CN110656447A - Sewing machine - Google Patents

Abstract

The present invention relates to a sewing machine capable of suppressing the occurrence of upper thread entanglement and clumps when sewing is started. The sewing machine has a sewing mechanism and a thread clamping mechanism. The sewing mechanism has a needle. The needle has an eye through which the upper thread can be passed to hold the upper thread. The sewing mechanism performs sewing on the fabric by moving the needle up and down. The thread tensioning mechanism has a thread tensioning disc and a thread tensioning motor. The thread tension motor rotates the thread tension reel on which the upper thread is wound. The CPU of the sewing machine controls the thread tension motor to rotate the thread tension disc when the sewing mechanism starts sewing the fabric. At this time, the CPU moves the upper thread in the retracting direction by a predetermined amount based on the amount by which the upper thread is passed through the eye of the needle. The retraction direction is the reverse of the direction in which the upper thread is fed to the eye of the needle.

Description

sewing machine

technical field

The present invention relates to a sewing machine.

Background technique

There is known a sewing machine capable of adjusting the length of the upper thread passed on the needle. The sewing machine described in Japanese Patent Laid-Open No. 1994-190172 includes a first thread gripper, a first gripping device, a thread pulling portion, a second gripping device, a second gripping device, and a second gripping device in this order from the upstream side of the upper thread supply path. Wire Clamps and Wire Clamps. The first holding device and the second holding device are both: holding the upper thread in the open state, and releasing the upper thread in the closed state. The thread pulling part can pull the upper thread from the side of the first thread gripper. The thread tensioner has a thread take-up spring and a stopper body. The thread take-up spring can swing. The stopper body is engaged with the stopper driver of the sewing machine. The upper thread is pulled by the thread pulling part while the first holding device and the second holding device are switched between the open state and the closed state by the sewing machine, and then the sewing machine starts sewing. At this time, the second gripping device and the stopper driver are in an open state, and the upper thread is gripped by the second gripping device. The stopper body moves to a position where the swing of the thread take-up spring is prohibited, thereby prohibiting the upper thread from being successively released from the thread gripper due to the swing of the thread take-up spring. The sewing machine consumes the upper thread at the tip of the needle in the starting seam.

Since the above-mentioned sewing machine consumes the upper thread at the needle tip for sewing, it is necessary to make the upper thread at the needle tip to have a certain length before sewing. When the length of the upper thread at the needle point is longer, the upper thread pulled under the fabric becomes longer. Therefore, there is a possibility that the upper thread at the needle tip becomes tangled under the cloth before being consumed in the starting seam, and a so-called bird's nest (Japanese: 鳳の巣) occurs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a sewing machine capable of suppressing the occurrence of the upper thread being tangled and clumped under the cloth at the time of starting sewing.

The sewing machine of claim 1 has: a sewing part having a needle bar equipped with a machine needle, the needle bar can move up and down, and the sewing part can use the machine that moves up and down to sew the cloth; thread clamping The thread tensioning mechanism has: a thread tensioning disc on which the upper thread is wound; and a driving part for rotating the thread tensioning disc, and the thread tensioning mechanism adjusts the a supply amount of the upper thread to the needle; a sewing control unit that controls the sewing unit to sew the fabric; and a thread adjustment control unit that controls the sewing control unit When sewing the fabric, the thread adjustment control unit controls the drive unit to control the supply amount of the upper thread to the needle. The sewing machine is characterized in that the thread adjustment control unit has The thread retraction control unit controls the drive unit to move the upper thread in the retracting direction by a predetermined amount when the fabric is started to be sewn by the sewing control unit. The direction is the reverse direction of the feeding direction of the upper thread to the needle, and the predetermined amount is a predetermined amount based on the amount by which the upper thread is threaded on the needle. By controlling the drive unit by the thread retraction control unit, it is possible to reduce the amount of the upper thread remaining on the cloth when sewing starts. Therefore, the sewing machine can prevent the upper thread from becoming tangled under the cloth when starting sewing.

In the sewing machine of claim 2, when starting the sewing of the cloth by the control of the sewing control unit, the driving unit may be controlled by the thread retraction control unit a plurality of times so that the upper thread is controlled. The predetermined amount is moved in total by adding up the plurality of movements. The upper thread retracting portion moves the upper thread a plurality of times, so that the upper thread is less likely to be detached from the needle, that is, the thread is lost, compared to the case where the upper thread is moved only once. Therefore, the sewing machine can suppress the occurrence of thread breakage at the start of sewing.

In the sewing machine according to claim 3, the thread retraction control unit may cause the upper thread to pierce the cloth for the first time after the needle pierces the cloth for the first time after the sewing control unit starts sewing. Before the needle pierces the cloth for the second time, the needle is moved to the retracting direction at least once. Thread loss is easily caused by friction between the upper thread held by the needle that moves up and down and the fabric. The timing of the movement of the upper thread is after the needle pierces the fabric for the first time and before the needle pierces the fabric for the second time. Therefore, the sewing machine can suppress the occurrence of thread detachment when the needle pierces the cloth for the first time.

