JP7108169B2 - Stitch stabilization bobbin thread controller - Google Patents

Description

It is a technique related to the structure of the sewing machine and the sewing technique.

The most important factors that affect the quality of sewn products are the balance of the shape formed by the upper and lower threads of the seam and the tension balance of the upper and lower threads. However, the frictional force itself is very unstable, and it is very difficult to stabilize the quality of stitching.

The present invention does not rely entirely on the frictional force to achieve these balances, but rather controls the amount of bobbin thread used in the most important stitches to achieve these balances, thereby stabilizing and improving seam quality. be.

Problems to be solved by the present invention

The most important factor that determines the quality of the sewn product is the balance of the shape formed by the upper and lower threads of the seam and the tension balance of the upper and lower threads.

In a conventional sewing machine, these balances are the frictional force between the opposing discs (thread tension discs) pressed by the spring in the upper thread tensioner and the upper thread, and the 5 lower thread tensions built into the bobbin case or bobbin case. It was taken by the frictional force between the spring and the lower thread. In other words, these frictional forces, the resistance to deformation of the material to be sewn and the upper and lower threads, the frictional forces of the upper and lower threads, the frictional forces of the upper and lower threads, the frictional forces of the upper and lower threads, and the frictional forces of the sewing machine parts with which the upper and lower threads come into contact. maintained by striking a balance between

However, the frictional force itself is very unstable, and it is very difficult to control the frictional force, i.e., the force required to stabilize the quality of sewing. In addition, the spring pressure of the upper thread tension device and the 5 lower thread tension spring is constantly changed in response to changes in the settings of the sewing machine (feed amount of the material to be sewn, sewing speed, etc.), that is, the frictional force generated by both is changed. had to adjust.

Means to solve problems

The present invention does not rely on these frictional forces, but rather controls the amount of the three bobbin threads used in the seam to stabilize and improve the quality of the seams.

A similar idea is to control the thread amount of the needle thread to stabilize and improve the sewing quality, and some are actually installed in actual machines. However, the final role to complete the first stitch is not the needle thread, but the 3rd bobbin thread. Since the needle thread is required, it is necessary to supply and collect the needle thread other than the length of the needle thread that is consumed in the first stitch. Unnecessary needle thread tension is required for sewing, and furthermore, when the first stitch is completed, the formation of the next stitch has already started. ) and it is difficult to cope with changes in the stitch shape, and although it is effective to some extent, the sewing conditions are limited.

Effect of the invention

For this reason, the present invention focuses on the 3 bobbin threads, which have significantly fewer requirements for the upper thread, and controls the thread length of the 3 bobbin threads consumed in the stitch. It stabilizes and improves sewing quality.
That is, the present invention provides a "stitch stabilizing bobbin thread control device" that solves the problems that have been imposed on lockstitch sewing machines for more than 200 years since the history of lockstitch sewing machines.

Detailed description of the invention

First, the seam forming mechanism and the seam forming process are described.

The lockstitch is a stitch in which two upper and lower threads are twisted together, and an object to be joined, that is, several pieces of cloth are sandwiched between the twists of the two threads to join the cloths.
Therefore, since it is a seam that tightens the sutured material between the strands with two threads, the mechanism is similar to that of tying things with a string, basically adjusting and completing the suture strength in a single stitch cycle. Let This suture strength varies depending on the material to be sewn and the characteristics of the seam (length, pattern, etc.), and in principle it is adjusted by the tension of the upper and lower threads. It is not constant, and it is important for the design to apply an appropriate tension (including no tension) to each major phase. In a typical sewing machine, tension fluctuations during a single stitch cycle are controlled by keeping the tension of the bobbin thread constant and changing only the tension of the needle thread.

