TWI861152B - Method for preventing seam ravel of chain stitch and seam ravel preventing apparatus for chain stitch - Google Patents

Abstract

Raveling of a seam is prevented by selflooping a needle thread loop with a needle thread in such a manner that a sewing operation of at least one stitch is performed while a needle thread loop caught by a looper is located at an advancing end side of the looper in relation to a lowered position of a needle and a looper thread extending from the looper to a sewing fabric is located in front of the lowered position of the needle after normal double chain snitching ends. Here, a thread hanging hook passes through the needle thread loop and moves to a threading position to catch a rear thread portion of the needle thread loop in accordance with an approaching movement of the thread hanging hook to the needle thread loop and the looper thread while the looper advances, the rear thread portion of the needle thread loop caught by the thread hanging hook is moved leftward to be separated from the vertical movement path of the needle to widen an interval between the front thread portion and the rear thread portion of the needle thread loop in accordance with a separating operation starting when the needle is lowered to a predetermined position, and the needle is lowered into the needle thread loop having a wide interval. Accordingly, since it is possible to accurately and reliably perform a selflooping operation regardless of the type or thread condition of the needle thread and the looper thread, it is possible to provide a method and an apparatus for preventing seam ravel of a chain stitch reliably exhibiting a predetermined seam ravel preventing function.

Description

Method for preventing seam thread and device for preventing seam thread

The present invention relates to a method for preventing stitching and a device for preventing stitching for implementing the method. The method for preventing stitching uses a sewing machine such as a double chain stitch sewing machine or a flat stitch sewing machine to form a stitching of a double chain stitch formed by general sewing by a needle thread and a looper thread, thereby preventing stitching from being generated at the sewing end portion of the double chain stitch sewing after the double chain stitch formed by general sewing is completed.

The double chain stitch sewing machine is equipped with one or more needles that hold the needle thread and rise and fall, and a curved needle that holds the curved needle thread and moves forward and backward in a direction roughly orthogonal to the up and down movement path of the needle. The needle penetrates the sewing fabric on the needle plate and descends, and rises to be pulled out of the sewing fabric. The curved needle moves forward and backward under the needle plate in conjunction with the rise and fall of the needle, and hooks the loop of the needle thread held by the rising needle (needle thread loop) when advancing. The needle penetrates the sewing fabric and descends, hooking the curved needle thread held by the withdrawn curved needle.

The double chain stitch sewing machine repeats the above-mentioned actions to form a double chain stitch seam on the sewn fabric. FIG28 is a top view of the structure of the double needle double chain stitch seam observed from the back side of the sewn fabric. As shown in FIG28, the double chain stitch seam is formed by winding the bent needle thread 10 around the needle thread loops 20a, 20b formed by the needle threads 20, 20 on the back side of the sewn fabric to interconnect. In the conventional double chain stitch structure shown in FIG. 28, when the end of the curved needle thread 10 cut at the end of sewing is pulled in the direction indicated by the arrow in the same figure, the curved needle thread 10 is pulled out from the final needle thread loop 20a, 20b formed by the needle threads 20, 20. The result of this pulling out gradually moving toward the start side of sewing is that there is a problem of the whole seam generating a thread.

This kind of thread sewing also occurs in the double chain stitch seams formed by more than 3 needle threads and curved needle threads, and also occurs in all sewing machines that form double chain stitch seams such as flat stitch sewing machines.

In order to prevent the occurrence of the above-mentioned ripping which is unique to the double chain stitching, various ripping prevention methods and ripping prevention devices for ripping have been proposed previously. One of them is the ripping prevention method and ripping prevention device proposed by the present applicant (e.g., Japanese Patent Gazette No. 5494598). The method and device for preventing thread sewing are used to make the thread loop hooked by the curved needle be located at a position closer to the front end of the curved needle than the descending position of the needle after the double chain stitching of general sewing is completed, and the curved needle thread extending from the curved needle to the sewing fabric is located at a position closer to the front side than the descending position of the needle. Then, the needle is lowered into the thread loop and at least one stitch is sewn. The thread held by the needle makes the thread loop held by the curved needle self-connected, thereby preventing thread sewing of the double chain stitching.

According to the method and device, as long as the needle holding the needle thread can be surely lowered into the needle thread held by the curved needle for self-connection, the thread tangling that is unique to the double chain stitch can be prevented.

However, in the prior art method and device for preventing the wire from twisting proposed by the present applicant, there is still room for improvement in order to effectively prevent the self-tie action of the wire. Furthermore, in the following description of the prior art, each component and element is labeled with the same symbol as the component and element in the embodiment of the present invention described below.

That is, in the case of the prior art, as shown in Fig. 29 (a), (b) and Fig. 30 (a), (b), after normal sewing, when the curved needle 1 is in the advanced state, the hook 3 that moves toward the needle thread loop 20a and the curved needle thread 10 held by the curved needle 1 together with the curved needle thread holder 6 (omitted from the figure) is formed in a manner that its front end portion is pointed, and a hook portion 3b is provided that protrudes inwardly from the inclined curved surface 3f that is bent and inclined toward the right front relative to the moving direction from the pointed front end portion 3e.

When using the prior art of the thread hook 3 of the above-mentioned shape, it is necessary to initially set the moving path of the thread hook 3 to the state shown in Figures 29(a) and (b) or the state shown in Figures 30(a) and (b) before sewing, or adjust the relative position of the thread hook 3 and the curved needle thread retaining body 6 in the following manner: the thread hook 3 moved to the thread hanging position becomes a state of securely hooking the needle thread loop 20a held by the curved needle 1, and when moving away from the thread hanging position, it can securely hook the rear thread portion 20ab of the needle thread loop 20a hooked by the hook portion 3b and move it to the left. In the prior art, not only is it necessary to perform a delicate and complicated adjustment operation of the initial setting or relative position adjustment of the moving path of the thread hook 3, but also when the adjustment operation is inappropriate, for example, as shown in Figures 30 (a) and (b), when the thread hook 3 moved to the thread hanging position is set or adjusted to a moving path that cannot reliably hook the needle thread loop 20a, there is a possibility that the hook portion 3b of the thread hook 3 is mistakenly hooked on the rear thread portion 20ab of the needle thread loop 20a, and the expected thread tangling prevention function cannot be achieved reliably.

For example, when sewing thinner or softer fabrics, this problem may occur easily when the tension applied to the needle thread 20, 20 and the curved needle thread 10 is reduced in order to obtain a good processing state or due to the type of needle thread 20, 20 used.

The present invention is completed in view of the actual situation, and its purpose is to provide a method for preventing seams from becoming tangled and a device for preventing seams from becoming tangled for implementing the method. The method for preventing seams from becoming tangled can accurately and reliably prevent the occurrence of the tangling action that is unique to double chain stitch seams, regardless of the type or condition of the needle thread and the curved needle thread, and can reliably exert the desired tangling prevention function.

In order to achieve the above-mentioned purpose, the method for preventing the thread from being tangled in the seam of the present invention is characterized in that: the thread loop formed by the needle moving up and down while holding the thread is hooked by a curved needle moving in a direction substantially orthogonal to the up and down movement path of the needle, and the thread loop is interconnected by the curved needle thread held by the curved needle, thereby forming a double chain seam formed by ordinary sewing on the sewn fabric on the needle plate, and After the double chain stitch formed by the general sewing is completed, the needle thread loop hooked by the curved needle is located at a position closer to the front end of the curved needle than the descending position of the needle, and the curved needle thread extending from the curved needle to the sewing fabric is located at a position closer to the front side than the descending position of the needle. Thereafter, the needle is lowered into the needle thread loop and at least one stitch is sewn, and the needle thread held by the needle is used to sew the fabric. The needle thread loop held by the above-mentioned curved needle is made to self-connect, thereby preventing the stitching of the above-mentioned double chain stitch. The method is to make the curved needle thread holding body and the hook move toward the above-mentioned needle thread loop and the curved needle thread when the above-mentioned curved needle is in an advanced state. Accompanied by the approaching movement, the above-mentioned curved needle thread holding body captures the curved needle thread, so that the captured curved needle thread is located at a position further forward than the descending position of the above-mentioned needle, and the above-mentioned hook is attached to the above-mentioned needle thread. The hook passes through the loop and moves to the thread-hanging position, and becomes hooked on the back thread of the needle thread loop. When the needle drops to a predetermined position, the back thread of the needle thread loop hooked by the thread-hanging hook moves to the left to leave the up-and-down movement path of the needle, thereby expanding the gap between the front thread and the back thread of the needle thread loop, and the needle drops into the loop with the expanded gap to perform the self-connection.

Furthermore, the thread-binding prevention device of the present invention is characterized in that: the sewing machine is equipped with a needle thread holding mechanism, a bent needle thread holding mechanism and a control unit, the sewing machine is provided with a needle that holds the needle thread and moves up and down, and a bent needle that holds the bent needle thread and moves forward and backward in a direction substantially orthogonal to the up and down movement path of the needle, and the needle thread loop formed by the needle below the needle plate is hooked by the forward movement of the bent needle, and the needle thread loops are interconnected by the bent needle thread held by the bent needle to form a double chain stitch seam on the sewn fabric on the needle plate; the needle thread holding mechanism has a hook disposed under the needle plate and swinging in a plane substantially parallel to the needle plate, and approaches and moves relative to the bent needle. The needle thread holding mechanism has a needle thread holding body that moves together with the hook, and performs approaching and retreating movements relative to the needle, and holds the needle thread extending from the needle to the sewing fabric at a position more forward than the needle's descending position; the control unit controls the needle thread holding mechanism and the approaching and retreating movements of the needle thread holding mechanism in association with the movements of the needle and the needle, and the conveying movement of the fabric; and the control unit controls the needle thread holding mechanism after the formation of the double chain stitch formed by the general sewing is completed. The mechanism and the curved needle thread holding mechanism perform an approaching action so that the needle thread loop is located at a position closer to the front side of the curved needle than the lowered position of the needle, and the curved needle thread extending from the curved needle to the sewing fabric is located at a position closer to the front side than the lowered position of the needle. Thereafter, the needle is lowered into the needle thread loop and at least one stitch is sewn, and the needle thread held by the needle is used to make the needle thread loop held by the curved needle self-connected, thereby preventing the stitching of the double chain stitch; and the control unit performs a control action in the following manner: in the advanced state of the curved needle, the curved needle thread holding body in the curved needle thread holding mechanism and the thread hook in the needle thread holding mechanism are directed upward. The needle thread loop and the curved needle thread move close to each other, and along with the close movement, the curved needle thread holding body captures the curved needle thread, so that the captured curved needle thread is located at a position further forward than the descending position of the needle, and the hanging thread hook passes through the needle thread loop and moves to the hanging thread position, and becomes a state of hooking the rear thread portion of the needle thread loop, and along with the descending position of the needle When the needle thread holder and the hook start to move away from each other at the predetermined position, the back thread of the needle thread loop hooked by the hook moves to the left to leave the up-and-down movement path of the needle, thereby expanding the gap between the front thread and the back thread of the needle thread loop, and the needle is lowered into the needle thread loop with the expanded gap to perform the self-connection.