In the sewing machine of claim 4, the sewing section may have a thread take-up lever that lifts the upper thread by moving up and down in synchronization with the up-and-down movement of the needle bar, and the The thread adjustment control unit has a judgment unit that judges whether or not the thread take-up lever is pulling up the upper thread, and when the judging unit determines that the thread take-up lever is pulling up the upper thread, The thread retracting control unit moves the upper thread. When the upper thread is lifted by the thread take-up lever, the upper thread is easily stretched. Since the upper thread retracting control unit rotates the thread tension disc while the thread take-up lever is pulling up the upper thread, the upper thread is easily moved in the retracting direction. Therefore, the sewing machine can further suppress the occurrence of the upper thread being tangled and clumped under the cloth at the time of starting sewing.

In the sewing machine of claim 5, the sewing machine may include a stitch count input unit, and the stitch count input unit may be used to input the number of stitches for limiting the start of sewing performed by the control of the sewing control unit, and the thread The retraction control unit moves the upper thread by the predetermined amount within the number of stitches input by the number of stitches input unit. In the sewing machine, the period for starting the sewing can be limited according to the number of stitches input by the input unit. Therefore, the sewing machine can diversify the way in which the upper thread is moved by the thread retraction control unit.

In the sewing machine of claim 6, the sewing machine may include a timing input unit, and the timing input unit may be used to input the timing at which the thread retraction control unit moves the upper thread, and the thread retraction control unit may cause the upper thread to be moved by the thread retraction control unit. The wire moves in the retracting direction at the timing input by the timing input unit. The timing at which the upper thread is moved by the thread retracting control unit changes according to the timing input by the timing input unit. Therefore, the sewing machine can diversify the way in which the upper thread is moved by the thread retraction control unit.

In the sewing machine of claim 7, the sewing machine may include a movement amount input unit, the predetermined amount can be input by the movement amount input unit, and the thread retraction control unit may move the upper thread by the movement amount input. the specified amount input from the part. The movement amount by which the upper thread is moved by the thread retraction control unit is changed according to the predetermined amount input by the movement amount input unit. Therefore, the sewing machine can diversify the way in which the upper thread is moved by the thread retraction control unit.

In the sewing machine of claim 8, the thread adjustment control unit may include a thread supply control unit that causes the upper thread to be moved before the thread retraction control unit moves the upper thread. Before the needle pierces the cloth for the first time, it is moved in the supply direction, and the thread retraction control unit causes the upper thread to move the upper thread after the needle pierces the cloth for the first time. the specified amount. The upper thread is moved in the feeding direction before the upper thread is moved by the thread retracting control unit. Therefore, the sewing machine can prevent the occurrence of a shortage of the upper thread threaded on the needle when the needle pierces the cloth for the first time, and can reliably prevent the thread from coming off.

Description of drawings

FIG. 1 is a perspective view of the sewing machine 1 .

FIG. 2 is a cross-sectional view of the thread clamping mechanism 60 .

FIG. 3 is a schematic view of the output shaft 18 and the coil 33 of the thread clamping motor 16 .

FIG. 4 is a block diagram of the electrical configuration of the sewing machine 1 .

5 is an explanatory diagram showing the needle bar movement curve, the thread take-up lever thread amount curve, the shuttle thread amount curve, and the supply amount of the upper thread 6 .

6A to 6D are explanatory diagrams showing the flow of the hook 39 to catch the thread 6 .

FIG. 7 is a flowchart of the sewing process.

FIG. 8 is a flowchart of the sewing process connected to FIG. 7 .

FIG. 9 is a front view of the needle 10 and the cloth 99 before sewing is started.

FIG. 10 is a flowchart of normal processing.

FIG. 11 is a front view when the needle 10 pierces the cloth 99 for the first time.

FIG. 12 is a front view when the needle 10 pierces the cloth for the first time and then moves to the upper position of the cloth 99 .

Detailed ways

Embodiments of the present invention will be described. The following description uses left and right, front and rear, and up and down as indicated by arrows in the drawings. The sewing machine 1 shown in FIG. 1 is a knotting machine for forming a knotted stitch on a cloth 99 .

1 to 5, the schematic structure of the sewing machine 1 will be described. The sewing machine 1 has a base portion 2 , a support portion 3 , and an arm portion 4 . The base part 2 is the base of the sewing machine 1, and is provided on a table extending horizontally. The stand portion 2 has a stand main body portion 7 and a cylindrical stand portion 8 . The stand main body 7 has a substantially box shape. The cylindrical base portion 8 extends forward from the base main body portion 7 . The inside of the stand main body portion 7 and the inside of the cylindrical stand portion 8 communicate with each other. The cylindrical base portion 8 has a needle plate 26 on the upper surface of the front end portion. The cloth 99 is placed on the needle plate 26 by the operator. The needle plate 26 has a needle receiving hole. The pillar portion 3 extends upward from the rear portion of the stand main body portion 7 . The arm part 4 is extended forward from the upper part of the support|pillar part 3, and is opposed to the base part 2. As shown in FIG. The front end part of the arm part 4 is the front end part 5 . The distal end portion 5 has a right wall portion 5A and a through hole 5B (see FIG. 2 ). The right wall portion 5A is a wall portion located on the right side of the distal end portion 5 . The through hole 5B penetrates the right wall portion 5A in the left-right direction.

