CN107201602B - Fabric sewing method and double-thread lockstitch sewing machine - Google Patents

Abstract

The invention relates to a sewing method of fabric, which comprises the following steps: a first step of making the cutting end part of the looper thread cut by the thread cutting device in a free state; a second step of making the curved needle thread cutting end part become a downstream side facing the sewing advancing direction of the curved needle (3) and shifting along the posture approximately along the sewing advancing direction; a third step of holding the vicinity of the tip of the looper thread cut end portion; a fourth step of guiding the midway part of the looper thread between the left and right needles by the rotation half-cycle action of the sewing machine and holding the needle thread in a state of preventing the needle thread from moving in a direction other than the sewing advancing direction; and a fifth step of releasing the holding of the front end portion of the cut end portion of the looper thread at a set position within an operation range during which the looper reaches a position near the retreating end from a position near the advancing end during the subsequent rotational operation, and performing predetermined sewing while maintaining the cut end portion of the looper thread in a free state after the fifth step.

Description

Fabric sewing method and double-thread lockstitch sewing machine

Technical Field

The present invention relates to a method for sewing a fabric including a round fabric, such as a T-shirt or an underwear, by using a double-thread lockstitch sewing machine represented by a double-needle horizontal tubular sewing machine, for example, by sewing a front and a rear fabric, which are processed into a ring shape, to an end stitch sewing for preventing an end portion from being opened, and to a double-thread lockstitch sewing machine used for the sewing.

Background

For example, in the case of sewing the end stitches of the round material using a two-needle double-thread lockstitch sewing machine, while feeding the sewn portion of the round material (the overlapped material portion where the end edge portions are folded back and overlapped on the back side of the material) along the upper surface of the needle plate in a predetermined sewing direction, a plurality of needle thread loops are formed under the needle plate by the up-and-down movement of a plurality of needles arranged in parallel in the direction orthogonal to the sewing advancing direction, and grasping the plurality of needle loops by advancing the looper which is capable of advancing and retreating in a direction substantially orthogonal to a sewing advancing direction between one side portion and the other side portion in the parallel direction of the plurality of needles, looping the plurality of grasped needle loops by the looper held by the looper, thereby forming a double lock stitch on the entire circumference of the sewn portion (overlapped fabric portion) of the dome fabric.

As shown in fig. 24(a) and 24(B), the above-described two-needle double-lock stitch sewing machine for forming a two-lock stitch includes: two left and right needles 1a and 1b arranged in parallel in a direction orthogonal to the sewing direction H so as to hold the left and right needle lines NTa and NTb (see fig. 25) to reciprocate in the vertical direction with respect to the needle plate 2; a looper 3 which can hold a looper thread LT (see fig. 25) and retreat in a direction substantially orthogonal to a vertical reciprocating path of the needles 1a and 1b, and which can grasp needle thread loops NTa 'and NTb' (see fig. 25) formed by the needles 1a and 1b below the needle plate 2 during the retreat; and a thread cutting device 4 which is reciprocatingly driven between an advancing position P1 to the left front side close to the needle plate 2 and the looper 3 and a retreating position P2 to the right rear side of the advancing position P1, and which performs a cutting action by moving from the retreating position P2 to the advancing position P1 after a predetermined sewing operation is completed, that is, when the sewing is completed, and forms a double-thread lock stitch a of a predetermined length on the sewing material W by looping the needle thread loops NTa 'and NTb' with the looper thread LT held by the looper 3.

The thread cutting device 4 is used for cutting the machine thread parts NTa1, NTb1 and the curved thread part LT1 protruding to the back side of the sewing fabric W when the sewing of the double lock stitch A with a predetermined length formed on the sewing fabric W is finished, and the thread cutting device 4 comprises: a movable cutter 5; a fixed cutter 6; a looper thread holding member 7 made of a plate spring, which is disposed below the movable knife 5 and elastically holds and holds an end of the looper thread LT to be cut between the looper thread holding member and the movable knife 5; and a thread holding auxiliary spring 8 for adjusting a holding force of the looper thread holding member 7. Further, the thread cutting device 4 including the movable knife 5, the fixed knife 6, the looper thread holding member 7, and the thread holding assist spring 8 is reciprocatingly driven and moved between the retreat position P2 and the advance position P1, and the reciprocating driving and moving mechanism 9 is further provided for reciprocatingly driving and moving only the movable knife 5 between an outer position on one side of the needle falling position (advance position) and an outer position on the other side of the needle falling position after the thread cutting device 4 is moved to the advance position P1.

The reciprocating drive moving mechanism 9 has the same configuration as that of a reciprocating drive moving mechanism of a double-needle horizontal-tubular double-lock-stitch sewing machine in an embodiment of the present invention to be described later, and therefore the same reference numerals are given to corresponding components as those of the reciprocating drive moving mechanism to be described in the embodiment of the present invention.

As shown in fig. 24(a) and (B), in the thread cutting device 4 of the conventional double-thread lockstitch sewing machine having the basic configuration, a looper thread catching portion 10 is formed at a side edge portion of a front end of a movable knife 5, the looper thread catching portion 10 catches a looper thread portion LT1 protruding to a back side of the sewing fabric W when the movable knife 5 is driven backward from an outer position on the other side of the needle falling position to an outer position on the one side, and an organic thread catching portion 11 is formed at a side edge portion of the movable knife 5 closer to a base end than the looper thread catching portion 10, and the organic thread catching portion 11 catches right and left machine thread portions NTa1 and NTb1 protruding to the back side of the sewing fabric W by being sequentially caught when the movable knife 5 is driven backward from the outer position on the other side of the needle falling position to the outer position on the one side (for example, see japanese utility model publication No. 6-32072).

Next, a thread cutting operation performed by the thread cutting device 4 of the conventional double-thread lockstitch sewing machine will be described.

First, as shown in fig. 25(a), after the thread cutting device 4 is moved to the advanced position P1, which is an outer position on one side of the needle fall position at the end of sewing, only the movable knife 5 is driven forward in the arrow x direction from the advanced position P1 toward an outer position on the other side of the needle fall position as shown in fig. 25 (b). As shown in fig. 25(c), immediately after the looper thread catching portion 10 on the tip side of the movable knife 5 passes over the looper thread portion LT caught between the vicinity of the tip of the looper 3 and the back side of the sewing fabric W by the forward driving movement, the moving direction of the movable knife 5 is reversed, and the looper thread portion LT1 is caught by the looper thread catching portion 10 and caught. Next, as shown in fig. 25(d), the movable knife 5 is driven backward in the arrow y direction from the outer position on the other side of the needle drop position toward the advance position P1, and the left and right needle thread portions NTa1, NTb1 protruding to the back side of the sewing fabric W are caught by the needle thread catching portion 11 and caught. Then, as shown in fig. 25(e), the movable knife 5 is further driven backward in the arrow y direction, and the needle thread portions NTa1, NTb1 caught by the needle thread catching portion 11 and the looper thread portion LT1 caught by the looper thread catching portion 10 are cut by the sliding contact of the catching portions 11, 10 with the fixed knife 6. Then, as shown in fig. 25(f), the needles 1a, 1b are moved upward of the needle plate 2, and the leading end portion of the cut end portion LT2 of the looper thread LT1 held by the looper 3 is elastically held by being nipped between the movable cutter 5 and the looper thread holding member 7 for the next sewing. Then, at the start of the next sewing, as the fabric moves in the sewing advancing direction H, the leading end portion of the looper thread cutting end portion LT2 elastically held between the movable knife 5 and the looper thread holding member 7 is automatically pulled out from between the movable knife 5 and the looper thread holding member 7 (holding is released).

Disclosure of Invention

In the conventional double-lock stitch sewing machine having the above-described configuration, the position at which the thread cutting device 4 cuts the needle thread portions NTa1, NTb1 and the looper thread portion LT1 is a position away from the needle drop position which does not fall within the vertical reciprocating path of the needles 1a, 1b, and is located further to the right side than the right needle 1b, so that the cut end portions LT2 of the left and right needle thread portions NTa1, NTb1 and the looper thread portion LT1 after cutting become residual threads having a predetermined length. In particular, since the distal end of the looper thread cut end portion LT2 is elastically held between the movable knife 5 and the looper thread holding member 7 at an outer position on the right side of the right needle 1b apart from the needle drop position, the looper thread cut end portion LT2 does not form a part of the double-thread lock stitch a at the start of sewing when sewing the next fabric portion, but projects long outward of the stitch a in a whisker shape as shown in fig. 26, and this causes a problem in the finished state that the appearance and quality of the sewn product are deteriorated.

In particular, in the case where the looper thread is a thread formed by bundling a plurality of pole filaments, the cut end portion of the looper thread is cared about to form a plurality of pole filaments when cut by the thread cutting device, and the careless thread is projected in different directions outside the stitch or stands on the surface of the fabric, so that the appearance is deteriorated and further defective finishing is likely to occur.

In order to solve such a problem of completion, a sewing operator has conventionally performed a manual operation using, for example, a pair of hand scissors to cut off a cut end portion of a looper thread extending from a stitch of a sewn fabric W after sewing. However, in this case, troublesome manual work is required to cut the thread each time sewing of one sewn article is completed, which not only causes a decrease in sewing work efficiency but also causes the following problems: the sewing worker is burdened with the work, and the work of the sewing worker is hindered by the freedom of the hand, so that the operability of the fabric is deteriorated, and the sewn fabric is easily damaged by hand scissors or the like.

The present invention has been made in view of the above problems, and an object thereof is to provide a method of sewing a fabric and a double-thread lockstitch sewing machine, which can suppress the remaining length of a cut end portion of a looper thread to be short regardless of the type of thread, and which does not deteriorate the appearance, even without performing troublesome manual work such as cutting the cut end portion of the looper thread using a pair of hand scissors or the like, which causes a decrease in sewing work efficiency, an increase in work load, deterioration in fabric operability, fabric damage, and the like.