In the method and device for preventing stitching of seams of the present invention, after the bent needle is advanced to complete the normal sewing, the needle thread loop hooked by the bent needle is located at a position closer to the forward end of the bent needle than the descending position of the needle, and the bent needle thread extending from the bent needle to the sewing fabric is located at a position closer to the front side than the descending position of the needle by the bent needle thread retaining body, and the hanging The hook hooks the rear thread of the needle and thread loop, causing the hooked rear thread of the needle and thread loop to move to the left to leave the up-and-down movement path of the needle. In this state, the needle is lowered into the needle and thread loop, and the needle and thread held by the lowered needle are used to self-connect the needle and thread loop. The self-connecting part can be used to press the curved needle thread to prevent the curved needle thread from being derailed, thereby reliably preventing the stitching of the seam at the stage of occurrence. The self-connection of the needle and thread can press the curved needle thread well even when the tension applied to the needle and thread is relatively small, thereby preventing the stitching from occurring.

In particular, when the thread-twisting prevention action of sewing is performed by self-connection as described above, the thread hook passes through the needle and thread loop and moves to the thread-twisting position to hook the rear thread portion of the needle and thread loop. Therefore, even if the moving path of the thread hook is initially set or its position is adjusted relative to the curved needle thread retaining body, there is no need for subtle and complicated adjustments as described in the prior art. Only by performing an extremely simple and easy initial setting or position adjustment so that the pointed front end of the thread hook can pass through the needle and thread loop, the thread hook can accurately and surely capture and hook the rear thread portion of the needle and thread loop during the thread-twisting prevention action. This has the following effects: Regardless of the type of needle and thread or the thread condition, the distance between the front thread part and the rear thread part of the needle and thread loop can be expanded reliably and stably to make the needle descend to the needle and thread loop with a larger distance to achieve the desired thread tangling prevention.

In the method and device for preventing stitching of seams of the present invention, it is preferred that the stitch thread holder and the thread hook move closer together, and the stitch thread holder that captures the stitch thread pushes the front thread portion of the needle thread loop to move to the right through the captured stitch thread so that the needle thread leaves the up-and-down movement path of the needle, and is constructed in this manner.

In this case, the curved needle thread holder can be moved to catch the curved needle thread and position the caught curved needle thread at a position further forward than the lowered position of the needle, so that the front thread portion of the needle thread loop can be pushed to the right away from the up-and-down movement path of the needle. By this pushing movement, the distance between the front thread portion and the rear thread portion of the needle thread loop can be further expanded, and the self-connecting action of lowering the needle into the needle thread loop can be performed more reliably.

Furthermore, in the method and device for preventing stitching of stitches of the present invention, it is preferred that a plurality of the needles are arranged in parallel in the forward direction of the bent needle, so that at least one of the plurality of thread loops formed by each needle including the thread loop located at the forward end side of the bent needle is located at a position closer to the forward end side of the bent needle than the descending position of the needle and performs a predetermined self-connection.

In this case, even when there are multiple thread loops, only the thread loop at least on the leading end of the curved needle is positioned in the above manner, so that self-connection can be surely implemented and the thread of the seam can be more surely prevented.

Furthermore, in the method and device for preventing stitching of stitches of the present invention, it is preferred that when the thread hook hooks the rear thread portion of the needle and thread loop, the front end of the needle is located within the range from the lower surface of the needle plate to the lower surface of the bent needle.

In this case, the hook hooks the rear thread of the needle thread loop. When the hooked rear thread of the needle thread loop is moved to the left to leave the up-and-down movement path of the needle, the needle thread loop is securely hooked relative to the curved needle, and the needle thread loop does not move as a whole in the direction of the curved needle's entry (left). As a result, the needle passes through and descends into the needle thread loop securely and smoothly, and self-connection can be implemented securely, thereby securely preventing the thread from being tangled during the seam.

Furthermore, in the method and device for preventing stitching of seams of the present invention, it is preferred to stop the conveying of the sewing fabric or make the conveying distance of the sewing fabric smaller than that of normal sewing and implement the sewing action of at least one self-connected needle.

In this case, the density of the self-connected part formed by the needle thread can be increased, thereby strengthening the pressing of the curved needle thread and making the expected thread-binding prevention effect more certain.

Furthermore, in the method and device for preventing seam threading of the present invention, it is preferred to stop the conveying of the sewing fabric from the stage before the sewing action of the at least one needle, or convey the sewing fabric at a conveying distance smaller than that during normal sewing.

In this case, the density of the self-connected part formed by the needle thread including other parts, that is, the interconnected part, becomes higher, and the pressing of the curved needle thread is further strengthened, which can further ensure the expected anti-threading effect.

Furthermore, in the method for preventing stitching of the present invention, it is preferable to make the above-mentioned curved needle thread be located at a position further forward than the descending position of the above-mentioned needle, and then suppress the delivery of the curved needle thread to the above-mentioned curved needle.

In this case, by suppressing the feeding of the bent needle thread to the bent needle, the position of the bent needle thread can be reliably maintained, and the self-joining can be reliably implemented without being affected by the existence of the bent needle thread, thereby reliably maintaining the expected thread-snapping prevention effect, and the tightening of the bent needle thread is strengthened, and the bent needle thread itself can be prevented from being derailed, thereby seeking to improve the quality of the seam.

Furthermore, in the thread-binding prevention device of the present invention, it is preferred that the thread holding mechanism comprises: a thread hook and a stop rod, which are arranged under the needle plate and swing in a plane substantially parallel to the needle plate; a hook actuator, which swings the thread hook from a standby position away from the bent needle to a thread-hanging position close to the bent needle; and a stop actuator, which swings the stop rod. The hook is swung from a retreat position away from the swinging area of the hook to a limited position abutting against a part of the hook; and the control unit selectively controls the hook actuator and the stop actuator to hold the needle thread loop hooked by the hook at the hook position at a holding position between the hook position and the standby position by abutting against the stop rod.

By constructing in the above manner, the needle and thread can be positioned in a simple structure that can be arranged in a limited space under the needle plate. In addition, the thread hook and the stopper can be swung between the standby position and the thread hanging position and the two positions of the retreat position and the limited position, respectively, thereby simplifying the structure of each actuator and the control unit that controls them, and the thread-binding prevention effect of the seam can be achieved with a simple structure.

Furthermore, in the thread-binding prevention device of the present invention, it is preferred that the thread holding mechanism comprises: a thread hook, which is arranged below the needle plate and swings in a plane substantially parallel to the needle plate; a swing rod and a stop rod, which are arranged at a position farther from the needle plate than the thread hook and swing in a plane substantially parallel to the needle plate; a connecting rod, which connects the thread hook to the swing rod; a hook actuator, which acts on the thread hook via the connecting rod to make the thread hook move away from the needle plate; The standby position of the bending needle swings to a thread-hanging position close to the bending needle; and the stop actuator swings the stop rod from the engagement position in which the stop rod is engaged with a part of the swing rod to a retreat position away from the engagement position; and the control unit selectively controls the hook actuator and the stop actuator, and the needle thread loop hooked by the thread-hanging hook at the thread-hanging position is held at a holding position between the thread-hanging position and the standby position by the engagement of the stop rod and the swing rod.

By constructing in the above manner, the needle and thread can be positioned in a simple structure that can be arranged in a limited space under the needle plate. In addition, the swing lever and the stop lever are arranged at a position far away from the needle plate, and the thread hook can be arranged near the needle plate. Therefore, it can be applied to sewing machines with limited space under the needle plate, such as sewing machines with cylindrical machine bases.

Furthermore, in the sewing thread prevention device of the present invention, it is preferred that the bend needle thread holding body of the bend needle thread holding mechanism is installed on the above-mentioned thread hanging hook, and is constructed in a manner of moving between the above-mentioned thread hanging position, the holding position and the standby position together with the thread hanging hook, and the bend needle thread holding body hooks the bend needle thread extending from the above-mentioned bend needle toward the above-mentioned sewing fabric during the movement from the above-mentioned standby position to the above-mentioned thread hanging position, and in the above-mentioned holding position, the bend needle thread holding body is moved to the front side of the lowering position of the above-mentioned needle. The above-mentioned needle thread holding mechanism for holding the hooked needle thread in position has a needle thread holding body installed on the above-mentioned hooking hook and moving between the above-mentioned hooking position, holding position and standby position together with the hooking hook. The needle thread holding body hooks the needle thread extending from the above-mentioned needle to the above-mentioned sewing fabric during the movement from the above-mentioned standby position to the above-mentioned hooking position, and holds the hooked needle thread at a position more forward than the descending position of the above-mentioned needle in the above-mentioned holding position.

In this case, the needle thread holder installed on the hook and moving together with the hook hook hooks the needle thread and holds its position, so that the needle thread can be positioned together with the needle thread with a simple structure.

Furthermore, in the seam tangle prevention device of the present invention, it is preferred that the above-mentioned curved needle thread retaining body is installed in a manner that the position thereof can be adjusted relative to the above-mentioned thread hook.

In this case, by adjusting the position of the curved needle thread holder relative to the thread hook, the relative positions of the needle thread and the curved needle thread can be appropriately set, so that self-connection can be performed reliably to ensure the prevention of thread tangling in the seam.

1: Curved needle

2: Needle

3: Hanging hook

3a: Arm

3b: Hook

3c: Class

3d: Stopper

3e: Front end

3f: Slope

3g: Support arm

4: Stop rod

4a: Front end of the stopper rod

4b: Class

5: Tangent mechanism

6: Curved needle thread retainer

6a: Wire receiving part

8: Control Department

9: Swinging rod

10: Curved needle thread

11: Needle plate

20: Needlework

20a: Needle loop (last loop on the right)

20b: Needle loop (last loop on the left)

20c: left needle and thread loop

20d: left needle and thread loop

20af: Frontline Department

20ab: Backline

21: Pedal switch

21a: Step into the signal

21b: Reverse pedal signal

22: Needle position signal

23: Cutting signal

24: Needle and thread removal signal

30: Axis

31: Connecting rod

32: Wire-operated solenoid (hook actuator)

33: Swing arm

34: Axis

35: Connecting rod

40: Axis

41: Connecting rod

42: Stop solenoid (stop actuator)

43: Swing arm

44: Axis

45: Pressure plate

46: fitting recess

47: Stop cylinder (stop actuator)

48: Output rod

49: Air pipe

50: Tangent hook

51: Thread cutter

52: Hook 1

53: Second hook

54: Base

55a,55b: Support arm

55c: Stop screw

55d: coil spring

56: Slide

57: Tangent rod

57a: Axis

58: Tangent actuator

59: Leaf spring

60: Tangent hook

80: Sewing machine motor

81: Cloth pressing cylinder

82: Pneumatic thread blower

83: Fabric feed reduction mechanism

84: Bend needle thread suppression mechanism

90: Axis

91: Pressure plate

92: Wire-operated cylinder (hook actuator)

93: Output rod

94: Air pipe

95: Spring fixing rod

96:Reset spring

97: Spring fixing rod

98:Reset spring

A: Needle drop position

M: Double chain seam

P: Needle plate

[Figure 1] is a top view schematically showing the main components of the seam thread prevention device of the first embodiment.