As shown in FIG. 4 , the sewing machine 1 includes a control device 30 , an operation unit 46 and a pedal 38 . The control device 30 is fixed to the lower surface of the table. The control device 30 controls the operation of the sewing machine 1 . The operation part 46 is fixed to the upper surface of the table. The operation unit 46 has a display unit 48 and an input unit 47 . The display unit 48 can display various kinds of information. The input unit 47 can detect various information input by the operator. The input unit 47 includes a power button.

As shown in FIG. 1 , the sewing machine 1 has a sewing mechanism 12 . The sewing mechanism 12 has a needle bar 11 which is equipped with a machine needle 10 and can move up and down, and can form a stitch 98 on a cloth material 99 by using the machine needle 10 that moves up and down. The sewing mechanism 12 includes a main motor 27 (see FIG. 4 ), an upper shaft 15 , a link, a thread take-up mechanism, a needle bar vertical movement mechanism, a shuttle mechanism 40 , and a cloth feeder 20 . The main motor 27 is supported at the rear of the arm portion 4 . The upper shaft 15 extends in the front-rear direction inside the arm portion 4 . The rear end portion of the upper shaft 15 is connected to the output shaft of the main motor 27 via a coupling. The upper shaft 15 can be rotated by the driving of the main motor 27 . The front end portion and the rear end portion of the upper shaft 15 are coaxial with each other. The upper shaft 15 has a crank portion near the rear end portion. The crank portion is a curved portion that exhibits curvature at positions deviated from the axes of the front end portion and the rear end portion of the upper shaft 15 . The link extends in the vertical direction inside the strut portion 3 . The upper end of the connecting rod is connected to the crank part so that the connecting rod can rotate relative to the crank part.

The thread take-up mechanism and the needle bar up-and-down movement mechanism are supported by the top end portion 5 . The thread take-up mechanism has a thread take-up crank and a thread take-up lever 51 . The thread take-up crank is connected to the front end portion of the upper shaft 15, and the thread take-up lever 51 is provided on the thread take-up crank. When the thread take-up crank rotates together with the upper shaft 15 , the thread take-up lever 51 moves up and down in conjunction with the up and down movement of the needle bar 11 . The thread take-up lever 51 has a hole for the upper thread. The thread take-up lever 51 holds the upper thread 6 (refer to FIG. 6A ) passed through the upper thread hole. The upper thread 6 is drawn out one after another from the supply source of the upper thread, and is drawn out to the upper thread hole of the thread take-up lever 51 via the thread clamping mechanism 60 described later.

The needle bar up and down movement mechanism has a needle bar crank connecting rod, a needle bar 11 and the like. The needle bar crank link is rotatably connected to the thread take-up crank, and extends in the vertical direction. The needle bar 11 extends in the up-down direction, and is connected to the needle bar crank link. The lower end of the needle bar 11 is fitted with the machine needle 10 . The needle 10 has a needle eye 10A at the lower end (see FIG. 9 ). The needle 10 can hold the upper thread 6 through the needle hole 10A by threading the upper thread 6 perforated by the upper thread through the thread take-up lever 51 . The needle bar 11 and the needle 10 move up and down together through the reciprocating motion of the needle bar crank link by the rotation of the thread take-up crank.

The shuttle mechanism 40 is provided inside the base portion 2 . The shuttle mechanism 40 has the lower shaft and the hook 39 . The lower shaft extends in the front-rear direction inside the base body portion 7 and the inside of the cylindrical base portion 8 and is rotatable. The lower shaft is connected to the link via the connecting portion, and the lower shaft is capable of reciprocating rotation in conjunction with the reciprocating motion of the link. The rotary hook 39 is provided at the front end of the lower shaft and below the needle-accommodating hole. The hook 39 is rotatable about the lower shaft. As shown in FIG. 6A , the hook 39 has a hook tip 36 . The hook tip 36 is a part of the outer peripheral portion of the hook 39 and protrudes toward the side in the clockwise direction in a front view centered on the lower axis. The bobbin case 32 can be fitted in the hook 39 . The bobbin case 32 accommodates the bobbin on which the lower thread 9 is wound. The bobbin case 32 has a lead-out portion 34, and the lead-out portion 34 can be used to lead the lower thread 9 that has been successively released from the bobbin to the outside.

The sewing machine 1 has a thread trimming mechanism inside the base portion 2 . The thread cutting mechanism includes a fixed blade, a movable blade, and a thread cutting electromagnetic element 161 (refer to FIG. 4 ). The movable knife is connected to the thread cutting electromagnetic element 161 . When the thread cutting electromagnetic element 161 is driven, the movable knife moves, and the upper thread 6 and the lower thread 9 are cut by the thread cutting mechanism.