In order to achieve the above object, a method of sewing a fabric according to a first aspect of the present invention is a method of sewing a fabric, in which a fabric is fed along an upper surface of a needle plate in a predetermined sewing direction of travel, a plurality of needle loops are formed below the needle plate by vertical movement of a plurality of needles arranged in parallel in a direction substantially orthogonal to the sewing direction of travel, the plurality of needle loops are grasped by forward movement of a looper capable of advancing and retreating between one side portion and the other side portion of the plurality of needles in the parallel direction in the direction substantially orthogonal to the sewing direction of travel, and the plurality of grasped needle loops are looped around a looper held by the looper, thereby forming a multi-needle double-stitch seam stitch on the fabric, the method comprising: a first step of, when the looper is located at a substantially advancing end after completion of sewing, setting a cut end portion of the looper thread, which is cut by a thread cutting device disposed on the other side portion in the parallel direction of the machine needle and connected to a thread hole at a front end portion of the looper, to a free state; a second step of changing a cut end portion of the looper thread in the free state to a posture facing a downstream side in a sewing advancing direction of the looper and substantially along the sewing advancing direction; a third step of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction; a fourth step of rotating the needles and the looper for forming a loop or forming a stitch on a next fabric for at least half a turn, thereby guiding a middle portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles, and maintaining the state in which the movement of the middle portion of the looper thread from the guided set position is prevented except for a sewing direction of travel; and a fifth step of releasing the holding of the vicinity of the tip end of the cut end portion of the looper thread at a set operation position within a rotational operation range from a position where the needle is located in the vicinity of a top dead center and the looper is located in the vicinity of an advancing end to a position where the needle is located in the vicinity of a bottom dead center and the looper reaches the vicinity of a retreating end in the rotational operations of the needle and the looper after the fourth step, and performing predetermined sewing while maintaining the cut end portion of the looper thread in a free state after the fifth step.

A method of sewing a fabric according to a second aspect of the present invention is a method of sewing a fabric, in which a overlapped fabric portion overlapped by folding back an end edge portion of a round fabric toward a back side of the fabric is fed along an upper surface of a needle plate in a predetermined sewing traveling direction, a plurality of needle loops are formed under the needle plate by vertical movement of a plurality of needles arranged in parallel in a direction substantially orthogonal to the sewing traveling direction, the plurality of needle loops are caught by forward movement of a looper capable of moving forward and backward in a direction substantially orthogonal to the sewing traveling direction between one side portion and the other side portion in the parallel direction of the plurality of needles, and the plurality of caught needle loops are looped by a looper held by the looper, thereby forming a double-lock stitch over an entire circumference of the overlapped fabric portion of the round fabric, the method comprises the following steps: a first step of, when the looper is located at a substantially advancing end after completion of sewing, setting a cut end portion of the looper thread, which is cut by a thread cutting device disposed on the other side portion in the parallel direction of the machine needle and connected to a thread hole at a front end portion of the looper, to a free state; a second step of changing a cut end portion of the looper thread in the free state to a posture facing a downstream side in a sewing advancing direction of the looper and substantially along the sewing advancing direction; a third step of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction; a fourth step of rotating the needles and the looper for forming a loop or forming a stitch on a next fabric for at least half a turn, thereby guiding a middle portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles, and maintaining the state in which the movement of the middle portion of the looper thread from the guided set position is prevented except for a sewing direction of travel; and a fifth step of releasing the holding of the vicinity of the tip end of the cut end portion of the looper thread at a set operation position within a rotational operation range from a position where the needle is located in the vicinity of a top dead center and the looper is located in the vicinity of an advancing end to a position where the needle is located in the vicinity of a bottom dead center and the looper reaches the vicinity of a retreating end in the rotational operations of the needle and the looper after the fourth step, and performing predetermined sewing while maintaining the cut end portion of the looper thread in a free state after the fifth step.

A double-chain stitch sewing machine according to a third aspect of the present invention includes: a needle plate for placing a fabric and guiding the fabric to be fed in a predetermined sewing advancing direction; a plurality of needles which are arranged in parallel in a direction substantially orthogonal to a sewing advancing direction and move up and down while holding a needle thread; a looper that holds a looper thread, is capable of advancing and retreating in a direction substantially orthogonal to the sewing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and grips, during the advancing operation, a plurality of needle thread loops formed by the needles below a needle plate; and a thread cutting device which is arranged on the other side portion of the parallel direction of the machine needle and cuts the sewn looper thread and the machine needle thread, wherein the plurality of machine needle thread loops caught by the advancing operation of the looper are looped by the looper held by the looper, thereby forming a double lock stitch on the fabric, the double lock stitch sewing machine is characterized by comprising: a curved needle thread cutting end portion transfer means for transferring the curved needle thread cutting end portion, which is cut by the thread cutting device and connected to the thread hole at the curved needle tip portion in a free state, to a position facing a downstream side in a sewing advancing direction of the curved needle and along a substantially sewing advancing direction when the curved needle is positioned at the substantially advancing end after completion of sewing; a looper thread holding means capable of holding the vicinity of the tip of the cut end portion of the looper thread transferred to the downstream side in the sewing direction and capable of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread transferred to the downstream side in the sewing direction; a looper thread holding member comprising: a looper thread guide section which guides a midway portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles by rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric; and a looper thread holding groove part for holding the state that the passing movement of the midway part of the looper thread guided to the set position by the guiding part is stopped except the sewing advancing direction; and a control unit for controlling the needle and the looper to perform a rotational operation in a state where a midway portion of the looper thread is held by the looper thread holding member, wherein the holding by the looper thread holding unit is released at a set operation position within a rotational operation range from a position where the needle is located near a top dead center and the looper is located near a forward end to a position where the needle is located near a bottom dead center and the looper reaches near a backward end, and after the control operation of the control unit, the cut end portion of the looper thread is freely held to perform predetermined sewing on the next fabric.

A double-chain stitch sewing machine according to a fourth aspect of the present invention includes: a needle plate for placing a superposed fabric portion where an end edge portion of a fabric of a round object is folded back to a back side of the fabric to be superposed, and guiding feeding of the superposed fabric portion in a predetermined sewing advancing direction; a plurality of needles which are arranged in parallel in a direction substantially orthogonal to a sewing advancing direction and move up and down while holding a needle thread; a looper that holds a looper thread, is capable of advancing and retreating in a direction substantially orthogonal to the sewing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and grips, during the advancing operation, a plurality of needle thread loops formed by the needles below a needle plate; and a thread cutting device which is disposed on the other side portion in the parallel direction of the machine needle and cuts the sewn looper thread and the machine needle thread, wherein the looper held by the looper winds the plurality of machine needle thread loops caught by the forward movement of the looper to form a double-lockstitch stitch over the entire circumference of the overlapped fabric portion of the round fabric, and the double-lockstitch sewing machine for sewing the round fabric is characterized by comprising: a curved needle thread cutting end portion transfer means for transferring the curved needle thread cutting end portion, which is cut by the thread cutting device and connected to the thread hole at the curved needle tip portion in a free state, to a position facing a downstream side in a sewing advancing direction of the curved needle and along a substantially sewing advancing direction when the curved needle is positioned at the substantially advancing end after completion of sewing; a looper thread holding means capable of holding the vicinity of the tip of the cut end portion of the looper thread transferred to the downstream side in the sewing direction and capable of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread transferred to the downstream side in the sewing direction; a looper thread holding member comprising: a looper thread guide section which guides a midway portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles by rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric; and a looper thread holding groove part for holding the state that the passing movement of the midway part of the looper thread guided to the set position by the guiding part is stopped except the sewing advancing direction; and a control unit for controlling the needle and the looper to perform a rotational operation in a state where a midway portion of the looper thread is held by the looper thread holding member, wherein the holding by the looper thread holding unit is released at a set operation position within a rotational operation range from a position where the needle is located near a top dead center and the looper is located near a forward end to a position where the needle is located near a bottom dead center and the looper reaches near a backward end, and after the control operation of the control unit, the cut end portion of the looper thread is freely held to perform predetermined sewing on the next fabric.

A fabric sewing method according to a fifth aspect of the present invention is a fabric sewing method for forming a multi-needle double-thread lockstitch stitch on a fabric by feeding the fabric in a predetermined sewing traveling direction along an upper surface of a needle plate, forming a plurality of needle loops under the needle plate by vertical movement of a plurality of needles arranged in parallel in a direction substantially orthogonal to the sewing traveling direction, gripping the plurality of needle loops by forward movement of a looper capable of advancing and retracting in a direction orthogonal to the sewing traveling direction between one side portion and the other side portion of the parallel direction of the plurality of needles, and looping the plurality of gripped needle loops by the looper held by the looper, the fabric sewing method including: a first step of, when the looper is located at a substantially advancing end after completion of sewing, setting a cut end portion of the looper thread, which is cut by a thread cutting device disposed on the other side portion in the parallel direction of the machine needle and connected to a thread hole at a front end portion of the looper, to a free state; a second step of changing a cut end portion of the looper thread in the free state to a posture facing a downstream side in a sewing advancing direction of the looper and substantially along the sewing advancing direction; a third step of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction; a fourth step of guiding the midway portion of the looper thread held near the tip portion to a position between the needles at both ends in the parallel direction among the plurality of needles after rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric, and holding the midway portion of the looper thread in a state in which the movement of the midway portion is prevented from the guided position except for the sewing direction; and a fifth step of releasing the holding of the vicinity of the tip end of the cut end portion of the looper thread after the needle and the looper are rotated after the fourth step to form a double lock stitch on the next fabric, and performing a process of sewing the cut end portion of the looper thread into the double lock stitch in accordance with the fifth step.

A double-chain stitch sewing machine according to a sixth aspect of the present invention includes: a needle plate for placing a fabric and guiding the fabric to be fed in a predetermined sewing advancing direction; a plurality of needles which are arranged in parallel in a direction substantially orthogonal to a sewing advancing direction and move up and down while holding a needle thread; a looper that holds a looper thread, is capable of advancing and retreating in a direction substantially orthogonal to the sewing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and grips, during the advancing operation, a plurality of needle thread loops formed by the needles below a needle plate; and a thread cutting device which is arranged on the other side portion of the parallel direction of the machine needle and cuts the sewn looper thread and the machine needle thread, wherein the plurality of machine needle thread loops caught by the advancing operation of the looper are looped by the looper held by the looper, thereby forming a double lock stitch on the fabric, the double lock stitch sewing machine is characterized by comprising: a curved needle thread cutting end portion transfer means for transferring the curved needle thread cutting end portion, which is cut by the thread cutting device and connected to the thread hole at the curved needle tip portion in a free state, to a position facing a downstream side in a sewing advancing direction of the curved needle and along a substantially sewing advancing direction when the curved needle is positioned at the substantially advancing end after completion of sewing; a looper thread holding means capable of holding the vicinity of the tip of the cut end portion of the looper thread transferred to the downstream side in the sewing direction and capable of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread transferred to the downstream side in the sewing direction; a looper thread holding member comprising: a looper thread guide section for guiding a midway portion of the looper thread held near the tip portion to a position between the needles at both ends in the parallel direction among the plurality of needles by rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric; and a looper thread holding groove part for holding the state that the passing movement of the midway part of the looper thread guided to the position by the guiding part is stopped except the sewing advancing direction; and a control unit for controlling the needle and the looper to rotate in a state that the middle part of the looper thread is held by the looper thread holding member, then releasing the holding by the looper thread holding unit, forming a double lock stitch on the next fabric, and performing a process of sewing the cut end part of the looper thread into the double lock stitch formed on the next fabric in accordance with the control operation of the control unit.

