JPH02149289A - Feed lifting lock stich sewing machine and method for preventing puckering in the same - Google Patents

Abstract

PURPOSE:To prevent failure in sewing such as puckering and uneven material feeding when sewing thin material by arranging upper and lower feed dogs in such a manner that their sandwiching faces may sandwich the material therebetween at positions past the dropping point of a needle along the direction of feeding of material, and providing lifting means for maintaining the rising position of a presser until a tightening force acts on sewing thread. CONSTITUTION:An upper feed dog 5 falls down to hold material W, at which time a presser 4 is lifted by lifting means 45 in conjunction with lifting of the upper feed dog 5 by a lower feed dog 6, so that the material W is not substantially pressed. Besides, a tightening force begins acting on sewing thread from that point G of time which is just before a balance reaches is upper dead point, but, while the upper and lower feed dogs 5, 6 sandwich the material W therebetween, the presser 4 maintains its rising position even under the action of the tightening force; the tightening force that may cause the material to pucker and deform will therefore not act on the material. The upper and lower feed dogs 5, 6 are both arranged past the dropping point P of a needle along the direction of feeding of material in order to prevent uneven feeding between upper and lower materials by feeding the sewed material W in a pulling manner, and also to prevent the material W from puckering when a seam alreadly formed is pulled back by the tightening force exerted by the sewing thread.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vertical feed lockstitch sewing machine useful for sewing two pieces of thin fabric together, and a bunkering prevention method using the same. It has some characteristic improvements.

[Conventional technology]

Puckering is a typical sewing defect. The first cause of this is when there are problems with the fabric properties, such as the fabric being slippery or thin. Second, there may be improper adjustment of the sewing machine, such as inappropriate thread tension or too strong presser foot pressure.

Puckering is likely to occur when sewing two thin fabrics made of different materials.In such cases, no matter how carefully the sewing machine is adjusted, it is impossible to completely prevent bunkering from occurring. The current situation is that this is not possible.

As a conventional technique for preventing bunkering, JP-A-62'-1
There is a publication No. 6786. This is a form in which a lower needle is provided on a part of the lower feed dog, and the lower needle is inserted into two pieces of fabric to feed the fabric.When feeding the fabric, the presser foot is raised.
This prevents the fabric from receiving frictional resistance from the presser foot.

Incidentally, in conventional general sewing machines, the fabric is always pressed down with a presser foot to prevent the fabric from slipping when the fabric is fed, and the presser foot maintains a pressing position against the fabric even when the fabric is fed. As an exception, there is a differential vertical walking feed sewing machine in which the presser foot and the upper feed dog alternately move up and down to perform a walking motion. It is for sewing materials,
Not applicable to thin fabrics.

[Problem to be solved by the invention]

As mentioned above, in the prior art example in which the fabric is fed by the cooperative action of the lower needle and the lower feed dog, the fabric does not receive any sliding resistance from the presser foot 4 when feeding the fabric, so it is not effective in preventing sewing errors. be.

However, the biggest drawback is that the life of the lower needle is extremely short.

For commercial use, the lifespan is one day at most, or two days at best. Moreover, there is a disadvantage that the fabric feeding speed cannot be increased. The fabric is easily damaged by a deformed or worn lower needle. There were disadvantages such as the puncture marks of the lower needle tend to remain on the fabric and reduce the product value, and the puncture marks were particularly noticeable when sewing curved lines.

Further, in the above-mentioned conventional example, there was a problem in the lowering timing of the presser foot that was raised during fabric feeding. That is, to explain with reference to FIG. 5, the presser foot was already set to clamp the fabric between point G, when the upper thread is pulled and a tightening force is applied to the seam, and point 11. . This is because, as long as the upper feed dog is not provided, unless the fabric is pressed down with the presser foot, the fabric will lift up and the thread tightening effect cannot be effectively exerted. Therefore,
During the above-mentioned time point (GH), the pressing action of the presser foot continues to work, which disadvantageously causes the fabric to be compressed, especially when sewing thin fabrics. Therefore, the objects to be sewn are non-slip materials such as vinyl and leather, and materials with piles such as Helvesoto and Velveteen +4
, stockinette, and other stretchable materials, that is, welfare fabrics.