As shown in FIGS. 1 and 4, the cloth feeding device 20 includes a movable body 31, a swing shaft, a cloth feeding table 37, a swing motor 41, a cloth feeding plate, a rack shaft 22, a moving motor 42, a pressing arm 23, and a cloth pressing motor 43. The movable body 31 is provided inside the stand main body 7 so as to be able to move back and forth. The swing shaft is a shaft that is fixed to the movable body 31 and extends in the vertical direction, and protrudes upward from the stand main body 7 . The cloth feed table 37 is connected to the movable body 31 inside the machine base main body 7, and is provided on the swing shaft so as to be able to swing. Therefore, the cloth feed table 37 can move back and forth together with the movable body 31, and can swing in the left-right direction about the swing shaft. The swing motor 41 is connected to the cloth feed table 37 . Driven by the swing motor 41, the cloth feed table 37 swings around the swing shaft. The cloth feed plate is arranged on the upper surface of the base portion 2 . The cloth feed plate supports the cloth 99 . The cloth feed plate can move back and forth integrally with the cloth feed table 37 and can swing integrally with the cloth feed table 37 . The feed plate has a hole at the front end. The needles 10 moving up and down pass through the holes on the feed plate to reach the needle receiving holes on the needle plate 26 .

The rack shaft 22 extends in the front-rear direction above the base body portion 7 and can move back and forth. The front end portion of the rack shaft 22 is connected to the upper end portion of the swing shaft. The rear end portion of the rack shaft 22 is located inside the strut portion 3 . The moving motor 42 is provided in the inside of the support|pillar part 3, and the moving motor 42 can move the rack shaft 22 back and forth. In this case, the cloth feed table 37 , the cloth feed plate, the swing shaft, and the movable body 31 move back and forth integrally with the rack shaft 22 .

The pressing arm 23 extends upward from the cloth feed table 37 and extends forward from the upper side of the machine base 2 . The pressing arm 23 can move back and forth integrally with the feed table 37 and can swing integrally with the feed base 37 . The presser arm 23 has a presser foot 24 , a shaft portion 29 and a rod portion 25 . The presser foot 24 is provided above the needle plate 26 and at the front end portion of the presser arm 23 so as to be able to move up and down. The shaft portion 29 has the left-right direction as the axial direction, and is provided at a substantially central portion in the front-rear direction of the press arm 23 . The rod parts 25 are respectively provided on the left surface and the right surface of the pressing arm 23 , and are rotatable around the shaft part 29 . The front end portion of the lever portion 25 is connected to the presser foot 24 . The cloth press motor 43 is provided inside the support column 3 . The cloth press motor 43 is connected to the rear end portion of the lever portion 25 via a link mechanism provided inside the arm portion 4 . When the lever portion 25 rotates around the shaft portion 29 in accordance with the driving of the cloth press motor 43, the presser foot 24 moves up and down. The presser foot 24 can press the cloth 99 between the presser foot 24 and the cloth feed plate.

As shown in FIGS. 1 and 2 , the sewing machine 1 has a thread clamping mechanism 60 on the right wall portion 5A. The thread tensioning mechanism 60 includes a thread tensioning barrel 62, a thread tensioning base 63, a thread take-up spring 65, a thread tensioning motor 16, a thread tensioning disc 69, and an encoder 21 (refer to FIG. 4). The thread tensioning mechanism 60 can supply the suture between the thread tensioning disc 69 and the stitches 98 using the power of the thread tensioning motor 16 . The thread tension barrel 62 is an annular member, and is fixed to the inner side of the through hole 5B of the right wall portion 5A by a fastening member. The thread tensioning seat 63 is an annular member, and is fixed to the inner side of the thread tensioning barrel 62 by the screw 14 . The thread take-up spring 65 is fixed on the outer side of the thread tensioning seat 63 and is wound between the thread tensioning seat 63 and the thread tensioning barrel 62 . One end portion of the thread take-up spring 65 is exposed rightward from the right wall portion 5A. The thread tension motor 16 is fixed to the inner side of the arm portion 4 . The thread tension motor 16 has an output shaft 18, and the output shaft 18 penetrates the center hole of the thread tension holder 63 and protrudes to the right of the right wall portion 5A. The output shaft 18 is rotatable in the left-right direction as an axial direction, and a tension disc 69 is fixed to the right end of the output shaft 18 on the right side of the arm portion 4 by means of screws 28 . The upper thread 6 is wound around the thread tensioning disc 69 one to two times.

The thread tension motor 16 applies tension to the thread 6 by rotating the thread tension disc 69 via the output shaft 18 . The thread clamping motor 16 is a two-phase bipolar pulse motor. The thread tension motor 16 has a plurality of coils 33 (see FIG. 3 ). The plurality of coils 33 are arranged along the rotational direction of the output shaft 18 . The number of coils 33 in this embodiment is four. The sewing machine 1 can supply current to each coil 33 bidirectionally. The sewing machine 1 controls the rotation angle (rotation position) of the output shaft 18 by the electromagnetic force generated by the plurality of coils 33 energized. The encoder 21 is used to detect the rotation angle of the output shaft 18 . The left end portion of the output shaft 18 is a code wheel to which the encoder 21 is fixed inside the arm portion 4 . By switching the rotation direction of the output shaft 18 (that is, the thread tension disc 69 ) by the thread tension motor 16 , the upper thread 6 can be moved in the feeding direction and the retracting direction. The supply direction is the direction in which the needle thread 6 is supplied to the eyelet 10A of the needle 10 . The retraction direction is the reverse of the supply direction.