Effects of the invention

According to the fabric sewing method and the double-thread lockstitch sewing machine according to the first to fourth aspects of the present invention having the above-described features, the cut end portion of the looper thread which is cut by the thread cutting device and connected to the thread hole of the looper tip portion in a free state after the predetermined sewing operation (after completion of sewing) at the other side portion (the outer position on the left side of the needle drop position) in the parallel direction of the plurality of needles is shifted in a posture toward the downstream side in the sewing traveling direction of the looper and along the substantially sewing traveling direction, the vicinity of the tip portion of the cut end portion of the looper thread after the shift is held at the shift position, and then the needle and the looper for forming the loop or the stitch on the next fabric are rotated at least half a revolution, whereby the halfway portion of the looper thread held at the tip portion can be guided to the set position in the range where the vicinity of each of the needles at both ends in the parallel direction of the plurality of needles are connected, the method includes the steps of holding a midway portion of the looper thread at the guide position in a state of preventing the midway portion from moving in a direction other than a sewing direction, releasing the holding of the needle near the tip end portion of the cut end portion of the looper thread at a set operation position within a rotational operation range during a period in which the needle reaches a position near the bottom dead center from a position near the top dead center and the looper reaches a position near the retreating end from a position near the advancing end in the subsequent rotational operation of the needle and the looper, and then performing predetermined sewing on the lower fabric while maintaining the cut end portion of the looper thread in a free state. Further, by moving the cut end portion of the looper thread sequentially in the sewing traveling direction from the guide holding position, the looper thread end can be left in a position within a range connecting the outer sides of the left and right needle thread portions which is the largest in a range connecting the vicinities of the left and right needle thread portions formed by the both end needles in the parallel direction at the time of a predetermined sewing operation, that is, within the substantial width of the stitch formed by the subsequent sewing operation. Therefore, even when a curved needle thread in which a plurality of pole threads are formed by cutting is used as the curved needle thread, the front end of the curved needle thread cutting end portion including the plurality of pole threads formed by cutting can be prevented from protruding greatly to the outside of the stitch or rising from the surface of the fabric to cause poor appearance and defective finishing.

Further, according to the fabric sewing method and the double-thread lockstitch sewing machine according to the fifth and sixth aspects of the present invention having the above-described features, the cut end portion of the looper thread which is cut by the thread cutting device and connected to the thread hole of the front end portion of the looper in a free state after the predetermined sewing operation (after completion of sewing) at the other side portion (the outer position on the left side of the needle drop position) in the parallel direction of the plurality of needles is shifted in a posture toward the downstream side in the sewing traveling direction of the looper and along the substantially sewing traveling direction, the vicinity of the front end portion of the cut end portion of the looper thread after the shift is held at the shift position, and then the needle for forming the empty loop or forming the stitch on the next fabric and the looper are rotated at least half a revolution, whereby the halfway portion of the looper thread whose front end portion is held can be guided to the position between the two end needles in the parallel direction of the plurality of needles, the half-way portion of the looper thread is held at the guide position in a state of being prevented from moving in a direction other than the sewing direction, and the holding of the vicinity of the tip portion of the cut end portion of the looper thread is released after the next rotational operation of the needle and the looper, and a stitch of the double lock stitch is formed on the next fabric, whereby the entire cut end portion of the looper thread can be sequentially moved in the sewing direction from the guide holding position between the two end needles. Thus, even if the looper thread is cut into a predetermined length by the thread cutting device, the cut end portion of the looper thread can be guided to the formation site of the double lock stitch and reliably sewn into the stitch during the next fabric sewing operation, and the portion of the cut end portion of the looper thread near the tip can be prevented from protruding outward of the stitch in a whisker shape.

As described above, according to the first to sixth aspects of the present invention, after completion of sewing or before starting sewing of the next fabric, the sewing worker does not need to perform troublesome and time-consuming manual work of shortening the cut end portion of the looper thread by using, for example, a hand scissors, and the like, and accordingly, the sewing work efficiency can be improved, the work load of the sewing worker can be reduced, the operability of the fabric can be improved due to the increased freedom of the hand of the sewing worker, the completion of sewing can be improved, and the fabric can be prevented from being damaged by the hand scissors and the like, and therefore, the appearance and quality of the sewn product can be improved.

In particular, as in the second and fourth aspects of the present invention, when end stitch sewing is performed with a round fabric as a sewing object, a sewing start portion and a sewing end portion are slightly overlapped and sewn, and at this time, a cut end portion of a looper thread of a predetermined length after previous sewing, which has protruded outward in a beard shape from a stitch of the sewing start portion, is guided to a set position in a range connecting respective adjacent portions of two end needles in a parallel direction and is sequentially passed and moved from the guide and hold position in a sewing advancing direction, whereby the cut end portion of the looper thread is divided into a short length and a processing is performed such that the thread end is left in a substantial width of the stitch, and therefore, there is no need to perform troublesome and time-consuming work such as restarting the sewing operation for overlapping and sewing after shortening the cut end portion of the looper thread by using a hand scissors or the like when the sewing operation is once interrupted, the end stitch sewing of the whole circumference of the round material fabric including the overlapped sewing of the sewing end part can be continuously performed in one step, and the time loss for processing the residual thread is eliminated, so the end stitch sewing operation of the round material fabric can be efficiently performed.

In the method of sewing a fabric according to the first and second aspects of the present invention, it is preferable that the fabric feed amount at the sewing start portion is set smaller than the fabric feed amount at the time of normal sewing in predetermined sewing performed with the cut end portion of the looper thread kept in a free state after the fifth step.

In this case, since the fabric feed amount at the time of performing predetermined sewing while keeping the cut end portion of the looper thread in a free state is smaller than the fabric feed amount at the time of normal sewing, the tip end of the cut end portion of the looper thread is positioned in a stitch having a complicated winding form between the two needle ends in the parallel direction, and the left and right protrusion of the residual thread to the needle thread portion can be suppressed, and the appearance can be further improved.

In the method of sewing a fabric according to the first and second aspects of the present invention, it is preferable that in the fourth step, a middle portion of the looper thread held in the vicinity of the tip portion is guided to a position between the two end needles in the parallel direction among the plurality of needles, and is held in a state in which movement of the middle portion of the looper thread from the guided position is prevented except for a sewing direction.

In this case, since the position at which the middle portion of the looper thread sequentially passes through and moves in the sewing direction as the holding of the vicinity of the tip portion of the looper thread is released is located between the two end needles in the parallel direction, it is possible to reliably leave the thread end of the short looper thread at a position within the width of the stitch formed by the next sewing operation, and to perform the processing in which the thread end hardly protrudes to the outside of the stitch.

In the double-lock stitch sewing machine according to the third and fourth aspects of the present invention, the transfer unit of the cut end portion of the looper thread is an air injection nozzle, and a looper thread guide member having a passage through which the cut end portion of the looper thread blown up by the air injected from the air injection nozzle is corrected to pass in a substantially horizontal posture along a substantially sewing traveling direction is provided between the air injection nozzle and the looper thread holding unit.

In this case, since the cut end portion of the looper thread is blown up by the air injected from the nozzle, the thread can be reliably transferred to the downstream side in the sewing traveling direction of the looper regardless of the type of thread, and since the air injection nozzle can be provided at a fixed position without requiring a movable portion, the structure is simple and the required space is small, and the air injection nozzle is suitable for being provided inside the sewing machine base. Further, by guiding the cut end portion of the looper thread blown up by the air through the passage of the looper thread guide member, the cut end portion of the looper thread which is liable to swing can be reliably corrected to a horizontal posture along the substantially sewing traveling direction as prescribed.

The double-thread lockstitch sewing machine according to the third and fourth aspects of the present invention may be a double-needle horizontal tubular double-thread lockstitch sewing machine suitable for sewing end stitches of a round material end, or a double-needle flat bed type double-thread lockstitch sewing machine.

Further, in the double-lock stitch sewing machine according to the sixth aspect of the present invention, it is preferable that the looper thread guide portion of the looper thread holding member includes an inclined edge whose position on the advancing end side of the looper is the highest or the lowest and whose position is gradually lowered or raised toward the entrance of the looper thread holding groove portion, and the halfway portion of the looper thread is guided to a position between the two end needles in a state of sliding contact with the inclined edge.

In this case, the halfway portion of the looper thread stretched in accordance with the retreating movement of the looper is brought into sliding contact with the inclined edge of the looper thread guide member, whereby the halfway portion can be surely guided to a position between the both end needles without fail.

Drawings

Fig. 1 is a perspective view of a double-needle type horizontal tubular double-thread lockstitch sewing machine according to an embodiment of the present invention, in which an upper surface portion of a sewing machine bed portion is partially removed.

Fig. 2 is a perspective view of a main part of the double-needle type horizontal tubular double-thread lockstitch sewing machine in a state where a sewing machine arm portion is cut off.

Fig. 3 shows a state in which the thread cutting device of the double-needle type horizontal double-thread lockstitch sewing machine is retracted to the retracted position, where (a) is a plan view of a main portion, and (B) is a vertical sectional view along the line III-III of fig. 3 (a).

Fig. 4 shows a state in which the thread cutting device is advanced to the advanced position and the movable knife is driven and moved forward to the leftmost side, (a) is a plan view of a main portion, and (B) is a longitudinal sectional view taken along line IV-IV of fig. 4 (a).

Fig. 5 is an exploded perspective view for explaining the structure of the reciprocating drive movement mechanism in the thread cutting device.

Fig. 6 is a view of an example of a stitch structure of a double lock stitch viewed from the back side of a sewn fabric.

Fig. 7 is a view of another example of the stitch structure of the double lock stitch viewed from the back side of the sewn fabric.

Fig. 8 is a view of another example of the stitch structure of the double lock stitch viewed from the back side of the sewn fabric.

Fig. 9 is a view of a further example of a stitch structure of a double lock stitch viewed from the back side of a sewn fabric.

Fig. 10 is an external perspective view showing a state where end stitches of a round material fabric are sewn according to a first sewing method of the present invention.

Fig. 11 is an enlarged perspective view of a main part showing a state of a first step of the first sewing method, that is, a state immediately after a cut line is completed after sewing is completed.

