plate 11 has a needle drop hole 11a for allowing the sewing needle N to penetrate therethrough, and
Four feed dog insertion holes 1 are provided to the front, rear, left and right of the needle drop hole 11a.
1b to 11e are provided. Of these, needle drop hole 1
The front feed dog insertion hole 11d, which is arranged along a straight line that passes through 1a and is parallel to the cloth conveying direction X, has a distance d1 from the rear end to the needle drop hole 1a that is the same as that of a conventional needle plate. It is set narrower than d2 (see FIG. 7).

Reference numeral 12 denotes a feed dog main body which makes four movements in the vertical direction and the front-back direction by a feed dog drive mechanism (not shown). In the feed dog main body 12, the feed dog insertion holes 11b to 1b are formed.
A plurality of feed dogs 13 to 16 that can be loosely fitted to 1e are provided upright, and a large number of saw tooth-shaped tooth portions 13a to 16a are formed on the upper surface of each feed dog 13 to 16. Of these feed dogs 13 to 16, flat portions 13b and 14b are formed on the feed dogs 13 and 14 inserted into the left and right feed dog insertion holes 11b and 11c, respectively.
The flat portions 13b and 14b extend rearward from a position slightly forward of the needle drop hole 1a, and the height of the upper surface of the flat portions 13b and 14b is the top portion 13a of the tooth portions 13a and 14a located in front and rear thereof.
It is set to be the same as the height of 1, 14a1.

Further, the rearmost tooth portion 15b of the feed dog 15 located immediately before the needle drop hole 11a has a rear end face formed vertically upward and an inclined face inclined obliquely forward from the rear end face. (See FIG. 3). Therefore, the top part 15b1 of the last tooth part 15b is the feed dog 1
5 is at the same position as the rear end surface of the feed dog 15, that is, at the rearmost end of the feed dog 15. Immediately after the top 15b1 projects from the feed dog insertion hole 11d, the distance interval (minimum distance interval) da from the center of the needle drop hole 11a to the top 15b1 is set to be smaller than the stitch pitch. This is significantly shorter than the minimum distance db (see FIG. 7) in the conventional sewing machine.

The needle plate 11 and the feed dog 12 are made of carbon steel, stainless steel, chrome molybdenum steel or the like.

The puckering prevention device in this embodiment is constructed as described above, and the feed dog 1 is operated during the sewing operation.
2 performs four movements in synchronization with the lifting operation of the sewing needle N, and the cloth W
Are transported intermittently. Feed dog 1 in these four movements
2 projects upward from the vicinity of the rear surface of the feed dog insertion hole,
The cloth W being pressed on the needle plate 1 by the cloth pressing member 18.
The top part bites into and engages the lower surface of the cloth W, and the cloth W is conveyed forward.

Here, the feed dog 15 located immediately before the needle drop hole 11a has a tooth portion 15 at its rearmost end as shown in FIG.
Since b presses the bottom seam currently being formed from below,
Even if the balance T pulls up the upper thread I1, the tension generated by the pulling up operation does not affect the already formed stitches. In other words, the tension generated by the lifting operation of the balance T acts only on the seams currently being formed. Therefore, the operator can accurately generate the tension set by the thread tension regulator or the like for each stitch forming operation, and the accurate setting can be performed unless the influence on the front stitch is also taken into consideration. The tension setting work is much simpler than before, and even an inexperienced operator can set the tension accurately.

Moreover, in this embodiment, the feed dog 1
Since the flat portions 13b and 14b formed on the pins 3 and 14 hold the cloth W from the lower side behind the needle drop hole 11a, even when the cloth W to be handled is a thin cloth W, as shown in FIG. Since the cloth W does not bend or wrinkle, the cloth W can be fed into the needle drop hole 1a in a flat state. As described above, in this embodiment, since the holding state of the cloth W and the thread tension can be optimized, the occurrence of puckering can be surely suppressed regardless of the kind of the cloth W and the like, and good sewing can be performed. You can get quality.

In the above embodiment, the flat portion 13
b and 14b are formed in the intermediate portions of the feed dogs 13 and 14, and tooth portions 13a and 14a are formed in the front and rear thereof.
b and 14b may be extended to the rear end of each feed dog 13 and 14, and the tooth portions 13a and 14a may be formed only in front of the flat portions 13b and 14b.

Further, the tooth portion 15b immediately before the needle drop hole 11a.
Has a sharp shape, but instead of this tooth portion 15,
You may provide the tooth | gear part 25b which has a flat shape as shown in FIG.

Further, in the above embodiment, the feed dog 1
The case where the flat portions 13b and 14b are formed on the surfaces 3 and 14 has been described as an example. However, instead of the flat portions 13b and 14b,
By forming the tooth portions 13c and 14c having a narrow space between adjacent ones as shown in FIG. 6, it is possible to reduce the bending of the cloth W in front of the needle drop hole 1a. Of course, in this case, the flat portion 13
Although the cloth W is slightly bent as compared with the case where b and 14b are provided, depending on the thickness and rigidity of the cloth W, the bending can be suppressed to such an extent that there is almost no problem, and the tooth portions of all parts are Compared with the conventional one, which is formed with uniform adjacent intervals,
The holding state of the cloth W can be significantly improved.

Further, in each of the above embodiments, the feed dog 1
By forming the flat portions 13b and 14b or the tooth portions 13c and 14c having a small space between adjacent portions on the teeth 3 and 14, a means for supporting the cloth in a flat state is provided, and a tooth at the rear end of the feed dog 15 is provided. The case where the means for blocking the influence of the thread pulling operation of the balance from reaching the already formed seam by forming the portion 15b has been described as an example, but only one of both means is provided. Even with the provision, it is possible to significantly suppress the occurrence of puckering compared to the conventional case. In other words, the present invention is not limited to the above-described embodiment in which both means are provided, and any one means may be provided.