4 , the electrical configuration of the sewing machine 1 will be described. The control device 30 of the sewing machine 1 includes the CPU 91 . The CPU 91 can control the operation of the sewing machine 1 including the sewing mechanism 12 and the thread tension motor 16 . The CPU 91 is connected to a ROM 92 , a RAM 93 , a storage device 94 and an I/O interface (hereinafter referred to as I/O) 45 . The ROM 92 stores programs and the like for executing various processes such as the sewing process (refer to FIG. 7 ) which will be described later. The RAM 93 is used to temporarily store various values. The storage device 94 is nonvolatile, and the storage device 94 stores sewing data for forming the stitches 98 on the fabric 99 . The storage device 94 stores the first relational expression and the second relational expression. The first relational expression and the second relational expression are used to control the driving of the thread tension motor 16, and the first relational expression and the second relational expression are used to correlate the current flowing to each phase of the thread tension motor 16 and the electrical angle. formula. The CPU 91 controls the drive of the thread tension motor 16 so that the phase difference of the output shaft 18 becomes a predetermined target value (hereinafter referred to as a target value) larger than 0. The phase difference of the output shaft 18 is the absolute value of the difference between the reference phase of the output shaft 18 serving as a reference and the rotational angle phase of the output shaft 18 . The sewing machine 1 maintains the tension of the upper thread 6 at a predetermined tension by maintaining the phase difference of the output shaft 18 at a predetermined target value. Hereinafter, the rotational angle phase of the output shaft 18 will be referred to as the interline rotational angle.

The sewing period is the period during which the sewing machine 1 sews one stitch, that is, the period during which the upper shaft 15 makes one rotation. As shown in FIG. 5 , during the sewing machine 1 of the present embodiment sews one stitch, the thread take-up lever 51 starts from the upper dead center of the movable range, which is the upper dead center, passes through the lower end of the movable range, which is the bottom dead center, and then returns to the upper dead center. The period up to the point substantially corresponds to the period corresponding to the range of 60 degrees to 420 degrees of the rotation angle of the upper shaft 15 . Hereinafter, the rotation angle of the upper shaft 15 is referred to as an upper shaft angle. The upper shaft angle is a value based on the detection result of the encoder 27A of the main motor 27 . In FIG. 5 , the period during which the thread take-up lever 51 lifts the upper thread 6, that is, the period during which the thread take-up lever is lifted is a period corresponding to the range of 310° to 420° of the upper axis angle. The needle bar movement curve of the needle bar 11 , the hook thread amount curve of the rotary hook 39 , and the thread take-up lever thread amount curve of the thread take-up lever 51 all take the period during which the sewing machine 1 sews one stitch as a cycle. The value of the upper axis angle may be 0 degrees to 359 degrees. In this case, a counter for counting the number of stitches may be provided, and 1 may be added to the counter every time the upper shaft angle becomes 0 degrees.

The I/O 45 is connected to the drive circuit 81 to the drive circuit 87 . The drive circuit 81 is connected to the main motor 27 . The drive circuit 82 is connected to the swing motor 41 . The drive circuit 83 is connected to the moving motor 42 . The drive circuit 84 is connected to the cloth press motor 43 . The swing motor 41 , the movement motor 42 and the cloth pressing motor 43 are pulse motors. The output shaft of the main motor 27 is provided with an encoder 27A, the output shaft of the swing motor 41 is provided with an encoder 41A, the output shaft of the moving motor 42 is provided with an encoder 42A, and the output shaft of the cloth press motor 43 is provided with an encoder device 43A. The encoder 27A detects the rotational position of the output shaft of the main motor 27, and outputs the rotational position to the CPU 91 via the I/O 45, and the encoder 41A detects the rotational position of the output shaft of the swing motor 41, and outputs the rotational position to the CPU 91 via the I/O 45 position, the encoder 42A detects the rotational position of the output shaft of the moving motor 42, and outputs the rotational position to the CPU 91 via the I/O 45, and the encoder 43A detects the rotational position of the output shaft of the cloth pressing motor 43, and outputs the rotational position to the CPU 91 via the I/O 45 Output the rotational position. The CPU 91 obtains the detection result of the encoder 27A and sends a control signal to the drive circuit 81 , the CPU 91 obtains the detection result of the encoder 41A and sends a control signal to the drive circuit 82 , and the CPU 91 obtains the detection result of the encoder 42A and sends it to the drive circuit 83 When the control signal is sent, the CPU 91 acquires the detection result of the encoder 43A, and sends the control signal to the drive circuit 84 . Therefore, the CPU 91 can control the driving of the main motor 27 , the swing motor 41 , the movement motor 42 , and the cloth press motor 43 . Hereinafter, when the main motor 27 , the swing motor 41 and the movement motor 42 are reviewed, they are collectively referred to as drive motors.

The drive circuit 85 is connected to the thread tension motor 16 . The encoder 21 outputs the thread tension rotation angle of the thread tension motor 16 as a detection result to the CPU 91 . The CPU 91 controls the thread tension motor 16 by sending a control signal to the drive circuit 85 . The control method of the thread tension motor 16 will be described later.

The drive circuit 86 is connected to the display unit 48 . The CPU 91 displays various information on the display unit 48 by sending a control signal to the drive circuit 86 . The input unit 47 outputs the detected various information to the CPU 91 via the I/O 45 . The pedal 38 outputs the detection result to the CPU 91 via the I/O 45 . The CPU 91 acquires the operation direction and operation amount of the pedal 38 indicated by the detection result of the pedal 38 . The drive circuit 87 is connected to the tangential electromagnetic element 161 . The CPU 91 controls the driving of the thread cutting electromagnetic element 161 by sending a control signal to the drive circuit 87 .

