TWI734685B - Double loop stitch sewing machine with thread fray prevention device - Google Patents

Abstract

In addition to the fray prevention device for performing self-connection, the present invention also has a looper thread return tension imparting device. The looper thread portion located between the looper thread supply source device and the looper moves sideways, thereby bending the looper thread portion and applying a pulling force toward the looper thread supply source device to the looper thread supplied to the looper . Thereby, it is provided that the use of self-connecting to achieve the effect of preventing fraying will not cause the cutting process of the looper thread after the self-connecting and the retention of the looper thread after the cutting to occur, and it can be performed reliably with a good appearance as intended. A sewn double loop sewing machine with fray prevention device.

Description

Double loop stitch sewing machine with thread fray prevention device

The present invention mainly relates to a double-loop stitch sewing machine with a thread fraying prevention device, which uses a double-loop stitch sewing machine represented by a horizontal cylindrical shape. The stitches of the double-loop stitch are formed by needle thread and looper thread, thereby preventing stitches in the double loop. Frays occur in the sewing terminal part of the stitch.

A general double-loop stitch sewing machine such as a horizontal cylinder has a needle that holds the needle thread and rises and falls, and a looper that holds the looper thread and advances and retreats in a direction substantially orthogonal to the upward and downward movement path of the needle. The entry motion of the needle captures the needle thread loop formed under the needle plate, and the looper thread held by the looper connects the above-mentioned needle thread, and repeats the above-mentioned actions to form a double-loop suture stitch on the sewing material.

The structure of a general double-loop stitch formed by a double-loop stitch sewing machine is shown in Figure 27, with the end 10a of the looper thread 10 that is cut when the sewing is finished, stretched in the direction indicated by the arrow in Figure 27 At this time, the looper thread 10 escapes from the last needle thread loops 20a2, 20b2 formed by the needle threads 20a and 20b, and the looseness easily spreads to the sewing start side. As a result, the stitch M is frayed as a whole.

In order to prevent the fraying problem specific to the stitches formed by the double loop stitch sewing machine, the applicant has successfully developed a double loop with a fray prevention device as shown in Japanese Unexamined Patent Publication No. 2011-206527 and Unexamined Patent Publication No. 2013-6009 Sewing sewing machine (hereinafter referred to as the applicant's prior art).

As shown in Figure 28 and Figure 29, the applicant’s prior art, the fray prevention device of the double loop stitch sewing machine, is equipped with needles 2a, 2b, which hold needle threads 20a, 20b (refer to Figures 17~ Figure 23) and move up and down relative to the needle drop positions A and A, which are set at the approximate center of the needle plate 12 and spaced apart in the left and right directions (refer to Figures 17 to 23 described in the embodiment of the present invention); 1. It can hold the looper thread 10 and advance and retreat in the arrangement direction of the needle drop positions A and A. When entering, it captures the needle thread loops 20a2, 20b2 formed under the needle plate 12 (refer to the description in the embodiment of the present invention Figure 17~Figure 23); the hook 3, which is bent into an arc shape, can approach and move away from the looper 1, and can move away from the looper 1 in the standby position as shown in Figure 28 and Figure 29 Shown between the thread hanging position close to the looper 1 and the pivot 30 in the up-down direction as the center swings in a plane approximately parallel to the needle plate 12; the looper thread holder 6, which is bent into an arc shape, by The fixing screw 60 is fixed on the upper surface of the middle part of the hook 3 and swings integrally with the hook 3; the thread operating cylinder 32 drives the hook 3 and the looper thread holder 6 in the standby position and the hook 3 Swing; swing rod 9 and stop rod 4, which are arranged at a position far from the needle plate 12 than the hook 3, and are supported on the upper surface of the needle plate table 11 and in the up and down direction in a plane substantially parallel to the needle plate 12 The support shaft 90 swings at the center to keep the needle thread loops 20a2, 20b2 captured by the thread hook 3 at the thread hook position at the holding position between the thread hook position and the standby position; the stop cylinder 42 drives and stops The rod 4 swings from the engaging position of a part of the swing rod 9 to the retreat position away from the engaging position; the connecting rod 35, which links the hook 3 and the swing rod 9; the return spring 91, which is arranged at Between the connecting rod 35 and the spring hook 95 that is located on the left side of the thread operating cylinder 32 and protruding forward; and the control part 8, which selectively performs the thread operating cylinder 32 and the stopper cylinder 42 after the normal sewing is finished The movement is controlled to keep the needle thread loop 20b2 caught by the hook portion 3b at the front end of the thread hook 3 at the thread hook position at the aforementioned holding position, and the looper thread The thread receiving portion 6a at the front end of the holding body 6 is located on the upper side of the looper 1 in front of the hook portion 3b, and the sewing operation of at least one stitch is performed in this state (refer to FIG. 15 described in the embodiment of the present invention).

Furthermore, in the applicant’s prior art, namely the fray prevention device for a double-loop stitch sewing machine, the needle plate table 11 is configured as a one-piece object that is longer in the left and right direction. However, in the embodiment of the present invention, the needle plate table 11 is used as The left and right parts are divided into two parts for explanation. In addition, the constituent members and constituent parts that are the same as or corresponding to the constituent members and constituent parts of the fray prevention device of the double loop stitch sewing machine explained in the embodiment of the present invention described later are marked with the constituent members and constituent parts of the embodiment of the present invention. The symbols described in the fraying device have the same symbols, and detailed descriptions thereof are omitted.

According to the applicant’s prior art, the fray prevention device, when the conventional sewing is finished, the control unit 8 controls the hook 3, looper thread holder 6, stop lever 4, and swing lever 9 to perform each action. The sewing action of 1 stitch as described above, whereby, as shown in Figure 30, the looper thread 10 passes through the stitch M of the double loop stitch and is finally formed at the end of the right side of the back of the sewing material (the left side in Figure 30) In the needle thread loop 20b2, fold back in front of the needle thread 20b on the back side of the sewing material when the amount of 1 stitch used to prevent fraying is sewn, and pass through the last needle thread loop 20b2 on the right side As a result, the needle thread 20b and the looper thread 10 form a knot-like interconnection as shown in the figure. On the other hand, the needle thread 20a threaded from the left side of the back side of the sewing material (the right side in Fig. 30) when sewing with 1 stitch is passed through the last needle thread loop formed on the back side of the sewing material in conventional sewing. In 20a2, the last needle thread loop 20a2 is self-connected. Thereby, by the multiplying action of the self-connecting part on the left side and the knot-like interconnection on the right side, even if any direction force is applied to the looper thread 10, it can prevent the unique fraying of the stitch M of the double loop stitching. Wire.

As mentioned above, according to the applicant’s prior art, the double loop stitch sewing machine with fray prevention device, the above-mentioned fray prevention is continuously performed after the conventional sewing is finished. The sewing action of 1 stitch amount can effectively prevent the unique fraying of the stitches of double loop stitching. Therefore, there is no need to carry out other special operations such as reinforcement stitching after sewing, which can improve the efficiency of the sewing industry when a large number of sewing products are sequentially produced. However, in the prior art double-loop stitch sewing machine that the applicant has successfully developed, depending on the type of thread or the adjustment of the thread’s tightening, sometimes the looper thread is used for self-linking to prevent fraying. Create slack. As a result, there is a problem that the thread trimming device cuts the looper thread at the end of sewing and holds the end of the looper thread after the cut has a problem, which prevents the next sewing process from proceeding as planned. Hereinafter, this point will be described in detail.

In the applicant’s prior art, the double-loop stitch sewing machine, in order to use self-connection to obtain the fray prevention effect, as illustrated in Figure 18 and Figure 19 of the embodiment of the present invention, when the conventional sewing is finished, it is indispensable to hang The thread hook 3 moves closer to the looper 1 to keep the needle thread loop 20a2 closer to the entry end side of the looper 1 than the lowered position of the needle, and the looper thread holder 6 moves closer to the looper 1 and borrows The looper thread receiving portion 6a at the front end of the looper thread holding body 6 keeps the looper thread 10 extending from the sewing material at the left needle drop position. Depending on the type of thread or the adjustment of thread fastening, etc., it may not be possible to remove the slack of the looper thread 10 that is indispensable in order to obtain the anti-fray effect by using the self-connection.

Furthermore, if the looper thread 10 is slack, as shown in Fig. 31, as the needle rises, the needle threads 20a and 20b located on the back side of the looper 1 (the front side in Fig. 31) move downward as shown by the arrow d At this time, there is a situation where the looper thread 10 is slidably connected to the needle threads 20a, 20b and is wound under the looper 1. In this state, even if the thread cutting device 5 is activated, and as shown in Fig. 32, the movable knife 50 moves from the front left entry position approaching the looper 1 to the outside position on the other side (left side) of the needle drop position Drive forward movement in the arrow x direction, the looper thread on the tip side of the movable knife 50 The catching portion 50a also cannot smoothly hook the looper thread 10 between the front end of the looper 1 and the back side of the sewing material W. Not only that, but also the looper thread 10 and the needle threads 20a, 20b are hooked on The needle thread catching portion 50b of the movable knife 50 is cut. The cut needle threads 20a and 20b are lifted up to the needle plate 12 by a needle thread pick-up mechanism or the like as usual, and the cut looper thread 10 is in a free state with respect to the thread hole at the tip of the looper 1.

As a result, depending on the length of the looper thread 10 remaining in the thread hole at the front end of the looper 1 during the next sewing, the looper thread 10 will escape from the thread hole at the front end of the looper 1, and stitches cannot be formed, even if the stitches can be formed. There is also a problem (problem) that a long looper thread 10 remains at the sewing start part, which deteriorates the quality and appearance of the sewn product.

The present invention has been completed in view of the above-mentioned various circumstances, and its purpose is to provide a method that can use self-connection to obtain a fray prevention effect without causing problems in the cutting process of the hook thread after the self-connection and the retention of the hook thread after the cutting. , Double loop stitch sewing machine with fray prevention device that can make the next stitching as scheduled and with good appearance.