As can be seen from these fabric characteristics, the presser foot in the conventional example mentioned above is raised only to avoid frictional resistance with the fabric when feeding the fabric, and is similar to the walk-feed sewing machine described above. I can say that there is.

The present invention has been proposed in view of the above, and an object of the present invention is to reliably prevent sewing defects such as puckering and misalignment from occurring when sewing thin fabrics.

[Means to solve the problem]

In the present invention, the upper feed dog 5, the lower feed dog 6 that operates in cooperation with the upper feed dog 5, the presser foot 4 that presses the fabric W onto the throat plate 7 when forming stitches, and the presser foot 4 that raises the presser foot 4 when feeding the fabric. In a top and bottom feed lockstitch sewing machine each equipped with a lift means 45 to be operated, both the top and bottom feed dogs 5 and 6 are connected to these clamping surfaces 5a and 5a.
6a is arranged to hold the fabric W on the downstream side of the needle drop point P in the fabric feeding direction, and the lift means 45 holds the presser foot 4 at least until the bow tightening force is applied to the sewing thread (between time G and time 11). It is configured to maintain a rising position. Here, attention should be paid to the lowering timing of the presser foot 4.

More specifically, the lift means 45 is for switching the presser foot 4 to a raised position so that the presser foot 4 is not substantially pressed against the fabric W when the fabric is fed by the feed dogs 5 and 6; Upper feed drive mechanism 1 that feeds the feed dog 5
It is constructed so that the presser foot 4 is maintained in the raised position via the upper feed dog 5 by the upward force of the lower feed dog 6. Such a configuration leads to a simplified structure.

In the needle hole 41 opened on the presser foot 4 side, an upper thread guide groove 42 is formed which slopes upward from the stitch side toward the sewing needle 3 side. Further, a lower thread guide groove 40 is formed in the needle through hole 39 formed in the needle plate 7 so as to be inclined from the seam side to the hook side. Furthermore, the tension of the upper thread immediately after passing through the thread take-up is 3.
If it goes just below 0g, the needle thread will not be able to pull up the bobbin thread (the needle thread will come out on the wrong side of the fabric), and if it exceeds 50g, it will not be possible to achieve the desired purpose, so the tension of the needle thread should be 30g. It is desirable to set the weight to about 50g and to match the tension of the lower thread to the upper thread. This value was determined from the experience of the present inventor, who has been involved in the sewing industry for many years.

Further, in the bunkering prevention method of the present invention, the upper feed dog 5,
Using a vertical feed lockstitch sewing machine equipped with a lift means 45 that lifts the lower feed dog 6 and presser foot 4 when feeding the fabric, both feed dogs 5 and 6 located on the lower side in the fabric feeding direction from the needle drop point P are used to feed the fabric. While feeding W while being held, from time E, which is at the same time as both feed dogs 5 and 6 grip the fabric W (time D) or slightly later than this, to time H when a tightening force is applied to the sewing thread, The lift means 45 continues to maintain the presser foot 4 in the ascending position,
When forming a stitch, the presser foot 4 is lowered to press the fabric on the throat plate 7 with the presser foot 4.

[Effect]

To explain with reference to FIG. 5, at point D, just before the sewing needle 3 reaches the top dead center after stitch formation, the lower feed dog 6 rises and the upper feed dog 5 descends, causing the fabric W At the same time, as the upper feed dog 5 is lifted by the lower feed dog 6, the presser foot 4 is lifted by the lift means 45.

In other words, while the upper and lower feed dogs 5 and 6 are feeding the fabric, the presser foot 4 is in a raised position and does not substantially press the fabric W. Furthermore, a tightening force is applied to the sewing thread from point G just before the take-up reaches the top dead center, but while this tightening force is acting (G-1
At point 1), the upper and lower feed dogs 5 and 6 clamp the fabric W, and the presser foot 4 continues to maintain the upward position, thus tightening the fabric to give it a contracted shape. No force acts.