In addition, in the lockstitching, in order to stably maintain the strength of the seam, the intersection of the upper thread and the bobbin thread is pushed into the middle of the material to be sewn in the thickness direction. This method utilizes the frictional force between the cloth to be sewn and the sewing thread to increase the strength of the seam. By making the lengths of the two threads substantially equal, the tensile force in the sewing direction is efficiently supported by the two threads. The intersection of the needle thread and the bobbin thread is called a "knot point", and the percentage of the position of this knot point from the needle thread side with respect to the thickness of the material to be sewn is called the "stitch crossing ratio". If the stitches need to be beautiful (look straight) when viewed from the needle thread side, this knot point is intentionally shifted to the bobbin thread side. In general, when used for this purpose, it is said that a stitch crossing ratio of 60% has little effect on the stitch strength, and the stitch looks beautiful when viewed from the needle thread side.

Furthermore, there is a seam forming mechanism necessary to stably maintain the seam strength in the lock stitch. Basically, in the process of forming one stitch, the needle thread pulls the bobbin thread up to the top of the material to be sewn, and then , the bobbin thread pulls the knot into the sutured material and stabilizes the stitch. This is because, in a single stitch construction cycle, the upper thread is supplied with a large amount of needle thread compared to the amount of thread required for stitch construction in order to pass through the hook, and the needle thread is long in order to collect the thread. The distance to and from the needle thread, the fact that the needle thread undergoes large changes in tension during a single stitch construction cycle, and the fact that it is also in friction with numerous members other than the sutured material can cause the needle thread to This is because it is effective to entrust the control of the final knot position and seam strength to the bobbin thread, which has much better conditions in terms of these factors.

In this way, what is particularly important in the stitch forming mechanism is that "in order to maintain a constant stitch crossing rate for the stitches that are formed one after another, it is basically necessary to lower the upper thread once in the process of forming one stitch. The thread is pulled up to the top of the sutured material, after which the bobbin thread pulls the knot point into the sutured material to stabilize the seam." The function of this function is the "feed amount of bobbin thread", which appears in the "sewing machine motion diagram" [Fig. can be said to do Therefore, the expression "final stitch tightening amount" may be more appropriate than the expression "hooker thread feeding amount".

Next, the behavior of the needle thread and the bobbin thread in the process of forming a single stitch will be explained using [Fig. 5] "Sewing machine motion diagram".

A motion diagram is defined as the timing and behavior of each mechanism that forms a stitch, and the behavior of the sewing thread while the upper shaft rotates 360°, with the top dead center of the needle bar at 0°. It shows on a single graph whether

In the motion diagram, the top dead center of the needle bar is the starting point of 0°, but in fact, at this phase, the formation of a new stitch has not yet started and the previous stitch has not been completed. The starting point of the actual seam formation is at the top dead center of the balance or slightly past the top dead center of the balance. Also, the completion phase of the previous stitch is the phase in which the "bobbin thread feeding amount" tightens the bobbin thread, and the phase in which the vertical feed amount curve becomes 0, that is, the phase in which the feed dog sinks below the throat plate. It will be somewhere in between.
However, the starting point of the actual stitch formation changes subtly depending on the conditions of the material to be sewn and the feed amount, and compared to other mechanical parts, the phase of the top dead center of the needle bar can be measured more accurately. In order to maintain the accuracy of the phase, the top dead center of the needle bar is set to a reference value of 0°, the sewing material is removed, and as a result, the feed amount is not affected. For this reason, the motion diagram does not stop at 0° to 360°, but measures and displays from 0° to about 500°.

Now, it is undoubtedly the behavior of the sewing threads (top and bobbin threads) during the course of the stitch forming mechanism that constitutes the first stitch that determines the quality of the stitch.

Therefore, first, attention will be paid to the hook needle thread required amount and the take-up needle thread supply amount, which indicate the behavior of the needle thread during the first stitch cycle. The motion curves of other mechanisms mainly show movements for producing these two types of curves.

First, the needle thread amount required is a graph of the needle thread amount required by the sewing machine mechanism at each phase in one cycle from the previous stitch to the next stitch being completed. That is, one end of the measuring thread is fixed near the needle hole of the throat plate, and the movement of the other end passing through the needle thread hole is measured. For this reason, the needle thread consumption due to the feed amount is ignored.
Therefore, although the required amount of thread on the shuttle is named, it also changes depending on the movement of the needle, and the required amount starts to change when the thread eye of the needle passes through the needle eye of the throat plate.
This amount of change has an extreme value at the lowest point of the needle bar, decreases as the needle rises, but increases again after the hook tip of the hook catches the upper thread loop.