1 and 6A to 6D, the outline of the operation of the sewing machine 1 will be described. The cloth 99 is placed on the feed plate and the needle plate 26 . When the presser motor 43 is driven, the presser foot 24 is lowered, and the presser foot 24 presses the cloth 99 between the presser foot 24 and the cloth feed plate. The main motor 27, the movement motor 42, and the swing motor 41 are driven in synchronization with each other. The pressing arm 23 and the cloth feed plate move back and forth with the drive of the moving motor 42 , and swing back and forth in the left-right direction with the drive of the swing motor 41 . Therefore, the cloth feeder 20 moves the cloth material 99 back and forth and swings the cloth material 99 back and forth in the left-right direction. The upper shaft 15 is rotated by the main motor 27 being driven in synchronization with the moving motor 42 and the swing motor 41 . The needle bar up-and-down movement mechanism, the thread take-up mechanism and the hook 39 are driven in conjunction with each other. The needle 10 lowered together with the needle bar 11 penetrates the cloth material 99 and passes through the needle receiving hole. The upper thread 6 in the vicinity of the needle hole 10A that has descended below the needle-accommodating hole has a ring shape (see FIG. 6A ). When the hook 39 is rotated clockwise in the front view, the hook tip 36 catches the looped upper thread 6 . The needle 10 rises and separates from the cloth material 99 upward, and the hook 39 continues to rotate in the clockwise direction when viewed from the front. The hook tip 36 pulls the ring-shaped upper thread 6 in the rotational direction to expand the diameter of the ring-shaped upper thread 6 (see FIG. 6B ). When the looped upper thread 6 goes around the hook 39 and escapes from the hook 39 (see FIG. 6C ), the upper thread 6 and the lower thread 9 are intertwined. The rotation direction of the hook 39 is switched to the counterclockwise direction when viewed from the front, and the thread take-up lever 51 lifts up the upper thread 6 intertwined with the lower thread 9 (see FIG. 6D ). The diameter of the looped upper thread 6 is reduced, so that the sewing machine 1 completes one stitch. In this embodiment, the sewing machine 1 performs one-stitch sewing every time the upper shaft 15 rotates 360 degrees. The sewing machine 1 forms the stitches 98 on the fabric 99 by repeating the above-mentioned operations.

The sewing process will be described with reference to FIGS. 7 to 12 . The sewing process is a process in which the sewing machine 1 sews the cloth 99 . Before the start of the sewing process, the needle bar 11 is in the vicinity of the upper end of the movable range, and the upper thread 6 is passed through the needle eye 10A. For example, when the operator operates the input unit 47 to turn on the power of the sewing machine 1, the CPU 91 reads out the program from the ROM 92 to the RAM 93, and executes the sewing process.

As shown in FIG. 7, the CPU 91 executes initialization processing (S1). The CPU 91 reads various setting values from the storage device 94 into the RAM 93 . Based on the detection result of the input unit 47 , the CPU 91 acquires the amount of the upper thread 6 that is moved in the retracting direction, that is, the amount of the upper thread retracting ( S3 ). The upper thread retraction amount is a predetermined amount based on the amount of the upper thread 6 passed through the eye of the needle 10A, which is shorter than the length of the upper thread 6 actually passed through the eye of the needle 10A.

Based on the detection result of the input unit 47, the CPU 91 acquires the number of starting stitches that defines the predetermined number of stitches starting from the sewing machine 1 (S5). The number of starting stitches is, for example, two stitches. The CPU 91 acquires a mode in which the upper thread 6 is retracted in the retracting direction at the time of sewing (hereinafter referred to as the upper thread retracting mode) based on the detection result of the input unit 47 ( S7 ). The upper thread retraction mode includes automatic retraction mode and set retraction mode. In the automatic retraction mode, the sewing machine 1 retracts the upper thread 6 at the beginning of the period in which the thread take-up lever is lifted within the period of the number of stitches starting. In the set retraction mode, the sewing machine 1 retracts the upper thread 6 according to the number and timing specified by the operator. Either the automatic retraction mode or the set retraction mode is input by the operator using the input unit 47 .

The CPU 91 determines whether or not the upper thread retraction mode acquired in S7 is the automatic retraction mode (S9). When the CPU 91 determines that it is the automatic retraction mode ( S9 : YES), the CPU 91 shifts the process to S15 . When the CPU 91 determines that the retraction mode is set ( S9 : NO), the CPU 91 acquires the number of times the upper thread 6 is moved in the retracting direction at the start of sewing, that is, the number of times the upper thread retracts, based on the detection result of the input unit 47 ( S11 ). The number of times the upper thread is retracted is, for example, two times. The CPU 91 acquires the timing for retracting the upper thread 6, that is, the timing for retracting the upper thread (S13). For example, the CPU 9 displays the range of the upper axis angle corresponding to the number of stitches acquired in S5 on the display unit 48 . While looking at the display unit 48 , the operator inputs the upper axis angle corresponding to the desired timing of retracting the upper thread using the input unit 47 . Therefore, the upper thread retraction timing is within the number of stitches acquired in S5. When the upper axis angle is 330 degrees or 690 degrees, for example, the timing of retracting the upper thread is made. The timings corresponding to the two upper shaft angles are all within the lifting period of the thread take-up lever. When the upper axis angle is 330 degrees, the corresponding timing is after the needle 10 pierces the fabric 99 for the first time and before the second piercing into the fabric. When the upper axis angle is 690 degrees, the corresponding timing is after the needle 10 pierces the cloth 99 for the second time.

