JP7324393B2 - Method for preventing fraying of seams and device for preventing fraying of seams - Google Patents

Description

In the present invention, a sewing machine such as a double chain stitch sewing machine, an interlock stitch sewing machine, or the like is used to form a double chain stitch by normal sewing with a needle thread and a looper thread. The present invention relates to an anti-fraying method for preventing fraying from occurring at the seam end portion of a double chain stitch after finishing, and to an anti-fraying device for carrying out this method.

A double chainstitch sewing machine includes one or more needles that hold a needle thread and move up and down, and a looper that holds a looper thread and moves back and forth in a direction substantially orthogonal to the up-and-down movement path of the needle. ing. The needle penetrates the sewing material on the needle plate, descends, and rises so as to get out of the sewing material. The looper advances and retreats under the needle plate in conjunction with the upward and downward movement of the needle, and catches the needle thread loop (needle thread loop) held by the ascending needle when advanced. The needle descends through the fabric and catches the looper thread held by the incoming looper.

The double chainstitch sewing machine repeats the above-described operations to form double chainstitch stitches on the fabric to be sewn. FIG. 28 is a plan view of the stitch structure of the two-needle double chainstitch as viewed from the back side of the sewn material. As shown in FIG. 28, a double chain stitch is made by looping a looper thread 10 around needle thread loops 20a and 20b formed by needle threads 20 and 20 on the back side of the fabric to be sewn. It is formed. In the general double chainstitch stitch structure shown in FIG. has the problem that the needle threads 20, 20 come out of the final needle thread loops 20a, 20b formed by the needle threads 20, and as a result of such coming out successively toward the sewing start side, fraying occurs over the entire seam. ing.

Such fraying also occurs in double chainstitch stitches formed by three or more needle threads and looper threads. The same applies to sewing machines in general.

Various anti-fraying methods and anti-fraying devices for seams have been proposed for the purpose of preventing the occurrence of excessive fraying, which is characteristic of double chain stitches. As one of them, there is an anti-fraying method and an anti-fraying device by the present applicant (see, for example, Patent Document 1). This method and device for preventing fraying is such that after the double chain stitch by normal sewing is completed, the needle thread loop caught by the looper is positioned on the advancing end side of the looper rather than the lowering position of the needle, and the looper thread extends from the looper to the fabric to be sewn. is positioned in front of the lowering position of the needle, the needle is lowered into the needle thread loop to perform a sewing operation for at least one stitch, and the needle thread held by the needle holds the needle held by the looper. Disclosed is a method and apparatus for preventing fraying of double chain stitch stitches by self-looping thread loops.

According to this method and device, if the needle holding the needle thread in the needle thread loop held by the looper can be reliably lowered to perform self-thread looping, the fraying peculiar to the double chainstitch can be prevented. can be prevented.

Japanese Patent No. 5494598

However, in the anti-fraying method and apparatus according to the prior art by the present applicant, there remains a problem to be improved in the self-thread looping operation for ensuring the prevention of fraying. In addition, in the following description of the prior art, the same reference numerals as those used in the embodiments of the present invention described below are used to denote constituent parts and constituent elements.

That is, in the case of the prior art, as shown in FIGS. 29(a) and 29(b) and FIGS. (not shown) and the thread hook 3 are moved toward the needle thread loop 20a held by the looper 1 and the looper thread 10 on the rear side of the looper 1, and the looper thread 10 is captured by the looper thread holder 6. , the rear thread portion 20ab of the needle thread loop 20a is hooked by the thread hook 31, and moved leftward away from the vertical movement path of the needle, so that the front thread portion 20af and the rear thread portion 20ab of the needle thread loop 20a are separated. is widened, and the needle is lowered into the needle thread loop 20a with the widened interval to perform self-thread looping.

In the case of the prior art, the threading hook 3 that functions as described above is formed to have a pointed tip 3e, and the pointed tip 3e bends rightward and forward with respect to the moving direction and is inclined. It is formed in a shape provided with a hook portion 3b protruding inward following the inclined curved surface 3f.

In the case of the prior art using the threading hook 3 having the shape described above, the threading hook 3 moved to the threading position reliably catches the needle thread loop 20a held by the looper 1, and the threading position is reached. In order to reliably hook the rear thread portion 20ab of the needle thread loop 20a caught by the hook portion 3b when moving away from the hook portion 3b and move it to the left, the thread hook 3 is moved before the sewing operation. 29(a), (b) or 30(a), (b), or adjust the relative position of the thread hook 3 to the looper thread holder 6. 30(a) and 30(b). If the movement path is set or adjusted in a state where the thread hook 3 that has moved to the thread hooking position cannot reliably catch the needle thread loop 20a, then the hook portion 3b of the thread hook 3 causes the back thread of the needle thread loop 20a. There is a possibility that the portion 20ab may be erroneously hooked and the desired anti-fraying function may not be achieved.
This problem occurs, for example, when the tension applied to the needle threads 20, 20 and the looper thread 10 is reduced in order to obtain a good finished state when sewing thin or soft sewing fabrics, or when the tension applied to the needle threads 20, 20 is reduced. It is likely to occur depending on the type, etc.

Therefore, the present inventors stopped the looper when the looper 1 reached the advanced end of its movement path, and in this stopped state, the looper thread holder 6 and the thread hook 3 were separated from the needle thread loop 20a and the looper. When the stitches are prevented from fraying by self-thread looping, such as moving closer to the thread 10, the thread hook 3 passes through the needle thread loop 20a and moves to the thread hooking position, whereupon the needle thread loop 20a is moved. An attempt was made to adopt a method of catching the back yarn portion 20ab (hereinafter, this method is referred to as an improved technique of the prior art).

As described above, by adopting the improved technique of the prior art in which the thread hook 3 passes through the needle thread loop 20a to the thread hooking position and catches the rear thread portion 20ab of the needle thread loop 20a, the thread Even if the movement path of the hanging hook 3 is initially set or the position is adjusted with respect to the looper yarn holder 6, the yarn hanging hook 3 can be simply moved without the delicate and complicated adjustment described in the prior art. Only by performing a very simple and easy initial setting or position adjustment such that the pointed end portion 3e can pass through the needle thread loop 20, the post thread portion of the needle thread loop by the thread hook 3 during the fraying prevention operation is performed. It was found that 20ab can be reliably captured and hooked without mistakes.

However, it has been found that even in the above-described improved technique of the prior art, there is still a problem to be solved in the self-yarn looping operation for ensuring the prevention of fraying. Problems to be further improved will be described below.

That is, in the improved technique of the prior art, the looper reaches the advanced end of its forward/backward movement path and moves back and forth at the timing when the looper thread holder and the thread hook move toward the needle thread loop and the looper thread. was set when stopped. However, in this case, the looper, which has reached the advanced end and stopped, stops at a position shifted to the near side due to the back-and-forth circulatory movement accompanying the forward and backward movement of the looper. When the tip of the needle moves downward to a predetermined position, which is the next operation of the needle, the needle located in the middle part in the case of a single needle or, in particular, a three-needle needle (the middle part indicated by the dotted line in FIGS. 16 to 19A) In order to avoid such troubles, the looper thread holder and the thread hook should be connected to the needle thread loop and the looper. The timing of approaching the yarn may be set before the looper reaches the advancing end of its advancing/retreating motion path. Since the needle thread loop held in the narrow width portion of the needle thread is in a narrow state in which the width is not widened sufficiently, mistakes are likely to occur when the thread hook is passed through the needle thread loop. In order to eliminate the passing error, it is necessary to set the operation timing of the looper yarn holder and the yarn hook and the looper appropriately, but for that purpose, very difficult adjustment that requires precision is forced. There is a new problem (problem to be improved).

The present invention has been made in view of such circumstances, and the self-thread looping operation for preventing the occurrence of fraying peculiar to double chainstitch seams can be adjusted according to the type of needle thread and looper thread, thread tension, etc. A method for preventing fraying of seams, which can be performed reliably and stably under optimal timing without causing various troubles and mistakes, and can surely exhibit an intended function of preventing fraying. It is an object of the present invention to provide a seam anti-fray device for use in carrying out this method.

In order to achieve the above object, a method for preventing fraying of stitches according to the present invention provides a needle thread loop formed under a throat plate by a needle that moves up and down while holding the needle thread, along the vertical movement path of the needle. The needle thread loop is looped with another thread by the looper thread held by the looper, which advances and retreats in a substantially orthogonal direction, so that the sewing material on the needle plate is double chain stitched by normal sewing. A stitch is formed, and after the double chainstitch by the normal sewing is completed, the needle thread loop caught by the looper is moved to the advancing end side of the looper from the lowered position of the needle and from the looper to the sewing. The looper thread extending to the fabric is positioned on the front side of the lowered position of the needle, and then the needle is lowered into the needle thread loop to perform a sewing operation for at least one stitch, and the needle held by the needle. A method for preventing fraying of the stitches of the double chainstitch by looping the needle thread loop held by the looper with a thread, wherein the top dead center of the vertical movement stroke of the needle is set to 0 degrees and When the looper reaches a position in front of the advancing end in the range of 300 degrees to 340 degrees during the rising movement of the needle when set to 360 degrees, the advancing movement of the looper is stopped, and this stopped state. (2), by moving the looper thread holder and the thread hook toward the needle thread loop and the looper thread, the looper thread holder captures the looper thread and moves the captured looper thread to the needle lowered position. and the thread hook passes through the needle thread loop to the thread hooking position to catch the rear thread portion of the needle thread loop, and then the needle is moved to a predetermined position. As the looper thread holder and the thread hook begin to move away from each other when the looper thread holder and the thread hook move downward, the trailing thread portion of the needle thread loop caught by the thread hook is moved leftward away from the vertical movement path of the needle. Thereby, the gap between the front thread portion and the rear thread portion of the needle thread loop is widened, and the needle is lowered into the needle thread loop with the widened gap to perform the self-thread looping.

