JP2529524B2 - Seam puckering prevention device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine attachment for preventing seam puckering.

[0002]

2. Description of the Related Art There are various kinds of cloths applied for sewing, which have various thicknesses, elasticity, density (the number of warp threads and weft threads per unit length). When processing these various cloths, each time the type changes, especially when sewing difficult materials, change the sewing machine conditions or use the sewing machine attachment as necessary so that seam puckering does not occur. The method such as doing is taken.

For example, when changing the sewing machine conditions, there are methods such as reducing the thread tension as much as possible, reducing the number of revolutions, and lowering the feed dog. However, with this method, there are problems that the seam formation is not successful, the productivity is reduced, the fabric feeding is insufficient, and the seam pitch is disturbed. Moreover, the occurrence of seam puckering cannot be completely prevented. Further, it takes time and labor to change the sewing machine conditions for various fabrics.

On the other hand, most of the attachment-based methods prevent seam puckering by preventing displacement between the fabrics to be sewn together. For example, the actual application Sho 62-8
When the feed dog is projected on the work cloth support surface of 6177 to feed the work cloth, a pressing member for pressing the work cloth toward the lower surface of the presser foot is provided above and below the needle. A sewing machine is disclosed which is arranged between a work cloth support surface and a work cloth in the vicinity of a moving passage. Further, in Japanese Patent Application No. 64-62190, a stopping mechanism which faces a presser foot for restraining a work cloth on a needle plate and which causes a lowering cloth to hit and stop in synchronization with a lifting mechanism of a feed dog protruding and retracting on the upper surface of the needle plate. There is disclosed a device for preventing the sewing of the cloth to be processed by arranging. In all of these methods, the work cloth in front of the sewing needle, that is, the work cloth before sewing is pressed against the presser foot to prevent the gap between the cloths to be sewn together, thereby preventing puckering. It cannot be prevented.

[0005]

Other methods for preventing the tension of seams and preventing seam puckering due to shrinkage of the seam are known. This is a method of pressing the already formed seam behind the needle from above onto the rear feed dog with a special pressing metal fitting. In this method, it is difficult to adjust the pressing timing that presses the formed seam and prevents the tension of the seam from being pulled by the tightening tension of the sewing thread, and the pressing mechanism is complicated and the function does not work effectively. In particular, it is difficult to prevent seam puckering, which tends to occur when the work cloth is thin, has low elasticity, and has high density.

The present inventor investigated and studied the main causes of seam puckering generated in such difficult-to-sew materials by various methods, and as a result, the fastening of the sewing thread in order to make the intersection of the upper and lower sewing threads between the upper and lower fabrics. It was confirmed that the tension was applied to the highest level, which also affected the already formed seams and caused the fabric to buckle. This buckling usually causes the feed dog to rise the highest and push up the presser foot when the tightening tension is the highest, so the distance between the needle plate surface and the lower surface of the presser foot greatly exceeds the thickness of the fabric, and the fabric tends to buckle. Because. Therefore, the present invention provides a seam puckering prevention device capable of preventing buckling caused by the above mechanism and preventing seam puckering.

[0007]

The seam puckering prevention device of the present invention has a pressing portion arranged at least rearward of the needle hole of the needle plate, and is interlocked with the feeding movement of the cloth feeding mechanism of the sewing machine to press the presser foot. By providing a stopper for moving the pressing portion up and down between the foot and the needle plate, the stitch portion formed closest to the needle hole is moved to the pressing portion at the time when the tightening tension of the sewing thread becomes substantially maximum. It is characterized in that it is pressed against the lower surface of the presser foot to suppress the fastening tension.