Fig. 12 is an enlarged perspective view of a main part showing a state in the second step of the first sewing method, namely, a state in which the looper thread cut end portion is shifted to the downstream side in the sewing advancing direction of the looper.

Fig. 13 is an enlarged perspective view of a main part showing a state of the third step of the first sewing method, that is, a state of holding the vicinity of the tip end of the looper thread cut end shifted to the downstream side in the sewing advancing direction of the looper while sandwiching the vicinity.

Fig. 14 shows a state of the third step similar to fig. 13, where (a) is an enlarged perspective view of a main part viewed from a sewing advancing direction, and (B) is a view along the V-V line of fig. 14 (a).

Fig. 15 shows a state of the fourth step of the first sewing method, that is, a state in which a midway portion of the looper thread cut end portion is guided between the left and right needles, (a) is an enlarged perspective view of a main portion viewed from the sewing advancing direction, and (B) is a view along line VI-VI of fig. 15 (a).

Fig. 16 shows a state where the middle portion of the needle thread cutting end portion is guided between the left and right needles and enters the holding groove portion after the fourth step of the first sewing method, (a) is an enlarged perspective view of a main portion viewed from the sewing advancing direction, and (B) is a view along line VII-VII of fig. 16 (a).

Fig. 17 shows a state of the fifth step of the first sewing method, that is, a state in which the looper advances to the vicinity of the drop needle, (a) is an enlarged perspective view of a main portion viewed from the sewing advancing direction, and (B) is a view along line VIII-VIII of fig. 17 (a).

Fig. 18 is a perspective view showing a main part of a state in which the looper reaches the vicinity of the advancing end by the operation of one rotation of the sewing machine from the state of fig. 17.

Fig. 19 is a perspective view showing a state where the looper reaches the vicinity of the advancing end by further one rotation of the sewing machine from the state of fig. 18 and a main part of the stitch at that time.

Fig. 20 is a perspective view showing a state where the looper reaches the vicinity of the advancing end by further one rotation of the sewing machine from the state of fig. 19 and a main part of the stitch at that time.

Fig. 21 is a perspective view showing a state where the sewing machine further performs one rotation from the state of fig. 18 to reach the vicinity of the advancing end in the second sewing method of the present invention and a main part of the stitch at that time.

Fig. 22 is a perspective view showing a state where the looper reaches the vicinity of the advancing end by further one rotation of the sewing machine from the state of fig. 21 and a main part of the stitch at that time.

Fig. 23 is a view of the stitch structure of the double-thread lock stitch by the second sewing method as viewed from the back side of the sewn fabric.

Fig. 24 shows a state where the entire thread cutting device of the conventional double-thread lockstitch sewing machine advances to the advanced position, (a) is a plan view of a main portion, and (B) is a longitudinal sectional view along line IX-IX of fig. 21.

Fig. 25(a) to (f) are perspective views sequentially showing main parts of a thread cutting operation of a thread cutting device of a conventional double-thread lockstitch sewing machine.

Fig. 26 is a view of an example of a conventional double-lock stitch structure as viewed from the back of a sewn fabric.

Description of the reference numerals

1a, 1b machine needle

2 needle plate

3 curved needle

3a front end line hole

4 tangent line device

50 air injection nozzle (transfer unit of curved needle thread cutting end part)

60 open-close type thread holding mechanism (looper thread holding unit)

70 looper thread guide member

71 passage way

80 looper thread holding member

81 inclined edge (curved needle and thread guiding part)

82 looper thread retaining groove portion

NTa, NTb machine needle thread

LT looper thread

Curved needle line part cut by projecting LT1

LT2 looper thread cut end portion

LT2a looper thread midway part

End of LTe looper thread

M double-thread lockstitch sewing machine

W sewing material (round material)

A double-thread lock-sewn stitch

H direction of sewing

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the same components as those of the conventional double-lock stitch sewing machine will be described with the same reference numerals.

Fig. 1 is a perspective view of a double-needle type horizontal tubular double-thread lockstitch sewing machine according to the present invention in a state where an upper surface portion of a sewing machine bed portion is partially removed. Fig. 2 is a perspective view of a main part of the double-needle type horizontal tubular double-thread lockstitch sewing machine in a state where a sewing machine arm portion is cut off.

In the above-described double-needle horizontal tubular double-thread lockstitch sewing machine M, the sewing machine arm portion 21 and the sewing machine bed portion 22 extend substantially parallel to each other from the upper and lower portions of the sewing machine main body 20 toward the left side. A sewing machine main shaft, a needle driving mechanism for reciprocating two left and right needles 1a and 1b (see fig. 3 and 4) arranged in parallel in a direction substantially orthogonal to a sewing traveling direction in the vertical direction, a presser foot driving mechanism for reciprocating a presser foot (not shown) in the vertical direction, a power transmission mechanism for transmitting power to the driving mechanisms, and the like are incorporated in the sewing machine arm 21, and the driving mechanism and the power transmission mechanism are well known and therefore, description thereof is omitted.

A needle plate 2 is fixed to an upper surface portion of the base portion 22 of the sewing machine, and the needle plate 2 has a needle fall groove portion forming a needle fall position. A looper 3, a thread cutting device 4, a reciprocating drive moving mechanism 9, and the like are incorporated in a sewing machine bed portion 22 at a lower portion of the needle plate 2, wherein the looper 3 keeps a looper thread LT to advance and retreat in a left-right direction substantially orthogonal to a vertical reciprocating path of the needles 1a and 1B, the reciprocating drive moving mechanism 9 reciprocally drives and moves a blade edge portion 6e of a fixed knife 6 of the thread cutting device 4 between an advance position P1 and a retreat position P2, and linearly reciprocally drives and moves only a movable knife 5 described later in a state where the thread cutting device 4 is moved to the advance position P1 in an x-y direction between an outer position on one side (right side) of a needle fall position and an outer position on the other side (left side), and the advance position P1 is close to the needle plate 2 and the looper 3 and a contact member 34 described later comes into contact with a stopper member 33 described later as shown in fig. 4(a) and 4(B) As shown in fig. 3(a) and 3(B), the retracted position P2 is located rearward and rightward of the advanced position P1.

The double-needle double-thread lockstitch sewing machine M configured as described above forms a double-thread lockstitch a of a predetermined length on the sewing material W as shown in fig. 6 to 9 by looping the needle loops NTa ', NTb' formed below the needle plate 2 by the needles 1a, 1b with the looper thread LT held by the looper 3.

The thread cutting device 4 is configured to: the thread cutting device 4 can be reciprocally driven and moved by the reciprocating drive movement mechanism 9 between the advanced position P1 near the needle plate 2 and the looper 3 and a retracted position P2 to the right and rearward of the advanced position P1. Further, the thread cutting device 4 includes: a movable knife 5 for cutting the left and right needle thread portions NTa1, NTb1 and the looper thread portion LT1 protruding to the back side of the sewing fabric W after the predetermined sewing operation is finished, that is, at the end of sewing; and a fixed cutter 6 having a blade portion 6e disposed at a position closest to the needle falling position within a range not falling within the vertical reciprocating path of the right needle 1b of the left and right needles 1a, 1b at the advancing position P1. Further, the looper thread holding member 7 made of a plate spring and provided in the conventional double-thread lockstitch sewing machine shown in fig. 24 and the thread holding auxiliary spring 8 for adjusting the holding force of the looper thread holding member 7 are provided, but the looper thread holding member 7 and the thread holding auxiliary spring 8 are moved to a position where they do not hold the cut end portion LT2 of the cut looper thread LT 1. Therefore, the cut end portion LT2 of the looper thread LT1 cut by the thread cutting device 4 after completion of sewing is coupled to the thread hole 3a at the tip end of the looper 3 as shown in fig. 11 and hangs down in a free state. The looper thread holding member 7 and the thread holding auxiliary spring 8 are moved to a position where they do not hold the looper thread cutting end portion LT2, but are moved to a position where they can maintain the state where the movable knife 5 elastically presses the fixed knife 6 in order to reliably cut the looper thread.

The movable knife 5 is formed of a strip-shaped plate material long in the left-right direction, a looper thread catching portion 10 is formed on the edge portion of the movable knife 5 near the front end side of the long strip-shaped plate material in the same manner as in the conventional art, and the looper thread catching portion 10 catches the looper thread portion LT1 protruding to the back side of the sewing fabric W when the movable knife 5 is driven and moved backward from the outer position on the other side (left side) toward the outer position on the one side (right side) toward the outer position on the other side of the needle drop position. Further, a needle thread catching portion 11 is formed in a side edge portion of the movable knife 5 closer to the base end than the looper thread catching portion 10, and when the movable knife 5 is driven backward from the outer position on the other side of the needle fall position to the outer position on the one side, the needle thread catching portion 11 catches the left and right needle thread portions NTa1, NTb1 protruding to the back side of the sewing material W while sequentially hooking them. When the movable knife 5 is driven and moved backward from the outer position on the other side (left side) of the needle drop position, which is the forward position P1, to the outer position on the one side (right side), the right and left needle thread portions NTb1 and NTa1 caught by the needle thread catching portion 11 and the looper thread portion LT1 caught by the looper thread catching portion 10 are moved to positions on the one side (right side) of the outer position on the one side (right side) of the needle drop position, and the needle thread catching portion 11 and the looper thread catching portion 10 are cut by sliding contact with the blade edge portion 6e of the fixed blade 6.

The reciprocating drive moving mechanism 9 configured to reciprocate the thread cutting device 4 between the advanced position P1 and the retracted position P2 and to linearly reciprocate only the movable knife 5 in the x-y direction between the outer position on one side (right side) and the outer position on the other side (left side) of the needle fall position in the state where the thread cutting device 4 has moved to the advanced position P1 is configured as shown in fig. 3(a), 3(B), 4(a), 4(B), and 5.

That is, the lower surface of the right end of the movable knife 5 is fixed to the movable knife base 24 by a screw 23. A U-shaped cutout portion 25 is formed at a substantially central portion in the longitudinal direction (left-right direction) of the movable cutter table 24, and a pair of left and right slits 26a, 26b that are long in the longitudinal direction of the movable cutter table 24 are formed at left and right positions across the cutout portion 25.

The fixed knife 6 is disposed on the upper surface of the movable knife 5, a knife table guide 27 is disposed to overlap the lower surface of the right end of the fixed knife 6, and the fixed knife 6 and the knife table guide 27 are fixed to the left end of a fixed knife table 29 by screws 28. The movable cutter table 24 is sandwiched between a headed bolt 48 inserted through the rear surface (lower surface) of the fixed cutter table 29 and flanged cylindrical nuts 31a, 31b inserted from the upper surface side at one end portions of the pair of left and right links 40a, 40b, and the flanged cylindrical nuts 31a, 31b are in a state of allowing the one end portions of the pair of left and right links 40a, 40b to rotate and in a state of being slidable within the length range of the pair of left and right slits 26a, 26b in the movable cutter table 24.