A device for preventing unraveling of seams according to the present invention includes a needle that holds a needle thread and moves up and down, and a looper that holds a looper thread and moves back and forth in a direction substantially orthogonal to the up-and-down movement path of the needle. a needle thread loop formed by the needle under the throat plate is grasped by the advance of the looper, and the looper thread held by the looper loops the needle thread loop with another thread to form a sewing material on the throat plate. A sewing machine for forming double chainstitch stitches by normal sewing has a thread hook arranged under the throat plate and swinging in a plane substantially parallel to the throat plate, and approaches the looper. and a needle thread holding mechanism that separates and holds the needle thread loop caught by the looper during the approaching operation on the advanced end side of the looper rather than the needle lowered position; and a looper thread holder that moves together with the thread hook. a looper thread holding mechanism that moves toward and away from the looper and holds the looper thread extending from the looper to the sewing material on the front side of the lowered position of the needle; the needle thread holding mechanism and the looper a control unit for controlling the contacting and separating operation of the thread holding mechanism in relation to the operation of the needle and the looper and the operation of feeding the material, and the control unit controls the double loop by the normal sewing; After the sewing stitches have been formed, the needle thread holding mechanism and the looper thread holding mechanism are brought closer to move the needle thread loop to the advance side of the looper from the needle lowered position and away from the looper. The looper threads extending to the sewing material are positioned on the front side of the lowered position of the needle, and then the needle is lowered into the needle thread loop to perform at least one stitch of sewing operation and held by the needle. A device for preventing fraying of seams configured to prevent fraying of the seams of the double chainstitch by looping the needle thread loop held by the looper with the needle thread, wherein the control In the section, when the top dead center of the vertical movement stroke of the needle is set to 0 degrees and 360 degrees, the looper moves forward in the range of 300 degrees to 340 degrees during the upward movement of the needle. is reached, the forward movement of the looper is stopped, and in this stopped state, the looper thread holder of the looper thread holding mechanism and the thread hook of the needle thread holding mechanism are directed toward the needle thread loop and the looper thread. The looper thread holder captures the looper thread along with the approaching movement, and positions the captured looper thread in front of the lowered position of the needle. , and moves to the thread hooking position to capture the rear thread portion of the needle thread loop. By hooking and moving the rear thread portion of the needle thread loop caught by the thread hook to the left so as to separate from the vertical movement path of the needle, the gap between the front thread portion and the rear thread portion of the needle thread loop is obtained. is widened, and the needle is lowered into the needle thread loop with the widened interval to perform the self-thread looping.

In the method for preventing fraying of seams and the device for preventing fraying of seams according to the present invention, after normal sewing is completed with the looper advanced, the needle thread loop caught by the looper is moved to the lower position of the looper than the lowered position of the needle. The looper thread extending from the looper to the sewing fabric is positioned on the front side of the lowering position of the needle by the looper thread holder, and the rear thread portion of the needle thread loop is caught by the thread hook. The needle is lowered into the needle thread loop in a state in which the rear thread portion of the captured needle thread loop is moved leftward away from the vertical movement path of the needle, and the needle thread held by the descending needle is used as the needle thread. By looping the loop with its own thread, the looper thread can be pressed by its own thread looping portion to prevent the looper thread from slipping off, and fraying of the seams can be reliably prevented at the stage of occurrence. The looper thread can be held down well by self-thread looping of the needle thread even when the tension applied to the needle thread and the looper thread is small, and fraying can be prevented.

Moreover, when performing the above-described self-thread looping operation to prevent fraying of the seam, the thread hook passes through the needle thread loop and moves to the thread hooking position, and then catches the rear thread portion of the needle thread loop. Thus, even if the moving path of the threading hook is initially set or the position is adjusted with respect to the looper thread holder, delicate and complicated adjustments as described in the prior art are not required, and simply Only by performing very simple and easy initial setting or position adjustment such that the pointed end of the thread hook can pass through the needle thread loop, the thread after the needle thread loop by the thread hook during the fraying prevention operation is performed. As a result, the space between the front thread portion and the rear thread portion of the needle thread loop is widened and the needle is automatically lowered into the wide needle thread loop. The thread looping operation can be reliably and stably performed regardless of the type of needle thread, thread tension, and the like.

In addition, according to the present invention, when the looper thread holder and the thread hook are moved closer to the needle thread loop and the looper thread in the operation of preventing the fraying of the stitches by looping the thread itself, the vertical motion stroke of the needle is used. In the range of 300 degrees to 340 degrees during the upward movement of the needle when the top dead center is set to 0 degrees and 360 degrees, and when the looper reaches a position before the advanced end as the looper advances is stopped, and in this halted state, the looper thread retainer and the thread hook are moved toward the needle thread loop and the looper thread by adopting the timing to make the looper narrower and wider toward the tip. The thread hook is passed through the needle thread loop in a state in which the needle thread loop held in the width portion is widened. During the downward movement to a predetermined position, which is the next movement of the stopped needle, against the tip of the threading hook that has passed through the thread loop, the single needle or, especially in the case of a three-needle needle, the needle located in the middle part collides. It is possible to reliably avoid the occurrence of troubles such as As a result, the operation necessary for self-yarn looping can be reliably and stably performed without causing any mistakes or troubles, and the expected anti-fraying function can be reliably exhibited.

In the method for preventing fraying of seams and the device for preventing fraying of seams according to the present invention, a plurality of needles are arranged side by side in the advancing direction of the looper, and among the plurality of needle thread loops formed by the respective needles, the It is preferable that at least one needle thread loop including the needle thread loop positioned on the advanced end side of the looper is positioned closer to the advanced end side of the looper than the needle lowered position to perform predetermined self-thread looping.
In this case, even if there are a plurality of needle thread loops, at least only the needle thread loops positioned on the advancing end side of the looper are positioned as described above, so that self-thread looping can be reliably carried out and fraying of the stitches can be further prevented. can be reliably prevented.

In the method and device for preventing fraying of stitches according to the present invention, when the thread hook catches the rear thread portion of the needle thread loop, the tip of the needle extends from the lower surface of the needle plate. It is preferable to be positioned within the range to the lower surface of the looper.
In this case, when the thread hook catches the rear thread portion of the needle thread loop and moves the caught rear thread portion of the needle thread loop to the left away from the vertical movement path of the needle, the needle thread loop is moved. Since the front thread portion is securely hooked on the needle, the entire needle thread loop does not move in the looper entry direction (to the left), thereby allowing the needle to pass through the needle thread loop reliably and smoothly. It descends, loops its own thread reliably, and can reliably prevent the seam from fraying.

Further, in the method for preventing fraying of seams and the device for preventing fraying of seams according to the present invention, the sewing operation for at least one stitch for the self-thread looping is stopped or the feeding of the sewing fabric is It is preferable to make the pitch smaller than that during normal sewing.
In this case, it is possible to increase the density of the self-thread looping portion of the needle thread, thereby strengthening the hold-down of the looper thread and further ensuring the desired anti-fraying effect.

Further, in the method for preventing fraying of seams and the device for preventing fraying of seams according to the present invention, at least one It is preferable to start from the stage before the sewing operation for the needle.
In this case, the density of the looping portion of the needle thread, that is, the portion of the looping of the other thread, is increased, and the holding of the looper thread is further strengthened to further ensure the desired anti-fraying effect. can be

Further, in the method for preventing fraying of seams according to the present invention, it is preferable that the looper thread is prevented from being fed to the looper after the looper thread is positioned forward of the lowered position of the needle.
In this case, by suppressing the feed-out of the looper thread to the looper, the position of the looper thread is reliably maintained, and the self-thread looping is performed reliably without being affected by the presence of the looper thread, thereby preventing the desired fraying. The stopping effect can be reliably maintained, and the tightness of the looper thread can be strengthened to prevent the looper thread from coming off, thereby improving the quality of the stitches.

Further, in the device for preventing unraveling of seams according to the present invention, the needle thread holding mechanism is disposed under the needle plate, and includes a thread hook and a stopper lever that swing in a plane substantially parallel to the needle plate. a hook actuator for swinging the yarn hook from a standby position away from the looper to a yarn hook position close to the looper; a stopper actuator for swinging from a position to a restrained position abutting on a part of the yarn hook, wherein the controller selectively controls the hook actuator and the stopper actuator so that the yarn hook moves the yarn. It is preferable that the needle thread loop caught at the hooking position is held at a holding position between the thread hooking position and the standby position by contact with the stopper lever.
With this configuration, it is possible to position the needle thread with a simple configuration that can be arranged in the limited space below the throat plate. In addition, the yarn threading hook and the stopper lever can be swung between two positions, i.e., the standby position, the threading position, the retracted position, and the restraining position, and the structure of each actuator and the control section for controlling them can be simplified. It is possible to achieve the effect of preventing fraying of seams with a simple configuration.

Further, in the device for preventing unraveling of seams according to the present invention, the needle thread holding mechanism includes a thread hook arranged under the needle plate and swinging in a plane substantially parallel to the needle plate; A swing lever and a stopper lever, which are arranged at a position farther from the needle plate than the hanging hook and swing in a plane substantially parallel to the needle plate, are connected to the thread hanging hook and the swing lever. a hook actuator acting on the yarn hook through the connecting rod to swing the yarn hook from a waiting position away from the looper to a yarn hooking position close to the looper; and the stopper. a stopper actuator for swinging the lever from an engagement position where the lever is engaged with a part of the swing lever to a retracted position away from the engagement position, wherein the control unit controls the hook actuator and the stopper actuator. The needle thread loop caught by the thread hooking hook at the thread hooking position is held at a holding position between the thread hooking position and the standby position by the engagement of the stopper lever and the rocking lever. It is preferably configured to hold.
With this configuration, it is possible to position the needle thread with a simple configuration that can be arranged in the limited space below the throat plate. In addition, since the swing lever and the stopper lever are located away from the throat plate, the threading hook can be placed in the vicinity of the throat plate. can be applied to sewing machines with limited

Further, in the seam fraying preventing device according to the present invention, the looper thread holder of the looper thread holding mechanism is attached to the thread hook and moves along with the thread hook to the thread hooking position, the holding position and the standby position. The looper thread holder catches the looper thread extending from the looper to the sewing material during movement from the standby position to the thread hooking position, and catches the caught looper thread. The looper thread holding mechanism, which holds the looper thread at the holding position on the front side of the lowered position of the needle, is attached to the threading hook, and the looper thread holding mechanism is attached to the threading hook between the threading position, the holding position, and the standby position. A moving looper thread holder is provided, and the looper thread holder captures the looper thread extending from the looper to the sewing material during movement from the standby position to the thread hooking position, and holds the captured loop thread. It is preferable that the needle is held in front of the lowered position of the needle.
In this case, the looper thread is held by the looper thread holder attached to the thread hook and moved together with the thread hook, so that the looper thread can be positioned with a simple configuration along with the needle thread.