[0008]

The function of this seam puckering prevention device is such that the fastening tension of the sewing thread is large, and the feed dog rises above the throat plate surface and pushes up the presser foot to increase the distance between the throat plate surface and the lower surface of the presser foot. The portion of the stitch formed on the work cloth that is closest to the needle hole is pressed against the lower surface of the presser foot by the stopper. By pressing the formed seam in this way, the influence of fastening tension on the seam is suppressed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view of a needle plate 2 of a seam puckering prevention device 1 and a stopper 4 provided on the needle plate surface 3, and FIG. 1 (A) is a plan view of the needle plate 2, and FIG. (B)
1 is a cross-sectional view of the stopper 4 taken along line XX, and FIG.
[Fig. 6] is an S-S cross-section explanatory diagram. FIG. 2 is an exploded view of the seam puckering prevention device 1, and is an explanatory view of the needle plate 2, the stopper 4, and the feed dog 15.

The seam puckering prevention device 1 includes a needle plate 2, a stopper 4 provided on the needle plate surface 3 and a feed dog 15.
Consists of The needle plate 2 is a plate for sewing, which is provided perpendicularly to the ascending / descending line of the sewing needle.
It has a, 11b, 11c and a stopper 4. The main element of the present invention in this embodiment is that the stopper 4 is provided. As shown in FIG. 1 (A), the stopper 4 is composed of a rectangular spring plate, is fitted into the recess 3a of the needle plate surface 3 so as to be flush with the needle plate surface 3, and its base portion 5 is the needle plate surface. 3 is cantilevered. The tip portion 6 has a central convex portion 6a and feed dog contact portions 6b on both sides thereof.
The central convex portion 6a has a through hole 7a overlapping the needle hole 7 of the needle plate 2 and a pressing portion 6c further on the tip side thereof as shown in the XX cross-sectional view.
And The pressing portion 6c is curved in a convex state upward. The feed dog abutting portion 6b has a tip bent downward as shown in the S-S sectional view. Guide groove 1 mentioned above
1a and 11c are provided on both sides of the needle hole 7 with the needle hole 7 in between.
The guide groove 11b is provided immediately behind the needle hole 7, and the guide groove 1b
Shorter than 1a and 11c. The feed dog 15 is composed of three rows of racks as shown in FIG. 2, and each of the guide grooves 11a, 11b,
It has racks 15a, 15b, and 15c corresponding to 11c. These racks 15a, 15b, 15c penetrate the respective guide grooves 11a, 11b, 11c so that they can be projected and retracted on the needle plate surface 3, respectively.
Has an inner width and length of. The racks 15a and 15c have guide surfaces 17a and 17c, which form cut steps, on the inner side and on the cloth insertion side (front side). The feed dog 15 has an elliptical motion through a vertical and horizontal rotating function provided below the needle plate 2 by a known method, and performs a cloth feeding action on the needle plate surface 3. In synchronization with the elliptic movement, the stopper 4 slides the feed dog contact portions 6b on both sides onto the guide surfaces 17a and 17c, and the pressing portion 6c of the stopper 4 moves up and down. The pressing portion 6c rises to the same height as the tooth crest surface when the feed dog 15 rises to the maximum.

FIGS. 3, 4, 5, 6, 7, 8, 9, 10 show one-stroke operation of the sewing machine when the seam puckering prevention device 1 of the present invention is used (the feed dog 15 is raised from the lowest position, The operating positions and states of the stopper 4, the feed dog 15, the balance 26, and the needle 28 in the operating state (reaching the lowest position again) are shown. In particular, FIGS. 4, 6, 8 and 10 show the stopper portion in the previous figure. An enlarged view is shown. FIG. 11 shows an operation timing diagram of each part of the sewing machine when the seam puckering prevention device 1 of the present embodiment is applied, and the vertical axis shows positional changes of the stopper 4, the feed dog 15, the balance 26, and the needle tip 29. . The horizontal axis indicates the crank angle, and the numbers in parentheses indicate the positions corresponding to the states shown in FIGS. 3, 5, 7, and 9.