Next, the thread take-up thread supply amount represents the amount of change in the thread path length from the previous stitch to the thread tension device via the thread hole of the thread take-up. Therefore, in the same way as for the hook upper thread required amount, one end of the thread to be measured is fixed near the needle hole of the throat plate and the needle thread consumption due to the feed amount is ignored. don't let As a result, the thread take-up thread supply amount changes in the same phase as the take-up vertical amount, and the amount is approximately doubled.

The difference between the thread take-up needle thread supply amount and the required hook thread amount for each phase is the needle thread slack. A thread take-up spring provided between the thread take-up and the upper thread tension device absorbs the slack in the upper thread.

The needle thread required amount decreases after the bottom dead center of the needle bar, and the thread take-up needle thread supply amount continues to increase. This slack becomes a loop through which the blade point of the hook catches the needle thread. The thread take-up spring plays a major role in maintaining this loop at a stable and appropriate size.

However, although the motion diagram describes "thread take-up spring stroke", this is not a numerically correct expression. The thread take-up thread supply amount is 0 to start the stitch forming process for one stitch, but the previous stitch forming process for one stitch is not completed at this point. Therefore, the actual take-up needle thread supply amount is the thread amount obtained by subtracting the thread amount consumed in the previous stitch during the period from the start of the take-up thread supply amount to the completion of the previous stitch. The thread take-up spring moves in the mechanism to absorb the "slack" thread amount, which is the amount of thread minus the required amount of upper thread on the hook, minus the amount of thread necessary to make the upper thread loop. The stroke becomes the true thread take-up spring stroke.

Subsequently, to form a stitch, the "hook" enlarges the captured top thread loop and passes it through the bobbin of the bobbin thread store. The amount of upper thread required for this series of movements is the true "required amount of upper thread for the hook". As you can see from the motion diagram, the "required amount of thread on hook" suddenly decreases when it exceeds the maximum required amount. This is to release the upper thread from the hook tip, so the loop must be made smaller at once. Otherwise, the hook blade point may catch the same loop again and cause a sewing failure. Basically, the "thread take-up spring" performs the first role of reducing the loop released from the blade point of the hook and the role of generating the thread tension for passing through the rotation stop of the inner hook. In other words, the characteristics of the thread take-up spring, which plays the first role of reducing the loop released from the blade point of the hook and the role of generating thread tension for passing through the rotation stop of the inner hook, is the characteristic of the thread take-up spring, which is required for stable stitching. is an important element for the formation of

The problem here is that in this phase, the needle has already risen above the cloth (material to be sewn) and has not penetrated the cloth (material to be sewn). Therefore, when the thread at the bottom of the cloth passes through the cloth, it comes into direct contact with the material to be sewn (cloth) and receives resistance. is not sufficiently pulled up, and the needle thread becomes slack under the sewn material. In order to minimize the time during which this slack occurs, a quick-return mechanism is adopted for the take-up lever to rapidly reduce the "supply amount of upper thread of the take-up". In this phase, the horizontal feed is also started to generate a slight effect of absorbing upper thread slack due to the feed amount.

Next, the tightening and completion of stitches based on the hook bobbin thread payout amount will be described.