Further, in the seam fraying prevention device according to the present invention, it is preferable that the looper thread holder is attached to the thread hook so that its position can be adjusted.
In this case, by adjusting the position of the looper thread holder with respect to the thread hook, the relative position of the needle thread and the looper thread can be appropriately set, and the self-thread looping can be reliably performed for sewing. Eye fray prevention can be ensured.

FIG. 2 is a plan view schematically showing the configuration of the essential parts of the device for preventing fraying of seams according to the first embodiment; FIG. 2 is a plan view schematically showing the configuration of the main part of the seam anti-fraying device according to the first embodiment; FIG. 2 is a plan view schematically showing the configuration of the main part of the seam anti-fraying device according to the first embodiment; FIG. 2 is a block diagram of a control system of a sewing machine provided with the stitch anti-fraying device according to the first embodiment; 4 is a time chart showing operation contents of a control unit; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 10 is an explanatory view of the operation of the seam fraying preventing device; FIG. 4 is a perspective view of the essential parts showing details of the operating state of the thread hook and the looper thread holder. FIG. 4 is a perspective view of the essential parts showing details of the operating state of the thread hook and the looper thread holder. FIG. 4 is a perspective view of the essential parts showing details of the operating state of the thread hook and the looper thread holder. (a) is a plan view of a main part showing a state in which the thread hook passes through the needle thread loop, and (b) is a vertical cross-sectional view. (a) is a plan view of a main part showing a state immediately after the thread hook has passed through the inside of the needle thread loop, and (b) is a vertical cross-sectional view. (a) is a plan view of the main part showing a state in which the thread hook hooks the rear thread portion of the needle thread loop, and (b) is a vertical cross-sectional view. (a) is a plan view of the main part showing a state in which the thread hook moves by hooking the rear thread portion of the needle thread loop, and (b) is a vertical cross-sectional view. FIG. 10 is a plan view schematically showing the configuration of the essential parts of a stitch anti-fraying device according to a second embodiment; It is a bottom view which shows roughly the structure of the principal part of the anti-fraying device of the seam which concerns on the same 2nd Embodiment. FIG. 11 is an explanatory view of the operation of the stitch anti-fraying device according to the second embodiment; FIG. 11 is an explanatory view of the operation of the stitch anti-fraying device according to the second embodiment; FIG. 2 is a view of the double chain stitch stitch structure obtained by the present invention, viewed from the back side of the sewn fabric. FIG. 22 is an explanatory diagram of the anti-fraying effect of the seam structure shown in FIG. 21; 4 is a time chart showing another embodiment of the operation contents of the control unit; FIG. 27 is a view of the stitch structure of the two-needle double chainstitch obtained by the operation of FIG. 26 viewed from the back side of the sewn material; FIG. 2 is a view of a general stitch at the end of sewing and a stitch structure at the end of sewing obtained by a conventional anti-fraying device, viewed from the back side of the sewn fabric. (a) is an enlarged plan view of a main part for explaining an example of setting and position adjustment of a moving path of a threading hook to a threading position according to the prior art, and (b) is a longitudinal left side view. (a) is an enlarged plan view of the main part for explaining another example of setting and position adjustment of the moving path of the threading hook to the threading position according to the prior art, and (b) is a longitudinal left side view.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 3 are plan views from above schematically showing the configuration of the seam anti-fraying device according to the first embodiment. The device shown in FIGS. 1 to 3 is installed in a sewing machine for forming double chain stitch stitches, such as a double chain stitch machine and interlock stitch machine. In the following description, "left, right" and "front, back" indicated by arrows in FIG. 1 are used. Here, "front" is the side closer to the sewing worker, "rear" is the side farther from the sewing worker, and "left and right" are "left and right" when viewed from the front. .

The sewing machine has one looper 1 and two needles 2, 2 (see FIGS. 6-12). The needles 2, 2 are raised and lowered by the operation of the needle bar drive mechanism. A and A in FIGS. 1 to 3 indicate lowered positions (needle drop positions) of the needles 2 and 2. FIG. The needle drop positions A, A are set substantially in the center of the throat plate P with a space therebetween in the left-right direction.
Some sewing machines are equipped with one looper 1 and three needles 2, 2M, 2. There are cases where the two needles 2, 2 are used and cases where the three needles 2, 2M, 2 are used. However, in the first embodiment, a sewing machine with two needles 2, 2 will be described.

The illustrated looper 1 advances and retreats in the direction in which the needles 2, 2 (needle drop positions A, A) are arranged (leftward and rightward retreats) by the operation of the looper drive mechanism. Not circular movement back and forth. In FIG. 1, the looper 1 in the left-advance position is indicated by a solid line, and the looper 1 in the right-retraction position is indicated by a broken line. The tip of the looper 1 at the left advance position extends leftward beyond the needle drop positions A, A of the needles 2, 2, and the tip of the looper 1 at the right retreat position extends to the needle drop positions of the needles 2, 2. A, located far to the right of A. The forward and backward movement direction of the looper 1 may be any direction substantially perpendicular to the vertical motion path of the needle 2, and the configuration of the present invention described below can be realized regardless of the movement direction of the looper 1. can be done.

The sewing machine sews the sewing material (not shown) on the throat plate P by raising and lowering the needles 2 and 2 and moving the looper 1 to the left and to the right. The sewing material is fed backward on the throat plate P (in the direction indicated by the white arrow in FIG. 1) by the operation of the feeding mechanism provided inside the sewing machine bed. The feed mechanism has a feed dog. The feed dog protrudes above the throat plate P, moves backward, retracts under the throat plate P, and returns to the forward direction, repeating the operation. The sewing material is intermittently fed rearward by applying a moving force only while the feed dog protrudes above the throat plate P. - 特許庁

The needle bar drive mechanism, looper drive mechanism, and feed mechanism are known mechanisms that operate in synchronism with each other through power transmission from the sewing machine main shaft. The needles 2, 2 respectively hold needle threads 20, 20 (see FIGS. 6 to 12), pierce the sewing fabric while the feed movement is stopped, and rise after reaching below the throat plate P. to exit above the sewn fabric. The looper 1 holds the looper thread 10 (see FIGS. 6 to 12), moves to the left when the needles 2, 2 start to rise, and loops 20a, 20a, 20a of the needle threads 20, 20 formed under the needle plate P. 20b. The sewing material is fed and moved after the needles 2, 2 are pulled out. The needles 2, 2 go down through the sewing material that has finished the feeding movement, and catch the looper thread 10 held by the looper 1 that is retreating to the right. The sewing machine repeats the above operations to perform normal sewing so as to form double chain stitch stitches on the sewing fabric.

The sewing machine as described above has a device for preventing unraveling of seams, which is a needle thread holding mechanism having a thread hook 3, a stopper lever 4, a thread operating solenoid 32 as a hook actuator, and a stopper solenoid 42 as a stopper actuator. and a looper thread holding mechanism having a looper thread holding body 6 that holds the looper thread. The thread hook 3 of the needle thread holding mechanism is supported above the sewing machine bed on the rear side of the throat plate P so as to be able to swing around a vertical support shaft 30 . The stopper lever 4 is supported so as to be able to swing around a vertical support shaft 40 arranged behind the support shaft 30 .

The threading hook 3 has an arc-shaped curved shape and is connected to the end of an arm 3a extending rearward from a support shaft 30 so as to be folded forward left. The tip 3e of the threading hook 3 faces the needle drop positions A, A of the needles 2, 2 from the rear left side. A hook portion 3b having a shape protruding rearward is provided following 3f. A base portion of the threading hook 3 (a portion connected to the arm 3a) is connected to a thread operating solenoid 32 via a connecting rod 31. As shown in FIG. The yarn operating solenoid 32 is a rotary solenoid configured to obtain a rotational output of a predetermined angle by energization of an exciting current. is fixed as A swing arm 33 is fixed to the output end of the yarn operating solenoid 32 , and a connecting rod 31 connects the middle portion of the yarn hook 3 and the tip of the swing arm 33 .

1 shows the demagnetized state of the thread operating solenoid 32, and FIG. 2 shows the energized state of the thread operating solenoid 32. As shown in FIG. When the yarn operating solenoid 32 is in the demagnetized state, the swing arm 33 is in the swing position shown in FIG. When the yarn operating solenoid 32 is energized, the swinging arm 33 swings clockwise as indicated by the arrow in FIG. 1 to reach the swinging position shown in FIG. The swinging motion of the swinging arm 33 is transmitted to the threading hook 3 via the connecting rod 31, and the threading hook 3 rotates counterclockwise about the support shaft 30 as indicated by the arrow in FIG. As shown in FIG. 2, the hook portion 3b at the tip of the threading hook 3 is located between the left and right needle drop positions A, A. As shown in FIG. In this manner, the yarn hooking hook 3 swings from the waiting position shown in FIG. 1 to the yarn hooking position shown in FIG.

The intermediate portion of the stopper lever 4 is supported by the support shaft 40 and has an arched shape with a concave front. A base portion of the stopper lever 4 extending forward right is connected to a stopper solenoid 42 via a connecting rod 41 . The stopper solenoid 42 is a rotary solenoid similar to the yarn operating solenoid 32, and is fixed at a position separated to the right of the stopper lever 4 with its output end directed upward. A swing arm 43 is fixed to the output end of the stopper solenoid 42 , and a connecting rod 41 connects the base of the stopper lever 4 and the tip of the swing arm 43 .

FIG. 1 shows the demagnetized state of the stopper solenoid 42. As shown in FIG. When the stopper solenoid 42 is in a demagnetized state, the swing arm 43 is positioned at the swing position shown in FIG. Rotate clockwise as indicated by the symbol. The swinging motion of the swinging arm 43 is transmitted to the stopper lever 4 via the connecting rod 41, and the stopper lever 4 swings clockwise about the support shaft 40 as indicated by the arrow in FIG. do.