[Figure 2] is a top view schematically showing the main components of the seam thread prevention device of the same first embodiment.

[Figure 3] is a top view schematically showing the main components of the seam thread prevention device of the same first embodiment.

[Figure 4] is a block diagram of a control system of a sewing machine having the same seam thread prevention device as the first embodiment.

[Figure 5] is a timing diagram showing the operation contents of the control unit.

[Figure 6] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 7] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 8] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 9] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 10] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 11] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 12] is a diagram illustrating the operation of the seam thread prevention device.

[Figure 13] is a three-dimensional diagram showing the detailed operation status of the thread hook and the curved needle thread retaining body.

[Figure 14] is a three-dimensional diagram showing the detailed operation status of the thread hook and the curved needle thread retaining body.

[Figure 15] is a three-dimensional diagram showing the detailed operation status of the thread hook and the curved needle thread retaining body.

[Figure 16] is a three-dimensional diagram showing the detailed operation status of the thread hook and the curved needle thread retaining body.

[Figure 17] (a) is a top view of the main part showing the state of the needle thread passing through the loop of the hook, and (b) is a longitudinal cross-sectional view.

[Figure 18] (a) is a top view of the main part showing the state of the thread before the thread hook hooks the needle thread loop, and (b) is a longitudinal cross-sectional view.

[Figure 19] (a) is a top view of the main part showing the state where the hook hooks the front thread of the needle thread loop and moves, and (b) is a longitudinal cross-sectional view.

[Figure 20] is a top view schematically showing the main components of the seam thread prevention device of the second embodiment.

[Figure 21] is a bottom view schematically showing the main components of the seam thread prevention device of the same second embodiment.

[Figure 22] is an explanatory diagram of the operation of the seam thread prevention device of the same second embodiment.

[Figure 23] is an operation diagram of the same second embodiment of the seam thread prevention device.

[Figure 24] is a diagram showing the double chain seam structure obtained by the present invention when viewed from the back of a self-sewn fabric.

[Figure 25] is an illustration of the anti-threading effect of the seam structure shown in Figure 21.

[Figure 26] is a timing diagram showing other implementation forms of the control unit's action content.

[Figure 27] is a diagram showing the seam structure of double-needle double-chain stitch obtained by the action in Figure 26, observed from the back of the self-sewn fabric.

[Figure 28] is a diagram showing the normal seam at the end of sewing and the seam structure at the end of sewing obtained by using a known thread-binding prevention device when viewed from the back of a sewn fabric.

[Figure 29] (a) is an enlarged top view of the main part for explaining a setting and position adjustment example of a moving path of the hanging hook to the hanging position in the prior art, and (b) is a longitudinal left side view.

[Figure 30] (a) is an enlarged top view of the main part for explaining another setting of the moving path of the hanging hook to the hanging position and an example of position adjustment in the prior art, and (b) is a longitudinal left side view.

The following is a detailed description of the embodiments of the present invention based on the drawings. Figures 1 to 3 roughly show the top view of the structure of the seam thread prevention device of the first embodiment. The device shown in Figures 1 to 3 is installed on a sewing machine that forms a double chain seam seam, such as a double chain seam sewing machine and a flat seam sewing machine. In the following description, "left, right" and "front, back" indicated by arrows are used in Figure 1. Here, "front" is the side close to the sewing operator, "back" is the side far from the sewing operator, and "left, right" is the "left, right" when viewed from the front.

The sewing machine has a looper 1 and two needles 2, 2 (see Figures 6 to 12). Needles 2, 2 rise and fall by the action of the needle base drive mechanism. A, A in Figures 1 to 3 indicate the descending position (needle drop position) of needles 2, 2. Needle drop positions A, A are spaced apart in the left and right directions and are set approximately in the center of the needle plate P.

The curved needle 1 shown in the figure moves forward and backward (leftward and rightward) along the arrangement direction of needles 2, 2 (needle drop positions A, A) by the action of the curved needle driving mechanism. In Figure 1, the curved needle 1 in the leftward position is represented by a solid line, and the curved needle 1 in the rightward position is represented by a dotted line. The front end of the curved needle 1 in the leftward position extends to the left beyond the needle drop positions A, A of needles 2, 2, and the front end of the curved needle 1 in the rightward position is separated and positioned to the right of the needle drop positions A, A of needles 2, 2. Furthermore, the direction of the forward and backward movement of the curved needle 1 can be roughly orthogonal to the up and down movement path of the needle 2, and the structure of the present invention shown below can be realized regardless of the direction of the movement of the curved needle 1.

The sewing machine sews the sewing fabric on the needle plate P (not shown) by the rising and falling movements of needles 2, 2 and the leftward and rightward movements of the bent needle 1. The sewing fabric is transported and moved backward (in the direction indicated by the hollow arrow in Figure 1) on the needle plate P by the movement of the cloth push mechanism installed inside the sewing machine base. The cloth push mechanism has a cloth push tooth. The cloth push tooth repeats the following movements: protruding from the needle plate P and moving backward, sinking under the needle plate P and moving back and forth. The moving force is applied to the sewing fabric only when the cloth push tooth protrudes from the needle plate P, and it is transported and moved intermittently in the backward direction.

The needle base drive mechanism, the bent needle drive mechanism and the cloth pushing mechanism are known mechanisms that operate synchronously with each other through the transmission from the main shaft of the sewing machine. The needles 2, 2 hold the needle threads 20, 20 (see Figures 6 to 12) respectively, and pass through the sewing fabric during the stop of the transmission movement. After reaching the bottom of the needle plate P, they rise and are pulled out above the sewing fabric. The bent needle 1 holds the bent needle thread 10 (see Figures 6 to 12), and moves to the left when the needles 2, 2 start to rise, hooking the loops 20a, 20b of the needle threads 20, 20 formed under the needle plate P. After the needles 2, 2 are pulled out, the sewing fabric is conveyed and moved. Needles 2, 2 penetrate the sewing fabric that has finished conveying and moving and descend, hooking the curved needle thread 10 held by the curved needle 1 in the right retreat. The sewing machine repeats the above actions and performs general sewing to form a double chain seam on the sewing fabric.

As described above, the sewing machine has a thread tangling prevention device having a needle thread holding mechanism and a curved needle thread holding mechanism, wherein the needle thread holding mechanism has a thread hook 3 and a stopper rod 4, a thread operating solenoid 32 as a hook actuator, and a stopper solenoid 42 as a stopper actuator, and the curved needle thread holding mechanism has a curved needle thread holding body 6 described below. The thread hook 3 of the needle thread holding mechanism is supported by the upper part of the sewing machine base on the rear side of the needle plate P in a manner that allows it to swing around the spindle 30 in the up-and-down direction. The stopper rod 4 is supported in a manner that allows it to swing around the spindle 40 in the up-and-down direction disposed behind the spindle 30.

The hook 3 has an arc-shaped curved shape and is connected to the end of an arm 3a extending backward from the central axis 30 in a manner of folding back to the left front. The front end 3e of the hook 3 faces the needle drop position A, A of the needles 2, 2 from the left rear, and the front end 3e is formed in a pointed manner, and is provided with a hook portion 3b that protrudes backward from an inclined surface 3f inclined relative to the moving direction. The base of the hook 3 (the portion connected to the arm 3a) is connected to the line operating solenoid 32 via a connecting rod 31. The wire-operated solenoid 32 is a rotary solenoid configured to obtain a rotation output of a predetermined angle by supplying an excitation current. The wire-operated solenoid 32 is fixed at the right rear position of the hook 3 with the output end facing upward. A swing arm 33 is fixed to the output end of the wire-operated solenoid 32, and a connecting rod 31 connects the middle portion of the hook 3 to the front end of the swing arm 33.

FIG1 shows the demagnetized state of the wire-operated solenoid 32, and FIG2 shows the excited state of the wire-operated solenoid 32. When the wire-operated solenoid 32 is in the demagnetized state, the swing arm 33 is located at the swing position shown in FIG1. When the wire-operated solenoid 32 is excited, the swing arm 33 swings clockwise as shown by the arrow in FIG1, and becomes the swing position shown in FIG2. The swing of the swing arm 33 is transmitted to the hook 3 via the connecting rod 31. The hook 3 swings counterclockwise around the spindle 30 as shown by the arrow in FIG1, and the hook portion 3b at the front end of the hook 3 is located between the left and right needle drop positions A and A as shown in FIG2. Thus, the hook 3 swings from the standby position shown in FIG. 1 to the hook position shown in FIG. 2 according to the excitation of the wire operating solenoid 32.

The stopper rod 4 has an arcuate shape, the middle part of which is supported by the spindle 40 and is concave and curved in the front. The base of the stopper rod 4 extending to the right front is connected to the stopper solenoid 42 via a connecting rod 41. The stopper solenoid 42 is a rotary solenoid similar to the wire-operated solenoid 32, and is fixed in a separated position on the right side of the stopper rod 4 with the output end facing upward. A swing arm 43 is fixed to the output end of the stopper solenoid 42, and the connecting rod 41 connects the base of the stopper rod 4 to the front end of the swing arm 43.

FIG1 shows the demagnetized state of the stop solenoid 42. When the stop solenoid 42 is in the demagnetized state, the swing arm 43 is located at the swing position of FIG1. When the stop solenoid 42 is excited, the swing arm 43 swings clockwise as shown by the arrow in FIG1. The swing of the swing arm 43 is transmitted to the stop rod 4 via the connecting rod 41. The stop rod 4 swings clockwise around the spindle 40 as shown by the arrow in FIG1.

When the stop solenoid 42 is in a demagnetized state, the front end portion 4a extending to the left front of the stop rod 4 overlaps a portion of the hook 3 in the standby position as shown in FIG1. The hook 3 has a step 3c arranged in a manner of raising the front side at the rear position of the overlapping portion of the stop rod 4. The front end portion 4a of the stop rod 4 can overlap the lower position of the hook 3 at the position before the step 3c. In addition, the stop rod 4 has a step 4b between the spindle 40 and the base. The step 4b is arranged in a manner of raising the rear side, as shown in FIG1, and can cross at the lower position of the connecting rod 31.