Upper and lower feed dogs 5 and 6 are located below the needle drop point P in the material feed direction.
The reason for this arrangement is to feed the fabric W after sewing in a pulling manner, to prevent misalignment of the upper and lower fabrics, and to prevent the already formed seams from being pulled back by the tightening force of the sewing thread to the fabric W. This is to prevent seam shrinkage from occurring. This point will become clearer if compared with a method in which both feed dogs 5 and 6 are positioned above the needle drop point P in the material feeding direction and push out the material W.

〔Example〕

1 to 5 show an embodiment of a vertical feed lockstitch sewing machine according to the present invention.

In Fig. 2, ■ is the upper feed drive mechanism, 2 is the needle bar □, 3
is the sewing needle, 4 is the presser foot, 5 is the upper feed dog, 6 is the lower feed dog, 7
is the needle plate.

The upper feed drive mechanism 1 includes a vertical movement means IA that gives the upper feed dog 5 a vertical movement, a back and forth movement means IB that gives the upper feed dog 5 a back and forth movement, and biases the upper feed dog 5 and the presser foot 4 downward. pressure means iC. Each of these means IA-IB
-1c, the upper feed dog 5 is driven along an elliptical trajectory.

The vertical movement means IA includes a vertical lever 9, an upper intermediate link 10, a bell crank-shaped fork lever 11, and the like. A fork lever 11 swingably supported by a bracket 13 at the lower end of a presser bar 12 via a pin 14 is vertically operated by a vertical lever 9 via an upper intermediate link 10. The fork lever 11 has an operating fork 15 at one end.

The longitudinal movement means IB includes a longitudinal movement lever 17, a lower intermediate link 18, an upper tooth holder 19, a support lever 20 swingably supported by the bracket 13, and the like. The lower intermediate link 18, the upper tooth holder 19 and the support lever 20 are connected to the pin 2
Connect using 1 as a common axis. A pair of brackets is provided upright on the upper part of the tip of the upper tooth holder 19, and a roller 22 is freely rotatably supported between the brackets, and this is connected to the fork lever 1.
It is held and supported in a relatively movable manner by one operation fork 15.

In this way, the operation of the vertical movement means IA is transmitted from the operation fork 15 to the upper tooth holder 19 via the roller 22, and the posture of the upper feed dog 5 fixed to the lower surface thereof is controlled in cooperation with the output operation of the longitudinal movement means IB. .

The pressure means IC includes a vertically long bushing 25 supported on the fixed wall of the arm 24, the presser rod 12 passed through the bushing 25, a tappet body 26 supported inside the lower end of the presser rod 12 so as to be movable up and down, and the presser rod 12. It consists of a push rod 27 inserted into the tappet body 26 and connected to the tappet body 26, and spring means for biasing these.

The presser bar 12 is supported by a bushing 25 so as to be movable up and down, and can be manually switched between an upper standby position and a lowered operating position by switching an operating lever (not shown). A presser foot 4 is attached to the lower end of this presser bar. Although the manual switching means for the presser foot 4 is not shown, it is the same as known means.

In order to press the presser foot 4 to the needle plate 7 with the fabric in between in the operating position, a spring receiving arm 28 supported on the frame side so as to be vertically slidable is fixed to the upper end of the presser foot 12, and this is connected to the presser foot spring. Press 29 downward to apply pressure. The spring pressure of this spring 29 is determined by the adjustment screw 3 attached to the upper wall of the arm 24.
It can be adjusted at 0. Conventionally, the pressing force of the presser foot 4 is generally 5 to 6.
kgf, but here it is 2.2 to 3 kgf.
Set it extremely weakly.

In order to apply appropriate clamping pressure to the upper feed dog 5, the tip of a cantilevered leaf spring 31 is brought into contact with the upper end of the push rod 27. The spring pressure of this leaf spring 31 can also be adjusted with an adjusting screw 32. In the present invention, the upper and lower feed teeth 5.
Since it is necessary to feed the fabric using only the spring 6, the leaf spring 31 is set to generate a slightly larger spring force than usual.