When the stopper solenoid 42 is in the demagnetized state, the left front end portion 4a of the stopper lever 4 overlaps a part of the yarn hook 3 at the standby position, as shown in FIG. The threading hook 3 has a stepped portion 3c provided at a rear position of the overlapping portion of the stopper lever 4 so as to raise the front side. The tip portion 4a of the stopper lever 4 can overlap the lower position of the threading hook 3 at the front position of the stepped portion 3c. Further, the stopper lever 4 has a step portion 4b between the support shaft 40 and the base portion. The stepped portion 4b is provided so as to raise the rear side, and as shown in FIG.

When the threading hook 3 swings to the threading position, the stopper solenoid 42 is demagnetized. The stopper lever 4 is pushed by the threading hook 3 and swings clockwise to allow the threading hook 3 to swing. After the threading hook 3 has passed, the stopper lever 4 assumes the position indicated by the solid line in FIG. 2 (restricted position). When the yarn hook 3 swings to the yarn hooking position, the stopper solenoid 42 is energized together with the yarn operating solenoid 32 to move the stopper lever 4 to the position (retracted position) indicated by the chain double-dashed line in FIG. You may let In this case, the threading hook 3 can be swung without interfering with the stopper lever 4 at all. The stopper lever 4 is brought to the restrained position by demagnetizing the stopper solenoid 42 after the yarn hook 3 is completely swung. The distal end portion 4a of the stopper lever 4 in the restrained position faces the rear side of the stopping portion 3d of the threading hook 3 that protrudes outward from the middle. The stopping portion 3d of the threading hook 3 is provided on the rear side of the stepped portion 3c and is positioned at approximately the same height as the tip portion 4a of the stopper lever 4. As shown in FIG.

When the yarn operating solenoid 32 is demagnetized in the state shown in FIG. 2, the swing arm 33 swings counterclockwise and the yarn hook 3 swings clockwise as indicated by the arrow in FIG. move. This swinging is restrained by the stopping portion 3d of the threading hook 3 coming into contact with the tip portion 4a of the stopper lever 4, and the threading hook 3 stops at the holding position shown in FIG. At this time, the hook portion 3b projecting backward from the tip of the threading hook 3 moves from the threading position shown in FIG. 2 (between the left and right needle drop positions A, A) to the holding position shown in FIG. A), hook the rear thread portion 20ab of the needle thread loop 20a of the left needle 2, and hold it at the position shown in FIG. 3, as will be described later in detail.

When the stopper solenoid 42 is energized in the state shown in FIG. 3, the swing arm 43 swings clockwise as indicated by the arrow in FIG. This swing causes the stopper lever 4 to swing clockwise, and the tip 4a of the stopper lever 4 comes off the stopper 3d of the thread hook 3 as indicated by the chain double-dashed line in FIG. The hanging hook 3 returns to the standby position shown in FIG. 1 when the restraint by the stopper lever 4 is released. The stopper lever 4 returns to the position shown in FIG. 1 by demagnetizing the stopper solenoid 42 . The aforementioned normal sewing by the sewing machine is performed in the state shown in FIG. The stopper solenoid 42 corresponds to a stopper actuator. As described above, by selectively energizing the yarn operating solenoid 32 and the stopper solenoid 42, the yarn hooking hook 3 swings between the waiting position, the yarn hooking position and the holding position.

A looper thread holder 6 as a looper thread holding mechanism is integrally attached to the thread hook 3 . The looper thread holder 6 has an arcuate curved shape similar to that of the thread hook 3, and is fixed to the midpoint of the thread hook 3 by fixing screws 60, 60 passed through two locations in the longitudinal direction of the base. It is fixed on the upper surface of the part. The tip of the looper thread holder 6 extends forward along the left side of the thread hook 3 and faces the needle drop positions A, A in front of the tip of the thread hook 3. is provided with a bifurcated yarn receiving portion 6a. The position of the looper thread holder 6 with respect to the thread hook 3 can be adjusted by loosening the fixing screws 60 , 60 . This position adjustment is performed so that the looper thread 10 is reliably held by the thread receiving portion 6a at the leading end.

The looper thread holding body 6 of the looper thread holding mechanism attached in this manner is moved between the above-described waiting position, threading position and holding position together with the thread hook 3 by the operation of the thread operating solenoid 32 and the stopper solenoid 42. to swing. The yarn receiving portion 6a at the tip of the looper yarn holder 6 extends forward of the looper 1 through the upper portion of the looper 1 at the yarn hooking position shown in FIG. It is located in front of the needle drop position A.

The sewing machine further includes a thread cutting mechanism 5. The thread cutting mechanism 5 includes a thread cutting hook 50 and a thread cutting knife 51. - 特許庁The thread cutting hook 50 and the thread cutting knife 51 are attached to a common base 54 . The base 54 is supported by connecting its right end and middle portion to the front ends of the support arms 55a and 55b. The support arms 55a and 55b are capable of swinging around vertical support shafts at their respective rear ends. The swinging range of the right support arm 55a is restricted by a stopper screw 55c provided in the middle. The left support arm 55b is pulled leftward by a coil spring 55d.

The thread cutting knife 51 is a plate-like member fixed to the left end of the base 54, and has a blade portion on the edge extending leftward. The thread hook 50 has a first hook portion 52 and a second hook portion 53 projecting rearward from the tip portion sandwiched between the base 54 and the thread cutting knife 51. there is The first and second hook portions 52 and 53 are positioned apart from each other by a predetermined length in the left-right direction. In FIG. 1, the first and second hook portions 52 and 53 overlapping the lower position of the thread cutting knife 51 are indicated by broken lines.

The thread trimming hook 50 has an extension extending rightward from the overlapping portion with the thread trimming knife 51. The extension extends through a slider 56 that slides in the left-right direction using a base 54 as a guide. It is connected to one end (front end) of the thread trimming lever 57 . The thread trimming lever 57 is supported by a vertical support shaft 57a at its midpoint in the front-rear direction, and can swing about the support shaft 57a. Normally, the thread trimming lever 57 is at the pivoting position shown in FIGS. The thread trimming actuator 58 (see FIG. 4) connected to the shaft rotates clockwise.

The thread cutting hook 50 and the thread cutting knife 51 are at the standby positions shown in FIGS. 1 to 3 during normal sewing. This standby position is obtained when the thread trimming actuator 58 (see FIG. 4) is not operated and the thread trimming lever 57 is in the swing position shown in FIGS. The thread trimming hook 50 and the thread trimming knife 51 are moved rightward and rearward together with the base 54 by the action of the support arm 55a that swings rightward together with the thread trimming lever 57, so that the thread trimming knife 51 and the looper 1 move out of the forward and backward motion path. To position. The thread trimming hook 50 moves rightward together with the slider 56 connected to the thread trimming lever 57, and as shown in FIGS. It will be in a state where

The thread cutting lever 57 is swung by the operation of the thread cutting actuator 58 . As a result of this swinging, the right support arm 55a is released from the pressure, and as a result, the thread trimming hook 50 and the thread trimming knife 51 move toward the base in response to the swinging of the left support arm 55b urged by the coil spring 55d. It moves to the left front together with 54 and is positioned above the movement path of the looper 1 . The thread trimming hook 50 moves leftward together with the slider 56 by further swinging of the thread trimming lever 57 , and the first and second hook portions 52 and 53 of the thread trimming hook 50 move to the left of the thread trimming knife 51 . protrude to

The thread trimming lever 57 swings counterclockwise due to the action of the biasing force of the return spring when the thread trimming actuator 58 is put into a non-operating state. As a result, the thread trimming hook 50 moves backward to the right and overlaps with the lower portion of the thread trimming knife 51, and the thread trimming hook 50 and the thread trimming lever 57 move rearward together with the base 54, as shown in FIGS. returns to the standby position shown in .

FIG. 4 is a block diagram of a control system of a sewing machine equipped with the stitch anti-fray device configured as described above. The control unit 8 of the sewing machine receives a depression signal 21a and a pedal return signal 21b issued by a pedal switch 21, a needle position signal 22 issued when the needles 2, 2 are near the top dead center, and a thread issued as will be described later. A cut signal 23 and a needle thread wiper signal 24 are respectively inputted.

On the other hand, the output of the control section 8 is applied to the thread operating solenoid 32, the stopper solenoid 42 and the thread cutting actuator 58, respectively. The thread hook 3 and the looper thread holder 6 operate as described above according to operation commands given from the control section 8 to the thread operating solenoid 32 and the stopper solenoid 42, respectively. In accordance with the operation command given to 58, the forward/backward movement is performed as described above.

Further, the outputs of the control unit 8 are a sewing machine motor 80 which is a drive source for the main shaft of the sewing machine, a presser cylinder 81 which raises and lowers the presser foot for pressing the presser foot, and an air wiper 82 which bounces off the cut needle threads 20, 20 as will be described later. , a feed reduction mechanism 83 for adjusting the feed amount of the sewing material, and a looper thread restraining mechanism 84 for restraining the feeding of the looper thread 10 to the looper 1, respectively. The sewing machine motor 80 is driven or stopped according to the operation command from the control section 8, and the presser cylinder 81, the air wiper 82, the feed reduction mechanism 83 and the looper thread suppression mechanism 84 are driven according to the operation command from the control section 8. Operate.

The feed reduction mechanism 83 is a known mechanism that reduces the feed amount of the sewing material by changing the operating mode of the feed teeth of the feed mechanism. The feed reduction mechanism 83 operates, for example, to incline the movement path of the feed dog with respect to the throat plate P so as to shorten the projection time above the throat plate P. As shown in FIG. As a result, the time during which the feed teeth act on the material to be sewn on the throat plate P is shortened, and the feed pitch of the material to be sewn, that is, the amount of material to be fed during one operation of the feed mechanism is reduced.

The looper thread restraining mechanism 84 is a known mechanism that includes a thread tension disc that clamps the intermediate portion of the looper thread 10 to be fed into the looper 1, and an actuator that operates to increase or decrease the clamping strength of the thread tension disc. . The looper thread restraining mechanism 84 increases the holding strength of the thread tension disk and increases the resistance applied to the looper thread 10, thereby restraining the looper thread 10 from being fed out.