When the hook 3 swings to the hook position, the stop solenoid 42 is in a demagnetized state. The stop rod 4 is pressed by the hook 3 and swings clockwise, thereby swinging the hook 3. After the hook 3 passes, the stop rod 4 becomes the position (limited position) indicated by the solid line in FIG. 2. Furthermore, when the hook 3 swings to the hook position, the stop solenoid 42 can be excited together with the wire operating solenoid 32, so that the stop rod 4 moves to the position (retracted position) indicated by the two-point lock line in FIG. 1. In this case, the hook 3 can be swung without interfering with the stop rod 4. After the swing of the hook 3 is completed, the stopper rod 4 is demagnetized to a limited position by demagnetizing the stopper solenoid 42. The front end 4a of the stopper rod 4 at the limited position is opposite to the rear side of the stopper 3d protruding outward in the middle of the hook 3. The stopper 3d of the hook 3 is arranged at the rear side of the step 3c and is at a height position roughly the same as the front end 4a of the stopper rod 4.

When the thread operating solenoid 32 is demagnetized in the state shown in FIG. 2 , the swing arm 33 swings counterclockwise as shown by the arrow in FIG. 2 , and the thread hook 3 swings clockwise. The swing is limited by the stopper 3d of the thread hook 3 abutting against the front end 4a of the stopper rod 4, and the thread hook 3 stops at the holding position shown in FIG. 3 . At this time, the hook portion 3b protruding backward at the front end of the thread hook 3 moves from the thread hanging position shown in FIG. 2 (between the left and right needle drop positions A and A) to the holding position shown in FIG. 3 (left rear of the left needle drop position A), and as described in detail below, the rear thread portion 20ab of the needle thread loop 20a of the left needle 2 is hung and maintained in the position shown in FIG. 3 .

When the stop solenoid 42 is excited in the state shown in FIG. 3 , the swing arm 43 swings clockwise as shown by the arrow in FIG. 3 . By this swinging, the stop rod 4 swings clockwise, and the front end portion 4a of the stop rod 4 deviates from the stop portion 3d of the hook 3 as shown in the two-point lock in FIG. 3 , and the restriction of the hook 3 by the stop rod 4 is released, thereby returning to the standby position shown in FIG. 1 . The stop rod 4 returns to the position shown in FIG. 1 by demagnetizing the stop solenoid 42. The above-mentioned general sewing performed by the sewing machine is performed in the state shown in FIG. 1 . The stop solenoid 42 is equivalent to a stop actuator. As described above, the hook 3 is swung and moved between the above-mentioned standby position, hook position and holding position by selectively energizing the line operating solenoid 32 and the stop solenoid 42.

A bend thread retaining body 6 as a bend thread retaining mechanism is integrally mounted on the thread hook 3. The bend thread retaining body 6 has the same arc-shaped curved shape as the thread hook 3, and is fixed to the upper surface of the middle portion of the thread hook 3 by two fixing screws 60, 60 passing through the length direction of the base. The front end of the bend thread retaining body 6 extends forward along the left side of the thread hook 3, and faces the needle drop position A, A at the front position of the front end of the thread hook 3, and a bifurcated thread receiving portion 6a is provided at the front end. Furthermore, the position of the bend thread retaining body 6 relative to the thread hook 3 can be adjusted by loosening the fixing screws 60, 60. This position adjustment is implemented so that the needle thread 10 can be securely held by the thread receiving portion 6a at the front end.

The bend thread holding body 6 of the bend thread holding mechanism installed in the above manner swings and moves with the thread hook 3 between the above-mentioned standby position, thread hanging position and holding position by the movement of the thread operating solenoid 32 and the stop solenoid 42. The thread receiving part 6a at the front end of the bend thread holding body 6 passes through the upper part of the bend needle 1 at the thread hanging position shown in Figure 2 and moves forward to the front side of the bend needle 1, and is located in front of the needle drop position A on the left side at the holding position shown in Figure 3.

The sewing machine further has a thread cutting mechanism 5. The thread cutting mechanism 5 has a thread cutting hook 50 and a thread cutting knife 51. The thread cutting hook 50 and the thread cutting knife 51 are mounted on a common base 54. The base 54 is supported by connecting the right end and the middle part to the front end of the support arms 55a and 55b. The support arms 55a and 55b can swing around the vertical axis of each rear end. The swing range of the right support arm 55a is limited by the stop screw 55c provided in the middle part. The left support arm 55b is pulled to the left by the coil spring 55d.

The thread cutter 51 is a plate-shaped member fixed to the left end of the base 54, and has a blade at the end edge extending to the left. The thread cutter hook 50 has a first hook 52 and a second hook 53 protruding backward at the front end clamped between the base 54 and the thread cutter 51. The first and second hooks 52, 53 are located at positions separated by a predetermined length in the left-right direction. FIG1 shows the first and second hooks 52, 53 overlapping the position below the thread cutter 51 with dotted lines.

The thread cutter hook 50 has an extension extending to the right from the overlapping portion with the thread cutter 51, and the extension is connected to one end (front end) of the thread cutter lever 57 via a slide 56 that slides in the left and right direction with the base 54 as a guide. The thread cutter lever 57 is supported in the middle of the front and back direction by the spindle 57a in the up and down direction, and can be swung around the spindle 57a. The thread cutter lever 57 is usually in the swing position shown in Figures 1 to 3 with the support arm 55a as the stop part due to the spring force of the return spring (omitted from the figure), and is swung clockwise by the action of the thread cutter actuator 58 (refer to Figure 4) connected to the other end (rear end).

The thread cutter 50 and the thread cutter 51 are in the standby position shown in Figures 1 to 3 during normal sewing. The standby position can be obtained by keeping the thread cutter actuator 58 (see Figure 4) stationary and the thread cutter lever 57 in the swing position shown in Figures 1 to 3. The thread cutter 50 and the thread cutter 51 move to the right rear together with the base 54 by the action of the support arm 55a swinging to the right together with the thread cutter lever 57, and are positioned to a position away from the forward and backward movement path of the bending needle 1. In addition, the thread cutter 50 moves to the right together with the slider 56 connected to the thread cutter lever 57, as shown in Figures 1 to 3, to a state where a part of the front end protrudes from the blade of the thread cutter 51.

The thread trimmer lever 57 is swung by the action of the thread trimmer actuator 58. By this swing, the pressing of the right support arm 55a is released, and as a result, the thread trimmer hook 50 and the thread trimmer knife 51 move forward to the left together with the base 54 according to the swing of the left support arm 55b caused by the spring 55d, and are located above the forward and backward movement path of the needle 1. The thread trimmer hook 50 moves leftward together with the slider 56 by the further swing of the thread trimmer lever 57, and the first and second hook parts 52 and 53 of the thread trimmer hook 50 protrude to the left of the thread trimmer knife 51.

The thread trimmer lever 57 is in a non-actuated state by the thread trimmer actuator 58 and swings counterclockwise due to the thrust of the return spring. As a result, the thread trimmer hook 50 moves rightward and overlaps the lower part of the thread trimmer knife 51. In addition, the thread trimmer hook 50 and the thread trimmer lever 57 move backward together with the base 54 and return to the standby position shown in Figures 1 to 3.

FIG4 is a block diagram of the control system of a sewing machine having a sewing thread prevention device constructed in the above manner. The control unit 8 of the sewing machine inputs the stepping signal 21a and the stepping back signal 21b issued by the pedal switch 21, the needle position signal 22 issued when the needle 2, 2 is near the upper dead center, and the thread cutting signal 23 and the needle thread removal signal 24 issued in the manner described below.

On the other hand, the output of the control unit 8 is respectively given to the thread operating solenoid 32, the stop solenoid 42 and the thread cutting actuator 58 described above. The thread hook 3 and the hook thread holder 6 move in the manner described above according to the action instructions given by the control unit 8 to the thread operating solenoid 32 and the stop solenoid 42, and the thread cutting hook 50 moves forward and backward in the manner described above according to the action instructions given by the control unit 8 to the thread cutting actuator 58.

Furthermore, the output of the control unit 8 is respectively given to the sewing machine motor 80 serving as the driving source of the sewing machine main shaft, the cloth pressing cylinder 81 for raising and lowering the cloth pressing foot, the pneumatic thread blower 82 for making the cut needle threads 20, 20 fly in the manner described below, the feed reduction mechanism 83 for adjusting the feed amount of the sewn fabric, and the bend needle thread suppression mechanism 84 for suppressing the delivery of the bend needle thread 10 to the bend needle 1. The sewing machine motor 80 is driven or stopped according to the action command from the control unit 8, and the cloth pressing cylinder 81, the pneumatic thread blower 82, the cloth feed reduction mechanism 83 and the needle thread suppression mechanism 84 operate according to the action command from the control unit 8.

The feed reduction mechanism 83 is a well-known mechanism that reduces the amount of sewing fabric delivered by changing the action pattern of the feed teeth of the feed mechanism. The feed reduction mechanism 83 operates, for example, in such a way that the action path of the feed teeth is tilted relative to the needle plate P and the protrusion time on the needle plate P is shortened. As a result, the time that the feed teeth act on the sewing fabric on the needle plate P is shortened, and the delivery distance of the sewing fabric, that is, the amount of sewing fabric delivered between one action of the feed mechanism, is reduced.

The above-mentioned needle thread suppression mechanism 84 is a well-known mechanism, which has a clamping plate for clamping the middle part of the needle thread 10 fed into the needle 1, and an actuator that operates in a manner of increasing or decreasing the clamping strength of the clamping plate. The needle thread suppression mechanism 84 suppresses the delivery of the needle thread 10 by increasing the clamping strength of the clamping plate and increasing the resistance given to the needle thread 10.

The control unit 8 operates the thread hook 3 and the needle thread retaining body 6 in conjunction with the sewing machine motor 80, the cloth pressing cylinder 81, the pneumatic thread blower 82, the cloth feed reduction mechanism 83 and the needle thread suppression mechanism 84 at the end of sewing, thereby performing the thread tangling prevention action.

FIG5 is a timing diagram showing the content of the action of the control unit 8 for preventing thread tangling. The control unit 8 is a computer equipped with a CPU, ROM and RAM. The thread tangling prevention action according to the timing diagram of FIG5 is executed by a series of actions of the CPU according to the control program stored in the ROM. FIG6 to FIG12 are action explanation diagrams of the device of the present invention, showing the action states of the thread hook 3 and the bend needle thread holder 6, and the action state of the thread cutting hook 50 generated during the action of the control unit 8 according to the timing diagram of FIG5.