Separately from the leaf spring 31, a synchronized spring 33 is provided which presses down and urges the tappet body 26. This synchronized spring 33 is installed inside the presser bar 12, and a plug 34 is screwed and fixed to the upper end of the tappet body 26 and the upper end of the presser bar 12.
Interpose between. This synchronized spring 33 is connected to the operating fork 1
5 is brought into pressure contact with the roller 22, and serves to ensure that the tappet body 26 follows the vertical movement of the operating fork 15.

The lower feed dog 6 is driven along an elliptical trajectory by a known drive mechanism built into the bed 36, and cooperates with the upper feed dog 5 to feed the fabric W.
Send and operate. After the upper feed dog 5 contacts the lower feed dog 6 via the material W, the -hi feed dog 5 moves to follow the elliptical trajectory of the lower feed dog 6 until the feeding operation is completed.

In other words, during the dough feeding operation, the leaf spring 31 is pushed up against the lower feed dog 6, and at this time the leaf spring 31 acting on the upper feed dog 5
The fabric W is firmly clamped and fixed by the spring pressure of the synchronized spring 33.

In FIG. 3, on the upper surface of the lower feed dog 6, there are two long clamping surfaces 6b, 6b parallel to the fabric feeding direction, and a short one located at the center of these clamping surfaces 6b, 6b on the lower side in the fabric feeding direction. A clamping surface 6a of approximately 300 mm is provided.

The clamping and feeding operations of the dough W are performed by the substantially short clamping surface 6a and the clamping surface 5a of the upper feed dog 5.

As shown in FIG. 4, the clamping surfaces 5a and 6a of the two are located on the lower side of the needle drop point P in the fabric feeding direction, and the clamping surfaces 5a and 6a of the two clamp the fabric W at a position as close as possible to the needle drop point P. It deserves attention. This is effective for reliably feeding thin fabrics by pulling them.

The plate surface of the throat plate 7 is provided with feed windows 37, 37, 38 corresponding to the clamping surfaces 6a, 6b of the lower feed dog 6, and a needle through hole 39 is provided at a position adjacent to the center feed window 38. It's dawn.

As shown in FIG.
A bobbin thread guide groove 40 is formed which is inclined downwardly toward the hook side inside the bobbin thread 6 to prevent thread tightening due to sliding resistance of the bobbin thread when feeding the fabric.

An upper thread guide groove 42 having the same purpose is also formed in the needle hole 41 of the presser foot 4. Specifically, the needle thread guide groove 42 is formed so as to be inclined upwardly from the stitch side toward the sewing needle 3 side. Fourth
In the figure, reference numeral 43 indicates an upper feed tooth 5 formed on the presser foot 4.
This is an operating groove for loose fitting.

In order to avoid applying a tightening force to the seams, a lifting means 45 is provided for lifting the presser foot 4.

This lift means 45 is incorporated into the upper feed drive mechanism 1. That is, the upper feed drive mechanism 1 is configured so that the presser foot 4 is raised while the upper feed dog 5 cooperates with the lower feed dog 6 to clamp the fabric W.

That is, the upper feed dog 5 passes through the material W to the lower feed dog 6. , the upper feed dog 5 is pushed up by the lower feed dog 6,
At the same time, the tappet body 26 is operated by the operating fork 15 to release the tuning spring 3.
It is pushed up against 3.

Then, the spring pressure of the tuning spring 33 increases, and this spring pressure acts upwardly on the presser bar 12 via the plug 34. At this time, since the spring pressure of the presser foot spring 29 acting on the presser foot 4 is set to be weak at 2.5 to 3 kgf, the synchronized spring 3
3 becomes higher than the spring pressure of the presser foot spring 29, and the presser foot 4 is moved upward via the presser bar 12.

The presser foot 4 is maintained in the raised position until the fabric feeding is completed, and in this raised position, the presser foot 4 does not substantially press the fabric W.

In this way, the upper feed drive mechanism 1 is configured so that the presser foot 4 floats away from the fabric W at the same time as the fabric W is captured by the upper and lower feed dogs 5 and 6. The amount of rise of the presser foot 4 is set to be the same as the thickness of the fabric W in the free state before sewing, or slightly smaller than this, and when the fabric is fed as shown in FIG. It can be tilted up and down around the support shaft 46.