The control unit 8 operates the thread hook 3 and the looper thread holder 6 in association with the sewing machine motor 80, the presser cylinder 81, the air wiper 82, the feed reduction mechanism 83, and the looper thread suppression mechanism 84 when sewing is completed. By doing so, an anti-fraying operation is performed.

FIG. 5 is a time chart showing the operation of the control unit 8 for preventing fraying. The control unit 8 is a computer having a CPU, a ROM and a RAM, and the anti-fraying operation according to the time chart of FIG. 5 is executed by a series of operations of the CPU according to the control program stored in the ROM. 6 to 12 are explanatory diagrams of the operation of the device of the present invention, showing the operating states of the thread hook 3 and the looper thread holder 6 and the thread cutting hook during the operation of the control section 8 according to the time chart of FIG. 50 operating states are shown.

A sewing operator using a sewing machine stops depressing the pedal for driving the sewing machine when finishing sewing the sewing material, and then depresses the pedal again when executing the fraying preventing operation. A pedal switch 21 is attached to the pedal, and outputs a stepping signal 21a during a stepping operation, and outputs a stepping-back signal 21b when a stepping-back operation is performed.

When the sewing of the sewing material is completed and the pedal for driving the sewing machine is returned from the depressed state to the neutral state at time S1 in FIG. When neither of the signals 21b is applied, the needle position signal 22 applied to the input side is referred to and a rotation stop command is issued to the sewing machine motor 80 on the output side. As a result, the sewing machine can operate the needles 2, 2 in the vicinity of 245 degrees during the upward movement of the needles 2, 2 when the top dead center of the vertical movement stroke is set at 0 degrees and 360 degrees, and the looper 1 moves to the left. and temporarily stop at the position where the left needle thread loop 20a is caught at the tip thereof.

After that, the control unit 8 waits until the pedal is depressed back. When the stepping-back operation is performed at time S2 in FIG. 5 and the stepping-back signal 21b is given to the input side, the control unit 8 starts the fraying prevention operation described below. When the depression signal 21a is input from the pedal switch 21 again, the control section 8 returns to the normal sewing operation. The sewing operator can continue sewing the sewing material by depressing the pedal again.

In FIG. 5, the neutral state is maintained from time S1 to time S2, but maintaining such a neutral state is not an essential operation. may be configured to continuously transition from the depressed state to the reversed state. In this case, when passing through the neutral position in the transition process, there is a no-signal state in which neither the depression signal 21a nor the pedal-back signal 21b is given. As described above, the needles 2, 2 are in the vicinity of 245 degrees, the looper 1 advances to the left and rises to the position where the left needle thread loop 20a is caught at its tip, and the looper 1 reaches the vicinity of the left advance end. After realizing the state of advancing to , the anti-fraying operation is started.

Further, in the time chart of FIG. 5, the pedal depressing operation performed at time S2 is continued during execution of the anti-fraying operation described below. It is not essential, and the anti-fraying operation of the control unit 8 is continued even after the input of the step back signal 21b is stopped.

FIG. 6 shows the state of the needles 2, 2 and the looper 1 at the start of the anti-fraying operation. The needles 2, 2 are pulled out above the sewing material on which the double chain stitch stitch M is formed by normal sewing with the two needle threads 20, 20 and the looper thread 10. - 特許庁The looper 1 moves to the left below the sewing material and is in a state of catching two needle thread loops 20a, 20a formed by the needle threads 20, 20. In this state, the needle threads 20, 20 and the looper When the thread 10 is cut, a sewn end portion is formed as shown in FIG. 28 described above.

After starting the fraying prevention operation, the control section 8 first gives an operation command to the yarn operating solenoid 32 on the output side to excite the yarn operating solenoid 32 for a short period of time. When the yarn operating solenoid 32 is energized, the yarn hook 3 and the looper yarn holder 6 move from the standby position shown in FIG. 1 to the yarn hooking position shown in FIG. This movement occurs while the distal end portion 4a of the stopper lever 4 is expanded leftward as described above.

After the threading hook 3 has passed, the stopper lever 4 is moved to the restraining position indicated by the solid line in FIG. 2 by the action of the spring force of a return spring (not shown). The thread hook 3 and the looper thread holder 6 are returned to swing clockwise by the demagnetization of the thread operating solenoid 32 . This swinging motion is restrained by the stopping portion 3d of the thread hook 3 coming into contact with the tip portion 4a of the stopper lever 4 at the restraining position, and the thread hook 3 and the looper thread holder 6 are at the holding position shown in FIG. Stop.

FIG. 7 shows a state in which the tip portions of the thread hook 3 and the looper thread holder 6 have moved to the thread hooking position, and FIGS. 3 shows details of the operating state of the thread hook 3 and the looper thread holder 6 when the leading end moves from the standby position to the thread hooking position. As the thread hook 3 and the tip portion of the looper thread holder 6 move to the thread hooking position, the thread receiving portion 6a at the tip portion of the looper thread holder 6 moves from the tip portion of the looper 1 as shown in FIG. The looper thread 10 extending toward the sewing material is captured, and the captured looper thread 10 is pushed forward to be positioned in front of the lowered position (needle drop position A) of the left needle 2, and as shown in FIG. , through the looper thread 10, the front thread portion 20af of the needle thread loop 20a is pushed rightward away from the vertical movement path (lowered position) of the left needle 2. As shown in FIG.

On the other hand, as the thread hook 3 moves from the waiting position to the thread hooking position, as shown in FIG. 20ab is captured. The thread of the threading hook 3 is started when the needles 2, 2 are below the top dead center and the tip of the needle is lowered to a predetermined position set within the range from the lower surface of the throat plate P to the lower surface of the looper 1. As shown in FIG. 15, the hook portion 3b of the thread hooking hook 3 hooks and holds the rear thread portion 20ab of the left needle thread loop 20a along with the return movement from the hooking position to the left rear holding position. to move the rear thread portion 20ab to the left (advance end side of the looper 1) away from the vertical movement path (lowered position) of the left needle 2.

Here, when the thread hook 3 passes through the left needle thread loop 20a, as shown in FIGS. Since the following slope 3f is in sliding contact with the rear thread portion 20ab of the needle thread loop 20a and guides the entry of the thread hook 3, even if the needle thread loop 20a is narrow, the thread hook 3 can smoothly move the needle. After moving through the thread loop 20a, the rear thread portion 20ab of the needle thread loop 20a can be caught as shown in FIGS. 17(a) and 17(b). At this time, the pointed tip 3e of the threading hook 3 is positioned at a position where it does not collide with the needles 2, 2 (or the intermediate needle when three needles are used).

As shown in FIGS. 18(a) and 18(b), as the looper 1 moves forward, moves to the advanced end, and moves to the retracted position, the rear thread portion 20ab of the needle thread loop 20a becomes the thread hook. 19(a) and 19(b), when the needle thread loop 20a is captured by the hook portion 3b of the needle thread hook 3, and then when the thread hook 3 returns from the thread hooking position to the holding position, the needle thread loop 20a that has been captured by the needle thread loop 20a The thread portion 20ab can be pulled away from the looper 1 and the front thread portion 20af of the needle thread loop 20a to widen the space between the front thread portion 20af and the rear thread portion 20ab.

By the above operations of the thread hook 3 and the looper thread holder 6, the gap between the front thread portion 20af and the rear thread portion 20ab of the needle thread loop 20a on the left side is widened. As the left needle 2 descends, the left needle thread loop 20a held by the looper 1 is looped by the needle thread 20 held by the left needle 2 to form a double loop as shown in FIG. Stop fraying at the end of the stitching.

In the fraying prevention operation as described above, after operating the thread hook 3, the control unit 8 issues an operation command to the sewing machine motor 80, the feed reduction mechanism 83, and the looper thread suppression mechanism 84 on the output side at time S3 in FIG. give. This motion command refers to the needle position signal 22, and after the needles 2, 2 have descended to the bottom dead center of the up-and-down motion stroke, the range of 300 to 340 degrees, preferably 315 degrees, from near 245 degrees of the stop position. to 325 degrees, and is again positioned near the top dead center of 0 degrees (360 degrees). As a result, the sewing material is sewn by one stitch. Also, this sewing is performed with a feed amount smaller than that during normal sewing by operating the feed reduction mechanism 83 . Further, this sewing is performed in a state in which the looper thread 10 is suppressed from being fed to the looper 1 by the operation of the looper thread suppression mechanism 84 . This restraint of sending out is to prevent the looper thread 10 held by the thread receiving portion 6a of the looper thread holder 6 from loosening and causing the position of the looper thread 10 to be displaced. As a result, the formed seams have a good appearance, and the quality of the seams can be improved.

The thread hook 3 and the looper thread holder 6 hold the needle thread 20 and looper thread 10 shown in FIG. Descending, the left needle 2 passes through the needle thread loop 20a held by the threading hook 3 and continues until it catches the loop 20a. At this time, the looper thread 10 held by the looper thread holder 6 is positioned across the front side of the left needle 2 as shown in FIG. Therefore, the left needle 2 does not pick up the looper thread 10, which is only picked up behind the looper 1 by the right needle 2. FIG.

The control unit 8 gives a short-time operation command to the stopper solenoid 42 at the timing when the left needle 2 catches the needle thread loop, and excites the stopper solenoid 42 . This excitation causes the stopper lever 4 to move from the restrained position indicated by the solid line in FIG. As a result, the thread hook 3 and the looper thread holder 6 return from the holding position to the standby position as shown in FIG.

The looper 1 retreats to the right as the needles 2, 2 descend, and escapes from the captured needle thread loop 20a. As a result, as shown in FIG. 9, the needle 2 on the right side catches the looper thread 10 as in normal sewing, while the needle 2 on the left side catches the looper thread 10 instead of the needle thread. The loop 20a is captured.

In this state, looper 1 changes to leftward movement, and needles 2, 2 change to upward movement. As shown in FIG. 10, the looper 1 moving left catches the loops 20a, 20a of the left and right needle threads 20, 20, and the rising needles 2, 2 come out above the sewing material. As a result, the needle thread 20 caught by the looper 1 loops the looper thread 10 with another thread at the position of the needle 2 on the right side, whereas at the position of the needle 2 on the left side, the previously formed needle thread loop 20a is looped. Self-thread looping is performed.