In order to achieve the above-mentioned object, in the double-loop stitch sewing machine with fray prevention device of the present invention, the double-loop stitch sewing machine includes: a needle that holds the needle thread and moves up and down; and a looper that holds the looper thread and can move up and down with the aforementioned needle The movement path is approximately orthogonal to the forward and retreat movement, and the needle captures the needle thread loop formed under the needle plate when entering the movement; the looper thread held by the looper is used to capture the needle thread captured by the entry motion of the looper The thread loops are interconnected to form double loop stitches on the sewing material; the double loop stitch sewing machine with thread trace fray prevention device is equipped with a needle thread holding mechanism that can approach and move away from the aforementioned curved needle , Keep the needle thread loop captured by the looper needle closer to the lower position of the needle when approaching The entering end side of the looper needle; looper thread holding mechanism, which can approach and move away from the looper needle, when approaching, the looper thread extending from the looper needle to the sewing material is kept lower than the previous needle The position is on the front or rear side; and the control part, which performs the approach and phase of the needle thread holding mechanism and the looper thread holding mechanism in association with the movement of the needle and the looper, and the feeding action of the sewing material. The control of the departure action; the control part sets the looper in the entering position and the needle in the ascending position to complete the conventional sewing, and then makes the needle thread holding mechanism and the looper thread holding mechanism approach the needle thread The loop is maintained at a position closer to the entry end side of the looper than the lowered position of the needle, and the looper thread is maintained at a position on the front or back side of the lowered position of the needle, and this state is maintained until the needle passes through the foregoing Until the needle thread loop caught by the looper descends, after that, the aforementioned position retention of the needle thread loop is released, and it is executed in conjunction with the lowering and raising of the needle, the advance and retreat motion of the looper, and the feeding motion of the sewing material. A sewing operation of at least 1 stitch including the movement of the needle passing through the needle thread loop and descending, whereby the needle thread held by the needle is used to make the needle thread loop held by the looper self-connect to prevent stitches Fraying; the double loop stitch sewing machine with thread fraying prevention device is equipped with a looper thread pull-back force imparting device, which is hooked across and located at the looper thread supply source device when the looper needle enters after the self-connection The looper thread portion between the looper and the looper moves laterally, thereby bending the looper thread portion and applying a pulling force toward the looper thread supply source device to the looper thread portion supplied to the looper, And the double loop stitch sewing machine with thread fray prevention device is provided between the looper thread supply source device and the looper needle, and at least the looper thread part located between the two is provided with a guide span and the looper thread portion between the two moves substantially linearly. Two looper thread guides. The looper thread return force imparting device is composed of a swing arm, looper thread hooking part and an actuator. The swing arm can be positioned close to the looper thread supply source device as the fulcrum axis in the horizontal Or big To cause the horizontal plane to reciprocate at the position opposite to the aforementioned looper thread guide and the side position where the looper thread is bent, the looper thread hooking portion is installed at the front end of the swing arm and hooked on the aforementioned two bends. Among the needle thread guides, the looper thread portion of the looper thread guide on the side of the looper thread supply source device, the actuator drives the swing arm to swing back and forth between the two positions.

According to the double loop stitch sewing machine with fray prevention device of the present invention having the above-mentioned features, when the looper is set to enter the state and the normal sewing is finished, the loop of the needle thread caught by the looper is held in the needle The lowered position is close to the position of the entering end of the looper, and the looper thread is maintained at a position closer to the front or back than the lowered position of the needle, and this state is maintained until the needle passes through the needle thread caught by the looper Then, the position holding of the needle thread loop is released, and the sewing operation of at least 1 stitch including the movement of the needle passing through the needle thread loop and descending is performed, thereby using the lowered needle The held needle thread makes the front needle thread loop self-connect, so that the self-connecting part squeezes the looper thread, so that regardless of the amount of tension applied to the needle thread and looper thread, the looper thread can be prevented from detaching, even if no reinforcement stitching is performed, etc. Other steps dedicated to preventing fraying can also prevent the stitches from fraying.

In addition, when the looper needle enters after the self-linked fray prevention action, the looper thread pull-back force imparting device is actuated to hook the looper thread that spans and is located between the looper thread supply device and the looper. Move to the side to bend it, and apply a pulling force toward the looper thread supply source device to the looper thread portion, thereby eliminating the need to keep the looper thread closer to the lowered position of the needle after the normal sewing is finished. The position of the front side or the back side, the slack of the looper thread, which is an indispensable action used to prevent fraying by self-connection. In this way, there will be no defects in cutting and holding of the looper thread after the looper thread is slack after the self-connection, so that the next sewing can be performed as intended and with a good appearance. .

The double loop sewing machine with fray prevention device of the present invention is preferably provided with a guide span between the looper thread supply device and the looper needle, and the looper thread portion between the two moves in a substantially straight line. At least two looper thread guides of the looper thread, the looper thread return force imparting device is composed of a swing arm, a looper thread hooking portion and an actuator, and the swing arm can take a position close to the looper thread supply source device as the fulcrum axis The looper thread hooking portion is installed at the front end of the swing arm and hooked on the front end of the swinging arm and swings back and forth in a horizontal or substantially horizontal plane at the position opposite to the aforementioned looper thread guide and the side position where the looper thread is partially bent. Among the two looper thread guides, the looper thread portion of the looper thread guide on the side of the looper thread supply source device, the actuator drives the swing arm to reciprocate between the two positions.

In this case, the looper thread return pulling force imparting device is composed of a swing arm that can reciprocately swing around the fulcrum axis in a horizontal or substantially horizontal plane, and an actuator that drives the swing arm to swing back and forth between two positions, so the structure is relatively Simple and compact, it can be accommodated in a small horizontal space in the sewing table of the sewing machine. Furthermore, the following effects can also be exerted, namely, according to the positional relationship between the two looper thread guides and the swing arm, the side of the looper thread part close to the looper thread supply source device is stretched linearly in the front and rear direction, and The side close to the looper is stretched obliquely in the front, back, left, and right directions, whereby the looper thread can be given a pulling force sufficient to remove its slack with a small amount of swing of the swing arm.

In particular, as the actuator in the looper thread pull-back device, it is preferably composed of a combination of a spring and a fluid pressure cylinder. The fluid pressure cylinder resists the elastic force of the spring and drives the swing arm from the side position to the position opposite to the looper thread guide.

In this case, the elastic force of the spring can be effectively used, according to the degree of slack of the looper thread The proper return tension of the looper thread can prevent abnormal return force (tension) acting on the looper thread, or can prevent poor cutting due to insufficient return force or poor maintenance of the looper thread after cutting.

Furthermore, in the double loop sewing machine with fray prevention device of the present invention, it is preferable that the control unit is used to stop the feeding of the sewing material during the self-connected sewing operation of at least 1 stitch, or it is smaller than that of the conventional sewing. Execute under the feeding action of the current feeding amount.

In this case, the self-connecting part can be made compact and the squeeze of the self-connecting part to the looper thread can be strengthened, which can further consolidate the effect of preventing the looper thread from the sewing terminal part from falling off and the fraying caused by the falling off. .

Furthermore, in the double loop sewing machine with a fray prevention device of the present invention, it is preferable that the looper thread holding mechanism and the needle thread holding mechanism are capable of approaching and separating with respect to the looper.

In this case, the driving mechanism of the needle thread holding mechanism can also be used as the driving mechanism of the looper holding mechanism, so the overall structure of the fray prevention device can be as small and simplified as possible, and at a low cost.

Furthermore, the double-loop stitch sewing machine of the present invention is suitable for a horizontal cylindrical double-loop stitch sewing machine, but it can also be a one-needle double-loop stitch sewing machine or a lockstitch double-loop stitch sewing machine other than the horizontal cylindrical shape.

1: curved needle

2a, 2b: needle

3: Hanging hook

4: stop member

6: Looper thread holding body

8: Control Department

10: Looper thread

10a: Looper thread part

12: Needle plate

20a, 20b: needle and thread

20a1, 20b1: needle thread part

20a2, 20b2: needle thread loop

84: Looper thread return pulling force imparting device

150, 150a, 150b: looper thread guide

151: pivot axis

152: swing arm

153: Actuator

153a: Spring

153b: Telescopic fluid pressure cylinder

154: Looper thread hooking part

A: Needle drop position

B: Sewing machine bed section

M: Double loop stitch stitches

H: Fray prevention device

W: Sewing material

Fig. 1 is a perspective view showing the overall appearance of the horizontal cylindrical double loop sewing machine according to the embodiment of the present invention with the upper cover of the sewing machine bed portion removed.

Fig. 2 is an enlarged perspective view of the main part of Fig. 1.

Fig. 3 is a perspective view showing the structure of the main part of the stitch fray prevention device in the horizontal cylindrical double-loop stitch sewing machine.

Fig. 4 is a perspective view showing a state in which a part of the main part of the stitch fray prevention device is removed.

Fig. 5 is a plan view showing the structure of the main part of the stitch fray prevention device.

Fig. 6 is a bottom view of the main part for explaining the structure of the stopper mechanism of the stitch fray prevention device and the first operation.

Fig. 7 is a bottom view of the main part explaining the structure and the second operation of the stopper mechanism.

Fig. 8 is a bottom view of the main part for explaining the configuration and the third operation of the stopper mechanism.

Fig. 9 is a bottom view of the main part for explaining the structure and the fourth operation of the stopper mechanism.

Fig. 10 is an exploded perspective view explaining the structure of the reciprocating drive movement mechanism of the thread cutting device in the horizontal cylindrical double loop sewing machine.

Fig. 11 shows a state where the thread cutting device is retracted to the retracted position by the reciprocating drive movement mechanism, (A) is a plan view of the main part, and (B) is a longitudinal sectional view along the line A-A of Fig. 11(A).