The operation of each of the above parts of the sewing machine will be described with reference to FIG. 11. First, in FIG. 11 (3), the pressing part 6c of the stopper 4 is at the same position as the needle plate surface 3 as shown in FIGS. The balance 26 is lowered almost to the lowest position, and the feed dog 15
Is also lower than the needle plate surface 3, and the needle 28 is in a state of penetrating the cloth and rising from the lowest position. In (5), as shown in FIGS. 5 and 6, the balance 26 rises, the needle 28 approaches the substantially highest position, and the feed dog 15 starts to rise upward from the needle plate surface 3 and, at the same time, the stopper 4 makes the feed tooth contact portion. 6b is slid on the guide surfaces 17a and 17c of the feed dog 15 and starts to rise. At this point, the tightening tension T of the sewing thread is being applied. In (7), as shown in FIGS. 7 and 8, the balance 26 is raised to the substantially highest level, the fastening tension T is exerted most strongly on the upper and lower sides of the work cloth 23, the feed dog 15 is raised to the highest position, and the stopper 4 is fed to the feed dog 15. Then, the pressing portion 6c is pushed up to the highest level, is raised to the same height as the tip of the feed dog 15, strongly presses the already formed seam portion 24 of the work cloth 23, and the fastening tension T is formed. The effect on the seam 24 is reduced. That is, in this state, the pressing portion 6c of the stopper 4 is pushed up to substantially the same height as the maximum height of the feed dog 15, the distance between the lower surface of the presser foot 25 and the pressing portion 6c, and the lower surface of the presser foot 25. Since the distance between the feed tooth 15 and the tip of the feed dog 15 is the same, and the pressing portion 6c strongly presses the stitch portion 24 to suppress the influence of the tension T of the sewing thread on the stitch portion 24. The buckling of the work cloth 23 can be prevented. This action prevents the occurrence of seam puckering. At the time of (7A), the balance 26 reaches the maximum, but the needle 28 begins to descend and the fastening tension T begins to weaken. When the feed dog 15 also begins to descend, the stopper 4 deviates from the guide surfaces 17a and 17c and suddenly descends on the needle plate surface 3, and the needle 28 also descends in parallel. In (9), FIGS.
As described above, the balance 26 begins to descend, the tightening tension T is not applied, the tip of the feed dog 15 is still above the needle plate surface 3, and the stopper 4 is lowered to the needle plate surface 3, and even at the highest portion. Since it is at the same height as the needle plate surface 3 and the lowest part is at a position lower than the needle plate surface 3 by about 0.5 mm, the feed dog 15
To promote the progress of the work cloth 23. In (9A), the feed dog 15 is lowered to the needle plate surface 3 and the cloth feeding action is stopped, and the needle 28 is in a state of penetrating the work cloth 23. After that, the position (3) is reached again. The above operation completes one stroke.

In order to examine the effect of the present embodiment, the fabric of the standard shown in Table 1 was selected as a sample of the material difficult to sew.

[0014]

[Table 1]

Fabric No. Features 1, 2, 3 are thin,
Due to the higher density, puckering is more likely to occur than the conventional one, and when the humidity is high, the puckering often occurs due to stretching of the fabric due to the high-granular expansion, resulting in a state similar to sewing shrinkage. NO. 4, 5, 6
Is a thin, high-density fabric that uses ultrafine fibers and fine count yarn,
Packing and scratches are likely to occur. In addition, some of them have slippery surfaces and are easily sewn. NO. 7 is
Completely different from the above 6 points, it is light and relatively thick and easy to stretch. Due to surface fluff, it shifts in one direction,
Easy to sew. In order to compare a standard lock stitch (when the needle plate 2 without the stopper is used) with the seam puckering prevention device 1 of this embodiment using these samples, a lock stitch automatic thread trimmer sewing machine was used. Used, sewing machine rotation speed 350
0 rpm, presser foot pressure 3 kg, bobbin thread tension 15 g, thread tightening ratio approx. 1
A sewing test was carried out by applying a load of 20 g to both ends of the fabric with 20%, a fabric width of 5 cm and a feed guide so that the fabric would automatically advance. The results are shown in Table 2.