When a sewing worker using a sewing machine finishes sewing fabric, he stops stepping on the pedal for driving the sewing machine, and then steps back on the pedal when performing the thread-binding prevention operation. The pedal switch 21 is attached to the pedal, and outputs a stepping signal 21a during the stepping operation, and outputs a stepping back signal 21b during the stepping back operation.

The control unit 8 finishes sewing the fabric. At the time point S1 in FIG. 5 , when the pedal for driving the sewing machine returns to the neutral state from the stepped state, that is, when the pedal switch 21 does not give any of the stepped signal 21a and the stepped back signal 21b, the control unit 8 issues a stop command to the sewing machine motor 80 on the output side with reference to the needle position signal 22 given to the input side. Thus, the sewing machine temporarily stops when the needles 2, 2 are near the top dead center and the bent needle 1 moves leftward.

Afterwards, the control unit 8 waits until the pedal is stepped back. When the pedal is stepped back at time S2 in FIG. 5 and the input side is given a step-back signal 21b, the control unit 8 starts the following thread-binding prevention action. Furthermore, when the pedal switch 21 inputs a step-in signal 21a again, the control unit 8 returns to the normal sewing action. The sewing operator can continue sewing the fabric by stepping on the pedal again.

Furthermore, in FIG. 5 , the neutral state is maintained from time point S1 to time point S2, but the maintenance of this neutral state is not a necessary operation, and the pedal operation at the end of sewing can also be continuously changed from the stepping state to the stepping back state. In this case, when passing through the neutral position during the transition process, there is a no-signal state in which neither the stepping-in signal 21a nor the stepping-back signal 21b is given. The control unit 8 takes this no-signal state as the starting point, and starts the thread-binding prevention action after the needles 2, 2 rise to the vicinity of the upper dead center and the bent needle 1 advances to the vicinity of the left end as described above.

Furthermore, in the timing diagram of FIG5 , the pedal return operation performed at time S2 can be continued during the execution of the tie-wire prevention action shown below, but the continuation of such a pedal return operation is not necessary, and the tie-wire prevention action of the control unit 8 can also be continued after the input of the pedal return signal 21b stops.

Fig. 6 shows the state of needles 2, 2 and bent needle 1 when the thread-binding prevention action starts. Needles 2, 2 are in a state of being pulled out to the top of the sewing fabric, where the seam M of the double chain stitch formed by the two needle threads 20, 20 and the bent needle thread 10 is formed by general sewing. Bend needle 1 moves to the left below the sewing fabric and is in a state of hooking two needle thread loops 20a, 20a formed by the needle threads 20, 20 respectively. In this state, if the needle threads 20, 20 and the bent needle thread 10 are cut, the sewing end portion shown in Fig. 28 described above is formed.

After the thread tangling prevention action starts, the control unit 8 first gives an action command to the thread operating solenoid 32 on the output side, and excites the thread operating solenoid 32 for a short time. By the excitation of the thread operating solenoid 32, the thread hook 3 and the bend needle thread retaining body 6 move from the standby position shown in Figure 1 to the thread hanging position shown in Figure 2. As described above, the movement is performed while the front end 4a of the stopper rod 4 is opened to the left.

After the hook 3 passes through, the stop rod 4 moves to the limited position indicated by the solid line in FIG. 2 by the elastic force of the return spring (omitted from the figure). The hook 3 and the bend thread retainer 6 are swung clockwise by the demagnetization of the thread operating solenoid 32. The swing is limited by the stop portion 3d of the hook 3 abutting against the front end portion 4a of the stop rod 4 in the limited position, and the hook 3 and the bend thread retainer 6 stop at the retaining position shown in FIG. 3.

FIG7 shows a state where the front end of the thread hook 3 and the bend thread retaining body 6 move to the thread hanging position, and FIG13 to FIG16 show the details of the movement state of the thread hook 3 and the bend thread retaining body 6 when the front end of the thread hook 3 and the bend thread retaining body 6 move from the standby position to the thread hanging position. As the thread hook 3 and the front end of the needle thread holder 6 move toward the thread hanging position, the thread receiving portion 6a at the front end of the needle thread holder 6 captures the needle thread 10 extending from the front end of the needle 1 toward the sewing fabric as shown in FIG13, and pushes the captured needle thread 10 forward to be located further forward than the descending position (needle drop position A) of the needle 2 on the left side, and as shown in FIG14, the front thread portion 20af of the needle thread loop 20a is pushed to the right through the needle thread 10, so that it leaves the up-and-down movement path (descending position) of the needle 2 on the left side as shown in FIG14.

On the other hand, along with the movement from the standby position to the thread hooking position, the thread hook 3 passes through the left thread loop 20a as shown in FIG. 15 and becomes a state of hooking the rear thread portion 20ab of the thread loop 20a. In addition, the thread hook 3 starts to return from the thread hanging position to the left rear holding position when the needle 2, 2 is below the upper dead point and the front end of the needle descends to a predetermined position set on the lower surface of the needle plate P to the lower surface of the above-mentioned curved needle 1. As shown in FIG. 16, the hook portion 3b of the thread hook 3 hooks and holds the rear thread portion 20ab of the needle thread loop 20a on the left side and moves the rear thread portion 20ab to the left (the front end side of the curved needle 1) so as to leave the up and down movement path of the left needle 2 (descended position).

Here, when the above-mentioned thread hook 3 passes through the needle and thread loop 20a on the left side, as shown in Figures 17 (a) and (b), the pointed front end portion 3e of the thread hook 3 goes first, and the inclined surface 3f thereafter slides on the rear thread portion 20ab of the needle and thread loop 20a to guide the entry of the thread hook 3, so even if the needle and thread loop 20a is narrow, the thread hook 3 will smoothly move through the needle and thread loop 20a, and as shown in Figures 18 (a) and (b) As shown in the figure, the rear thread portion 20ab of the needle thread loop 20a is firmly hooked, and when the thread hook 3 moves back from the thread hanging position to the holding position, as shown in Figures 19 (a) and (b), the hooked rear thread portion 20ab of the needle thread loop 20a is pulled to move away from the bent needle 1 and the front thread portion 20af of the needle thread loop 20a, thereby expanding the interval between the front thread portion 20af and the rear thread portion 20ab.

Through the above-mentioned actions of the hook 3 and the curved needle thread holder 6, the interval between the front thread part 20af and the rear thread part 20ab of the left needle thread loop 20a is enlarged, and the left needle 2 is lowered into the needle thread loop 20a with the enlarged interval, thereby using the needle thread 20 held by the left needle 2 to make the left needle thread loop 20a held by the curved needle 1 self-connected, as shown in Figure 24, to prevent the thread from tangling at the end of the double chain stitch.

In the above-mentioned thread-binding prevention action, after the thread hook 3 is operated, the control unit 8 gives an action command to the sewing machine motor 80, the cloth feed reduction mechanism 83 and the needle thread suppression mechanism 84 on the output side at the time point S3 in Figure 5. The action command is given in reference to the needle position signal 22 when the needles 2, 2 are lowered and then rise and are again in position near the top dead center. In this way, one stitch is sewn on the sewing fabric. In addition, the sewing is performed with a feed amount less than that of normal sewing by the action of the cloth feed reduction mechanism 83. In addition, the sewing is performed in a state where the needle thread 10 is suppressed from being sent to the needle 1 by the action of the needle thread suppression mechanism 84. The purpose of suppressing the feeding is to relax the needle thread 10 held by the thread receiving portion 6a of the needle thread holding body 6 to avoid the needle thread 10 from being misplaced. In this way, the appearance of the seam formed is good and the seam quality can be improved.

The above-mentioned hook 3 and the bend thread holder 6 continue to hold the needle thread 20 and the bend thread 10 shown in Figure 7 until the conveying movement of the sewing fabric is completed, the left and right needles 2, 2 pass through the sewing fabric and descend, and the left needle 2 passes through the needle thread loop 20a held by the hook 3 and hooks the loop 20a. At this time, the bend thread 10 held by the bend thread holder 6 is in place in a manner of crossing the front side of the left needle 2 as shown in Figure 7. Therefore, the left needle 2 does not capture the bend thread 10, and the bend thread 10 is only captured by the right needle 2 at the rear side of the bend needle 1.

When the left needle 2 hooks the needle thread loop, the control unit 8 gives a short-time action command to the stop solenoid 42, and excites the stop solenoid 42. By the excitation, the stop rod 4 moves from the limited position indicated by the solid line in FIG. 3 to the retreat position indicated by the two-point lock line, and the limit of the hook 3 is released. Thereby, the hook 3 and the bend needle thread holder 6 return from the holding position to the standby position as shown in FIG. 8, and the holding of the needle thread loop 20a and the bend needle thread 10 is released.

The above-mentioned curved needle 1 moves rightward together with the descent of needles 2, 2, and is pulled out from the captured needle thread loop 20a. By this pulling out, as shown in Figure 9, the needle 2 on the right side becomes a state of capturing the curved needle thread 10 in the same manner as in general sewing, while the needle 2 on the left side becomes a state of capturing the needle thread loop 20a instead of the curved needle thread 10.

In this state, the curved needle 1 is switched to the left, and the needles 2, 2 are switched to the rising state. As shown in Figure 10, the curved needle 1 that is moving left hooks the loops 20a, 20a of the needle threads 20, 20 on the left and right, and the rising needles 2, 2 are pulled out above the sewing fabric. In this way, the needle thread 20 hooked by the curved needle 1 is interconnected at the position of the needle 2 on the right side, and on the contrary, at the position of the needle 2 on the left side, the needle thread loop 20a formed earlier is self-connected.

The sewing action of one needle ends when needles 2, 2 rise to the vicinity of the upper dead point and the bent needle 1 reaches the vicinity of the left feed end. Afterwards, the control unit 8 waits until the thread cutting signal 23 is given. If the thread cutting signal 23 is given at the S4 time point in Figure 5, the thread cutting actuator 58 on the output side is given an action instruction, so that the thread cutting actuator 58 performs a predetermined action. In this way, the thread cutting hook 60 moves rightward after moving leftward.

The left-moving tangent hook 50 reaches the forward end shown in Figure 11 along the upper part of the curved needle 1. At this time, the first hook 52 provided at the front end of the tangent hook 50 passes through the loop of the needle thread 20, 20 held by the curved needle 1 and reaches the left side of the curved needle thread 10 extending from the front end of the curved needle 1 to sew the fabric, and the second hook 53 provided in the middle of the tangent hook 50 faces the needle thread 20 on the left side from the left side.