Based on the detection results of the encoder 21 and the encoder 27A, the CPU 91 acquires the rotation angle and the upper axis angle of the line clamp ( S15 ). The wire-pinch rotation angle acquired in S15 is the first reference phase (hereinafter referred to as the reference phase) of the output shaft 18 in the normal processing (S35) described later.

The CPU 91 acquires the set tension of the upper thread 6 based on the detection result of the input unit 47 ( S17 ). The CPU 91 acquires the target value corresponding to the set tension acquired in S17 (S19). The torque generated by the thread tension motor 16 and the set tension of the upper thread 6 have a correlation relationship with each other. The target value is the phase difference of the output shaft 18 when the value of the upper thread tension calculated based on the correlation stored in the storage device 94 is a predetermined tension. The CPU 91 acquires the target value by acquiring the phase difference corresponding to the set tension acquired in S17 based on the correlation stored in the storage device 94 .

The CPU 91 determines whether or not a sewing start instruction, which is an instruction to start sewing, has been detected based on the detection result of the pedal 38 ( S21 ). The CPU 91 stands by until the operator steps on the pedal 38 ( S21 : NO). When the operator steps on the pedal 38 after placing the cloth 99 on the cloth feed plate ( S21 : YES), the CPU 91 controls the driving of the cloth press motor 43 to lower the presser foot 24 ( S23 ). The presser foot 24 sandwiches the fabric 99 between it and the feed plate.

The CPU 91 starts energization of the plurality of coils 33 ( S25 ). The CPU 91 determines the type of energization based on the first relational expression, the second relational expression, the rotation angle of the wire clamp acquired in S15 , and the target value acquired in S19 , and starts energization of the plurality of coils 33 .

The CPU 91 drives the thread tension motor 16 to move the upper thread 6 in the supply direction (S27). As the upper thread 6 moves in the feeding direction (arrow A1 in FIG. 9 ), the length of the upper thread 6 passed through the eye of the needle 10A becomes longer. The CPU 91 starts the driving of the drive motor (S29). The needle bar 11, the hook 39, and the cloth feed table 37 operate in synchronization with each other.

The CPU 91 refers to the RAM 93, and judges whether or not the retraction of the face thread 6 has been completed (S30). The CPU 91 stores in the RAM 93 the accumulated movement amount of the movement of the upper thread 6 in the retracting direction in S39 described later. Immediately at the start of the sewing operation of the sewing machine 1, the amount of movement of the upper thread 6 in the retracting direction stored in the RAM 93 is 0 (S30: NO). The CPU 91 judges whether or not the upper thread retraction mode acquired in S7 is the automatic retraction mode (S31). When the CPU 91 determines that the retraction mode is set ( S31 : NO), the CPU 91 shifts the process to S33 . The CPU 91 judges whether or not the timing for retracting the face thread has come (S33). The CPU 91 judges whether or not the above-mentioned timing has come based on whether or not the upper-axis angle indicated by the detection result of the encoder 27A and the upper-axis angle indicated by the upper thread retraction timing acquired in S13 match. When the upper axis angle is smaller than 330 degrees ( S33 : NO), the CPU 91 executes normal processing ( S35 ).

As shown in FIG. 10 , the CPU 91 acquires the rotation angle of the wire clamp based on the detection result of the encoder 21 ( S61 ). The CPU 91 judges whether or not the phase difference is larger than the target value based on the reference phase, the target value acquired in S19 , and the rotation angle of the interline acquired in S61 ( S63 ). When the sewing operation starts, the reference phase is the upper axis angle acquired in S15, and the phase difference is theoretically 0 (S63: NO). The CPU 91 ends the normal processing and returns the processing to the sewing processing in FIG. 8 .

The CPU 91 determines whether or not a sewing stop instruction, which is an instruction to stop sewing, has been detected based on the detection result of the pedal 38 ( S43 ). When the operator has not stepped back on the pedal 38 ( S43 : NO), the CPU 91 shifts the process to S30 . When the CPU 91 repeatedly executes S30, S31, S33, S35, and S43, the needle 10 pierces the cloth 99 (see FIG. 11).

After the thread take-up lever 51 starts to lift the upper thread 6, the upper shaft angle becomes 330 degrees (S33: YES). At this time, the needle 10 is positioned above the cloth 99 (see FIG. 12 ). The CPU 91 controls the driving of the thread tension motor 16 to retract the upper thread 6 (S39). The upper thread 6 moves in the retracting direction (arrow A2 in FIG. 12 ). In the set retraction mode, the movement amount of the upper thread 6 moved by the driving of the thread tension motor 16 is the amount obtained by dividing the upper thread retraction amount obtained in S3 by the number of times of the upper thread retraction acquired in S11. In the present embodiment, the CPU 91 moves the upper thread 6 in the retracting direction by approximately half of the amount of the upper thread retracting acquired in S3, and rewrites the accumulated movement amount of the upper thread 6 in the retracting direction in the RAM 93. When the operator has not stepped back on the pedal 38 ( S43 : NO), the CPU 91 shifts the process to S30 .