FIG. 12 is an explanatory diagram showing the state where the thread cutting device is brought to the entering position by the reciprocating drive movement mechanism, and is an explanatory diagram of the first fray prevention operation of the stitch fray prevention device.

Fig. 13 is an enlarged plan view of the main part showing the structure of the looper thread tension applying device of the embodiment of the present invention and the state of conventional sewing.

Figure 14 shows the structure of the looper thread pullback force imparting device and the looper of the embodiment of the present invention An enlarged top view of the main part of the thread pulling back action state.

15 is a block diagram showing the structure of the control system of the horizontal cylindrical double loop sewing machine of the first embodiment including the stitch fray prevention device.

Fig. 16 is a time sequence diagram showing the operation content of the control unit for preventing the stitch fraying in time series.

Fig. 17 is an explanatory diagram of the first fray prevention operation of the stitch fray prevention device.

Fig. 18 is an explanatory diagram of the second fray prevention operation of the stitch fray prevention device.

Fig. 19 is an enlarged perspective view of the main part of the operating state of Fig. 18 viewed from a direction opposite to Fig. 18.

Fig. 20 is an explanatory diagram of the third fray prevention operation of the stitch fray prevention device.

Fig. 21 is an explanatory diagram of the fourth fray prevention operation of the stitch fray prevention device.

Figure 22 is an explanatory diagram of the fifth fray prevention action of the stitch fray prevention device.

Figure 23 (a) ~ (f) is a perspective view illustrating the main parts of the thread cutting device of the thread cutting device in sequence.

FIG. 24 is an enlarged perspective view of the main part of the state of FIG. 23(a) when viewed from the opposite direction of FIG. 23. FIG.

FIG. 25 is an enlarged perspective view of the main part of the state of FIG. 23(c) viewed from the direction opposite to that of FIG. 23. FIG.

Fig. 26 is a view of the stitch structure of the double-loop stitch of the horizontal cylindrical double-loop stitch sewing machine of the embodiment of the present invention viewed from the back of the sewn material.

Fig. 27 is a bottom view roughly showing the stitch composition of the sewing terminal part of a general double loop stitch.

FIG. 28 is a plan view roughly showing the structure of the main part of the stitch fray prevention device in the applicant's prior art.

FIG. 29 is a plan view for explaining the operation state of the main part of the stitch fray prevention device in the prior art of the applicant.

Fig. 30 is a view of the stitch structure of the double loop stitch obtained by the stitch fray prevention device in the prior art of the applicant, viewed from the back of the sewn material.

FIG. 31 is an enlarged perspective view showing the main part of the state corresponding to FIG. 24 in the applicant's prior art.

FIG. 32 is an enlarged perspective view showing the main part of the state corresponding to FIG. 25 in the applicant's prior art.

Hereinafter, an embodiment of the present invention will be described based on the drawings. In addition, the same configuration in the present embodiment as that of the double loop stitch sewing machine in the prior art of the applicant is given the same reference numerals for description.

Figure 1 is a perspective view showing the overall appearance of the horizontal cylindrical double-loop stitch sewing machine of the embodiment of the present invention with the upper cover of the sewing machine bed portion removed, Figure 2 is an enlarged perspective view of the main part of Figure 1, Figures 3 and 4 It is a perspective view showing the structure of the main part of the stitch fraying prevention device equipped with the horizontal cylindrical double loop stitch sewing machine. Figure 5 is a top view showing the structure of the main part of the stitch fraying prevention device, Figures 6 to 9 It is a bottom view of the main part explaining the structure of the stop mechanism of the fray prevention device and the first to fourth operations.

In addition, FIG. 10 is an exploded perspective view illustrating the structure of the reciprocating drive movement mechanism in the thread trimming device of the horizontal cylindrical double loop stitch sewing machine, and FIG. 11 shows the reciprocating drive The moving mechanism retreats the thread cutting device to the retracted position. Fig. 11(A) is a plan view of the main part, Fig. 11(B) is a longitudinal sectional view along the line AA of Fig. 11(A), and Fig. 12 shows the reciprocation The moving mechanism is driven to enter the thread trimming device to the entering position, and the movable knife is driven to move to the leftmost position. Figure 12(A) is a plan view of the main parts, and Figure 12(B) is along the line of Figure 12(A). Longitudinal section view of line BB.

Furthermore, in the following description, the expressions such as "left and right" and "front and back" indicated by arrows in FIGS. 3 to 5 and 10 to 12 are used for the description. Here, "front" refers to the side close to the sewing manufacturer, "back" refers to the side away from the sewing manufacturer, and "left and right" refers to the "left and right" when viewed from the front side of the sewing manufacturer.

As shown in FIGS. 1 and 2, in the horizontal cylindrical double loop stitch sewing machine of the present embodiment, the sewing machine arm portion C and the sewing machine bed portion B extend to the left from the upper and lower positions of the sewing machine body D substantially parallel to each other. Inside the arm C of the sewing machine is assembled a transmission rotating shaft, a needle drive mechanism that reciprocates the left and right needles 2a, 2b up and down, a pressing drive mechanism that reciprocates the cloth pressing member up and down, or a power transmission mechanism for each drive mechanism. However, the driving mechanism or power transmission mechanism is well known, so the description will be omitted.

In addition, as shown in Fig. 5, the horizontal cylindrical double-loop stitch sewing machine is provided with a looper 1, left and right needles 2a, 2b (refer to Figs. 17 to 23), a needle plate table 11 installed on the upper surface of the sewing bed portion B of the sewing machine, The stitch fray prevention device H arranged on the needle plate base 11, the needle plate 12 installed on the aforementioned needle plate base 11, and the looper thread return tension applying device 84 are provided.

A reciprocating drive movement mechanism 70 and the like are assembled in the sewing machine bed portion B below the needle plate 12. The reciprocation drive movement mechanism 70 and the like make it possible to hold the looper thread 10 and reciprocate with the needles 2a and 2b. Looper 1, which advances and retreats in orthogonal left and right directions The thread cutting device 5 and the edge portion 51e of the fixed knife 51 of the thread cutting device 5 reciprocally drive between the entry position P1 and the retreat position P2, and only make the following description when the thread cutting device 5 has moved to the aforementioned entry position P1 The movable cutter 50 moves linearly reciprocatingly between the outer position on one side (right side) of the needle drop position and the outer position on the other side (left side) along the xy direction. The entry position P1 is shown in Figure 11 (A ), (B) is generally close to the position of the aforementioned needle plate 12 and looper 1, and the stop member 34 described later abuts against the stop member 33 described later on the left front position, the retracted position P2 is shown in the figure 12(A) and (B) are located to the rear right from the aforementioned entry position P1.

The aforementioned left and right needles 2a, 2b are attached to the lower end of a needle bar (not shown) that rises and falls in conjunction with the rotation of a transmission rotating shaft (not shown) in the sewing machine arm C. A and A in Fig. 3 and Fig. 5 indicate the needle drop positions (down positions) of the needles 2a and 2b. Needle drop positions A and A are set at approximately the center of the needle plate 12 at intervals in the left-right direction.

The looper 1 advances and retreats in the arrangement direction of the needles 2a, 2b approximately orthogonal to the up and down reciprocating path of the needles 2a, 2b through the action of the looper driving mechanism, which is arranged in the sewing bed portion B of the sewing machine and is not shown. (Left forward and right retreat) action. The solid line in Figure 5 shows the state of the looper 1 in the left forward position, and the broken line in Figure 5 shows the state of the looper 1 in the right retracted position. As shown by the solid line in Figure 5, the front end of the looper 1 at the left advance position exceeds the needle drop positions A and A and extends to the left. As shown by the dotted line in Figure 5, the looper 1 at the right retreat position The front end is located at and away from the needle drop position A and A to the right.

The horizontal cylindrical double loop stitch sewing machine sews the sewing material (not shown) provided on the needle plate 12 by the ascending and descending actions of the needles 2a and 2b and the left and right retreat actions of the looper 1. The sewing material is squeezed onto the needle plate 12 by the cloth pressing member, and is fed in the direction of arrow Y in FIG. 5 by the action of the feeding mechanism provided in the sewing bed B of the sewing machine. The feeding mechanism has Feed teeth, the feed teeth repeatedly protrude from the needle plate 12 and move backward, submerged under the needle plate 12, and return to the forward direction. The feed teeth make the sewing material intermittently move toward the arrow Y Feeding movement in the direction.

The above-mentioned needle bar, looper driving mechanism, and feeding mechanism are known mechanisms that operate synchronously with each other by transmission from a transmission rotating shaft (not shown). The needles 2a, 2b hold the needle threads 20a, 20b (refer to Figures 17 to 23) and pass through the sewing material to the needle plate 12, after which, they rise and pass through the sewing material above the sewing material. The looper 1 holds the looper thread 10 (refer to Figures 17 to 23) and moves to the left in accordance with the start of the ascent of the needles 2a and 2b, and captures the loops 20a2, 20b2 of the needle threads 20a and 20b formed under the needle plate 12. When the needles 2a and 2b are ascending, the sewing material is fed and moved. The needles 2a, 2b pass through the sewing material that is moved by the feed and descend, and catch the looper thread 10 held by the looper 1 in the right retreat. The double-loop stitch sewing machine repeats the above actions to form a double-loop stitch on the sewing material.

Hereinafter, first, the stitch fray prevention device H equipped with the horizontal cylindrical double loop stitch sewing machine described above will be described in detail. The fray prevention device H is equipped with a needle thread holding mechanism, a looper thread holding mechanism, a stopper mechanism, and a thread hook 3 (described later) that links the aforementioned needle thread holding mechanism and a stopper member 4 (described later) of the aforementioned stopper mechanism. The connecting rod 35 as the connecting member and the control unit 8 (described later).