Flanged sleeves 41a, 41b inserted from the upper surface sides of the other end portions of the pair of left and right links 40a, 40b and allowed to rotate in the other end portions of the pair of left and right links 40a, 40b are screwed and fixed to the device mounting table 30 by flat head screws 42a, 42b, whereby the movable cutter table 24 and the fixed cutter table 29 are supported on the device mounting table 30 in a state of being capable of reciprocating in the left-right direction in accordance with the swinging motion of the pair of left and right links 40a, 40 b.

Further, the right flanged sleeve 41b of the flanged sleeves 41a, 41b is formed in an eccentric cam shape, so that by changing the pitch of the holes at both ends of the right link 40b, the right flanged sleeve 41b can finely adjust the position of the moving start point of the movable knife 5 in the advancing position P1 of the thread cutting device 4 with respect to the needle drop portion and the sewing advancing direction of the looper 3, with the flanged sleeve 41a of the left link 40a as a fulcrum.

A contact member 34 is formed on the fixed cutter table 29, and the contact member 34 contacts a stopper member 33 screwed and fixed to the device mounting table 30 at a position below the left link 40a of the pair of left and right links 40a, 40 b.

Further, an engaging projection 36 is formed at a rear portion of a longitudinal center portion of the fixed cutter table 29, the engaging projection 36 is brought into contact with and separated from a projection 35 projecting rearward from a position slightly rightward from a left end of the movable cutter table 24, and the movable cutter table 24 cannot be moved further rightward by the engaging projection 36 being brought into contact with the projection 35 alone. The movable cutter table 24 is screwed and fixed to the device mounting table 30, and is always elastically biased in the left direction by a spring 37 together with the fixed cutter table 29, and one end of the spring 37 is elastically contacted with the right end surface of the contact member 34.

The device mounting base 30 is formed with a groove 46 into which the fixed cutter base 29 is slidably fitted in the left-right direction, and is fixed to the sewing machine base 22 by a plurality of screws 47 arranged around the groove. A drive rod 45 is attached to the device mounting base 30, and the drive rod 45 is pivotally connected to a distal end portion of a piston 48 of a cylinder (not shown) by a stepped screw 43, and is capable of driving and swinging in the arrow a-b direction about a shaft 44 on the device mounting base 30. A thin circular portion 45a at the tip of the drive lever 45 engages with a U-shaped notch 25 formed at the substantially central portion of the movable cutter table 24.

According to the reciprocating drive moving mechanism 9 configured as described above, as shown in fig. 3(a) and 3(B), when the drive rod 45 is driven and swung in the B direction by the extension of the piston 48, the thread cutting device 4 is in a state in which the contact member 34 of the fixed cutter table 29 is elastically biased in the left direction by the spring 37, and thus the movable cutter table 24 is moved in the right direction to be in contact with the engagement projection 36, and is moved in the right direction against the elastic biasing force of the spring 37, the cylindrical nuts 31a and 31B of the pair of left and right links 40a and 40B are moved to be close to the leftmost one of the pair of left and right slits 26a and 26B, and the left end surface of the contact member 34 of the fixed cutter table 29 is separated from the stopper member 33. In this state, the thread cutting device 4 is located at the retracted position P2 and waits in an inclined posture so as not to hinder the movement of the looper 3.

Next, as shown in fig. 4(a) and 4(B), when the drive rod 45 is driven and swung in the a direction by the contraction of the piston 48, the contact member 34 of the fixed cutter table 29 moves in the left direction by the elastic biasing force of the spring 37. Accordingly, in the state where the engagement projection 36 abuts against the projection 35, the thread cutting device 4 is moved in the left direction until the left end surface of the abutment member 34 of the fixed cutter table 29 abuts against the stopper member 33 while the inclination angle of the inclined posture is reduced by the swing of the pair of right and left links 40a and 40 b. Thereby, the thread cutting device 4 moves to the advance position P1, and is in a posture substantially orthogonal to the sewing traveling direction.

When the piston 48 is further contracted from this state and the drive lever 45 is driven to swing in the a direction, the fixed cutter deck 29 is kept at the advanced position P1, the engagement projection 36 of the fixed cutter deck 29 is separated from the projection 35 of the movable cutter deck 24, and the movable cutter deck 24 is moved in the left direction (x direction) by the needle fall position of the needle plate 2. That is, only the movable knife 5 fixed to the movable knife table 24 is advanced (moved forward) leftward between the needle plate 2 and the looper 3. At this time, the movable cutter table 24 and the fixed cutter table 29 are supported on the apparatus mounting table 30 so as to be capable of reciprocating in the left-right direction in accordance with the swinging motion of the pair of left and right links 40a and 40b, and therefore the movable cutter 5 is controlled to linearly move by the pair of left and right links 40a and 40 b.

Subsequently, the drive lever 45 is driven to swing in the direction b by the extension of the piston 48, and the movable knife 5 moves from the leftmost position to the right (y direction) and moves back (moves backward) to the right to the lower portion of the fixed knife 6 waiting at the advanced position P1. When the piston 48 further extends from this state, the thread cutting device 4 moves backward to the retreat position P2 shown in fig. 3(a) and 3 (B).

In addition to the above-described configuration and apparatus, the double-lock stitch sewing machine M of the present embodiment includes: an air injection nozzle 50 disposed at an upstream side in the sewing direction H of the looper 3; an openable thread holding mechanism 60 disposed at a position facing the air injection nozzle 50 on a downstream side in a sewing direction H of the looper 3; a looper thread guide member 70 disposed between the air jet nozzle 50 and the openable thread holding mechanism 60 above a forward/backward movement path of the looper 3; a looper thread holding member 80 disposed on the downstream side of the looper 3 in the sewing direction H and closer to the retreating side of the looper 3 than the openable thread gripping mechanism 60; and a control unit for controlling the opening and closing operation of the openable wire clamping mechanism 60.

The air injection nozzle 50, the openable thread clamping mechanism 60, the looper thread guide member 70, and the looper thread holding member 80 among the above-described components are housed and arranged inside the sewing machine base 22. However, in order to avoid complication due to overlapping of the above-described components with the above-described components of the reciprocating drive movement mechanism 9, the description of the above-described components is omitted in fig. 1 and 2. The control unit is incorporated in a control unit (not shown) for controlling the overall operation of the double-lock stitch sewing machine.

The air injection nozzle 50 functions as a looper thread transferring means for injecting air toward a cut end portion LT2 (hereinafter, referred to as a looper thread cut end portion LT2) of a looper thread portion LT1 which is cut by the thread cutting device 4 when the looper 3 is positioned at the substantially forward end after completion of sewing and is connected to the thread hole 3a at the forward end portion of the looper 3 so as to hang down freely as shown in fig. 11, thereby causing the looper thread portion cut end portion LT2 to pass over the upper portion of the looper 3 and blow up and transfer to the downstream side in the sewing traveling direction H of the looper 3 as shown in fig. 12.

The openable and closable wire clamping mechanism 60 is constituted by a fixed clamping piece 61 and a slide piece 62 which is openable and closable, wherein the slide piece 62 is moved in the distance direction with respect to the fixed clamping piece 61 by an air cylinder (not shown). As shown in fig. 13, the looper thread temporarily holding means functions to temporarily hold the vicinity of the tip end of the looper thread cut end portion LT2 transferred by blowing air ejected from the nozzle 50 to the downstream side in the sewing direction H of the looper 3 by closing the fixed holding piece 61 and the slider 62, and to release the holding of the vicinity of the tip end of the looper thread cut end portion LT2 by opening the fixed holding piece 61 and the slider 62.

The looper thread temporarily nipping and holding means is not limited to the openable thread nipping mechanism 60 described above, and is a means capable of forcibly nipping and holding the looper thread cut end portion LT2 by opening and closing the fixed nipping piece 61 and the slider 62 and releasing the nipping and holding. For example, the following structure may be adopted: the looper thread cut end portion LT2 is held by the fixed holding piece 61 and the slide piece 62 with the elastic force of a spring or the like, and when the looper thread cut end portion LT2 is pulled to the stitch of the next fabric sewing start portion, the looper thread cut end portion LT is pulled out from the holding position against the elastic force of the spring or the like, and the holding by holding is released.

The looper thread guide member 70 has a passage 71, and as shown in fig. 12, the looper thread cut end portion TL2 blown up by the air injected from the nozzle 50 and passing over the upper portion of the looper 3 is corrected to have a substantially horizontal posture along the substantially sewing traveling direction H and passes through the passage 71. The upper surface portion 72 of the passage 71 in the looper thread guide member 70 is formed as a transparent window so that whether or not the looper thread cut end portion LT2 has been corrected to be in a substantially horizontal posture along the substantially sewing direction H through the passage 71 can be visually checked. Further, a looper thread sliding groove 73 is formed in the right wall portion 74 of the passage 71 in the looper thread guide member 70, and when the halfway portion LT2a of the looper thread cut end portion LT2 is guided toward the looper thread holding member 80, the looper thread sliding groove 73 slidably guides the portion in the vicinity of the tip end portion held by the openable thread holding mechanism 60 to the downstream side in the sewing traveling direction H (see fig. 14(B) to 17 (B)).

The looper thread holding member 80 includes: a looper thread guide 81 for guiding a middle portion LT2a of a looper thread cut end portion LT2 held by the openable thread holding mechanism 60 in the vicinity of the tip thereof to a substantially central position between the left and right needles 1a and 1b as shown in fig. 15(a) and 16(a) by rotating the needles 1a and 1b and looper 3 by half a revolution in order to form an empty loop or form a stitch on the next fabric; and a looper thread holding groove portion 82 for holding a halfway portion LT2a of the looper thread cutting end portion LT2 guided to a substantially central position between the left and right needles 1a, 1b by the guide portion 81 in a state of being prevented from moving in a direction other than the sewing direction H as shown in fig. 16 to 19.

More specifically, the looper thread holding member 80 is a member having a substantially laterally V-shaped overall shape when viewed in the sewing direction H, and the V-shaped open portion is formed in the storage guide 83 of the looper thread halfway portion LT2 a. The looper thread guide part 81 includes an inclined edge along the upper side of the storage guide part 83, the inclined edge being highest at the position on the advancing end side of the looper 3 and gradually lowering toward the entrance of the looper thread holding groove part 82, and the halfway portion LT2a of the looper thread cut end portion LT2 is guided to the substantially central position between the left and right needles 1a and 1b in a state of sliding contact with the guide part 81 including the inclined edge, and is dropped and held in the looper thread holding groove part 82.