FIG. 5 shows the related operations of the thread take-up, sewing needle 3, presser foot 4, and feed dogs 5 and 6 below -L. This shows a one-cycle vertical movement of each member relative to the fabric W up to three points starting from point A when the sewing needle 3 is at the bottom dead center, and time progresses to the left in the figure. The time intervals between each time point are not necessarily the same. Incidentally, the timing of operation of the balance pin and the sewing needle is the same as that of the conventionally known one.

As can be seen from this timing table, between the time when the balance has risen slightly from the bottom dead center (point D, which is a little before the sewing needle 3 reaches the top dead center) and the point E (at this time, the sewing needle 3 is at the top dead center). , the upper feed dog 5 is pushed up by the lower feed dog 6, and the presser foot 4
will float away from the fabric W. While the presser foot 4 is rising, the fabric is fed by the upper and lower feed dogs 5 and 6.

Next, the balance descended slightly from top dead center (point 11).
At this point, the upper feed dog 5 is separated from the lower feed dog 6, and the presser foot 4 is now pressed against the fabric W in preparation for forming the next stitch.

The sewing thread is tightened between time 0, just before the balance reaches the top dead center, and time 11, when the balance reaches the top dead center. This 11
Even at this point, the presser foot 4 is still being lifted by the lift means 45, and is floating away from the fabric W.

Therefore, when a tightening force is applied to the sewing thread, the presser foot 4
6, the fabric tends to tilt with the upper end in the fabric feeding direction facing upwards, and at the same time, the fabric W held between the upper and lower feed dogs 5 and 6 also slightly rises along with the tilting of the presser foot 4. , avoid applying excessive tightening force to the seams. Moreover, the tension of the upper thread after passing through the thread take-up is adjusted to 30 to 50 g, in reality around 40 g, and the tension of the lower thread is adjusted accordingly. As a result, the fabric W is not stretched and shrunk by the sewing thread, which is effective in preventing bunkering. At this time, the sewing thread forming the seam is in a state where almost no tension is generated, and in combination, puckering does not occur, especially when sewing a wrinkled thin fabric. In addition, since the fabric W is fed by holding the area around the already formed seam between the upper and lower feed dogs 5 and 6 and pulling the fabric W downward in the feeding direction from the needle drop point P, there is no possibility of sewing between the upper and lower fabrics. Not only can it prevent the occurrence of
The stitches are prevented from being pulled back toward the sewing needle 3 side by the tightening force of the sewing thread, and the fabric portion sandwiched between the stitches is also prevented from being stretched.

Various thin fabrics were sewn using the above-mentioned top-feed lockstitch sewing machine, and high-quality sewing was possible in all cases. An example of sewing is shown below.

Thickness of the fabric used when combining two pieces (0.5 mm) Fabric material (silk) (polyester) Presser foot pressing force (2.5 kgf) Presser foot lift amount (O, '7 mm from the needle plate surface) Needle thread tension (taken/bottle) (40 g at the lower part of the bobbin thread tension) (35 g at the middle part) [Another embodiment] In the above embodiment, the upper feed drive mechanism 1 is
However, for example, the pressing force of the presser foot 4 may be released by lifting the presser bar 12 with a cam.

〔Effect of the invention〕

In the present invention, since the presser foot 4 is lifted off the fabric surface by the lift means 45 at least until the sewing thread is drawn by the thread take-up (time point G-11), excessive tightening force is applied to the seam. By avoiding this, it is possible to reliably prevent the cloth W from being stretched by the sewing thread.

On the downstream side of the needle drop point P in the fabric feeding direction, the fabric is fed by pulling the sewn fabric W with the upper and lower feed dogs 5 and 6, and the pressing force on the fabric W' by the presser foot 4 is released. This prevents the upper and lower fabrics from shifting in the fabric feeding direction, and the already formed seams are pulled back by the tightening force of the sewing thread, causing the part of the fabric caught between the seams to shrink. can be prevented.