The needle thread holding mechanism has a thread hook 3 and a reciprocating thread operating cylinder 32. The reciprocating thread operating cylinder 32 causes the thread hook 3 to be at a standby position away from the looper 1 and close to the looper 1. Between the positions, the support shaft 30 in the up and down direction is driven to swing. The fulcrum 30 as the swing center of the hook 3 is arranged near the right rear corner of the needle plate 12 and is supported on the aforementioned needle plate base 11.

The hook 3 has an arc-shaped curved shape, and is connected to the front end of the support arm 3e extending from the support shaft 30 to the left in a manner of folding back forward. The front end of the hook 3 is on the lower side of the needle plate 12, and is adjacent to the needle drop positions A and A from the rear of the left side, and a hook 3b protruding outward is formed at the front end. The support arm 3e has an extended portion 3c extending forward from the support shaft 30, and one end of the connecting rod 35 is connected to the front end of the extended portion 3c.

As shown in FIG. 5, at the base of the hook 3, a looper thread holding body 6 having an arc-shaped curved shape as a looper thread holding mechanism is jointly fastened and fixed by two fixing screws 60, 60. The front end of the looper thread holding body 6 extends substantially along the left side of the hook 3 to the front, and the position before the front end of the hook 3 is close to the needle drop positions A and A. At the front end of the looper thread holding body 6, a looper thread receiving portion 6a branched into two is formed. The looper thread holder 6 is configured to be able to adjust the position relative to the hook 3 by loosening the fixing screws 60, 60. By adjusting the position, the looper thread receiving portion 6a at the front end can hold the looper thread 10 better. really.

The aforementioned stopper mechanism is composed of the following components as shown in Figures 6-9: the stopper member 14 is fixed to the front end (left end) of the output rod 31 of the aforementioned wire-operated cylinder 32 through a fixing screw 36, and by using The actuating air supplied through the air pipe 33 causes the wire-operated cylinder 32 to expand and contract to linearly reciprocate and move in the left and right directions; the swing lever 9 can be engaged with a part of the stop member 14 and can release the engagement; a spring 96, which engages the swing lever 9 with a part of the stop member 14 and swings and springs the hook 3 in the direction of the standby position; and one-way movable type (extrusion drive type in the left direction) The stopper cylinder 42 resists the swinging force of the spring 96 and forcibly releases the engagement of the swing lever 9 with a part of the stopper member 14.

The output rod 41 of the aforementioned stopper cylinder 42 is configured to be supplied by a permeable air pipe 43 The actuating air is given to drive the stopper cylinder 42 to the left, and accordingly, the swing lever 9 is made to swing in the counterclockwise direction against the swinging force of the spring 96.

The rocking rod 9 is supported on the upper surface of the rocking rod mounting platform 92 in such a way that it can swing with the support shaft 90 in the vertical direction as the center. The front end of the rocking rod 9 has an engaging claw 9a that can be engaged with a part of the stop member 14, and as shown in FIG. When the member 14 is driven to move in the left direction, that is, when the hook 3 moves to the standby position, it contacts the side of the stop member 14 by the elastic force of the spring 96, and when the wire-operated cylinder 32 is contracted When the aforementioned stopper member 14 is driven to move to the right, as shown in FIG. 7, the elastic force of the spring 96 causes the swing lever 9 to swing in the clockwise direction with the support shaft 90 as the center to become the front end engagement pawl 9a. A state of being engaged with a part of the stop member 14.

Also, as shown in FIG. 8, the retracted line-operated cylinder 32 (refer to FIG. 4) is again expanded by a small amount, whereby the engaging pawl 9a at the front end of the swing lever 9 is engaged with a part of the stopper member 14. , Thereby temporarily stopping the driving movement of the stop member 14 in the left direction. In the state where the stopper member 14 is temporarily stopped in this way, the thread hook 3 moves to the holding position between the standby position and the thread hook through the connecting rod 35 and stops there. At this time, the hook portion 3b at the front end of the thread hook 3 moves from the thread hooking position (needle drop position A, A) shown in FIG. 5 to the rear left, thereby hooking the needle threads 20a, 20b and holding it in the aforementioned holding position .

Furthermore, as shown in FIG. 9, the output rod 41 is extruded and driven to the left as the stopper cylinder 42 expands, thereby causing the swing lever 9 to swing counterclockwise against the swinging force of the spring 96 , So as to release the engagement of the engagement pawl 9a at the front end of the swing lever 9 with a part of the stop member 14, so as to cancel the temporary stop of the stop member 14. Thereby, the thread-operating cylinder 32 performs the maximum expansion action, so that the thread-hanging hook 3 swings and resets to standby through the connecting rod 35. Location.

As described above, in this embodiment, the thread hook 3 of the needle thread holding mechanism swings between the aforementioned standby position, thread hook position, and holding position by the telescopic action of the thread operating cylinder 32 and the stopper cylinder 42.

In addition, in the horizontal cylindrical double-loop stitch sewing machine of this embodiment, the needle plate table 11 installed on the upper surface of the sewing machine bed section B is shown in Figures 3 to 5, and is divided into the left needle plate table section 11L and the right side. The throat plate base 11R consists of these two parts. The needle plate 12 is detachably mounted on the upper surface of the left needle plate base portion 11L through a fixing screw 100, and is supported by a support shaft 30 as the swing center of the thread hook 3 of the needle thread holding mechanism.

In the vicinity of the left end of the left needle plate base 11L divided into two parts (2 places), specifically, the front end (left end) of the sewing machine arm C shown by the imaginary line in Fig. 5 Screw holes 101 are formed in a part separated from the installation part of the aforementioned needle plate 12, and the left needle plate base portion 11L is screwed into the screw holes 101 through the fixing screw member 102 so as to be fastened and fixed and can be released ( It can be installed on the upper surface of the sewing machine bed B in the manner of detachable).

In addition, on the upper surface of the sewing machine bed portion B and the aforementioned left needle plate portion 11L, as shown in FIG. , And the pin hole 104 for the positioning pin 103 to fit into, by inserting the pin hole 104 from above and fitting it into the positioning pin 103, the left needle plate base portion 11L is positioned at a predetermined position relative to the sewing machine bed portion B In this state, by screwing the aforementioned fixing screw member 102 into the screw hole 101, the left needle plate base portion 11L can be fastened and fixed to the upper surface of the sewing machine bed portion B.

Furthermore, in the first embodiment, although the positioning pin 103 is sewn from the sewing machine B. The case where the upper surface protrudes upward and the pin hole 104 is formed in the left needle plate base 11L is described and illustrated. However, the positioning pin 103 may also protrude downward from the lower surface of the left needle plate base 11L, and the pin The hole 104 is formed on the upper surface of the bed portion B of the sewing machine.

On the other hand, the right needle plate base portion 11R divided into two parts constitutes a cylinder mounting base portion that supports the thread operating cylinder 32 and the stopper cylinder 42 (hereinafter, the right needle plate base portion 11R is referred to as a cylinder mounting base portion) The above-mentioned stop mechanism is arranged under the cylinder mounting base 11R. In detail, on the lower surface of the cylinder mounting base 11R, as shown in FIGS. 5 to 8, the wire-operated cylinder 32 is fixedly supported by the mounting screw 105, and the stopper cylinder 42 is arranged on the wire in a state of overlapping two stages. In the lower part of the cylinder 32, the stop cylinder 42 is fixedly supported by the cylinder mounting base 11R through the mounting screw 106.

The above-mentioned cylinder mounting base portion 11R is assembled to the back surface of the sewing machine bed portion B in a fixed state through a fixing screw member 107. Here, the fixed state means that when the fray prevention device H is assembled to the sewing machine bed portion B, the fixing screw member 107 is tightened to fix it in a predetermined position, and it is fixed without position adjustment after assembly. In the state of the established assembly position.

One end (right end) of the aforementioned connecting rod 35 is rotatably connected to the stop member 14 of the stop mechanism by a pin 108. The cylinder mounting base 11R at the position corresponding to the connection part of the stopper member 14 with the pin 108 of the one end of the connecting rod 35 is to allow the stop of linearly reciprocating movement in the left and right directions following the expansion and contraction of the wire-operated cylinder 32 The linear reciprocating movement of the member 14 is formed with a slit 109 that is long in the left-right direction.

In addition, at the other end of the connecting rod 35, the connecting end portion 35a of the extension portion 3c connected to the hook 3 is bent downward by the approximate thickness of the extension portion 3c. At the connecting end portion 35a of the connecting rod 35 bent downward, the pin 110 protrudes upward, on the other hand, The extension part 3c is formed with a connection hole 111 which can be inserted and pulled upward from above the pin 110 with respect to the pin 110.

Thereby, when the left throat plate base portion 11L is released from the sewing machine bed portion B and removed from the sewing machine bed portion B, there is no need to perform a fixing screw for fixing the connecting rod 35 and the extension portion 3c. Unscrew the operation to release the interlocking state of the two. Only by lifting the left needle plate base 11L upward, the connecting hole 111 of the extension part 3c can be pulled upward from the pin 110 to release the connecting rod. 35 and the extension part 3c (thread hook 3) linked state. In addition, when the left needle plate base portion 11L is attached to the sewing machine bed portion B, only by moving the left needle plate base portion 11L from the upper direction toward the sewing machine bed portion B, the connecting hole 111 can be inserted into the pin from above. 110 and the connecting rod 35 and the extended portion 3c (the hook 3) are returned to the interlocking state. Furthermore, the connecting end portion 35a of the connecting rod 35 does not necessarily have to be bent downward. That is, the connecting rod 35 may have a flat plate shape over its entire length.