The quick-return function of the thread take-up quickly collects the "slack" upper thread while moving the thread take-up top dead center, that is, from the previous stitch to the thread take-up thread hole and the maximum thread path to the tension device. However, the thread length spent for one stitch such as the feed pitch is insufficient compared to the thread length in the maximum thread path at the start of the stitch (top dead center of the thread take-up). This short thread length is pulled out from the upper thread tension device in the process of moving to the top dead center of the thread take-up, and at this time, thread tension is generated in the stitches. As a result, the bobbin thread is pulled up to the top of the material to be sewn and the seam is tightened, as shown in <<Explanatory Diagram of Mechanism of Lockstitch Stitch Formation>>. At this time, the feed dog is located above the throat plate to hold the stitches so that the gap between the previous stitch and the current stitch is not drawn in, and the horizontal feed also acts to stably tighten the stitches. can be read from

The bobbin thread then pulls the knot point into the suture material. This is done by the "hook bobbin thread feeding amount", but in this phase the thread take-up top dead point has passed and the next stitch formation process has started. The tension in the needle thread between the tensioners is reduced and the needle thread is slack, allowing the stitch to be drawn into the material to be sewn relatively easily with constant bobbin thread tension. Therefore, basically, the tension of the sewing thread forming the seams is the pressure of the bobbin thread tension spring against the frictional force between the sewing material and the sewing thread and the bending resistance force for forcibly bending the sewing thread. It is determined by the balance between the thread tension spring and the frictional force between the bobbin thread. Thus, the hook bobbin thread pay-out amount is the key to ultimately determining the stability and quality maintenance of the stitches.

The mechanism for generating the hook thread feeding amount for tightening the bobbin thread for stabilizing the stitches is similar to that shown in FIG. 1. A bobbin thread pay-out lever provided outside the hook is responsible for the bobbin thread pay-out amount of the member corresponding to the 8th stabilizing bobbin thread control member. The member corresponding to the thread guide member A on the thread supply side is the 5 bobbin thread tension spring, and there is no member corresponding to the 4 thread holding and operating member. Furthermore, since the member corresponding to the second thread guide member B is the edge of the needle hole of the throat plate, the distance a between the thread guide members A and B is easily changed, thereby stably feeding the bobbin thread. The current situation is that the amount cannot be maintained.

However, even so, these unstable elements are inherent in the needle thread during the process of forming one stitch compared to the needle thread. Compared to the fact that the amount of thread is much larger than the bobbin thread, the tension applied to the thread changes, and the bobbin thread is entrusted with the final knot position and seam strength management, it can be solved. If the present invention is used as a solution to this problem, it is possible to form high-quality and stable seams.

In the present invention, since the gap a between the 1st supply side thread guide member A and the 2nd sewing side thread guide member is always fixed and maintained at a constant value, the movement of the 8th stitch stabilizing bobbin thread control member is controlled. By doing so, the amount of change b+c−a in the amount of thread between the thread guide members A and B can be accurately obtained, that is, the amount of bobbin thread required for the first stitch can be accurately supplied. This amount of change b+c−a corresponds to the bobbin thread amount spent in the section of FIG. Therefore, when the bobbin thread is supplied from the yarn supply side to the amount of change in the amount of yarn b+c−a between the thread guide members A and B, "(the amount of change in the amount of thread between the thread guide members A and B b+c−a)= (Amount of bobbin thread spent in the section of Fig. 2C)" does not hold true, that is, the knot positions of the top and bottom threads vary, and the stitches are not stabilized, degrading the sewing quality. The holding and operating member operates to fix the 3 bobbin thread and cut off the bobbin thread supply from the bobbin thread supply side.

By the way, as you can see from the above explanation and the motion diagram, the amount of change in the bobbin thread due to the bobbin thread tightening phase (b + c - a) and the conventional "bobbin thread payout amount" are very small. The required amount of bobbin thread cannot be satisfied for the seam of 1, and the bobbin thread is pulled out against the bobbin thread tension given by the bobbin thread tension spring, corresponding to the phase where the bobbin thread is required, and FIG. The amount of bobbin thread used in section C is drawn out when the upper thread is tightened. From such a phenomenon, it seems that conventionally, the idea that it is impossible to stabilize the stitches by controlling the length of the bobbin thread has taken root as a general recognition.

In the scope of claims [Claim 1], there is no 4 thread holding and operating member, and the expression "5 the lower thread tension spring itself serves as a thread holding member" is because the lower thread is tightened by a non-contact method such as magnetic force. This is because the spring pressure of the 5th lower thread tension spring can be increased in phase to play the role of the 4th thread holding and operating member.