The thread cutting hook 50 moves rightward after reaching the forward end. The first hook portion 52 captures the curved needle thread 10, and the second hook portion 53 captures the two needle threads 20, 20 in sequence. The curved needle thread 10 and the needle threads 20, 20 captured in this way are pulled to the withdrawal end of the thread cutting hook 50. At this time, as shown in FIG. 12, the needle threads 20, 20 hooked by the second hook portion 53 are cut by sliding on the blade of the front end of the thread cutting knife 51, and the curved needle thread 10 hooked by the first hook portion 52 is also cut by sliding on the blade of the front end of the thread cutting knife 51, and is kept at a position closer to the curved needle 1 side than the cutting position. The thread cutting mechanism 5 equipped with a thread cutting hook 50 and a thread cutting knife 51 cuts the needle threads 20, 20 and the curved needle thread 10 through the above actions.

The needle thread suppression mechanism 84 continues to operate until the above thread cutting action is completed, and a predetermined tension is applied to the needle thread 10 extending from the front end of the needle 1 to the sewing fabric. The first hook 52 at the front end of the thread cutting hook 50 can securely capture the needle thread 10 that is not loose.

As shown in Figures 11 and 12, the thread cutter 50 is pressed against the sliding part of the thread cutter 51 by the elastic force of the leaf spring 59 that is in elastic contact with the front side of the lower surface, and the thread cutter 51 can cut the needle thread 20, 20 and the curved needle thread 10 reliably under the pressure of the leaf spring 59. The cut curved needle thread 10 is held between the lower surface of the thread cutter 50 and the leaf spring 59 as shown in Figure 12.

After the cutting action is completed in the above manner, the control unit 8 waits until the needle thread removal signal 24 is given. If the needle thread removal signal 24 is given at the time point S5 in Figure 5, an action command is issued to the pneumatic thread blower 82 on the output side to make the pneumatic thread blower 82 act. The pneumatic thread blower 82 blows out air to make the cut ends of the continuous needle threads 20, 20 on the needle 2, 2 side fly up. Thereafter, the control unit 8 issues an action command to the cloth pressing cylinder 81 on the output side at the time point S6 in Figure 5, so that the cloth pressing cylinder 81 acts and the cloth pressing foot rises, thereby ending a series of actions.

In this way, the operator can remove the finished fabric from the needle plate P, set the new fabric and start the next sewing. At this time, the curved needle thread 10 is held under the needle plate P by the thread cutter 50 and the thread cutter 51, and the needle threads 20, 20 fly up to the needle plate P, as shown in Figure 12, and become a state of hanging from the needles 2, 2 respectively. Therefore, the operator does not need to do anything to the needle threads 20, 20 and the curved needle thread 10 to start the next sewing.

Furthermore, the cutting of the needle threads 20, 20 and the curved needle thread 10 by the thread cutting mechanism 5, the flying of the needle threads 20, 20 by the action of the pneumatic thread blower 82, and the lifting of the presser foot by the action of the cloth pressing cylinder 81 are not necessary actions in the present invention. Moreover, in the implementation form, these actions are performed continuously with the thread-binding prevention action according to the thread cutting signal 23 and the thread removal signal 24 given from the outside, but can also be performed with a series of actions corresponding to the appropriate operation of the operator after the sewing of one needle for preventing thread-binding is completed.

FIG. 20 is a top view showing the main structure of the second embodiment of the seam thread prevention device from above, FIG. 21 is a bottom view from below, and FIG. 22 and FIG. 23 are similar operation explanation diagrams. In the following description, FIG. 22 and FIG. 23 use "left, right" and "front, back" indicated by arrows. Here, as in FIG. 1 to FIG. 3, "front" refers to the side close to the seam maker, "back" refers to the side far from the seam maker, and "left, right" refers to the "left, right" when viewed from the front.

The thread-binding prevention device of the second embodiment of the present invention is provided with a thread hook 3, a curved needle thread retaining body 6 and a stopper rod 4, and further provided with a swing rod 9. As shown in FIG. 20, the thread hook 3 is supported by the upper surface of the needle plate base 11 on which the needle plate P is mounted in such a manner that it can swing around the spindle 34 in the vertical direction. The spindle 34 is located near the needle plate P on the right rear side of the needle plate P.

The hook 3 has an arc-shaped curved shape and is connected to the front end of the support arm 3g extending to the left from the central axis 34 in a forward-folding manner. The front end 3e of the hook 3 is formed in a pointed manner, facing the needle drop positions A, A of the needles 2, 2 from the left rear side under the needle plate P, and is provided with a hook portion 3b extending outward from the inclined portion 3f connected to the pointed front end 3e. The support arm 3g also extends forward of the central axis 34, and one end of the connecting rod 35 is connected to the extended end.

The curved needle thread holder 6 has an arc-shaped curved shape, and is installed on the base of the thread hook 3 by two fixing screws 60, 60 in a position-adjustable manner, similar to the curved needle thread holder 6 in the first embodiment. The front end of the curved needle thread holder 6 extends forward along the left side of the thread hook 3, and faces the needle drop position A, A at the front position of the front end of the thread hook 3, and a bifurcated thread receiving portion 6a is formed at the front end.

The swing rod 9 is supported by the upper surface of the needle plate 11 in a manner that it can swing around the spindle 90 in the vertical direction. The spindle 90 is positioned away from the spindle 34 of the hook 3 to the right. The swing rod 9 extends forward from the spindle 90, and the other end of the connecting rod 35 is connected to the front end of the swing rod 9.

The swing rod 9 has a pressure plate 91 formed integrally by bending the right side near the front end downward. As shown in FIG. 21, a wire-operated pressure cylinder 92 is fixed on the lower surface of the needle plate base 11 on the left side of the swing rod 9. The wire-operated pressure cylinder 92 is a cylinder having an output rod 93 protruding to the right. The front end of the output rod 93 faces the pressure plate 91. The output rod 93 moves forward by the action of the actuating air supplied to the wire-operated pressure cylinder 92 through the air pipe 94, pressing the pressure plate 91 to the right.

The needle plate base 11 is provided with a spring fixing rod 95 protruding forward on the left side of the wire-operated pressure cylinder 92, and a return spring 96 is arranged between the spring fixing rod 95 and the pressure plate 91. The return spring 96 is a coil spring that pulls the pressure plate 91 to the left, and is arranged between the connecting rod 35 and the wire-operated pressure cylinder 92. In Figures 20, 22, and 23, the middle part of the connecting rod 35 is broken to show a part of the return spring 96.

When the thread operating cylinder 92 is in a non-actuated state, the swing rod 9 is pulled to the left by the elastic force of the return spring 96 to a swing position as shown in FIG. 20. The hook portion 3b at the front end of the thread hook 3 and the thread receiving portion 6a at the front end of the needle thread retaining body 6 are in a separated standby position at the left rear of the needle drop position A, A of the needles 2, 2 as shown in FIG. 20.

When the wire-operated pressure cylinder 92 is actuated, the output rod 93 advances and presses the pressure plate 91 to the right. By this pressing, the swing rod 9 swings counterclockwise against the elastic force of the return spring 96 as shown by the arrow in FIG. 22 . The support arm 3g of the thread hook 3 swings counterclockwise around the spindle 34, and the hook portion 3b at the front end of the thread hook 3 and the thread receiving portion 6a at the front end of the needle thread retaining body 6 move forward to the right front as shown by the arrow in Figure 22, and reach the thread hanging position shown in Figure 22. Similar to the first embodiment, the hook portion 3b is located behind the needle 1 at a position beyond the needle thread loop on the left side (the front end side of the needle 1), and the thread receiving portion 6a is located in front of the hook portion 3b on the upper side of the needle 1.

As shown in FIG. 21 , the stopper rod 4 is supported by the lower surface of the needle plate base 11 in a manner that it can swing around the spindle 44 in the vertical direction. The spindle 44 is located near the spindle 90 of the swing rod 9. The stopper rod 4 extends to the right from the spindle 44. The stopper rod 4 has a pressing plate 45 formed integrally by bending the rear side near the front end downward, and also has a fitting recess 46 formed by cutting off the middle part of the front edge.

A stopper cylinder 47 is fixed near the rear end on the lower surface of the needle plate 11. The stopper cylinder 47 is an air cylinder having an output rod 48 protruding backward. The front end of the output rod 48 faces the pressure plate 45. The output rod 48 moves forward by the action of the actuating air supplied to the stopper cylinder 47 through the air pipe 49, pressing the pressure plate 45 backward.

On the upper surface of the needle plate 11, a spring fixing rod 97 is protruded to the right on the upper side of the stop cylinder 47, and a return spring 98 is arranged between the spring fixing rod 97 and the front end of the stop rod 4. The return spring 98 is a coil spring that pulls the front end of the stop rod 4 backward. In Figures 20, 22 and 23, a part of the needle plate 11 is cut off to show the connection between the return spring 98 and the stop rod 4.

When the stopper cylinder 47 is in a non-actuated state, the stopper rod 4 is pulled forward by the elastic force of the return spring 98, as shown in FIG21, and is in a position where the front edge is pressed against the pressure plate 91 of the swing rod 9. When the line operating cylinder 92 is actuated in this state, the pressure plate 91 moves to the right along the front edge of the stopper rod 4. The stopper rod 4 is pulled by the elastic force of the return spring 98 at the time point when the moving pressure plate 91 is aligned with the engaging recess 46 provided at the front edge, and swings counterclockwise in FIG21, as shown in FIG22, and becomes a state where the bottom surface of the engaging recess 46 is pressed against the pressure plate 91 of the swing rod 9.

When the thread operating cylinder 92 becomes non-actuated in this state, the swing rod 9 is pulled to the left by the elastic force of the return spring 96 and swings clockwise as shown by the arrow in Figure 23. The swing is limited by the position where the pressure plate 91 slides in the fitting recess 46 of the stopper rod 4 and the pressure plate 91 is fitted in the left edge of the fitting recess 46. At this time, the thread hook 3 and the bend thread holding body 6 swing clockwise around the spindle 34, and the hook portion 3b at the front end of the thread hook 3 and the thread receiving portion 6a at the front end of the bend thread holding body 6 move backward to the left and rear, and are positioned at a holding position near the thread hook position. During this movement, the hook portion 3b hooks the needle thread loop on the left side and pulls it back, so that it is located at the front end side of the curved needle 1, and the thread receiving portion 6a presses the curved needle thread extending from the curved needle 1 to the sewing fabric, so that it is located at the front side of the descending position of the needle 2.

When the stopper cylinder 47 is actuated in this state, the output rod 48 advances and presses the pressure plate 45 of the stopper rod 4 backward. By this pressing, the stopper rod 4 swings against the elastic force of the return spring 98. The fitting recess 46 provided in the stopper rod 4 moves backward and releases the fitting with the pressure plate 91. Thereby, the swing rod 9 swings clockwise by the elastic force of the return spring 96, and the hook 3 moves from the holding position to the left rear and returns to the standby position shown in FIG. 20. The stopper rod 4 is put into a non-actuated state by the stopper cylinder 47, and is swung by the elastic force of the return spring 98 to return to the swing position shown in FIG. 20.