Furthermore, the swing bar mounting base 92 that supports the swing bar 9 of the stop mechanism so as to swing around the pivot 90 in the up-and-down direction is provided through a slit 93 that is long in the left-right direction and a fixing screw 94. It is mounted on the cylinder mounting base 11R so that the position can be adjusted from left to right. After the cylinder mounting table portion 11R is assembled to the sewing machine bed portion B in a fixed state through the fixing screw member 107, the swing bar mounting table 92 can also be adjusted to the left and right relative to the cylinder mounting table portion 11R, thereby arbitrarily By adjusting the timing of the looper 1 passing through the needle thread loops 20a2, 20b2 held on the hook 3, the self-connection for preventing the thread fraying can be reliably performed.

As described above, in the horizontal cylindrical double loop stitch sewing machine of this embodiment, the needle plate base 11 is divided into two parts: the left needle plate base portion 11L and the right needle plate base portion 11R. When the stitch fray prevention device H is assembled on the sewing machine bed part B, the left The left needle plate base portion 11L and the right cylinder mounting base portion 11R of the needle plate base 11 divided into two parts on the right are separately mounted on the sewing machine bed portion B. Therefore, compared to when the left and right needle plate parts 11L and 11R are integrated to form a large left and right needle plate table for operation, the overall orientation of the fray prevention device H can be easily performed with less labor. Installation (assembly) of sewing machine bed B.

Moreover, when the needle plate base 11 (the left needle plate base 11L and the right cylinder mounting base 11R) is temporarily assembled to the sewing machine stitch base B, for example, when it is necessary to correct the looper 1, or its operating member is equal to The lower part of the needle plate table 11 is housed inside the sewing machine bed section B and when the position or movement trajectory of the members constituting the sewing is adjusted to adjust the sewing condition, or it is necessary to adjust the sewing machine under the needle plate table 11 to be housed in the sewing machine bed section B. When various parts are repaired or replaced, there is no need to remove from the sewing machine bed part B. The line-operated cylinder 32 and the stop cylinder 43 connected to the air pipes 33 and 43 are installed firmly at the predetermined position during assembly. The table portion 11R can secure a sufficiently large working space by only releasing the left side throat plate table portion 11L to the sewing machine bed portion B and removing it, so that the adjustment or maintenance of the sewing condition can be easily performed.

Next, the thread cutting mechanism 5 provided in the horizontal cylindrical double loop stitch sewing machine of this embodiment will be described. The thread cutting mechanism 5 is shown in Figures 10 to 12, and is configured such that the thread cutting device 5 can be approached to the aforementioned entry position P1 of the needle plate 12 and the looper 1 through the reciprocating drive movement mechanism 70 and to the right of the entry position P1. The rear retreat position P2 reciprocates driving movement. Furthermore, the thread cutting device 5 has a movable cutter 50 for thread cutting, which cuts the left and right needle thread portions 20a1 protruding from the back side of the sewing material W after a predetermined sewing operation, that is, when the sewing ends. 20b1 and looper thread portion 10a; the fixed cutter 51, which is not within the range of the upper and lower reciprocating movement path of the right needle 2b of the aforementioned left and right needles 2a and 2b in the aforementioned entry position P1, is arranged at a position close to the needle drop position Knife 51e; the looper thread clamping member 52 made of leaf spring, which is arranged in the aforementioned The lower part of the movable cutter 50, and the elastic clip holding the end of the cut looper thread 10 between the movable cutter 50 and the aforementioned movable cutter 50; and the thread clamp auxiliary spring 53, which is used to adjust the looper thread clamp Clip retention force of the clip member 52.

The aforementioned movable cutter 50 is shown in FIGS. 10 and 12, and is composed of a strip-shaped plate material that is long in the left-right direction. At a position near the front end of the movable cutter 50 composed of the long strip-shaped plate, there is formed Needle thread catching portion 50b, the needle thread catching portion 50b is hooked when the movable cutter 50 is driven back and moved from the outer position on the other side (left side) of the aforementioned needle drop position to the outer position on one side (right side) Hook and catch the right and left needle thread parts 20b1, 20a1 on the needle plate 12 protruding from the back side of the sewing material W, and a looper thread catching part 50a is formed at the front end of the movable knife 50, which catches the looper thread The portion 50a hooks and catches and protrudes from the needle plate when the movable knife 50 is driven and moved back and forth from the outer position on the other side (left side) of the aforementioned needle drop position to the outer position on one side (right side). The looper thread portion 10a on the back side of the sewing material W on the top 12 is sewn. Furthermore, when the movable knife 50 is driven to move back and forth, the needle thread portions 20b1, 20a1 captured by the needle thread catching portion 50b and the looper thread portion 10a captured by the looper thread catching portion 50a are moved to one of the positions closer to the needle drop position. The outer position of the side (right side) is closer to the position of the other side (right side), and is cut by the sliding connection between the catching portions 50b, 50a and the edge portion 51e of the fixed knife 51.

The reciprocating drive movement mechanism 70 is configured as shown in FIGS. 10, 11 (A), (B), and FIGS. 12 (A), (B), which causes the thread cutting device 5 to operate at the entrance position P1 and the withdrawal position P2. It is driven to move back and forth between, and when the thread cutting device 5 has moved to the aforementioned entry position P1, only the movable knife 50 is placed at the outer position on one side (right side) of the needle drop position and on the other side (left side) The external positions are linearly reciprocated and moved along the xy direction.

That is, the above-mentioned movable cutter 50 is fixed to the movable cutter table 124 through the screw 123 on the lower surface of the right end portion thereof. A U-shaped notch 125 is formed at approximately the center of the longitudinal direction (left-right direction) of the movable cutter table 124, and a U-shaped notch 125 is formed at the left and right positions sandwiching the notch 125 along the length of the movable cutter table 124. A pair of left and right slits 126a, 126b.

The fixed cutter 51 is arranged on the upper surface of the movable cutter 50. On the lower surface of the right end of the fixed cutter 51, the cutter table guide 127 and the right end of the looper thread clamping member 52 are arranged to overlap. The fixed cutter 51, the cutter table guide 127 and the looper thread clamping member 52 are fixed to the left end of the fixed cutter table 129 by screws 128. The movable cutter table 124 is inserted into the left and right pair of connecting rods by a head bolt 148 inserted through the back (lower surface) of the fixed cutter table 129 and from the upper surface side of the pair of left and right links 140a, 140b. The cylindrical flange nuts 131a, 131b at one end of 140a, 140b are clamped so that the cylindrical flange nuts 131a, 131b allow the rotation of one end of the pair of left and right connecting rods 140a, 140b, and can The state of sliding movement within the length range of a pair of left and right slits 126a and 126b of the aforementioned movable cutter table 124.

At the other end of the aforementioned pair of left and right links 140a, 140b, a flange inserted from the upper surface side of the pair of left and right links 140a, 140b and allowed to rotate in the other end of the pair of left and right links 140a, 140b The bushings 141a and 141b are screwed to the device mounting table 130 through countersunk screws 142a and 142b. Thereby, the movable cutter table 124 and the fixed cutter table 129 can be supported by the device mounting table 130 in a state that they can reciprocate in the left and right directions following the swing movement of the pair of left and right links 140a and 140b.

Furthermore, the flange bushing 141b on the right side of the flange bushings 141a and 141b is formed in an eccentric cam shape. The flange bushing 141a of 140a serves as a fulcrum for When entering the position P1, the needle drop position of the movable cutter 50 and the position of the entry movement starting point in the sewing material feeding direction relative to the looper 1 are finely adjusted.

In the aforementioned fixed cutter table 129, a stopper member 134 is formed below the left side link 140a of the pair of left and right links 140a, 140b. The stopper member 134 abuts against the stopper member 133, and the stopper The member 133 is screwed to the aforementioned device mounting table 130.

In addition, at the rear portion of the central portion in the longitudinal direction of the fixed cutter table 129, there is formed an engagement that protrudes rearward from a position slightly to the right of the left end of the movable cutter table 124 and abuts or separates from the protrusion 135 Protrusion 136. In addition, by making the engagement protrusion 136 abut on the protrusion 135, the movable cutter table 124 cannot move further to the right alone. Furthermore, the movable cutter table 124 is screwed to the device mounting table 130, and is elastically compressed by a spring 137 whose one end elastically contacts the right end surface of the stop member 134 and is always moved in the left direction.

The device mounting table 130 is formed with a groove 146 into which the fixed cutter table 129 can be slidably inserted in the left and right directions, and the device mounting table 130 is fixed to the sewing machine through a plurality of screws 147 arranged around it. Desk B. In addition, a drive rod 145 is mounted on the device mounting table 130. The drive rod 145 is pivotally connected to the front end of the piston 148 of the thread cutting cylinder 48 through a shoulder screw 143, and can be centered on the shaft 144 on the device mounting table 130 Drive swing in the direction of arrow ab. The tapered round portion 145 a at the front end of the driving rod 145 is engaged with the U-shaped notch 125 formed at the substantially central portion of the movable cutter table 124.

According to the reciprocating drive movement mechanism 70 constructed in the above manner, as shown in FIGS. 11(A) and (B), when the drive rod 145 is driven to swing in the b direction by the extension of the piston 148 of the thread cutting cylinder 48, the thread cutting device 5 Move to the right against the elastic force of the spring 137 to become a card The engagement protrusion 136 is in contact with the protrusion 135, and the cylindrical nuts 131a, 131b of the pair of left and right links 140a, 140b move to the leftmost state of the pair of left and right slits 126a, 126b, and the cutting table is fixed. The left end surface of the stop member 134 of 129 is separated from the stop member 133. In this state, the thread cutting device 5 is in the retracted position P2, and stands by in an inclined posture that does not hinder the movement of the looper 1.

Furthermore, as shown in Figure 12 (A) and (B), if the drive rod 145 is driven to swing in the a direction by the contraction of the piston 148, the stop member 134 of the fixed cutter table 129 is driven by the elasticity of the spring 137 The elastic force moves to the left. Subsequently, when the aforementioned engaging protrusion 136 and the protrusion 135 abut, the thread cutting device 5 reduces the inclination angle of the aforementioned inclined posture by the swing of the pair of left and right links 140a, 140b, and at the same time, fixes the cutter table 129 The left end of the stop member 134 moves to the left until it abuts the stop member 133. Thereby, the thread cutting device 5 moves to the entry position P1, and becomes a posture substantially orthogonal to the sewing advancing direction.