The looper thread holding member 80 is fixed to a needle bed support 90 on the front (downstream) side in the sewing direction H of a pair of front and rear needle beds (not shown) provided in the sewing machine bed section 22 in the sewing direction H in order to prevent the swing of the left and right needles 1a and 1 b. In a state where the halfway LT2a of the looper thread cut end portion LT2 is held in the looper thread holding groove portion 82 of the looper thread holding member 80, when the needles 1a and 1b and the looper 3 are operated by the control means to rotate substantially once, the holding by the openable thread holding mechanism 60 is released, and then the control operation of forming the double-thread lockstitch a on the lower fabric portion is performed, whereby the looper thread cut end portion LT2 is processed in a state where the tip (thread end) thereof stays within the substantial width of the double-thread lockstitch a on the next fabric portion.

Next, as a first sewing method using the double-needle horizontal tubular double-thread lockstitch sewing machine M according to the present embodiment configured as described above, a sewing operation for stitch sewing an end portion of a round material fabric W such as an end portion of a T-shirt will be described with reference to fig. 10 to 20.

First, as shown in fig. 10, a superposed fabric portion where fabric edge portions are folded back to the back side of the fabric at an end portion of the round fabric W and superposed is placed on the needle plate 2, and then the superposed fabric portion of the round fabric W is fed and guided in a predetermined sewing traveling direction H, and the sewing machine M is started to perform a rotating operation. The end stitch sewing is performed through the same steps as shown in fig. 25(a) to (e) by the ascending and descending operation of the left and right needles 1a and 1b, the advancing and retreating operation of the looper 3, and the feeding operation of the round material W, which are generated along with the rotating operation of the sewing machine M, to form the double-lockstitch stitch a on the entire circumference of the overlapped material portion of the round material W.

After the completion of the sewing (end stitch sewing), the needle thread portions NTa1, NTb1 and the looper thread portion LT1 are cut by the thread cutting device 4. At this time, since the cutting position is an outer position which is distant from the needle drop position so as not to fall into the vertical reciprocating path of the needles 1a and 1b and is located on the right side of the right needle 1b, the cut end portions LT2 of the left and right needle thread portions NTa1 and NTb1 and the looper thread portion LT1 after cutting have a predetermined residual length.

After the cutting, the left and right needle thread portions NTa1, NTb1 are lifted upward within the width of the stitch a, and the stitch a is formed in the sewing start portion of the next fabric by an appropriate residual length. On the other hand, the looper thread cut end portion LT2 cut to remain in a predetermined length largely projects outward of the stitch a in a whisker shape as shown in fig. 26.

Therefore, in the first sewing method according to the present embodiment, the following steps are performed in order to treat the looper thread cut end portion LT2 so as to have a short residual length and to arrange it at a position within a substantial width of the double-thread lockstitch formed at the sewing start portion of the next fabric with high aesthetic quality.

The first step is as follows: first, the looper thread cutting end portion LT2 to be cut does not sandwich and hold the tip portion thereof between the movable cutter 5 and the looper thread sandwiching member at an outer position distant from the needle drop position and on the right side of the right needle 1b as in the conventional structure, but hangs down at a position distant to the left side from the position of the left needle 1a in a free state connected to the thread hole 3a at the tip portion of the looper 3 located at the substantially forward end as shown in fig. 11.

The second step is as follows: next, in a state where the fixed clamp piece 61 and the slider 62 of the openable and closable thread clamp mechanism 60 are opened, air is injected from the air injection nozzle 50 toward the looper thread cutting end portion LT2, and thereby the looper thread cutting end portion LT2 is blown up and shifted toward the downstream side in the sewing direction H of the looper 3 so as to pass through the upper portion of the looper 3, as shown in fig. 12. At this time, the looper thread cut end portion LT2 is corrected to be in a substantially horizontal posture along a substantially sewing traveling direction H by guiding the looper thread cut end portion TL2 blown up so as to pass over the upper portion of the looper 3 to the passage 71 of the looper thread guide member 70 by the jet air from the nozzle 50 and passing the same through the passage 71.

The third step: then, while the nozzle 50 stops injecting the air, the slider 62 of the openable and closable thread holding mechanism 60 is slid toward the fixed piece 61 to close the two pieces 62 and 61, thereby holding the vicinity of the tip end of the looper thread cut end portion LT2 as shown in fig. 13 and 14.

The fourth step: in this state, in order to form an empty loop or form a stitch on the next fabric, the needles 1a and 1b and the looper 3 are rotated by half a revolution in accordance with the operation of the sewing machine M, and thereby, as shown in fig. 15(a), the halfway portion LT2a of the looper thread LT1 held by the openable and closable thread holding mechanism 60 in the vicinity of the tip end portion is stored in the storage guide portion 83 of the looper thread holding member 80 in accordance with the backward movement of the looper 3, and is then guided to the substantially central position between the left and right needles 1a and 1b in a state of sliding contact with the guide portion 81 including the inclined edge. At the same time, the portion near the tip end held by the open-close type thread holding mechanism 60 is slidably guided toward the downstream side in the sewing advancing direction H in the looper thread sliding groove 73 as shown in fig. 15 (B). By continuing this state, the looper thread midway portion LT2 guided to the substantially central position between the left and right needles 1a and 1B is dropped and held in the looper thread holding groove portion 82 as shown in fig. 16(a), and the vicinity of the tip end portion held by the openable thread holding mechanism 60 is moved to the innermost end portion (the most downstream portion in the sewing traveling direction H) in the looper thread sliding groove 73 as shown in fig. 16 (B).

The fifth step: then, when the left and right needles 1a and 1b and the looper 3 are rotated in accordance with the operation of the sewing machine M and the looper 3 reaches the vicinity of the needle drop (the vicinity of the middle portion of the left and right needles 1a and 1 b), the looper 3 advances toward the rear side of the needles 1a and 1b while lifting up the looper thread portion near the thread hole 3a at the front end portion of the looper 3 as shown in fig. 17. Then, by the continuous operation of the sewing machine M, the left and right needles 1a and 1b and the looper 3 are rotated, and at a set operation position between a position in the vicinity of the advancing end before the looper 3 reaches the advancing end and a position in the vicinity of the retreating end after approximately half a rotation of the advancing end in the reverse direction, as shown in fig. 18, the slide piece 62 of the openable and closable thread holding mechanism 60 is slid to a side away from the fixing piece 61 to open the two pieces 62 and 61, thereby releasing the holding of the vicinity of the tip end of the looper thread cutting end portion LT 2.

After the fifth step, the lower fabric is subjected to a predetermined sewing operation to form the double-thread lock stitch a by rotating the left and right needles 1a and 1b and the looper 3. At this time, since the looper thread cut end portion LT2 is released from the pinching hold in the stage before the predetermined sewing operation, the looper thread cut end portion LT2 is used as a looper thread constituting a stitch for starting sewing, and the length thereof, that is, the remaining thread of the looper thread becomes short. The looper thread cut end portion LT2 is moved to a free state so that the halfway portion LT2a passes through the looper thread holding groove portion 82 of the looper thread holding member 80, and after the first needle sewing operation, the thread end LTe of the shorter looper thread cut end portion LT2 is located within the width of the stitch a at the sewing start position as shown in fig. 19, for example.

Then, the next fabric is continuously sewn in a predetermined manner, and after the second and subsequent sewing operations, the short looper thread cut end portion LT2 is in a state where the thread end LTe is still located within the width of the stitch a at the sewing start position as shown in fig. 20, for example.

The double lock stitch a obtained by sewing the next fabric by the above-described operations of the first to fifth steps and the subsequent steps is in the configuration shown in fig. 6 to 9. In the stitch a having any of the configurations shown in fig. 6 to 9, since the length of the looper thread cut end portion LT2, that is, the remaining thread of the looper thread is relatively short, the thread end LTe does not protrude out to any of the right and left sides of the stitch a to a large extent.

In the stitch a having the configuration shown in fig. 6 to 9 in detail, the end terminal LTe of the looper thread cut end portion LT2 projects outward of the right or left needle thread portion as shown in fig. 7 and 8, but the projecting amount is small, and the looper thread cut end portion LT2 can be finished to such an extent that the appearance is not visually deteriorated due to the large projection outward of the right or left needle thread portion or the rising from the surface of the fabric.

In particular, after the fifth step, the feed amount of the fabric W for about at least one to three needles immediately after the start of sewing in the predetermined sewing in which the looper thread cut end portion LT2 is set to be smaller than the fabric feed amount in the normal sewing thereafter, so that the pitch between the left and right needle thread portions becomes smaller, and the looper thread cut end portion LT2 is in a state of being pressed by the looper thread and the machine needle thread forming the stitch a of the next fabric, and therefore, the protrusion of the thread end LTe of the looper thread to the left and right sides of the machine needle thread portion can be suppressed, and the appearance can be further improved.

As described above, according to the first sewing method, the remaining length of the looper thread cut end portion LT2 cut by the thread cutting device 4 can be made as short as possible, and the thread end thereof can be left at a position within the substantial width of the stitch a, so that even when a looper thread that is cared about by cutting and becomes a plurality of very thin threads is used as the looper thread, it is possible to suppress the appearance deterioration and the finish failure caused by the tip end portion (thread end) of the looper thread cut end portion LT2 including a plurality of very thin threads that are frayed being largely protruded to the outside of the stitch a or rising from the surface of the fabric.

Therefore, according to the first sewing method, after the sewing is completed or before the sewing of the next fabric is started, the sewing worker does not need to perform troublesome and time-consuming manual work of shortening the cut end portion LT2 of the looper thread using, for example, hand scissors, and the like, and accordingly, the efficiency of the sewing work can be improved, the work load of the sewing worker can be reduced, the operability of the fabric can be improved due to the increased freedom of the hand of the sewing worker, the completion of the sewing can be improved, and the sewn fabric W is not damaged by the hand scissors and the like, and therefore, the appearance and quality of the sewn product can be improved.