In the second embodiment of the stitching prevention device, the thread hook 3 and the needle thread holding body 6 are moved between the standby position, the thread hook position and the holding position by selectively operating the thread operating cylinder 92 and the stopper cylinder 47, thereby implementing the same thread hook prevention method as the first embodiment. The thread operating cylinder 92 is equivalent to the hook actuator, and the stopper cylinder 47 is equivalent to the stopper actuator.

The action of the seam thread prevention device of the second embodiment can be achieved by taking the wire-operated cylinder 92 and the stopper cylinder 47 as the control object, and more specifically, by taking the supply and exhaust valves for supplying and exhausting the actuating air to the wire-operated cylinder 92 and the stopper cylinder 47 as the control object, and by the control unit 8 constructed in the manner shown in FIG. 4 performing the same control action as the timing diagram shown in FIG. 5.

FIG. 24 is a diagram showing the double-needle double-chain stitch structure obtained by the present invention from the back of the sewn fabric, and FIG. 25 is an explanatory diagram of the anti-threading effect of the stitching shown in FIG. 24. Furthermore, in these figures, the left-right relationship is opposite to that of FIG. 6 to FIG. 12, but the left and right in FIG. 6 to FIG. 12 are used in the following description. In addition, in FIG. 24 and FIG. 25, the conveying direction of the sewn fabric is the direction shown by the hollow arrow, and in FIG. 24 and FIG. 25, the upper side becomes the downstream side of the conveying direction, and the lower side becomes the upstream side of the conveying direction.

As shown in FIG24, the curved needle thread 10 passes through the needle thread loop 20a (hereinafter referred to as the right final loop 20a) formed on the right side (left side in FIG24) of the back side of the sewing fabric at the end of the double chain stitch seam M, and turns back before the needle thread 20 on the same side that is pulled out to the back side of the sewing fabric during the needle sewing to prevent the thread from getting tangled, and is cut at the position where it passes through the right final loop 20a again.

On the other hand, the left side (right side in FIG. 24) needle thread 20 pulled out to the back of the sewing fabric during one stitch is passed through the left side needle thread loop 20b (hereinafter referred to as the left final loop 20b) formed on the back of the sewing fabric at the end of general sewing, so that the left final loop 20b is self-connected to form a single chain stitch seam. Therefore, the curved needle thread 10 is pressed between the left side needle thread 20 and the left final loop 20b as shown in the figure.

In Figures 24 and 25, the left final loop 20b is shown in a relaxed state to clearly show the entanglement with the needle thread 20, but in fact the left final loop 20b is tightened after the needle thread 20 passes through, and becomes the same state as the right final loop 20a. Therefore, the curved needle thread 10 is firmly pressed by the needle thread 20 and the left final loop 20b, and is limited to a state of being built between the left final loop 20b and the left needle thread loop 20c formed one circle ago, as shown in the figure. This limitation can be maintained regardless of the direction of the force applied to the curved needle thread 10, so it can reliably prevent the occurrence of the tangle line unique to the double chain stitch seam M at the generation stage.

As described above, the conveying distance of the sewn fabric during one-stitch sewing is smaller than the conveying distance of the sewn fabric during general sewing. Therefore, as shown in FIG. 24, the interval L between the withdrawal position of the needle thread 20 during one-stitch sewing and the left final loop 20b is smaller than the interval _L0 between the left final loop 20b and the left needle thread loop 20c formed one turn ago. Thereby, the pressing of the curved needle thread 10 between the left needle thread 20 and the left final loop 20b is strengthened, and the occurrence of thread tangling caused by the derailment of the curved needle thread 10 can be more reliably prevented.

From the perspective of strengthening the pressing of the curved needle thread 10, the above interval L is preferably as small as possible. On the other hand, when the above interval L is small, for example, in thinner sewing fabrics, there is a risk of damage to the sewing fabric due to insufficient strength between the withdrawal position of the needle thread 20 and the left final loop 20b. Therefore, the above interval L, that is, the conveying distance of the sewing fabric during one needle sewing, needs to be appropriately set according to the type of sewing fabric.

FIG25 shows a state where the cut end of the curved needle thread 10 is pulled in the direction indicated by the arrow in the figure. When the pulling is performed, as described above, the loop of the curved needle thread 10 before the needle thread 20 on the same side is reduced and the needle thread 20 is pulled into the right final loop 20a. As a result, the needle thread 20 is sandwiched between the curved needle thread 10 and the right final loop 20a, and a "knot" as shown in the figure is formed by the needle thread 20 and the curved needle thread 10. The "knot" also exerts resistance on the bend needle thread 10, which prevents the bend needle thread 10 from being derailed. Therefore, when the situation becomes the state shown in Figure 25, the thread of the double chain stitch can be more reliably prevented by the synergistic effect of the self-connecting part on the left side and the "knot" on the right side.

Furthermore, in the seam formed in the above manner, the length of the cut end of the curved needle thread 10 protruding from the right final loop 20a is sufficiently short as shown in FIG. 25, so the seam maker does not need to process the cut end and can form a high-quality seam with a good appearance.

In the above implementation form, the feeding distance of the sewing fabric is changed during the sewing of the stitch for self-connection, but the change can also be implemented from the stage before the sewing of the stitch. Figure 26 is a timing diagram showing other implementation forms of the action content of the control unit 8.

When the thread-binding prevention action is performed, as described above, the sewing operator returns the pedal to the neutral position at the end of the sewing operation, and then performs the pedal-back operation. When the sewing of the fabric is completed, at the time point S1 in FIG. 26, when the pedal returns to the neutral state, the control unit 8 issues a stop command to the sewing machine motor 80 on the output side with reference to the needle position signal 22 given on the input side. In this embodiment, the sewing machine temporarily stops when the needles 2, 2 are lowered to the vicinity of the bottom dead center and the bent needle 1 retreats to the right. The control unit 8 waits until the pedal is stepped back. At the time point S2 in Figure 26, the pedal is stepped back. When the input side is given a step-back signal 21b, the control unit 8 starts the following anti-wire action.

Furthermore, as described in the description of FIG. 5, the maintenance of the neutral state of the pedal from time point S1 to time point S2 is not a necessary operation, and the continuation of the pedal return operation after time point S2 is not a necessary operation. In such cases, the control unit 8 starts the following anti-wire action with the no-signal state generated when the neutral state passes, that is, the state where neither the step-in signal 21a nor the return signal 21b is given, as the starting point, and continues the action even after the input of the return signal 21b stops.

The control unit 8 that has started the thread-binding prevention action first gives an action command to the cloth feed reduction mechanism 83, and then gives an action command to the sewing machine motor 80 at the time point S3. The action command refers to the needle position signal 22 and is given during the period when the needles 2, 2 rise from the stop position and are in position near the top dead center. In this way, half-needle sewing is performed on the sewing fabric. Since the cloth feed reduction mechanism 83 is in an action state, the sewing is performed with a transmission distance smaller than that of normal sewing.

Through the above actions, needles 2, 2 rise to the vicinity of the top dead center, and the bent needle 1 advances to the vicinity of the left end. Afterwards, the control unit 8 gives an action command to the thread-operating solenoid 32 on the output side at time S4, excites the thread-operating solenoid 32 for a short time, and then gives an action command to the sewing machine motor 80 and the bent needle thread suppression mechanism 84 on the output side at time S5.

The action command given to the sewing machine motor 80 refers to the needle position signal 22 and is given when the needles 2, 2 at the top dead center descend and then rise and are positioned near the top dead center again. In this way, one stitch is sewn on the sewing fabric. At this time, the feed reduction mechanism 83 continues to operate, and the bend needle thread suppression mechanism 84 operates, and the sewing of one stitch is performed with a transmission distance smaller than that during normal sewing, while suppressing the bend needle thread 10 from being sent to the bend needle 1.

Afterwards, the control unit 8 issues an action command to the thread cutting actuator 58 at time S6, and issues an action command to the pneumatic thread blower 82 at time S7, and further issues an action command to the cloth pressing cylinder 81 at time S8, so as to complete a series of actions. The actions of S4 to S8 in Figure 26 are the same as the actions of S2 to S6 in Figure 5. During the action, a needle for self-connection is sewn, and the thread cutting mechanism 5 cuts the needle thread 20, 20 and the curved needle thread 10. The action of the pneumatic thread blower 82 causes the cut needle thread 20, 20 to fly, and then the action of the cloth pressing cylinder 81 causes the press foot to rise.

Figure 27 is a diagram of the double-needle double-chain stitch seam structure obtained by the above action, observed from the back of the self-sewn fabric. This figure, like Figure 25, shows the state where the cut end of the curved needle thread 10 is pulled in the direction indicated by the arrow in the figure. The ripping of the double-chain stitch seam M can be prevented reliably by the synergistic effect of the self-connecting part on the left side (the right side in Figure 27) and the "knot" on the right side (the left side in Figure 27).

In this embodiment, before sewing the stitch for self-connection, sewing of half stitch is performed in a state where the conveying warp of the sewing fabric is reduced. Therefore, in the stitching structure shown in FIG. 27, not only the interval _L1 between the withdrawal position of the last stitch 20 and the left final loop 20b, but also the interval _L2 between the left stitch loop 20c one stitch before the left final loop 20b is smaller than the interval _L0 between the left stitch loop 20d one stitch before. Therefore, the self-connection part including the interconnection part at the front position of the part becomes dense, the pressing of the bend stitch 10 is further strengthened, and the occurrence of the thread ripping starting from the thread breakage of the bend stitch 10 at the sewing end part can be more reliably prevented.

Furthermore, in the above embodiment, the double chain stitch formed by two needle threads 20, 20 and the curved needle thread 10 has been described, but the seam thread prevention device of the present invention and the seam thread prevention method implemented using the device can also be similarly applied to the seam of multi-needle double chain stitch using more than three needle threads, and can effectively prevent the generation of thread.

Furthermore, in each of the above embodiments, the description has been given of the situation in which one of the thread loops formed by hooking two threads 20, 20 located on the front end side of the curved needle 1 is hooked and one stitch sewing operation is performed in this state, but the hooked thread loops may also be multiple including one on the front end side of the curved needle 1, and the sewing operation performed in this holding state may also be two stitches or more.

Furthermore, in each of the above embodiments, the hook 3 hooks the needle thread 20 between the left rear and right front of the needle drop position A, but the hook 3 can also hook the needle thread 20 in other actions. Moreover, the needle thread 20 is not limited to the rear side of the curved needle 1 shown in the embodiment, but can also be hooked on the front side of the curved needle 1. Furthermore, in the present invention, as shown in the scope of the invention application, the needle thread loop can be located at a position closer to the front end side of the curved needle 1 than the descending position of the needle 2, and the hook 3 is not necessary to hold the needle thread 20 as shown in the embodiment.