If the piston 148 is further contracted from this state and the drive rod 145 is driven to swing in the a direction, the fixed knife table 129 is maintained at the aforementioned entry position P1, and at the same time, the movable knife table 124 moves to the left through the needle drop position of the needle plate P Move in the direction (x direction). That is, only the movable cutter 50 fixed to the movable cutter table 124 is moved leftward (moved forward) between the needle plate 12 and the looper 1. At this time, the movable cutter table 124 and the fixed cutter table 129 are supported by the device mounting table 130 in a state that can reciprocate in the left and right directions following the swing movement of the left and right pair of links 140a, 140b, so the movable cutter 50 It is controlled by a pair of left and right links 140a, 140b to move linearly.

Then, since the piston 148 is extended, the drive rod 145 is driven to swing in the b direction. Along with this, the movable cutter 50 moves in the right direction (y-direction) from the leftmost position, and retreats to the right (backward movement) to the lower part of the stationary cutter 51 in the standby of the aforementioned entry position P1. By further contracting the piston 148 from this state, the thread cutting device 5 is moved backward to Fig. 11(A), The retreat position P2 shown in (B).

In addition to the configuration and device described above, the double loop stitch sewing machine of the present embodiment further includes a looper thread tension applying device 84.

As shown in FIGS. 1 and 2, the looper thread tension applying device 84 is arranged inside the sewing machine bed portion B above the reciprocating drive movement mechanism 70 of the thread cutting device 5. The looper thread retraction force applying device 84 is provided with a plurality of looper thread guides 150, which are fixedly arranged for supplying a looper thread across and located on a thread clamping plate (it is well known, so the illustration and details are omitted) Description of the structure) The looper thread portion 10a between the looper 1 and the looper 1 is drawn out in a substantially straight line and guided to move; the swing arm 152 can be horizontally positioned with the position near the looper thread supply source device as the fulcrum shaft 151 Or swing back and forth between a position opposed to the aforementioned looper thread guide 150 and a front side position in a substantially horizontal plane; and an actuator 153, which swings back and forth between the aforementioned two positions to drive the swing arm 152; A looper thread hooking portion 154 is installed at the front end of the arm 152. The looper thread hooking portion 154 hooks the two looper thread guides 150, which are spaced apart from each other by a short distance, and face each other. The looper thread portion 10a between the guides 150a and 150b is close to the looper thread portion 10a of the looper thread guide 150a of the looper thread supply source device.

As shown in FIG. 14, the actuator 153 is composed of a combination of a spring 153a and a single-acting telescopic fluid pressure (air pressure) cylinder 153b. The spring 153a makes the swing arm 152 from the hook thread hooking portion 154 and the bending The position opposite to the needle thread guide 150a is swinging and springing toward the front side position. The single-acting telescopic fluid pressure (air pressure) cylinder 153b, as shown in FIG. 13, acts on the swing arm 152 roughly The arm portion 152a integrally extended at a right angle causes the swing arm 152 to swing back and drive from the front side position to the position where the looper thread hooking portion 154 and the looper thread guide 150a oppose.

The looper thread retraction force applying device 84 constructed in the above-mentioned manner operates so that the state shown in FIG. 13 becomes the state shown in FIG. 14 when the looper 1 after the above-mentioned self-connection enters the operation. As a result, the looper thread portion 10a is bent forward to form a straight side and a hypotenuse of a substantially right triangle when viewed from above, and the looper thread portion 10a supplied to the looper 1 is given the direction from the looper thread supply device. The aforementioned looper thread is supplied with the pull-back force on the side of the source device. As a result, the slack of the looper thread 10 can be removed. The slack of the looper thread 10 is caused by the looper thread holding body 6 holding the looper thread 10 at the front side of the lowered position of the needle after the normal sewing is finished. 1. It is produced by the indispensable action used to obtain the anti-fraying effect by using Alinket.

Furthermore, as the spring 153a of the actuator 153 of the aforementioned looper thread return force applying device 84 that imparts a return force to the looper thread portion 10a, when an excessively strong return force is applied to the looper thread portion 10a, sewing wrinkles may occur. Therefore, it is desirable to set it so as to provide an elastic spring force that can provide an appropriate pull back force to the extent that sewing wrinkles and the like are not generated.

Fig. 15 is a block diagram showing the structure of the control system of the horizontal cylindrical double loop sewing machine of the present embodiment including the above-mentioned fray prevention device H and the thread cutting device 5.

Input the step-in signal 21a and the step-back signal 21b from the pedal switch 21, the needle position signal 22 sent when the needles 2a and 2b are near the top dead center, and the thread cutting signal 23 and the needle thread take-up signal to the control unit 8 of the double loop sewing machine. Go to signal 24.

On the other hand, the control unit 8 outputs operation control signals to the thread operating cylinder 32, the stopper cylinder 42, and the thread trimming cylinder 48, respectively. The thread hook 3 and the looper thread holder 6 operate in accordance with the operation control signal output from the control unit 8 to the thread operating cylinder 32 and the stop cylinder 42 as described above, and the thread cutting cylinder 48 operates in accordance with the thread cutting signal 23 output from the control unit 8. Perform telescopic actions separately.

Furthermore, the control unit 8 also separately sends the sewing machine as the driving source of the transmission rotating shaft The machine motor 80, the cloth pressing cylinder 81 that raises and lowers the cloth pressing member, the air brush 82 that jumps up the needle threads 20a, 20b that are cut in the manner described later, the feed reduction mechanism 83 that adjusts the feed amount of the sewing material, and the looper thread The pull-back force imparting device 84 outputs an action control signal.

The feeding reduction mechanism 83 shortens the action of the feeding teeth on the needle plate P by changing the action pattern of the feeding teeth in the feeding mechanism, for example, tilting the motion path of the feeding teeth relative to the needle plate 12 to shorten the protruding time on the needle plate P. The sewing time of sewing material on the needle plate 12, or by changing the length of the rod that makes the feeding teeth cyclically actuate, reducing the unit feeding pitch of the feeding teeth, etc., thereby reducing the amount of sewing material fed, this kind of feeding is reduced The mechanism 83 is a well-known mechanism, so detailed illustration and description are omitted.

After the sewing of the stitch forming the double loop stitch is completed, the control unit 8 makes the thread hook 3 operate in association with the sewing machine motor 80, the cloth pressing cylinder 81, the air brush 82, the feed reduction mechanism 83, and the looper thread return tension applying device 84 , Thereby performing the stitch fraying action and thread trimming action of preventing double loop stitching.

FIG. 16 is a time sequence diagram showing the operation content of the control unit 8 for fray prevention in time series. The control unit 8 is a computer equipped with a CPU, a ROM and a RAM. The fray prevention and thread trimming operations shown in the timing chart of FIG. 16 are executed by a series of operations of the CPU according to the control program stored in the ROM.

Figures 17 to 22 are explanatory diagrams of the fray prevention operation of the fray prevention device H in the horizontal cylindrical double loop stitch sewing machine of this embodiment, and show the action of the control unit 8 shown in the timing chart of Figure 16 The action state of the thread hook 3 and the looper thread holding body 6 produced.

At the end of regular sewing, the sewing manufacturer using the sewing machine stops the stepping operation of the pedal used for the sewing machine drive, and then performs the anti-fray action, but in this case, the previous The pedal performs a step-back operation. The pedal switch 21 is arranged on a pedal, and outputs a step-in signal 21a during a step-in operation, and outputs a step-back signal 21b when a step-in operation is performed.

The control unit 8 ends the normal sewing, and at the time point S1 in Fig. 16, when the pedal used for driving the sewing machine returns to the neutral state from the step-in state, that is, when the step-in signal 21a is not output from the pedal switch 21 and the step-back is In the state of any one of the signals 21b, a stop command is output to the sewing machine motor 80 with reference to the needle position signal 22 supplied to the input side. Thereby, the sewing machine is temporarily stopped in a state where the needles 2a and 2b are located near the top dead center and the looper 1 is advancing to the left.

After that, the control unit 8 stands by until the pedal is pressed back. When the step-back operation is performed at time S2 in Fig. 16, when the step-back signal 21b is input on the input side, the control unit 8 first provides an operation start command to the feed reduction mechanism 83 at time S3 to reduce the unit feed pitch of the feed teeth, etc. , Make the feed rate of sewing material smaller than (reduce) the feed rate of conventional sewing, after that, start the following anti-fray action. Furthermore, the start period (S3) of the feed tooth of the aforementioned feed reduction mechanism 83 for the smaller feed amount of the sewing material is set so that the needle thread loops 20a2, 20b2 are positioned on the needles 2a, 2a and 2b by the hook 3 The lowering position of 2b is before the needle 1 before the position on the entry end side of the looper 1.

Furthermore, when the control unit 8 inputs the step-in signal 21a from the pedal switch 21 again, the normal sewing operation is restored, so the sewing manufacturer can continue the normal sewing by stepping in the pedal again. In addition, in Fig. 15, the neutral state is maintained from the time point S1 to the time point S2, but it is not necessary to maintain such a neutral state. The operation of the pedal at the end of conventional sewing can also continuously move from the step-in state to the step-back state. . In this case, when passing the neutral position during the migration process, it becomes a no signal state where neither the step-in signal 21a nor the step-back signal 21b is output. 2a, 2b rise to the top end Click nearby and move the looper 1 to the left to start the anti-fray movement.

Moreover, in the timing diagram of Fig. 16, the stepping back operation of the pedal at time S2 continues during the execution of the fray prevention action described below, but this stepping back operation does not need to continue until the fray prevention action ends. So far, after the input of the step-back signal 21b is stopped, the fray prevention action can also be continuously executed by the action of the control unit 8.