Therefore, according to the present invention, sewing defects such as puckering and misalignment can be completely eliminated and thin fabrics can be sewn reliably, and the quality of the sewing can be improved to improve the product value. . The tension of the upper thread immediately after passing through the thread take-up is 3.
If the tension is set to 0 to 50 g and the tension of the bobbin thread is adjusted accordingly, this effect will be more effectively exhibited.

Further, according to the present invention as set forth in claim 2, the lifting means 45 of the presser foot 4 is incorporated in the upper feed drive mechanism 1 of the upper feed dog 5, and the upper feed dog 5 is pushed up by the lower feed dog 6. Since the presser foot 4 is raised using the operating force, there is an advantage that the structure can be simplified and the operation can be ensured by sharing the same constituent members.

[Brief explanation of the drawing]

Figures 1 to 5 illustrate the sewing machine according to the present invention, with Figure 1 being a schematic longitudinal sectional side view of the main parts, and Figure 2 being a partially cutaway longitudinal sectional view showing the upper feed drive mechanism and its surrounding structure. A side view, FIG. 3 is a plan view around the throat plate, FIG. 4 is a sectional view taken along line A--A in FIG. 3, and FIG. 5 is an operation timing table. 1... Upper feed drive mechanism, 3... Sewing needle, 4... Presser foot, 5... Upper feed dog, 5a... Upper feed dog clamping surface, 6... Lower feed dog, 6a... Lower feed dog clamping surface, 7... Throat plate, 39... Needle through hole, 40... Lower thread guide groove, 41... Needle hole, 42... Needle thread guide groove, 45... Lifting means, P... Needle drop point, W... Fabric.

Claims (1)

[Claims] 1. Upper feed dog (5), lower feed dog (6), presser foot (4),
Lifting means (for lifting the presser foot (4) when feeding the fabric
45), and the upper and lower feed dogs (5, 6) are provided with these clamping surfaces (5a, 6).
a) is on the lower side of the needle drop point (P) in the fabric feeding direction.
), and the lift means (45) is configured to maintain the presser foot (4) in the raised position at least until a tightening force is applied to the sewing thread (between time G and time 11). A top and bottom feed lockstitch sewing machine. 2. An upper feed dog (5), a lower feed dog (6) that operates in cooperation with the upper feed dog, and a presser foot (4) that presses the fabric (W) onto the throat plate (7) during stitch formation. The upper and lower feed dogs (5 and 6) are attached to these clamping surfaces (5a and 6).
a) is on the lower side of the needle drop point (P) in the fabric feeding direction.
), and when feeding the fabric using both feed dogs (5, 6), the presser foot (4) is placed so as to hold the fabric (W).
The lift means (45) is equipped with a lift means (45) that switches to a raised position so that the upper feed dog (5) is not pressed substantially. and the lift means (45) is configured to maintain the presser foot (4) in a raised position via the upper feed dog (5) by the upward force of the lower feed dog (6). Feed lockstitch sewing machine. 3. The vertical feed lockstitch sewing machine according to claim 1 or 2, wherein the tension of the upper thread immediately after passing through the thread take-up is set to 30 to 50 g. 4. The needle hole (41) drilled in the presser foot (4) includes an upper thread guide groove (42) that slopes upward from the stitch side toward the sewing needle (3) side, and the needle plate (7) The needle threading hole (39) formed in the lower thread guide groove (4) slopes downward from the seam side to the hook side.
The vertical feed lockstitch sewing machine according to claim 1 or 2, comprising: 0). 5. Upper feed dog (5), lower feed dog (6), presser foot (4) Lift means (4) for lifting the presser foot (4) when feeding the fabric.
Using a top and bottom feed lockstitch sewing machine equipped with 5), the fabric (W) is fed while being held between the two feed dogs (5 and 6) located on the downside in the fabric feeding direction from the needle drop point (P), and the fabric (W) is fed in both feeds. At the same time as the teeth (5, 6) clamp the fabric (W) (
The lift means 45
A method for preventing puckering in a vertical feed lockstitch sewing machine, in which the presser foot 4 is kept in a raised position with the presser foot 4, and the fabric (W) is pressed onto the throat plate 7 with the presser foot 4 during stitch formation.