The sewing operation for one stitch ends when the needles 2, 2 rise near the top dead center and the looper 1 reaches near the left advance end. After that, the controller 8 waits until the thread trimming signal 23 is given, and when the thread trimming signal 23 is given at time S4 in FIG. perform a predetermined operation. As a result, the thread cutting hook 60 moves leftward and then moves rightward.

Thread cutting hook 50 moving to the left reaches the advanced end shown in FIG. At this time, the first hook portion 52 provided at the tip of the thread trimming hook 50 is attached to the looper thread 10 extending from the tip of the looper 1 to the sewing fabric through the loop of the needle threads 20, 20 held by the looper 1. The second hook portion 53, which reaches the left side and is provided in the middle of the thread cutting 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 advanced end. The first hook portion 52 catches the looper thread 10, and the second hook portion 53 sequentially catches the two needle threads 20,20. The looper thread 10 and the needle threads 20, 20 thus captured are pulled to the retracted end of the thread cutting hook 50. As shown in FIG. At this time, as shown in FIG. 12, the needle threads 20, 20 caught by the second hook portion 53 are cut by being brought into sliding contact with the blade portion at the tip of the thread cutting knife 51, and are also cut by the first hook portion. Similarly, the looper thread 10 caught by 52 is cut by sliding contact with the edge portion of the thread cutting knife 51 and held on the looper 1 side of the cutting position. The thread cutting mechanism 5 having the thread cutting hook 50 and the thread cutting knife 51 cuts the needle threads 20, 20 and the looper thread 10 by the above operation.

The looper thread restraining mechanism 84 continues to operate until the above thread cutting operation is completed, and applies a predetermined tension to the looper thread 10 extending from the tip of the looper 1 to the sewing material. The first hook portion 52 at the tip of the thread cutting hook 50 can reliably catch the looper thread 10 without slack.

As shown in FIGS. 11 and 12, the thread cutting hook 50 is pressed against the sliding contact portion with the thread cutting knife 51 by the spring force of a leaf spring 59 elastically contacting the front side of the lower surface. The threads 20, 20 and the looper thread 10 are reliably cut under the pressing force of the leaf spring 59. As shown in FIG. The cut looper thread 10 is held between the lower surface of the thread cutting hook 50 and the leaf spring 59 as shown in FIG.

After finishing the cutting operation as described above, the control section 8 waits until the needle and thread wipe signal 24 is given. An operation command is issued to operate the air wiper 82 . The air wiper 82 blows out air and flips up the cut ends of the needle threads 20, 20 continuing to the needles 2, 2 side. After that, the control unit 8 issues an operation command to the presser foot cylinder 81 on the output side at time S6 in FIG.

As a result, the operator can remove the sewn fabric from the throat plate P, set a new sewn fabric, and start sewing the next time. At this time, the looper thread 10 is held under the throat plate P by the thread cutting hook 50 and the thread cutting knife 51, and the needle threads 20, 20 are sprung up on the throat plate P as shown in FIG. , it will be in a state of hanging down from the separate needles 2,2. Therefore, the operator can start sewing the next time without having to deal with the needle threads 20, 20 and the looper thread 10 in any way.

The cutting of the needle threads 20 and 20 and the looper thread 10 by the thread cutting mechanism 5, the jumping up of the needle threads 20 and 20 by the operation of the air wiper 82, and the lifting of the presser foot by the operation of the presser cylinder 81 are the same as those in the present invention. Not a required action. In the embodiment, these operations wait for the thread cutting signal 23 and the needle thread wiper signal 24 to be applied from the outside, and are performed continuously with the fraying prevention operation. After finishing sewing for a needle, it may be performed as a series of operations according to appropriate operations by the operator.

FIG. 20 is a plan view from above schematically showing the configuration of the essential parts of the device for preventing fraying of seams according to the second embodiment, FIG. 21 is a bottom view from below, and FIGS. , and are explanatory diagrams of the same operation. In the following description, "left, right" and "front, back" indicated by arrows in FIGS. 22 and 23 are used. Here, as in FIGS. 1 to 3, "front" is the side closer to the sewing worker, "rear" is the side farther from the sewing worker, and "left and right" are when viewed from the front. is the "left, right" of

The device for preventing unraveling of seams according to the second embodiment includes a thread hook 3 , a looper thread holder 6 and a stopper lever 4 , and further includes a swing lever 9 . As shown in FIG. 20, the threading hook 3 is supported on the upper surface of the throat plate base 10 to which the throat plate P is attached so as to be able to swing around a vertical support shaft 34 . The support shaft 34 is located near the throat plate P on the right rear side of the throat plate P. As shown in FIG.

The threading hook 3 has an arcuate curved shape, and is connected to the tip of a support arm 3a extending leftward from a support shaft 34 so as to be folded forward. A tip portion 3e of the threading hook 3 is formed to have a pointed tip, and faces the needle drop positions A, A of the needles 2, 2 from the rear left side on the lower side of the throat plate P. A hook portion 3b protruding outward is provided following the continuous slope portion 3f. The support arm 3a also extends in front of the support shaft 34, and one end of a connecting rod 35 is connected to the extended end.

The looper thread holder 6 has an arc-shaped curved shape, and is positioned at the base of the thread hook 3 by two fixing screws 60, 60, like the looper thread holder 6 in the first embodiment. Adjustable mounting. The tip of the looper thread holder 6 extends forward along the left side of the thread hook 3 and faces the needle drop positions A, A in front of the tip of the thread hook 3. A bifurcated yarn receiving portion 6a is formed in the .

The swing lever 9 is supported on the upper surface of the throat plate base 11 so as to be swingable around a vertical support shaft 90 . The support shaft 90 is positioned rightward away from the support shaft 34 of the threading hook 3 . The rocking lever 9 extends forward from the support shaft 90 , and the tip of the rocking lever 9 is connected to the other end of the connecting rod 35 .

The rocking lever 9 has a pressing plate 91 integrally formed by bending the right side near the tip portion downward. As shown in FIG. 21, a thread operating cylinder 92 is fixed to the left side of the rocking lever 9 on the lower surface of the throat plate base 11 . The yarn operating cylinder 92 is an air cylinder provided with an output rod 93 projecting rightward. The tip of the output rod 93 faces the push plate 91 . The output rod 93 advances under the action of working air supplied to the thread operating cylinder 92 through the air tube 94, and presses the push plate 91 rightward.

The throat plate base 11 is provided with a spring hooking bar 95 protruding forward on the left side of the thread operating cylinder 92 , and a return spring 96 is stretched between the spring hooking bar 95 and the push plate 91 . there is A return spring 96 is a coil spring that pulls and biases the push plate 91 in the left direction, and is arranged between the connecting rod 35 and the thread operating cylinder 92 . In FIGS. 20, 22 and 23, a part of the return spring 96 is shown by breaking the connecting rod 35 in the middle.

When the thread operating cylinder 92 is in a non-operating state, the swing lever 9 is pulled leftward by the spring force of the return spring 96 to the swing position shown in FIG. As shown in FIG. 20, the hook portion 3b at the tip of the thread hook 3 and the thread receiving portion 6a at the tip of the looper thread holder 6 are at standby positions separated to the left rear of the needle drop positions A, A of the needles 2, 2. be.

When the thread operating cylinder 92 is actuated, the output rod 93 advances and presses the push plate 91 rightward. This pressure causes the swing lever 9 to swing counterclockwise against the spring force of the return spring 96, as indicated by the arrow in FIG. The support arm 3a of the threading hook 3 swings counterclockwise around the support shaft 34, and the hook portion 3b at the tip of the threading hook 3 and the thread receiving portion 6a at the tip of the looper thread holder 6 are arranged as shown in FIG. As indicated by the arrow in 22, it advances to the right front to reach the threading position shown in FIG. The thread receiving portion 6a is positioned above the looper 1 in front of the hook portion 3b.

As shown in FIG. 21, the stopper lever 4 is supported on the lower surface of the throat plate base 11 so as to be swingable around a vertical support shaft 44 . The support shaft 44 is positioned near the support shaft 90 of the rocking lever 9 . The stopper lever 4 extends rightward from the spindle 44 . The stopper lever 4 has a pressing plate 45 integrally formed by bending the rear side near the tip portion downward, and has an engaging recess 46 formed by notching the middle portion of the front edge.

A stopper cylinder 47 is fixed to the lower surface of the throat plate base 11 near the rear end thereof. The stopper cylinder 47 is an air cylinder with an output rod 48 projecting rearward. The tip of the output rod 48 faces the push plate 45 . The output rod 48 advances by the action of working air supplied to the stopper cylinder 47 via the air tube 49, and presses the push plate 45 rearward.

A spring hook 97 projects rightward from the upper side of the stopper cylinder 47 on the upper surface of the throat plate base 11 . It is stretched. The return spring 98 is a coil spring that pulls and biases the tip of the stopper lever 4 rearward. In FIGS. 20, 22 and 23, a portion of the throat plate base 11 is broken to show the connecting portion between the return spring 98 and the stopper lever 4. As shown in FIG.

When the stopper cylinder 47 is in a non-operating state, the stopper lever 4 is pulled forward by the spring force of the return spring 98, and as shown in FIG. in position. When the thread operating cylinder 92 is actuated in this state, the push plate 91 moves rightward along the front edge of the stopper lever 4 . The stopper lever 4 is pulled by the spring force of the return spring 98 when the moving push plate 91 is aligned with the engaging recess 46 provided on the front edge, and swings counterclockwise in FIG. 21, as shown in FIG. , the bottom surface of the engagement recess 46 is pressed against the push plate 91 of the swing lever 9. As shown in FIG.