Fig. 17 shows the states of the needles 2a, 2b, looper 1, thread hook 3, and looper thread holder 6 when the fray prevention operation starts. The needles 2a, 2b are in a state of passing above the sewing material in which the stitch M of the double loop stitching is formed by the two needle threads 20a, 20b and one looper thread 10. The looper 1 advances to the left under the sewing material, and is in a state where it has caught the needle thread loops 20a2, 20b2 formed by the needles 2a, 2b. In this state, when the needle threads 20a and 20b and the looper thread 10 are cut, as shown in FIG. 24, a general sewing end portion where frays are likely to occur is formed.

After the start of the fray prevention operation, the control unit 8 first provides an operation command to the line-operated cylinder 32 on the output side at time S2 in FIG. 16. Thereby, the thread operating cylinder 32 moves from the expanded state shown in FIG. 6 to the contracted state shown in FIG. It swings with the support shaft 30 as the center and moves from the standby position to the hanging position. At this time, the hook 3b at the front end of the hook 3 hooks the needle thread loop 20a1, and the swing lever 9 in the stop mechanism swings in the clockwise direction with the support shaft 90 as the center by the elastic force of the spring 96 , The front end of the engaging claw 9a can be engaged with a part of the stop member 14.

After that, the control unit 8 immediately provides an operation command to the wire-operated cylinder 32, which slightly expands from the state shown in FIG. 7 to the state shown in FIG. 8, and the stop member 14 is driven to move linearly to the left. When the line-operated cylinder 32 is slightly expanded, the front end of the rocking rod 9 is engaged The claw 9a is engaged with a part of the stopper member 14. Thereby, the driving movement of the stop member 14 in the left direction is temporarily stopped. In the state where the driving movement of the stop member 14 in the left direction is temporarily stopped, as shown in FIG. The hook portion 3b holds the needle thread loop 20a2 in the aforementioned holding position, and as shown in Figure 19, the looper thread holding body 6 enters the front side of the looper 1, and the looper thread receiving portion 6a at the front end is before the needle drop position A on the left Keep the looper thread 10. Therefore, when the looper thread holding body 6 returns to the aforementioned standby position, the looper thread 10 detached from the looper thread holding body 6 may slack.

The hook 3 and looper thread holding body 6 are shown in Figure 20, and continue to hold the needle threads 20a, 20b and looper thread 10 until the feeding movement of the sewing material is finished, and the needles 2a, 2b pass through the needle thread held by the hook 3 The loop 20a2 catches the needle thread loop 20a2. At this time, the looper thread 10 held by the looper thread holding body 6 traverses the position on the front side of the left needle 2a as shown in FIG. 20. Therefore, the needle 2a on the left does not capture the looper thread 10, but the needle 2b on the right only captures the looper thread 10 on the back side of the looper 1.

After the movement of the hook 3 and the looper thread holding body 6 are stopped at the aforementioned positions as described above, the control unit 8 provides an operation command to the sewing machine motor 80 at the time point S3 in FIG. 16. This operation command is provided during the period when the needles 2a and 2b are lowered with reference to the needle position signal 22 and then raised again to the position near the top dead center. In this way, the sewing operation for one stitch is performed on the sewing material. The sewing of one stitch is performed by the action of the feeding reducing mechanism 83, and the feeding amount is smaller than that of the conventional sewing.

Next, the control unit 8 provides an operation command to the stop cylinder 42 of the stop mechanism at the time point S4 in FIG. Thereby, as shown in FIG. 9, the swing lever 9 resists the swinging force of the spring 96 and swings in a counterclockwise direction, so as to release the engagement of the engaging claw 9a at the front end of the swing lever 9 on a part of the stop member 14 Close, and then release the temporary stop of the stop member 14. By releasing the stop of the stop member 14, the line-operated cylinder 32 is expanded to the maximum at the time point of S4. Thereby, as shown in FIG. 20, the hook 3 and the looper thread holding body 6 are swung around the support shaft 30 through the stopper member 14 and the connecting rod 35, and return to the standby position from the holding position.

In addition, the control unit 8 extends the stopper cylinder 42 and operates the looper thread retraction force applying device 84 at the time point S4 in FIG. 16 when the thread operating cylinder 32 is extended to the maximum. Thereby, the looper thread 10 separated from the looper thread holding body 6 is given a pulling force toward the looper thread supply source device side, and the slack generated in the looper thread 10 is removed. Specifically, one of the actuators 153 in the looper thread return force imparting device 84, which is the telescopic fluid pressure cylinder 153b, contracts, and the other side of the actuator 153, which is the elastic force of the spring 153a, makes the aforementioned swing arm 152 around the fulcrum. As shown in FIG. 14, the shaft 151 swings forward from the position where the looper thread hooking portion 154 of the arm front end opposes the looper thread guide 150 a to the front side position. Thereby, the looper thread portion 10a is bent to the front side so as to form a straight side and a hypotenuse of a substantially right triangle when viewed from above, and the looper thread portion 10a supplied to the looper 1 is supplied to the looper thread supply source. Pull back force on the device side. As a result, the slack of the looper thread 10 can be removed. The slack of the looper thread 10 is caused by the looper thread holding body 6 holding the looper thread 10 at the front side of the lowered position of the needle after the normal sewing is finished. 1. It is produced by the indispensable action used to obtain the anti-fraying effect by using Alinket.

In addition, the looper 1 performs a rightward retreat action together with the lowering of the needles 2a and 2b, and passes through the captured needle thread loop 20a2. With the looper 1 threading out, as shown in Fig. 21, the needle 2b on the right is in a state of catching the looper thread 10 in the same way as in normal sewing. On the other hand, the needle on the left The needle 2a is in a state of catching the needle thread loop 20a2 on the left side.

In this state, looper 1 is converted to left advance, and needles 2a and 2b are converted to up. As shown in Figure 22, the looper 1 on the left catches the needle thread loops 20a2, 20b2, and the rising needles 2a, 2b pass out above the sewing material. Thereby, the needle thread 20a captured by the looper 1 loops the previously captured needle thread loop 20a2 with the needle thread 20a, which is a so-called self-connection.

After the sewing of one stitch, the state where the needles 2a and 2b rise to the vicinity of the top dead center and the looper 1 reaches the left entry end is finished. After that, at the time point S5 in FIG. 16, if the thread cutting signal 23 is input to the control unit 8, the thread cutting cylinder 48 of the thread cutting device 5 is provided with an operation command to cause the thread cutting air cylinder 48 to perform a predetermined operation. Thereby, by reciprocatingly driving the moving mechanism 70, the thread cutting device 5 is moved as shown in FIG. After that, the thread trimming operation is performed. The thread cutting operation will be described in detail below based on FIG. 23.

First, as shown in Figure 23(a), when sewing is completed, the thread trimmer 5 moves to the outer position on one side of the needle drop position, that is, the aforementioned entry position P1. As shown in Figure 23(b), only move The cutter 50 drives and moves in the direction of arrow x from the aforementioned entry position P1 to an outer position on the other side of the needle drop position. By this forward driving movement, as shown in Fig. 23(c), when the looper thread catching portion 50a on the front end side of the movable cutter 50 just exceeds the gap between the vicinity of the front end of the looper 1 and the back side of the sewing material W After the looper thread 10 is set, the moving direction of the movable cutter 50 is immediately reversed, and the looper thread portion 10a protruding from the back side of the sewing material W is hooked and caught by the looper thread capturing portion 50a.

Next, as shown in Figure 23(d), the movable cutter 50 is driven to move back and forth in the arrow y direction from the outer position on the other side of the aforementioned needle drop position to the aforementioned entry position P1. At the time of the return driving movement, the needle thread parts 20a1, 20b1 on the left and right protruding from the back side of the sewing material W are hooked and caught by the needle thread catching part 50b. Furthermore, by further driving the movable knife 50 to move back in the arrow y direction, as shown in FIG. The needle thread portions 20a1, 20b1 captured by the capturing portion 50b and the looper thread portion 10a captured by the looper thread capturing portion 50b.

Thereafter, as shown in Figure 23(f), the needles 2a, 2b move to the upper side of the needle plate 12, and the end of the looper thread 10 held by the looper 1 is held by the movable cutter 50 and the looper thread clamp. Between member 52.

The looper thread return pulling force imparting device 84 continues to operate until the above-mentioned thread cutting action ends, and continues to impart a predetermined return pull force to the looper thread 10 extending from the front end of the looper 1 to the sewing material. As a result, as shown in Figure 22 and Figure 24, after the sewing operation of 1 stitch, the needles 2a and 2b rise to the vicinity of the top dead center, and then the needle thread located on the back side of the looper 1 (the front side in Figure 24) 20a and 20b move downward as shown by arrow d. Even so, the looper thread 10 is not slack. Therefore, the looper thread 10 does not slip on the needle threads 20a and 20b and is drawn under the looper 1.

Therefore, when the thread cutting device 5 is activated, and as shown in Figure 23 (b) and (c), the movable knife 50 is moved from the entry position toward the front left near the looper 1 to the other side of the needle drop position ( When the external position on the left side) is driven to move in the direction of arrow x, as shown in Fig. 25, the looper thread catching portion 50a on the front end of the movable knife 50 can hook the cross and the vicinity of the front end of looper 1 and the sewing seam securely. The looper thread 10 between the back side of the material W, and the needle thread catching portion 50b of the movable cutter 50 can reliably hook the needle threads 20a, 20b so that it can be cut reliably by sliding with the fixed cutter 51, The end of the cut looper thread 10 is securely clamped and held between the movable cutter 50 and the looper thread clamping member 52.

Therefore, it is possible to avoid the occurrence of defective cutting caused by the slack of the looper thread 10 after the connection and the occurrence of the defective condition of the looper thread retention after the cutting, and the next sewing can be carried out as reliably as required and with a good appearance.