In particular, in the case where the end stitch sewing is performed with the round material web W as the sewing object as in the present embodiment, the sewing start portion and the sewing end portion are slightly overlapped and sewn, and at this time, the looper thread cut end portion LT2 protruding in a beard shape from the first needle at the start of sewing to the back surface of the material W can be left at a position within the substantial width of the stitch a at the start of sewing of the next material by the operations after the first to fifth steps, and therefore, it is not necessary to restart the sewing operation and perform the overlapped sewing after the shortened cutting process by holding scissors or the like by hand once the sewing operation is interrupted in the middle of the sewing. Therefore, the end stitch sewing of the entire circumference of the round material fabric W including the overlapped sewing of the sewing end portion can be continuously performed at one time, the time loss for processing the left long looper thread cut end portion LT2 can be eliminated, the sewing operation efficiency can be further improved, and the finish condition with good appearance and aesthetic property can be obtained.

Next, as a second sewing method using the double-needle horizontal tubular double-thread lockstitch sewing machine M according to the above-described embodiment, a sewing operation for sewing an end stitch of a round fabric W such as an end of a T-shirt will be described with reference to fig. 21 and 22, similarly to the first sewing method.

Since the operations of the first step to the fourth step in the second sewing method are as shown in fig. 11 to 20 as in the first sewing method, the detailed description of the operations of the first step to the fourth step is omitted and only the fifth step and the following steps will be described.

The fifth step: after the fourth step, the left and right needles 1a and 1b and the looper 3 are rotated in accordance with the operation of the sewing machine M, and when the looper 3 reaches the vicinity of the drop needle (the vicinity of the middle portion of the left and right needles 1a and 1 b), the looper 3 advances toward the rear side of the needles 1a and 1b while lifting the looper thread portion of the thread hole 3a near the front end portion of the looper 3 upward. When the left and right needles 1a and 1b and the looper 3 are rotated by the continuous operation of the sewing machine M and the left and right needles 1a and 1b and the looper 3 are further rotated one turn from the state shown in fig. 20 where the looper 3 reaches the vicinity of the forward end to form a seam a of a double lock seam on the next material, as shown in fig. 21, the looper thread LT is positioned above the seam a. That is, the looper thread LT is located in the stitch a when the stitch a is viewed from the back.

Then, the slider 62 of the openable and closable thread holding means 60 is slid away from the fixing piece 61 to open the two pieces 62 and 61, and the holding of the looper thread cut end portion LT2 in the vicinity of the tip end portion is released, thereby continuing the formation of the double-lock stitch a on the next fabric.

Since the stitch formation by the fifth step, that is, the sewing of the next fabric portion is continued, the looper thread cut end portion LT2 from which the holding is released maintains the state in which the halfway portion LT2a is dropped into and held in the looper thread holding groove portion 82 of the looper thread holding member 80, the looper thread cut end portion LT2 sequentially passes through the looper thread holding groove portion 82 in the sewing traveling direction H as the sewing progresses. Thus, as shown in fig. 23, the looper thread cut end portion LT2 is processed to sew its entire length into the seam a of the double lock seam.

As described above, when the end stitch sewing is performed in which the double lock stitch a is formed on the entire circumference of the overlapped fabric portion of the round fabric W, the sewing start portion and the sewing end portion are slightly overlapped with each other, and the first to fifth steps are performed: the entire length of the looper thread cut end portion LT2 can be processed to be sewn into the stitch at the sewing start position of the next fabric portion by leaving a predetermined length on the back surface of the fabric W by the first sewing at the sewing start, allowing the looper thread cut end portion LT2 protruding in a whisker shape from the stitch a to be in a free state if left as it is, transferring the looper thread cut end portion LT2 to the downstream side in the sewing direction of travel H of the looper 3 in this state to hold the vicinity of the tip end portion, guiding the halfway portion LTa to the substantially central portion between the left and right needles 1a and 1b to hold the same, and sequentially moving the same from the holding position along the sewing direction of travel H.

Therefore, in the second sewing method, the sewing operator does not have to manually cut the fabric W with scissors, and the sewing efficiency can be improved, and the operability of the fabric W can be improved, and the completion of sewing can be improved. Further, since the fabric W is hardly damaged by the scissors, the appearance and quality of the sewn product can be improved.

Further, in the above-described embodiment, the air injection nozzle having a simple structure and occupying no space is used as the transfer means for transferring the looper thread cutting end portion LT2 to the downstream side in the sewing traveling direction H of the looper 3, but the present invention is not limited to this, and a gripping tool for gripping the looper thread cutting end portion LT2 may be provided and the looper thread cutting end portion LT2 may be transferred by moving the gripping tool to the downstream side in the sewing traveling direction H of the looper 3.

Further, as the operation position for releasing the clamping and holding of the vicinity of the tip end of the looper thread cutting end portion LT2 by opening the two pieces 62 and 61 of the openable and closable thread clamping mechanism 60, it is possible to set the operation position to an arbitrary position between a position in the vicinity of the advancing tip before the looper 3 reaches the advancing tip and a position in the vicinity of the retreating tip after the advancing tip rotates about half a turn in the reverse direction, and the more the operation position is set to be in the vicinity of the advancing tip of the looper 3, the more the remaining thread of the looper thread can be shortened.

In the above embodiment, the following description is made: the looper thread holding member 80 is constituted by a plate-like member having a substantially horizontal V-shape as a whole when viewed in the sewing traveling direction H, the V-shaped opening portion is formed in the housing guide portion 83 of the looper thread midway portion LT2a, and the guide portion 81 includes an inclined edge along the upper side of the housing guide portion 83, the inclined edge is highest at the position of the advancing end side of the looper 3, gradually decreases toward the entrance of the looper thread holding groove portion 82, however, in addition to this, a reverse slope inclined edge, that is, an inclined edge whose position is the lowest on the forward end side of the looper 3 and whose position gradually rises toward the entrance of the looper thread holding groove portion 82, may be included, and any plate-like member may be used as long as it has an inclined edge capable of guiding the halfway portion LT2a of the looper thread cutting portion LT2 between the left and right needles, the inclined edge (guide portion) 81 and the looper thread holding groove portion 82 may be formed of a wire material.

Further, although the above-described embodiment is applied to the two-needle horizontal tubular double-stitch sewing machine, the present invention is not limited to this, and may be applied to a two-needle flat bed type double-stitch sewing machine, and may also be applied to a multi-needle horizontal tubular or flat bed type double-stitch sewing machine having three or more needles. However, in the case of a multi-needle sewing machine with three or more needles, the halfway portion LT2a of the looper thread cut end portion LT2 is preferably guided and held between the needles at both ends in the parallel direction among the plurality of needles, and particularly preferably guided and held at a substantially central position in the parallel direction among the plurality of needles. Further, the same effects as those of the above embodiment can be obtained when the present invention is applied to any type of sewing machine.

Claims (18)

1. A method of sewing a fabric, which feeds the fabric along an upper surface of a needle plate in a predetermined sewing direction of travel, forms a plurality of needle loops under the needle plate by moving a plurality of needles arranged in parallel in a direction substantially orthogonal to the sewing direction of travel up and down, grasps the plurality of needle loops by advancing a looper capable of advancing and retreating in a direction substantially orthogonal to the sewing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and forms stitches of a multi-needle double-lock stitch on the fabric by looping the plurality of grasped needle loops with the looper held by the looper, the method comprising:

a first step of, when the looper is located at a substantially advancing end after completion of sewing, setting a cut end portion of the looper thread, which is cut by a thread cutting device disposed on the other side portion in the parallel direction of the needle and connected to a thread hole at a front end portion of the looper, to a free state;

a second step of changing a cut end portion of the looper thread in the free state to a posture facing a downstream side in a sewing advancing direction of the looper and substantially along the sewing advancing direction;

a third step of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction;

a fourth step of rotating the needles and the looper for at least half a turn to form an empty loop or to form a stitch on a next fabric, thereby guiding a middle portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles, and maintaining the state in which the movement of the middle portion of the looper thread from the guided set position is prevented except for a sewing direction of travel; and

a fifth step of releasing the holding of the vicinity of the tip end of the cut end portion of the looper thread at a set operation position within a rotational operation range from a position where the needle is positioned near a top dead center and the looper is positioned near an advancing end to a position where the needle is positioned near a bottom dead center and the looper reaches near a retreating end in the rotational operations of the needle and the looper after the fourth step,

after the fifth step, predetermined sewing is performed while keeping the cut end portion of the looper thread in a free state.

2. A sewing method of a fabric according to claim 1, characterized in that:

in the predetermined sewing performed with the cut end portion of the looper thread kept in a free state after the fifth step, the fabric feed amount at the sewing start portion is set smaller than the fabric feed amount at the time of normal sewing.

3. A sewing method of a fabric according to claim 1, characterized in that:

in the fourth step, the halfway portion of the looper thread held in the vicinity of the tip portion is guided to a position between the two end needles in the parallel direction among the plurality of needles, and is held in a state in which the movement of the halfway portion of the looper thread from the guided position is prevented except for the sewing direction.

4. A sewing method of fabric, which feeds a overlapped fabric part overlapped by folding back an end edge part of a round fabric to a back side of the fabric along an upper surface of a needle plate to a predetermined sewing advancing direction, forms a plurality of needle loops under the needle plate by up-and-down movement of a plurality of needles arranged in parallel in a direction substantially orthogonal to the sewing advancing direction, grabs the plurality of needle loops by advancing of a looper capable of advancing and retreating in a direction substantially orthogonal to the sewing advancing direction between one side part and the other side part of the parallel direction of the plurality of needles, and forms a double lockstitch stitch over the entire circumference of the overlapped fabric part of the round fabric by looping the plurality of the caught needle loops with the looper held by the looper, the method comprises the following steps:

a first step of, when the looper is located at a substantially advancing end after completion of sewing, setting a cut end portion of the looper thread, which is cut by a thread cutting device disposed on the other side portion in the parallel direction of the needle and connected to a thread hole at a front end portion of the looper, to a free state;

a second step of changing a cut end portion of the looper thread in the free state to a posture facing a downstream side in a sewing advancing direction of the looper and substantially along the sewing advancing direction;

a third step of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction;

a fourth step of rotating the needles and the looper for at least half a turn to form an empty loop or to form a stitch on a next fabric, thereby guiding a middle portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles, and maintaining a state in which movement of the middle portion of the looper thread from the guided set position is prevented except for a sewing direction of travel; and

a fifth step of releasing the holding of the vicinity of the tip end of the cut end portion of the looper thread at a set operation position within a rotational operation range from a position where the needle is positioned near a top dead center and the looper is positioned near an advancing end to a position where the needle is positioned near a bottom dead center and the looper reaches near a retreating end in the rotational operations of the needle and the looper after the fourth step,

after the fifth step, predetermined sewing is performed while keeping the cut end portion of the looper thread in a free state.