[0016]

[Table 2]

When the present embodiment was used, the sewing shrinkage ratio was reduced and the seam puckering was greatly improved. Further, the result obtained by using the conventional attachment was almost the same as that of the above-mentioned lock stitch, and this example was excellent. As described above, according to the present embodiment, it is not necessary to change the sewing conditions as in the conventional case when processing a fabric in which the seam puckering is likely to occur, and the seam puckering which is insufficient in the conventional attachment is prevented. It is also possible to prevent the seam puckering by only replacing the needle plate 2 provided with the stopper 4 and the feed dog 15 as compared with the method of pressing the work cloth 23 from above. Therefore, it is possible to expect great effects such as low cost and easy attachment / detachment.

[0018]

According to the present embodiment, the stopper of the seam puckering prevention device presses the seam immediately after it is formed, and suppresses the tightening tension of the suture to bring the intersection point of the upper and lower sutures to the middle of the upper and lower fabrics. This makes the fabric less likely to buckle and prevents seam puckering.

[Brief description of drawings]

FIG. 1 is an illustration of a seam puckering prevention device. (A) is a top view of the needle plate of the seam puckering prevention device. (B) is an XX sectional view of (A).
(C) is an SS sectional view of (A).

FIG. 2 is an exploded explanatory view of the seam puckering prevention device and is an explanatory view of a needle plate, a stopper, and a feed dog.

FIG. 3 is an operation explanatory view of the seam puckering prevention device, and is a view showing a state where the needle penetrates the work cloth and the stopper is separated from the feed dog.

FIG. 4 is an enlarged view of a stopper portion of FIG.

FIG. 5 is an explanatory view of the operation of the seam puckering prevention device, showing a state where the needle comes out of the work cloth, the feed dog moves upward to feed the work cloth, and the stopper slides to move upward. is there.

6 is an enlarged view of a stopper portion of FIG.

FIG. 7 is an operation explanatory view of the seam puckering prevention device, showing a state in which the stopper is raised to the maximum and presses the work cloth.

FIG. 8 is an enlarged view of a stopper portion of FIG.

FIG. 9 is an operation explanatory view of the seam puckering prevention device, and is a view showing a state in which the stopper has the downward feed teeth at a position slightly higher than the needle plate surface.

10 is an enlarged view of a stopper portion of FIG.

FIG. 11 is a timing diagram of the stopper, feed dog, balance, and needle tip of the example.

[Explanation of symbols]

1..Seam puckering prevention device 2 ..
3 ... Needle plate surface 3a ... Recess of needle plate 4 ... Stopper 6 ...
・ Tip of stopper 6a ・ ・ Central convex part 6b ・ ・ Feed dog contact part
6c ... Pressing part 7 ... Needle hole 7a ... Stopper through hole
15 ・ ・ Feed teeth 15a, 15b, 15c ・ ・ Feed tooth rack 17a, 17c ・ ・ Feed tooth guide surface 23 ・ ・ Work cloth 24 ・ ・ Seam part closest to the hole 25 ・ ・ Presser foot 26 ・ ・ Balance 28 ..Needles 29..Needle tips

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-293492 (JP, A) JP-A-61-62190 (JP, A) JP-A-59-141988 (JP, A) Actual development Sho-62- 86177 (JP, U) JP-B 8-15513 (JP, B2) JP-B Sho 60-21752 (JP, B2) JP-B 63-7191 (JP, Y2) JP-B 55-229 (JP, Y2) Actual Public Sho 57-49979 (JP, Y2) Actual Public Hei 1-18156 (JP, Y2)

Claims (2)

(57) [Claims] 1. A pressing portion disposed at least rearward of a needle hole of a needle plate, and the pressing portion is vertically moved between a presser foot and a needle plate in association with a feeding movement of a cloth feeding mechanism of a sewing machine. By providing a moving stopper, the stitch part formed closest to the needle hole can be
A seam puckering prevention device, characterized in that it is pressed against the lower surface of the presser foot by the pressing portion so that the fastening tension can be suppressed. 2. The seam puckering prevention device according to claim 1, wherein the stopper comprises a spring plate.