1 is an explanatory diagram of a basic form of the present invention; FIG. is an explanatory diagram of the lockstitch stitch formation mechanism, and in the figure, C is "(amount of change in thread amount between thread guide members A and B b + c - a) = (bobbin thread amount spent in the section of Fig. 2 C)" "C section" of is represented by a broken line. 1 is an external view of the present invention mounted on a 9 inner pot (also referred to as an inner pot) as an example of use of the present invention. FIG. In this example, the 1st thread supply side thread path member and the 2nd material side thread path member are integrated with the inner hook 9 and are not a single member. Although not shown in the figure, it is possible to install a slit in the yarn path portion where the yarn does not come in contact with it, or to add a function to prevent the yarn from falling out, so that a slit can be laid from the outside to the yarn path. By providing the slit, it becomes easier to thread the thread through the thread path. [Fig. 3] is a view explaining the present invention using a cross-section or the like of the inner hook of [Fig. 3]. FIG. A is a cross-sectional view of the thread guide viewed from the same direction as FIG. 3. View B is a view from arrow B in A, and view C is a view from arrow C in A. is. is an explanatory diagram of a general "sewing machine motion diagram".

1... thread supply side thread path member, 2... sewing material side thread path member, 3... bobbin thread,
4 Thread holding and operating member 5 Lower thread tension spring 6 Presser
7 (presser) movement amount, 8 stitch stabilizing bobbin thread control member, 9 bobbin hook,
10: Bobbin, 11: Lower thread tension spring base,
a ... the length (gap) of the bobbin thread between the supply side thread path member A and the sewn side thread path member,
b ... the bobbin thread length when the stitch stabilizing bobbin thread control member is activated;
c・・・Length of bobbin thread when stitch stabilizing bobbin thread control member is activated

Claims (2)

A lockstitch sewing machine having one thread supply side thread path member A and two material side thread path members B fixed and arranged at a constant distance a, wherein the one thread supply side thread path member A and the two materials to be sewn are provided. In the tightening phase of the 3 bobbin threads with respect to the 3 bobbin threads passing through the material side thread guide member B, the 4 thread holding operation member movably arranged on the thread supply side of the 1 thread supply side thread guide member A operates. The 4 thread holding and operating member, or the 4 thread holding and operating member via the 5 lower thread tension spring, or the 5 lower thread tension spring itself serves as a thread holding member to fix the movement of the 3 lower thread, and the cloth The thickness of the material to be sewn is detected from the 7 movement amounts of the 6 presser, and the 8th stitch stabilizing bobbin thread control member that moves the calculated movement amount is activated. A stitch stabilizing bobbin thread control device that changes the bobbin thread length between the material side thread guide members B (b+c−a), thereby tightening the three bobbin threads. In the apparatus of [claim 1], the first thread supply side thread path member A and the second sewing material side thread path member B are fixed or built in a member such as a bobbin case or an inner hook 9 that passes through the upper thread loop. The 4 thread holding and operating members, except for the 5 bobbin thread tension spring when acting as a thread holding and operating member, and the 8 stitch stabilizing bobbin thread control member are located outside the needle thread loop and serve their purpose in the 3 bobbin thread tightening phase. Alternatively, one or both of the 4th thread holding/operating member and the 8th stitch stabilizing bobbin thread control member together with 1st thread supply side threadway member A, 2nd material side threadway member B, are connected to the bobbin case or the bobbin case. A second thread holding and operating member that belongs to a member that slips through the upper thread loop and operates a 4-thread holding and operating member outside the needle thread loop and a second stitch that operates an 8-stitch stabilizing bobbin thread control member. 1 Thread supply side thread path member A, 2 Work piece side thread path member B, 4 Thread holding operation member, and 8 Stitches, in which a stable bobbin thread control member is arranged and performs its intended operation in 3 bobbin thread tightening phases. A lockstitch sewing machine having a stitch-stabilizing bobbin thread control member.

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