5. The sewing method of a fabric according to claim 4, characterized in that:

in the predetermined sewing performed with the cut end portion of the looper thread kept in a free state after the fifth step, the fabric feed amount at the sewing start portion is set smaller than the fabric feed amount at the time of normal sewing.

6. The sewing method of a fabric according to claim 4, characterized in that:

in the fourth step, the halfway portion of the looper thread held in the vicinity of the tip portion is guided to a position between the two end needles in the parallel direction among the plurality of needles, and is held in a state in which the movement of the halfway portion of the looper thread from the guided position is prevented except for the sewing direction.

7. A double-chain stitch sewing machine is provided with: a needle plate for placing a fabric and guiding the fabric to be fed in a predetermined sewing advancing direction; a plurality of needles which are arranged in parallel in a direction substantially orthogonal to a sewing advancing direction and move up and down while holding a needle thread; a looper that holds a looper thread, is capable of advancing and retreating in a direction substantially orthogonal to the sewing advancing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and grips, during the advancing operation, a plurality of needle thread loops formed by the needles below a needle plate; and a thread cutting device which is arranged on the other side portion of the parallel direction of the machine needle and cuts the sewn looper thread and the machine needle thread, wherein the looper held by the looper winds the plurality of machine needle thread loops caught by the advancing operation of the looper, thereby forming a double lock stitch on the fabric, the double lock stitch sewing machine is characterized by comprising:

a curved needle thread cutting end portion transfer means for transferring, when the curved needle is positioned at the substantially forward end after completion of sewing, the curved needle thread cutting end portion cut by the thread cutting device and connected to the thread hole at the curved needle tip portion in a free state to a posture along the substantially sewing advancing direction toward a downstream side in the sewing advancing direction of the curved needle;

a looper thread holding means capable of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction and capable of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction;

a looper thread holding member comprising: a looper thread guide section which guides a midway portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles by rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric; and a looper thread holding groove part for holding the state that the passing movement of the midway part of the looper thread guided to the set position by the guiding part is stopped except the sewing advancing direction; and

a control means for controlling the needle and the looper to perform a rotational operation in a state where a halfway portion of the looper thread is held by the looper thread holding member, and releasing the holding by the looper thread holding means at a set operation position within a rotational operation range from a position where the needle is located near a top dead center and the looper is located near a forward end to a position where the needle is located near a bottom dead center and the looper reaches near a backward end,

after the control action of the control unit, the cutting end part of the looper thread is kept in a free state to carry out specified sewing on the next fabric.

8. The double lockstitch sewing machine of claim 7, wherein:

the transfer unit of the cutting end part of the looper thread is an air injection nozzle, and a looper thread guide member having a passage through which the cutting end part of the looper thread blown up by the air injected from the air injection nozzle is corrected to a substantially horizontal posture along a substantially sewing traveling direction and is passed is provided between the air injection nozzle and the looper thread holding unit.

9. The double lockstitch sewing machine of claim 7, wherein:

the looper thread holding member is disposed so that the looper thread guide portion is positioned between the needles at both ends in the parallel direction among the plurality of needles.

10. The double lockstitch sewing machine of claim 7, wherein:

the double-thread lockstitch sewing machine is a double-needle type horizontal cylindrical double-thread lockstitch sewing machine.

11. A double-thread lockstitch sewing machine for sewing a round material fabric, comprising: a needle plate for placing a superposed fabric portion where an end edge portion of a fabric of a round object is folded back to a back side of the fabric to be superposed, and guiding feeding of the superposed fabric portion in a predetermined sewing advancing direction; a plurality of needles which are arranged in parallel in a direction substantially orthogonal to a sewing advancing direction and move up and down while holding a needle thread; a looper that holds a looper thread, is capable of advancing and retreating in a direction substantially orthogonal to the sewing advancing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and grips, during the advancing operation, a plurality of needle thread loops formed by the needles below a needle plate; and a thread cutting device which is arranged on the other side portion of the parallel direction of the machine needle and is used for cutting the sewn looper thread and the machine needle thread, wherein the looper thread held by the looper is used for looping the plurality of machine needle thread loops caught by the advancing action of the looper, thereby forming a double-lock stitch seam on the whole circumference of the overlapped fabric portion of the circular fabric, the double-lock stitch sewing machine for sewing the circular fabric is characterized by comprising:

a curved needle thread cutting end portion transfer means for transferring, when the curved needle is positioned at the substantially forward end after completion of sewing, the curved needle thread cutting end portion cut by the thread cutting device and connected to the thread hole at the curved needle tip portion in a free state to a posture along the substantially sewing advancing direction toward a downstream side in the sewing advancing direction of the curved needle;

a looper thread holding means capable of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction and capable of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction;

a looper thread holding member comprising: a looper thread guide section which guides a midway portion of the looper thread held near the tip portion to a set position in a range connecting respective adjacent portions of the needles at both ends in the parallel direction among the plurality of needles by rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric; and a looper thread holding groove part for holding the state that the passing movement of the midway part of the looper thread guided to the set position by the guiding part is stopped except the sewing advancing direction; and

a control means for controlling the needle and the looper to perform a rotational operation in a state where a halfway portion of the looper thread is held by the looper thread holding member, and releasing the holding by the looper thread holding means at a set operation position within a rotational operation range from a position where the needle is located near a top dead center and the looper is located near a forward end to a position where the needle is located near a bottom dead center and the looper reaches near a backward end,

after the control action of the control unit, the cutting end part of the looper thread is kept in a free state to carry out specified sewing on the next fabric.

12. The double-thread lockstitch sewing machine for sewing a round material as recited in claim 11, wherein:

the transfer unit of the cutting end part of the looper thread is an air injection nozzle, and a looper thread guide member having a passage through which the cutting end part of the looper thread blown up by the air injected from the air injection nozzle is corrected to a substantially horizontal posture along a substantially sewing traveling direction and is passed is provided between the air injection nozzle and the looper thread holding unit.

13. The double lockstitch sewing machine of claim 11, wherein:

the looper thread holding member is disposed so that the looper thread guide portion is positioned between the needles at both ends in the parallel direction among the plurality of needles.

14. The double lockstitch sewing machine of claim 11, wherein:

the double-thread lockstitch sewing machine is a double-needle type horizontal cylindrical double-thread lockstitch sewing machine.

15. A method of sewing a fabric, which feeds the fabric along an upper surface of a needle plate in a predetermined sewing direction of travel, forms a plurality of needle loops under the needle plate by moving a plurality of needles arranged in parallel in a direction substantially orthogonal to the sewing direction of travel up and down, grasps the plurality of needle loops by advancing a looper capable of advancing and retreating in a direction orthogonal to the sewing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and forms stitches of a multi-needle double-lock stitch on the fabric by looping the plurality of grasped needle loops with the looper held by the looper, the method comprising:

a first step of, when the looper is located at a substantially advancing end after completion of sewing, setting a cut end portion of the looper thread, which is cut by a thread cutting device disposed on the other side portion in the parallel direction of the needle and connected to a thread hole at a front end portion of the looper, to a free state;

a second step of changing a cut end portion of the looper thread in the free state to a posture facing a downstream side in a sewing advancing direction of the looper and substantially along the sewing advancing direction;

a third step of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction;

a fourth step of guiding the midway portion of the looper thread held near the tip portion to a position between the needles at both ends in the parallel direction among the plurality of needles after rotating the needles and the looper for at least half a turn in order to form an empty loop or form a stitch on the next fabric, and holding the midway portion of the looper thread in a state in which the movement of the midway portion is prevented from the guided position except for the sewing direction; and

a fifth step of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread after the needle and the looper are rotated after the fourth step, and forming a double lock stitch on the next fabric,

accompanying the fifth step, a process of sewing the cut end portion of the looper thread into a double lock stitch is performed.

16. A double-chain stitch sewing machine is provided with: a needle plate for placing the fabric and guiding the fabric to be fed in a predetermined sewing advancing direction; a plurality of needles which are arranged in parallel in a direction substantially orthogonal to a sewing advancing direction and move up and down while holding a needle thread; a looper that holds a looper thread, is capable of advancing and retreating in a direction orthogonal to the sewing advancing direction between one side portion and the other side portion of the plurality of needles in the parallel direction, and grips a plurality of needle thread loops formed by the needles below a needle plate during the advancing operation; and a thread cutting device which is arranged on the other side portion of the parallel direction of the machine needle and cuts the sewn looper thread and the machine needle thread, wherein the looper held by the looper winds the plurality of machine needle thread loops caught by the advancing operation of the looper, thereby forming a double lock stitch on the fabric, the double lock stitch sewing machine is characterized by comprising:

a curved needle thread cutting end portion transfer means for transferring, when the curved needle is positioned at the substantially forward end after completion of sewing, the curved needle thread cutting end portion cut by the thread cutting device and connected to the thread hole at the curved needle tip portion in a free state to a posture along the substantially sewing advancing direction toward a downstream side in the sewing advancing direction of the curved needle;

a looper thread holding means capable of holding the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction and capable of releasing the holding of the vicinity of the tip of the cut end portion of the looper thread shifted to the downstream side in the sewing direction;

a looper thread holding member comprising: a looper thread guide unit which guides a midway portion of the looper thread held near the tip portion to a position between the needles at both ends in the parallel direction among the plurality of needles after the needles and the looper are rotated at least for half a turn to form an empty loop or to form a stitch on the next fabric; and a looper thread holding groove section for holding a state in which the passing movement of the midway portion of the looper thread guided to the position by the guide section is prevented except for a sewing proceeding direction; and

a control unit for controlling the needle and the looper to rotate in a state that the midway of the looper thread is held by the looper thread holding member, and then releasing the holding by the looper thread holding unit to form a double-lock stitch on the next fabric,

the control unit is configured to control the operation of the sewing machine to sew the cut end portion of the looper thread into the double lock stitch formed on the lower fabric.

17. The double lockstitch sewing machine of claim 16, wherein:

the transfer unit of the cutting end part of the looper thread is an air injection nozzle, and a looper thread guide member having a passage through which the cutting end part of the looper thread blown up by the air injected from the air injection nozzle is corrected to a substantially horizontal posture along a substantially sewing traveling direction and is passed is provided between the air injection nozzle and the looper thread holding unit.

18. The double lockstitch sewing machine of claim 16, wherein:

the looper thread guide portion of the looper thread holding member includes an inclined edge which is positioned at the highest or lowest position on the advancing end side of the looper, and which gradually lowers or raises its position toward the entrance of the looper thread holding groove portion, and guides the halfway portion of the looper thread to a position between the both end needles in a state of sliding contact with the inclined edge.

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