In this state, when the yarn operating cylinder 92 is deactivated, the swing lever 9 is pulled leftward by the spring force of the return spring 96 and swings clockwise as indicated by the arrow in FIG. do. This rocking motion causes the push plate 91 to slide within the engagement recess 46 of the stopper lever 4 and is restrained at a position where the push plate 91 engages with the left edge of the engagement recess 46 . At this time, the thread hook 3 and the looper thread holder 6 swing clockwise around the support shaft 34, and the hook portion 3b at the tip of the thread hook 3 and the thread receiving portion 6a at the tip of the looper thread holder 6 are rotated. moves backward to the left and is positioned at the holding position near the threading position. During this movement, as in the first embodiment, the hook portion 3b catches the needle thread loop on the left side and pulls it back so that it is positioned on the advancing end side of the looper 1, and the thread receiving portion 6a moves from the looper 1 to the sewing material. push the looper thread extending to the needle 2 and position it on the front side of the lowered position of the needle 2.例文帳に追加

When the stopper cylinder 47 is actuated in this state, the output rod 48 advances and pushes the push plate 45 of the stopper lever 4 rearward. This pressure causes the stopper lever 4 to swing against the spring force of the return spring 98 . The engagement recess 46 provided in the stopper lever 4 moves rearward and disengages from the push plate 91 . As a result, the swing lever 9 swings clockwise under the action of the spring force of the return spring 96, and the threading hook 3 moves left rearward from the holding position and returns to the standby position shown in FIG. The stopper lever 4 swings due to the action of the spring force of the return spring 98 when the stopper cylinder 47 is put into a non-operating state, and returns to the swing position shown in FIG.

In the device for preventing frayed seams according to the second embodiment, the thread hook 3 and the looper thread holder 6 are moved between the standby position and the thread hooking position by selectively operating the thread operating cylinder 92 and the stopper cylinder 47 . It is possible to move between the position and the holding position and implement the fraying prevention method similar to that of the first embodiment. The yarn operating cylinder 92 corresponds to a hook actuator, and the stopper cylinder 47 corresponds to a stopper actuator.

The operation of the stitch anti-fraying device according to the second embodiment includes the thread operating cylinder 92 and the stopper cylinder 47, more specifically, the supply and discharge valves for supplying and discharging the operating air to the thread operating cylinder 92 and the stopper cylinder 47. This can be achieved by having the control unit 8 configured as shown in FIG. 4, which is the controlled object, perform the same control operation as the time chart shown in FIG.

FIG. 24 is a view of the seam structure of the two-needle double chainstitch obtained by the present invention, viewed from the back side of the sewn fabric, and FIG. 25 is an explanatory view of the anti-fraying effect of the stitches shown in FIG. In these figures, the left-right relationship is reversed from that in FIGS. 6 to 12, but the left and right in FIGS. 6 to 12 are used in the following description. In FIGS. 24 and 25, the direction in which the sewing material is fed is indicated by an outline arrow. It becomes the upstream side of the direction.

As shown in FIG. 24, the looper thread 10 is a right (left in FIG. 24) needle thread loop 20a (hereinafter referred to as a right final loop) formed on the back side of the sewing material at the end of the double chain stitch stitch M. 20a), is folded back in front of the needle thread 20 on the same side that slips out to the back side of the sewn fabric when sewing one stitch to prevent fraying, and is cut at the position where it passes through the right final looper 6a again. be.

On the other hand, the needle thread 20 on the left side (the right side in FIG. 24), which is pulled out to the back side of the sewing material when sewing one stitch, is formed on the back side of the sewing material at the end of normal sewing, as described above. 20b (hereinafter referred to as the left final loop 20b), and the left final loop 20b is looped to form a single chain stitch. Therefore, the looper thread 10 is held between the left needle thread 20 and the left final loop 20b as shown.

24 and 25, the left final loop 20b is shown in a loose state to clearly show the entanglement with the needle thread 20, but the actual left final loop 20b is tightened after the needle thread 20 passes through. , the same state as the right final loop 20a. Therefore, the looper thread 10 is firmly held by the needle thread 20 and the left final loop 20b, and as shown in the figure, is looped between the left final loop 20b and the left needle thread loop 20c formed one time before. Constrained in the passed state. Since this restraint is maintained against the acting force applied to the looper thread 10 in any direction, it is possible to reliably prevent the occurrence of fraying, which is peculiar to the double chainstitch seam M, at the stage of occurrence. can.

As described above, the feed pitch of the sewn material when sewing one stitch is smaller than the feed pitch of the sewn material during normal sewing. Therefore, as shown in FIG. 24, the distance L between the withdrawal position of the needle thread 20 and the left final loop 20b when sewing one stitch is equal to the left needle thread formed one stitch before the left final loop 20b. It is smaller than the distance _L0 between the loop 20c. As a result, the holding of the looper thread 10 between the left needle thread 20 and the left final loop 20b is strengthened, and fraying caused by the slipping of the looper thread 10 can be prevented more reliably.

From the viewpoint of strengthening the hold down of the looper thread 10, it is desirable to make the interval L as small as possible. On the other hand, if the distance L is small, for example, in a thin sewing material, the strength between the needle thread 20 withdrawal position and the left final loop 20b may be insufficient, and the sewing material may be damaged. Therefore, it is necessary to appropriately set the interval L, that is, the feed pitch of the sewing material when sewing one stitch, according to the type of the sewing material.

FIG. 25 shows a state in which the cut end of the looper thread 10 is pulled in the direction indicated by the arrow in the figure. When this pulling is performed, as described above, the loop of the looper thread 10 passing in front of the needle thread 20 on the same side contracts and is drawn into the right final loop 20a. As a result, the needle thread 20 is sandwiched between the looper thread 10 and the right final loop 20a, and the needle thread 20 and the looper thread 10 form a "knot" as shown. This "knot" also applies resistance to the looper thread 10 and acts to prevent the looper thread 10 from slipping off. Therefore, in the state shown in FIG. The synergistic action of the self-thread looping portion on the left side and the "knot" on the right side can more reliably prevent this.

In the stitches constructed as described above, the length of the cut end of the looper thread 10 projecting from the right final loop 20a is sufficiently short as shown in FIG. High quality seams with good appearance can be formed without the need for trimming.

In the above embodiment, the feed pitch of the sewn material is changed during the sewing of one stitch for self-thread looping. You may FIG. 26 is a time chart showing another embodiment of the operation contents of the control section 8. FIG.

When performing the fraying prevention operation, the sewing operator returns the pedal to the neutral position at the end of the sewing work, and then depresses the pedal, as described above. When the sewing of the sewing material is completed and the pedal is returned to the neutral state at time S1 in FIG. Issue a stop command. In this embodiment, the sewing machine stops when the needles 2, 2 descend to about 245 degrees of the up-and-down motion stroke, and the looper 1 moves back to the right and stops temporarily. The controller 8 waits until the pedal is depressed back, and when the pedal is depressed at time S2 in FIG. Start stopping action.

As described in the description of FIG. 5, maintaining the neutral state of the pedal from time S1 to time S2 is not an essential operation, and continuation of the pedal depressing operation after time S2 is also not an essential operation. . In these cases, the control unit 8 is triggered by a no-signal state that occurs when passing through the neutral state, that is, a state in which neither the stepping-on signal 21a nor the stepping-back signal 21b is given, and starts the following anti-fraying operation. This operation continues even after the input of the stepping back signal 21b is stopped.

After starting the fraying prevention operation, the control unit 8 first gives an operation command to the feed reduction mechanism 83, and then gives an operation command to the sewing machine motor 80 at time S3. This operation command refers to the needle position signal 22, and is given until the needles 2, 2 rise from the stop position (near 245 degrees of vertical movement stroke). As a result, the sewing material is sewn by half a stitch. Since the feed reduction mechanism 83 is in operation, this sewing is performed at a smaller feed pitch than during normal sewing.

By the above operation, the needles 2, 2 rise near the top dead center within a range of 300 to 340 degrees, preferably within a range of 315 to 325 degrees of the vertical motion stroke, and the looper 1 reaches a position just before the left end. It will be in a state where it has advanced to Thereafter, at time S4, the control unit 8 gives an operation command to the output side thread operating solenoid 32 to energize the thread operating solenoid 32 for a short period of time. An operation command is given to the mechanism 84 .

The operation command to the sewing machine motor 80 refers to the needle position signal 22, and the needles 2, 2 are in the range of 300 degrees to 340 degrees, preferably 315 degrees to 325 degrees of vertical movement stroke near top dead center. stops at around 90 degrees while descending beyond the top dead center of 0 degrees (360 degrees). In this stopped state, the tips of the needles 2, 2 are in the range from the lower surface of the throat plate P to the lower surface of the looper 1. As shown in FIG. Thereafter, at time S6, an operation command is given to the sewing machine motor 80, and the operation command is continued until the needles 2, 2 rise from the vicinity of 90 degrees and stop at the top dead center of 360 degrees (0 degrees). As a result, the sewing material is sewn by one stitch. At this time, the feed reduction mechanism 83 continues to operate, and the looper thread suppression mechanism 84 is in operation. 10 is suppressed.

After that, the control unit 8 issues operation commands to the thread trimmer actuator 58 at S7, to the air wiper 82 at S8, and to the presser cylinder 81 at S9, thereby completing a series of operations by activating them. . The operations of S4 to S8 in FIG. 26 are the same as the operations of S2 to S6 in FIG. 20, 20 and the looper thread 10 are cut, the cut needle threads 20, 20 are sprung up by the operation of the air wiper 82, and the presser foot is lifted by the operation of the presser cylinder 81.

FIG. 27 is a view of the stitch structure of the two-needle double chainstitch obtained by the above operation, viewed from the back side of the sewn material. Similar to FIG. 25, this figure shows a state in which the cut end of the looper thread 10 is pulled in the direction indicated by the arrow in the figure. This can be reliably prevented by the synergistic action of the self-thread looping portion on the right side in FIG. 27 and the "knot" on the right side (left side in FIG. 27).

In this embodiment, half a stitch is sewn with reduced feeding of the sewing material before one stitch is sewn for self-thread looping. Therefore, in the stitch structure shown in FIG. 27, not only the interval _L1 between the withdrawal position of the last needle thread 20 and the left final loop 20b but also the left needle thread loop 20c one stitch before the left final loop 20b is also smaller than the interval _L0 with the left needle thread loop _20c one stitch before. Therefore, the self-thread looping portion including the looping portion of the other thread in the front position is denser than the self-thread looping portion, and the holding of the looper thread 10 is further strengthened. can be more reliably prevented from occurring.

In the above embodiment, a double chainstitch stitch formed by two needle threads 20, 20 and a looper thread 10 has been described. The method of preventing fraying of seams using a device can also be applied to multi-needle double chainstitch stitches using three or more needle threads, and can effectively prevent the occurrence of fraying. can.