Furthermore, in each of the above embodiments, the needle thread holder 6 is mounted on the hook 3 and moves integrally with the hook 3 to hold the needle thread 10, but the needle thread holder 6 can also be constructed in a manner that holds the needle thread 10 by other actions. The needle thread holder 6 can also be set separately from the hook 3 and moved by a dedicated actuator different from the hook 3. Furthermore, in the present invention, as shown in the scope of the invention application, the needle thread 10 can be located at a position further forward than the descending position of the needle 2, and the needle thread holder 6 is not necessary for holding the needle thread 10 as shown in the embodiment.

1: Curved needle

3: Hanging hook

3a: Arm

3b: Hook

3c,4b: Steps

3d: Stopper

4: Stop rod

4a: Front end of the stopper rod

5: Tangent mechanism

6: Curved needle thread retainer

6a: Wire receiving part

30,40,57a: Axis

31,41: Connecting rod

32: Wire-operated solenoid (hook actuator)

33,43: swing arm

42: Stop solenoid (stop actuator)

50,60: Tangent hook

51: Thread cutter

52: Hook 1

53: Second hook

54: Base

55a,55b: Support arm

55c: Stop screw

55d: coil spring

56: Slide

57: Tangent rod

A: Needle drop position

P: Needle plate

Claims (17)

A method for preventing stitching of seams, wherein a needle thread loop formed by a needle moving up and down while holding the needle thread is hooked by a curved needle moving in a direction substantially orthogonal to the up and down movement path of the needle, and the needle thread loops are interconnected by the curved needle thread held by the curved needle, thereby forming a double chain seam formed by general sewing on the sewn fabric on the needle plate, and the double chain seam formed by general sewing is terminated. Then, the thread loop held by the curved needle is positioned closer to the front end of the curved needle than the lowered position of the needle, and the curved needle thread extending from the curved needle to the sewing fabric is positioned closer to the front side than the lowered position of the needle. Then, the needle is lowered into the thread loop and at least one stitch is sewn, and the thread loop held by the curved needle is self-adjusted by using the thread held by the needle. The method for preventing the stitching of the double chain stitch is characterized in that: When the bend needle is in the forward state, the bend needle thread holder and the hook are moved toward the needle thread loop and the bend needle thread. With the approaching movement, the bend needle thread holder captures the bend needle thread, so that the captured bend needle thread is located at a position further forward than the descending position of the needle, and The hook is located at the The needle and thread loop passes through and moves to the thread hanging position, and becomes a state of hooking the rear thread portion of the needle and thread loop. When the needle descends to a predetermined position, the back-movement movement starts, so that the rear thread portion of the needle and thread loop hooked by the thread hanging hook moves to the left to leave the up-and-down movement path of the needle, thereby expanding the interval between the front thread portion and the rear thread portion of the needle and thread loop, so that the needle descends into the needle and thread loop with the expanded interval to perform the above-mentioned self-connection. A method for preventing stitching in seams as claimed in claim 1, wherein, as the above-mentioned needle thread holder and the thread hook move closer to each other, the above-mentioned needle thread holder captures the needle thread, and the captured needle thread pushes the front thread portion of the needle thread loop to move to the right, so that it leaves the up-and-down movement path of the above-mentioned needle. A method for preventing stitching in seams as claimed in claim 1, wherein a plurality of the needles are arranged in parallel in the forward direction of the bent needle, so that at least one of the plurality of thread loops formed by each needle including the thread loop located at the forward end side of the bent needle is located at a position closer to the forward end side of the bent needle than the descending position of the needle and performs a predetermined self-connection. A method for preventing thread tangling in a seam as claimed in claim 1, wherein, when the thread hook hooks the rear thread portion of the needle and thread loop, the front end of the needle is located within the range from the lower surface of the needle plate to the lower surface of the bent needle. A method for preventing seams from becoming tangled as in claim 1, wherein the conveyance of the sewn fabric is stopped or the conveyance interval of the sewn fabric is made smaller than that of normal sewing and is applied to the sewing action of at least one of the self-connected needles. A method for preventing seams from becoming tangled as in claim 5, wherein, from the stage before the sewing action of the at least one needle, the conveyance of the sewn fabric is stopped, or the conveyance of the sewn fabric is carried out at a conveyance distance less than that during normal sewing. A method for preventing stitching in seams as claimed in claim 1, wherein, after the above-mentioned curved needle thread is positioned further forward than the descending position of the above-mentioned needle, the delivery of the curved needle thread to the above-mentioned curved needle is suppressed. A device for preventing stitching, which is a sewing machine equipped with a needle thread holding mechanism, a bent needle thread holding mechanism and a control unit, wherein the sewing machine has a needle that holds the needle thread and moves up and down, and a bent needle that holds the bent needle thread and moves forward and backward in a direction substantially orthogonal to the up and down movement path of the needle, and the bent needle hooks the needle thread by advancing forward. The needle thread loop formed below the needle plate is connected to each other by the curved needle thread held by the curved needle to form a double chain seam on the sewn fabric on the needle plate. The needle thread holding mechanism has a hook disposed below the needle plate and swinging in a plane substantially parallel to the needle plate, and moves toward and away from the curved needle, and moves in the approaching motion. During operation, the needle thread loop hooked by the above-mentioned curved needle is maintained at a position closer to the front end side of the above-mentioned curved needle than the descending position of the above-mentioned needle. The above-mentioned curved needle thread holding mechanism has a curved needle thread holding body that moves together with the above-mentioned hook, and performs approaching and retreating movements relative to the above-mentioned curved needle, and maintains the curved needle thread extending from the curved needle to the above-mentioned sewing fabric at a position closer to the front side than the descending position of the above-mentioned needle. The above-mentioned control unit controls the approaching and retreating movements of the above-mentioned needle thread holding mechanism and the curved needle thread holding mechanism in association with the movements of the above-mentioned needle and the curved needle, and the conveying movement of the above-mentioned fabric, and the control unit causes the above-mentioned needle thread holding mechanism and the curved needle thread holding mechanism to advance after the seam formation of the above-mentioned double chain stitch formed by general sewing is completed. The needle thread loop is moved closer to the position of the lowered position of the needle and the bent needle thread extending from the bent needle to the sewing fabric is moved closer to the position of the lowered position of the needle. Then, the needle is lowered into the needle thread loop and at least one stitch is sewn. The needle thread held by the needle is used to make the needle thread loop held by the bent needle self-connect, thereby preventing the stitching of the double chain stitch. The stitching prevention device is characterized in that the control unit performs the control action in the following manner: In the forward state of the bent needle, the bent needle thread holding body in the bent needle thread holding mechanism and the thread hook in the needle thread holding mechanism are moved closer to the position of the lowered position of the needle. The needle thread loop and the curved needle thread move toward each other, and the curved needle thread holder captures the curved needle thread so that the captured curved needle thread is located at a position further forward than the lowered position of the needle. The hook passes through the needle thread loop and moves to the hook position, and becomes hooked to the rear thread portion of the needle thread loop. When the needle thread retaining body and the thread hook are lowered to a predetermined position, the back thread portion of the needle thread loop hooked by the thread hook is moved to the left to leave the up-and-down movement path of the needle, thereby expanding the interval between the front thread portion and the back thread portion of the needle thread loop, and the needle is lowered into the needle thread loop with the expanded interval to perform the self-connection. As in claim 8, the device for preventing stitching of seams, wherein, as the above-mentioned bend thread holder and the thread hook move closer, the above-mentioned bend thread holder that captures the above-mentioned bend thread pushes the front thread portion of the above-mentioned needle thread loop to move to the right through the captured bend thread, so as to make it leave the up-and-down movement path of the above-mentioned needle. The device for preventing stitching of seams as claimed in claim 8, wherein, when a plurality of the needles are arranged in parallel in the forward direction of the curved needle, the needle thread holding mechanism holds at least one needle thread loop including the needle thread loop formed by the needle located at the forward end side of the curved needle. The device for preventing tangling of seams as claimed in claim 8, wherein the control unit performs control in the following manner: when the thread hook hooks the rear thread portion of the needle and thread loop, the front end of the needle is located within the range from the lower surface of the needle plate to the lower surface of the bent needle. The device for preventing seams from becoming tangled as in claim 8, wherein the control unit performs the sewing action of at least one stitch by making the conveying distance of the sewn fabric zero or less than that of normal sewing. The device for preventing seams from being tangled as in claim 12, wherein the control unit makes the conveying distance of the sewn fabric zero or less than that during normal sewing from the stage before the sewing action of the at least one needle. The thread-twisting prevention device of claim 8, wherein the needle thread holding mechanism comprises: the thread hook and the stop rod, which are arranged under the needle plate and swing in a plane substantially parallel to the needle plate; a hook actuator, which swings the thread hook from a standby position far from the bent needle to a thread-hanging position close to the bent needle; and a stop actuator, which swings the thread hook from a standby position far from the bent needle to a thread-hanging position close to the bent needle. The stop rod swings from a retreat position away from the swinging area of the above-mentioned thread hook to a limited position abutting against a part of the above-mentioned thread hook; the above-mentioned control unit selectively controls the above-mentioned hook actuator and the stop actuator, and the needle thread loop hooked by the above-mentioned thread hook at the above-mentioned thread hooking position is held at a holding position between the above-mentioned thread hooking position and the above-mentioned standby position by abutting against the above-mentioned stop rod. The thread tangle prevention device of claim 8, wherein the needle thread holding mechanism comprises: a thread hook, which is arranged under the needle plate and swings in a plane roughly parallel to the needle plate; a swing rod and a stop rod, which are arranged at a position farther from the needle plate than the thread hook and swing in a plane roughly parallel to the needle plate; a connecting rod, which connects the thread hook to the swing rod; a hook actuator, which acts on the thread hook through the connecting rod to make the thread hook self- The control unit selectively controls the hook actuator and the stop actuator, and the hook hook is engaged with the swing rod to keep the needle thread loop hooked by the hook hook at the hook thread position at a holding position between the hook thread position and the standby position. The stitching prevention device of claim 12 or 13, wherein: The bend thread holding body of the bend thread holding mechanism is mounted on the thread hook, and is configured to move with the thread hook between the thread hanging position, the holding position and the standby position; The bend thread holding body hooks the bend thread extending from the bend needle to the sewing fabric during the movement from the standby position to the thread hanging position, and holds the hooked bend thread at a position further forward than the descending position of the needle in the holding position. A device for preventing seams from tangling as claimed in claim 16, wherein the above-mentioned bend thread retaining body is installed in a manner that allows an adjustable position relative to the above-mentioned thread hook.

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