After the above thread cutting operation is completed, the thread cutting device 5 is moved to the retracted position P2 shown in Figure 11 (A) and (B) through the reciprocating drive movement mechanism 70, and waits for the next sewing in an inclined posture that does not hinder the movement of the looper 1 . On the other hand, the control unit 8 waits until the needle thread pick-up signal 24 is input, and if the needle thread pick-up signal 24 is input at the time point S6 in FIG. The air brush 82 blows out air to jump up the cut ends of the needle threads 20a and 20b that are continuous with the needles 2a and 2b. After that, the control unit 8 outputs an operation command to the cloth press cylinder 81 at the time point S7 in FIG. 16 to operate the cloth press cylinder 81 to raise the pressing member from the upper surface of the needle plate 12, thereby removing and using self-connection to prevent fraying. The sewing material W of the thread is ready for the next sewing.

In the above-mentioned sewing action of 1 stitch for preventing fraying, as shown in FIG. 26, the looper thread 10 passes through the stitch M and is finally formed in the needle thread loop 20b2 on the right side of the back of the sewing material W. During the sewing operation of one stitch of the fray, it is folded back in front of the right needle thread 20b passing through the back side of the sewing material W, passes through the last needle thread loop 20b2 on the right side again, and is drawn and cut.

On the other hand, in the sewing operation of 1 stitch for preventing fraying, the left needle thread portion 20a1 that passes through the back of the sewing material W passes through the last of the regular sewing and continues to be formed on the sewing material W In the last needle thread loop 20a2 on the back side, the last needle thread loop 20a2 is self-connected to form a single loop stitch M. Therefore, the looper thread 10 is strongly pressed by the needle thread 20a and the last needle thread loop 20b2, as shown in Fig. 26, and is restricted to the last needle thread loop spanning the left side. The state between 20b2 and the needle thread loop 20c formed last time. This restriction can be maintained even if a force in either direction is applied to the looper thread portion 10a, and therefore, the frays peculiar to the stitch M of the double loop suture can be prevented from being generated.

In addition, in the sewing operation of 1 stitch for preventing fraying, the feeding amount of the feeding teeth in the aforementioned feeding reducing mechanism 83 to the sewing material is smaller than the feeding amount of the sewing material during the conventional sewing, thereby enabling the automatic connection The distance between traces at the time of interconnection is smaller than the distance between traces at the time of previous interconnection. As a result, the pressing of the looper thread portion 10a between the needle thread 20a on the left and the last needle thread loop 20a2 on the left can be strengthened, and the resistance against falling off can be increased. Therefore, when it is in the state shown in Figure 26, it can be multiplied by the increase in the resistance of the looper thread 10 caused by the smaller the distance between the self-connecting portion and the stitch line when the interconnection before the self-connecting becomes smaller. Function to reliably prevent the fraying of the stitch M of the double loop stitching.

Furthermore, in the above-mentioned embodiment, the looper thread holding body 6 is configured so as to be able to approach and move away from the looper 1 integrally with the thread hook 3 in the needle thread holding mechanism. As explained, however, the looper thread holding body 6 can also be configured to be able to move closer to and away from the looper 1 separately from the thread hook 3 in the aforementioned needle thread holding mechanism.

In addition, in the above-mentioned embodiment, the looper thread holding body 6 is configured to enter the looper thread 1 and the looper thread receiving portion 6a at the front end of the looper thread 10 before the needle drop positions A and A. It has been explained, but it can also be configured in such a way that the looper thread receiving portion 6a that enters the rear side of the looper 1 and the front end holds the looper thread 10 at the rear of the needle drop positions A and A.

Furthermore, in the above-mentioned embodiment, for the throat plate base 11 on which the fray prevention device H is installed, a structure divided into two parts, the left throat plate base portion 11L and the right throat plate base portion 11R, is adopted, thereby improving the fray prevention device. H describes the ease of assembly work or maintenance of the sewing machine bed portion B. However, as the needle plate bed 11 in the fray prevention device H, it can also be used as in the prior art The general structure shown is a long one on the left and right.

Furthermore, in each of the above embodiments, a double-needle horizontal cylindrical double-loop stitch sewing machine is used as an application object, but it can also be applied to a one-needle horizontal cylindrical double-loop stitch sewing machine or a lockstitch double-loop stitch sewing machine.

B‧‧‧Sewing machine bed

C‧‧‧Sewing machine arm

D‧‧‧Sewing machine body

5‧‧‧Thread cutting device

12‧‧‧Needle plate

70‧‧‧Reciprocating drive moving mechanism

84‧‧‧Bender thread return tension imparting device

151‧‧‧Pivot point axis

152‧‧‧Swing arm

153‧‧‧Actuator

153a‧‧‧Spring

153b‧‧‧Expandable fluid pressure cylinder

Claims (5)

A double-loop stitch sewing machine with a thread fraying prevention device. The double-loop stitch sewing machine is provided with: a needle that holds the needle thread and moves up and down; and a looper that holds the looper thread and can be substantially orthogonal to the upper and lower movement path of the needle The direction advances and retreats, and the needle captures the needle thread loop formed under the needle plate when entering the motion; the looper thread held by the looper connects the needle thread loop captured by the entry motion of the looper, by This forms double-loop stitch stitches on the sewing material; the double-loop stitch sewing machine with thread fray prevention device is equipped with a needle thread holding mechanism, which can approach and move away from the aforementioned looper, and make it when approaching The loop of the needle thread captured by the looper is held on the side of the entry end of the looper than the lowered position of the needle; the looper thread holding mechanism can approach and move away from the looper, and make it move closer to the looper. The looper thread extending from the looper needle to the sewing material is maintained at the front or back side of the lowered position of the needle; and the control part, which interacts with the movement of the needle and looper, and the feed motion of the sewing material Control the approach and separation actions of the aforementioned needle thread holding mechanism and the aforementioned looper thread holding mechanism in an associated manner; the control part sets the aforementioned looper needle in the entering position and the aforementioned needle in the rising position to complete conventional sewing, The needle thread holding mechanism and the looper thread holding mechanism are moved closer to hold the needle thread loop at a position closer to the entry end of the looper than the lowered position of the needle, and the looper thread is held lower than the needle. The position is closer to the front side or the back side. Maintain this state until the needle passes through the needle thread loop captured by the looper and descends. After that, the position retention of the needle thread loop is released to cooperate with the lowering of the needle and Ascent, advance of the aforementioned curved needle The retreat action and the feeding action of the aforementioned sewing material execute the sewing action of at least 1 stitch including the movement of the needle passing through the needle thread loop and descending, thereby using the needle thread held by the needle to make the aforementioned bend The needle thread loop held by the needle is self-connected to prevent the thread from fraying; the double-loop stitch sewing machine with thread fray prevention device is equipped with a looper thread pull-back force imparting device, which enters the looper after the above-mentioned self-connection At the time, the hook crosses the looper thread part located between the looper thread supply source device and the looper and moves sideways, thereby bending the looper thread portion to the looper thread portion supplied to the looper. The looper thread supply source device is provided with a pull back force, and the double loop stitch sewing machine with thread fray prevention device is provided with a guide span between the looper thread supply source device and the looper needle. At least two looper thread guides that move the looper thread part in a substantially straight line. The looper thread return force imparting device is composed of a swing arm, a looper thread hooking part, and an actuator. The swing arm can approach The position of the aforementioned looper thread supply source device is that the fulcrum shaft swings back and forth in a horizontal or substantially horizontal plane in opposition to the position of the aforementioned looper thread guide and the side position where the looper thread is partially bent, and the looper thread hooking part is installed at The front end of the swing arm is hooked on the looper thread portion of the looper thread guide on the side of the looper thread supply source device among the two looper thread guides, and the actuator drives the swing arm in the two looper thread guides. Sway back and forth between positions. For example, the double-loop stitch sewing machine with thread fray prevention device in the first item of the scope of patent application, wherein the actuator in the looper thread return force imparting device is composed of a combination of a spring and a fluid pressure cylinder, and the spring swings the aforesaid The arm oscillates from the position opposite to the looper thread guide to the side position, and the fluid pressure cylinder resists the elastic force of the spring to guide the swing arm from the side position to the looper thread. Return to the opposite position of the lead Swing drive. For example, the double loop stitch sewing machine with thread fray prevention device in the first item of the scope of patent application, wherein the control part is used to stop the feeding of the sewing material during the self-connected sewing operation of at least 1 stitch. , Or under the feeding action which is less than the feeding amount in normal sewing. For example, the double loop stitch sewing machine with thread fray prevention device in the first item of the scope of patent application, wherein the looper thread retaining body as the looper thread retaining mechanism can be integrated with the needle thread retaining mechanism to approach the looper and Separate action. For example, the double-loop stitch sewing machine with thread fray prevention device in any one of items 1 to 4 of the scope of patent application, wherein the aforementioned needle thread holding mechanism has a thread hook and a hook actuator, and the thread hook spans and away from the aforementioned Between the standby position of the looper and the thread-hanging position close to the looper, the pivot in the up-and-down direction swings in a plane approximately parallel to the needle plate, and the hook actuator drives the thread-hanging hook to swing in the aforementioned standby Position and thread hanging position, and further equipped with: a stopper mechanism, which is arranged at a position farther from the needle plate than the thread hanging hook of the needle thread holding mechanism; The stopper member can temporarily stop and release the swing from the thread hanging position of the thread hanging hook to the standby position, so that the needle thread loop caught by the thread hanging hook at the thread hanging position is held in the aforementioned The holding position between the thread hanging position and the standby position; and a connecting member that links the thread hanging hook of the needle thread holding mechanism and the stop member of the stop mechanism; the control portion selectively controls the hook actuator and The actuator is stopped, and the needle thread loop caught by the thread hook at the thread hook position is held between the thread hook position and the standby position by abutment with the stop member.

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