Further, in each of the above embodiments, one of the needle thread loops formed by the two needle threads 20, 20 is caught on the forward end side of the looper 1, and in this state, one stitch is sewn. Although the case where the operation is performed has been described, a plurality of needle thread loops including one on the advancing end side of the looper 1 may be captured, and the sewing operation performed in this holding state may be two stitches or more. It may be more.

In each of the above-described embodiments, the thread hook 3 operates between the left rear and right front of the needle drop position A to catch the needle thread 20. Alternatively, the needle thread 20 may be caught by other actions. Further, the needle thread 20 may be caught not only on the rear side of the looper 1 shown in the embodiment, but also on the front side of the looper 1 . Further, in the present invention, the needle thread loop may be positioned closer to the advanced end side of the looper 1 than the needle 2 is lowered, as shown in the claims. Holding the needle thread 20 by the hanging hook 3 is not essential.

In each of the above-described embodiments, the looper thread holder 6 is attached to the thread hook 3 and operates integrally with the thread hook 3 to hold the looper thread 10. Thread retainer 6 can also be configured to retain looper thread 10 in other motions. The looper thread holder 6 may be provided separately from the thread hook 3 and operated by a dedicated actuator different from the thread hook 3 . Further, in the present invention, the looper thread 10 may be positioned forward of the lowered position of the needle 2 as shown in the claims. Holding the thread 10 is not essential.

1 looper 2 needle 3 thread hook 4 stopper lever 6 looper thread holder 8 controller 10 looper thread 20 needle thread 20a needle thread loop 20af front thread section 20ab rear thread section 32 thread operation solenoid (hook actuator)
42 stopper solenoid (stopper actuator)
47 stopper cylinder (stopper actuator)
92 thread operation cylinder (hook actuator)

Claims (15)

A needle thread loop formed by a needle that holds the needle thread and moves up and down under the throat plate is captured by the advance of a looper that advances and retreats in a direction substantially orthogonal to the vertical movement path of the needle, and the looper is held by the looper. By looping the needle thread loop with another thread, a double chainstitch stitch is formed by normal sewing on the sewing material on the needle plate, and after the double chainstitch by normal sewing is completed, the The needle thread loop caught by the looper is positioned on the advancing end side of the looper relative to the lowered position of the needle, and the looper thread extending from the looper to the sewing material is positioned to the front side of the lowered position of the needle, and then the needle is lowered into the needle thread loop to perform a sewing operation for at least one stitch, and the needle thread loop held by the looper is looped by the needle thread held by the needle; A method for preventing fraying of double chain stitching, comprising:
When the top dead center of the vertical movement stroke of the needle is set to 0 degree and 360 degrees, the looper reaches the position before the advanced end in the range of 300 degrees to 340 degrees during the upward movement of the needle as it advances. When the advance operation of the looper is stopped, and in this stopped state, the looper thread holder and the thread hook are moved closer to the needle thread loop and the looper thread, so that the looper thread holder catches the looper thread. The caught looper thread is positioned forward of the lowered position of the needle, and the thread hook passes through the needle thread loop and moves to the thread hooking position to move the trailing thread of the needle thread loop. to capture the part,
Next, when the needle is lowered to a predetermined position, the looper thread holder and the thread hook are separated from each other, so that the rear thread portion of the needle thread loop caught by the thread hook is removed from the vertical movement path of the needle. By moving it to the left so as to separate it, the space between the front thread portion and the rear thread portion of the needle thread loop is widened, and the needle is lowered into the needle thread loop with the widened space to perform the self-thread looping. A method for preventing fraying of seams, characterized in that A plurality of needles are arranged side by side in the advancing direction of the looper, and at least one needle thread loop including the needle thread loop positioned on the advancing end side of the looper among the plurality of needle thread loops formed by the respective needles. 2. A method for preventing fraying of seams according to claim 1, wherein the looper is positioned closer to the advanced end of the looper than the needle is lowered to perform predetermined self-thread looping. When the thread hook catches the rear thread portion of the needle thread loop, the tip of the needle is positioned within the range from the lower surface of the needle plate to the lower surface of the looper. Item 3. The method for preventing fraying of seams according to any one of items 2. (1) The sewing operation for at least one stitch for the self-thread looping is performed by stopping the feeding of the sewing material or by making the feeding pitch of the sewing material smaller than that during normal sewing. The method for preventing fraying of seams according to any one of claims 1 to 3. 5. Stopping the feeding of the sewing material or feeding the sewing material at a feed pitch smaller than that during normal sewing is performed from a stage before the sewing operation for at least one stitch. How to prevent fraying of seams described. 6. The looper according to any one of claims 1 to 5, wherein after the looper thread is positioned forward of the lowered position of the needle, feeding of the looper thread to the looper is suppressed. How to prevent seams from fraying. A needle having a needle that holds a needle thread and moves up and down, and a looper that holds a looper thread and moves back and forth in a direction substantially perpendicular to the up-and-down movement path of the needle, and the needle is formed under a throat plate. A sewing machine that catches a thread loop by advancing the looper, loops the needle thread loop with the looper thread held by the looper, and loops the needle thread loop with another thread to form a double chainstitch seam by normal sewing on the sewing material on the needle plate. to the
A needle thread loop is provided under the throat plate and swings in a plane substantially parallel to the throat plate. a needle thread holding mechanism that holds the needle thread on the advanced end side of the looper relative to the lowered position of the needle;
A looper thread having a looper thread holder that moves together with the thread hook, moves toward and away from the looper, and retains the looper thread extending from the looper to the sewing material on the front side of the lowered position of the needle. a retaining mechanism;
a control unit for controlling the contacting and separating operations of the needle thread holding mechanism and the looper thread holding mechanism in relation to the operations of the needle and the looper and the feeding operation of the cloth,
After finishing the formation of the double chainstitch by the normal sewing, the control unit causes the needle thread holding mechanism and the looper thread holding mechanism to move toward each other to move the needle thread loop from the needle down position. The looper thread extending from the looper to the sewing material is positioned on the advancing side of the looper and on the front side of the lowered position of the needle, and then the needle is lowered into the needle thread loop by at least one stitch. and looping the needle thread loop held by the looper with the needle thread held by the needle, thereby preventing fraying of the double chain stitch. A device for preventing fraying of seams,
The control unit
When the top dead center of the vertical movement stroke of the needle is set to 0 degree and 360 degrees, the looper reaches the position before the advanced end in the range of 300 degrees to 340 degrees during the upward movement of the needle as it advances. When the looper is stopped, the looper thread holder of the looper thread holding mechanism and the thread hook of the needle thread holding mechanism are moved toward the needle thread loop and the looper thread. the looper thread holder captures the looper thread in accordance with this approaching movement, and positions the captured looper thread in front of the lowered position of the needle;
The looper thread holding is started when the thread hook passes through the needle thread loop and is moved to the thread hooking position to catch the thread portion after the needle thread loop, and the needle is lowered to a predetermined position. As the body and the thread hook move away from each other, the rear thread portion of the needle thread loop caught by the thread hook is hooked and moved leftward away from the vertical movement path of the needle, thereby removing the needle thread loop. A seam characterized in that the gap between the front thread portion and the back thread portion is widened and the needle is lowered into the needle thread loop with the widened gap to perform the self-thread looping. anti-fray device. When a plurality of needles are arranged side by side in the advancing direction of the looper, the needle thread holding mechanism holds at least one needle thread loop including the needle thread loop formed by the needle positioned on the advancing end side of the looper. 8. The device for preventing fraying of seams according to claim 7, characterized in that: The control section is controlled so that the tip of the needle is positioned within a range from the lower surface of the throat plate to the lower surface of the looper when the thread hook catches the rear thread portion of the needle thread loop. The device for preventing fraying of seams according to any one of claims 7 and 8, characterized in that: 10. The controller according to any one of claims 7 to 9, wherein the sewing operation for at least one stitch is performed with a feeding pitch of the sewing material being zero or smaller than that during normal sewing. The anti-fraying device according to item 1. 11. The stitching method according to claim 10, wherein the control unit sets the feed pitch of the sewing material to zero or smaller than that during normal sewing from a stage prior to the sewing operation for at least one stitch. anti-fray device. The needle thread holding mechanism is
the thread hook and the stopper lever arranged under the throat plate and swinging in a plane substantially parallel to the throat plate;
a hook actuator for swinging the yarn hook from a waiting position away from the looper to a yarn hooking position close to the looper;
a stopper actuator for swinging the stopper lever from a retracted position out of the swinging range of the yarn hook to a restrained position where the stopper lever abuts on a part of the yarn hook, wherein the control unit comprises the hook actuator; and a stopper actuator to selectively control the needle thread loop caught by the thread hook at the thread hooking position and held at a holding position between the thread hooking position and the standby position by contact with the stopper lever. The device for preventing fraying of seams according to any one of claims 7 to 11, characterized in that The needle thread holding mechanism is
a threading hook disposed under the needle plate and swinging in a plane substantially parallel to the needle plate;
a rocking lever and a stopper lever disposed at a position further from the needle plate than the thread hook and rocking in a plane substantially parallel to the needle plate;
a connecting rod that connects the thread hook and the swing lever;
a hook actuator acting on the threading hook via the connecting rod to swing the threading hook from a standby position away from the looper to a threading position close to the looper;
a stopper actuator for swinging the stopper lever from an engagement position where the stopper lever is engaged with a part of the swing lever to a retracted position away from the engagement position;
The control section selectively controls the hook actuator and the stopper actuator, and the needle thread loop caught by the thread hook at the thread hooking position is threaded by the engagement between the stopper lever and the rocking lever. 12. The device for preventing unraveling of seams according to claim 7 , wherein the device is held at a holding position between the position and the standby position. The looper thread holder of the looper thread holding mechanism is
attached to the threading hook and configured to move with the threading hook between the threading position, the holding position and the standby position;
The looper thread holder catches the looper thread extending from the looper to the sewing material during movement from the standby position to the thread hooking position, and holds the caught loop thread at the holding position relative to the lowered position of the needle. 14. The device for preventing fraying of seams according to claim 12 or 13, wherein the device is held on the front side. 15. A device for preventing unraveling of seams according to claim 14, wherein said looper thread retainer is attached to said thread hook so as to be positionally adjustable.

Images