[0025]

As described above, according to the present invention, since the tooth portion of the feed dog presses the stitch being formed during the upper thread tightening operation by the balance or the like, the already formed stitch is not It is possible to prevent the pulling operation from being affected, and it is possible to accurately apply the tension set by the thread tension device or the like to each stitch. Therefore, according to the present invention, it is possible for any person to easily set an appropriate tension, it is possible to reduce the occurrence of puckering, and it is possible to significantly improve the quality of the sewn product.

By forming the upper surface of the portion of the feed dog rearward of the needle drop hole flat or by forming the tooth portion at an interval smaller than that of the tooth portion formed in the other portion, It is possible to feed the cloth W onto the needle drop hole without causing the cloth to bend or wrinkle, which also significantly reduces the occurrence of puckering.

[Brief description of drawings]

FIG. 1 is a plan view showing a needle plate and a feed dog according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a feed dog in the above embodiment.

FIG. 3 is an explanatory side view showing an engagement state between the feed dog and the cloth at the time of the upper thread pulling operation by the balance in the same embodiment.

FIG. 4 is an explanatory side view showing a state in which the cloth is held by the flat portion of the feed dog in the embodiment.

FIG. 5 is an explanatory side view showing the shape of a feed dog according to still another embodiment of the present invention.

FIG. 6 is an explanatory side view showing a state in which the cloth is held by the feed dog in another embodiment of the present invention.

FIG. 7 is an explanatory side view showing a stitch forming operation state in a lockstitch sewing machine which has been generally used conventionally.

FIG. 8 is a plan view showing a conventional needle plate and a feed dog.

FIG. 9 is an explanatory side view showing a state in which puckering has occurred as a result of forming stitches on the cloth W held by the conventional feed dog.

FIG. 10 is an explanatory side view showing an engaged state of the feed dog and the cloth during the upper thread pulling operation of the balance in the conventional technique.

11A and 11B are explanatory side views showing a state of occurrence of pucker ring, in which FIG. 11A shows the pucker ring generated when a stitch is formed in the state shown in FIG. 8 and FIG. The pucker ring generated when the seam is formed is shown in FIG.

[Explanation of symbols]

 N Sewing needle 11 Needle plate 11a Needle drop hole 11b, 11c, 11d, 11e Feed dog insertion hole 13, 14, 15, 16 Feed dog 13a, 14a, 15a, 16a Teeth 13b, 14b Flat 13c, 14c Teeth 15b Last tooth part 15b1 Top part 17 Cloth pressing member d1 Minimum distance interval

Claims (3)

[Claims] 1. A needle plate having a needle drop hole for penetrating a sewing needle and a plurality of feed dog insertion holes formed in front and rear of the needle drop hole in the cloth conveying direction, and in synchronization with a lifting operation of the sewing needle. Then, four combined movements of forward and backward movement and vertical movement are performed, and a large number of sawtooth-shaped tooth portions formed on the upper surface are located on the needle plate and a plurality of feed teeth protruding and retracting from the feed dog insertion holes. A cloth pressing member for pressing the cloth downward at least around the needle drop hole is provided, and when protruding from the feed dog insertion hole, the tooth portion of the feed dog is pressed against the lower surface of the cloth pressed by the cloth pressing member. In the sewing machine in which the cloth and the feed dog are engaged with each other to move the cloth forward together with the feed dog, the feed dog insertion hole formed on the straight line passing through the needle drop hole and parallel to the cloth conveying direction. Set the distance between the rear end of the When the feed dog protrudes from this feed dog insertion hole, the distance from the center of the needle drop hole to the last position of the feed dog becomes smaller than the stitch pitch and at the last position. A puckering prevention device for a sewing machine, characterized in that a top portion or a flat portion is provided on the bottom. 2. A needle plate having a needle drop hole for penetrating a sewing needle and a plurality of feed dog insertion holes formed in front of and in the rear of the needle drop hole in the cloth conveying direction, and in synchronization with the lifting operation of the sewing needle. Then, four combined movements of forward and backward movement and vertical movement are performed, and a large number of sawtooth shaped tooth portions formed on the upper surface are located on the needle plate and a plurality of feed teeth protruding and retracting from the feed dog insertion holes. A cloth pressing member for pressing the cloth downward at least around the needle drop hole is provided, and when protruding from the feed dog insertion hole, the tooth portion of the feed dog is pressed against the lower surface of the cloth pressed by the cloth pressing member. In the sewing machine in which the cloth and the feed dog are engaged with each other and the cloth is moved forward together with the feed dog, in the feed dog arranged on a straight line passing through the needle drop hole and parallel to the cloth conveying direction. At least behind the needle drop hole Sewing puckering preventing device, characterized in that the flat form. 3. A needle plate having a needle drop hole through which a sewing needle penetrates and having a plurality of feed dog insertion holes formed in front of and in the rear of the needle drop hole in the cloth conveying direction, and in synchronization with the lifting operation of the sewing needle. Then, four combined movements of forward and backward movement and vertical movement are performed, and a large number of sawtooth shaped tooth portions formed on the upper surface are located on the needle plate and a plurality of feed teeth protruding and retracting from the feed dog insertion holes. A cloth pressing member for pressing the cloth downward at least around the needle drop hole is provided, and when protruding from the feed dog insertion hole, the tooth portion of the feed dog is pressed against the lower surface of the cloth pressed by the cloth pressing member. In the sewing machine in which the cloth and the feed dog are engaged with each other and the cloth is moved forward together with the feed dog, the tooth portion of at least the needle drop position in the feed tooth is set to the other position. With adjacent spacing smaller than the tooth in Puckering prevention device of a sewing machine, characterized in that form.