After the upper axis angle exceeds 330 degrees ( S33 : NO), the CPU 91 executes normal processing ( S35 ). As the thread take-up lever 51 lifts the upper thread 6, the upper thread 6 is stretched and the tension of the upper thread 6 is increased. When the tension of the upper thread 6 exceeds the set tension acquired in S17, the phase difference exceeds the target value (S63: YES). The CPU 91 determines the energization type corresponding to each of the plurality of coils 33 ( S65 ). The CPU 91 determines the energization type that can eliminate the difference between the phase difference acquired in S63 and the target value, based on the first relational expression, the second relational expression, and the angle of rotation of the clamp line acquired in S61 . The CPU 91 energizes the plurality of coils 33 according to the energization type determined in S65 (S67). After the output shaft 18 is rotated, the phase difference becomes equal to the target value, and the tension of the upper thread 6 returns to the set tension acquired in S17. Based on the encoder 21 , the CPU 91 acquires the rotation angle of the thread clamping of the output shaft 18 after the rotation, and rewrites the rotation angle of the thread clamping in the RAM 93 using the acquired rotation angle of the thread clamping as a reference phase. The CPU 91 ends the normal processing.

As shown in FIG. 8, when the CPU 91 repeatedly executes S30 to S43, the sewing machine 1 forms a stitch 98 for one stitch and completes one stitch. The upper shaft angle reaches 690 degrees (S33: YES). The CPU 91 executes the second retraction of the opposite thread 6 (S39). The sum of the retracted amounts of the upper thread 6 twice agrees with the retracted amount of the upper thread acquired in S3. When the operator has not stepped back on the pedal 38 ( S43 : NO), the CPU 91 transfers the process to S30 . The accumulated movement amount of the upper thread 6 stored in the RAM 93 reaches the upper thread retraction amount acquired in S3 within the number of starting stitches acquired in S5 (S30: YES). At this time, the CPU 91 executes normal processing in the same manner as described above ( S35 ). When the CPU 91 repeatedly executes S30 , S35 , and S43 , the sewing mechanism 12 sequentially forms the stitches 98 on the cloth material 99 . When the operator steps back on the pedal 38 (S43: YES), the CPU 91 drives the thread trimming solenoid 161 to perform the thread trimming operation for cutting the upper thread 6 and the lower thread 9 (S45), stops the driving of the drive motor (S47), and The drive of the cloth press motor 43 is controlled, and the presser foot 24 is raised (S49), after which the sewing process is terminated. The sewn fabric 99 can be removed from the sewing machine 1 .

The sewing process in the case where the operator's input is the automatic retraction mode will be described. Hereinafter, a description overlapping with the above-described sewing process will be omitted. The operator inputs one stitch as the number of starting stitches (S5), and inputs the automatic retraction mode (S7, S9: Yes). The CPU 9 acquires the upper shaft angle and the thread clamping rotation angle (S15), acquires the set tension of the upper thread 6 (S17), and acquires the target value corresponding to the set tension (S19). When the operator steps on the pedal 38 ( S21 : YES), the CPU 91 controls the drive of the cloth press motor 43 , lowers the presser foot 24 ( S23 ), starts energization of the plurality of coils 33 ( S25 ), and causes the thread to be clamped The motor 16 is driven to move the needle thread 6 in the supply direction (S27). The CPU 91 starts the driving of the drive motor (S29). Since the movement amount of the upper thread 6 in the retracting direction is 0 (S30: NO), the CPU 91 transfers the process to S31, and determines that the upper thread retracting mode acquired in S7 is the automatic retracting mode (S31: YES). Based on the encoder 27A, the CPU 91 judges whether or not the thread take-up period has come (S37). Immediately at the start of sewing, the thread take-up period has not yet come ( S37 : NO), and the CPU 91 shifts the process to S35 . The CPU 91 repeatedly executes S35, S43, S30, S31, and S37. When the thread take-up period in the first needle starts (S37: YES), the CPU 91 retracts the upper thread 6 (S39). In the automatic retraction mode, the movement amount of the upper thread 6 moved by the driving of the thread tension motor 16 is the amount obtained by dividing the retraction amount of the upper thread acquired in S3 by the number of stitches acquired in S5. Therefore, the CPU 91 can complete the retraction of the face thread 6 within the number of starting stitches acquired in S5. In this embodiment, the CPU 91 moves the upper thread 6 in the retracting direction by the amount of the upper thread retraction acquired in S3 by executing the process of S39 once (S39). The operator continues to depress the pedal 38 (S43: NO). When the CPU 91 determines that the retraction of the opposite thread 6 has been completed ( S30 : YES), the CPU 91 executes normal processing ( S35 ). Until the operator steps back on the pedal 38 ( S43 : NO), the CPU 91 continues the above-described processing. When the operator steps back on the pedal 38 ( S43 : YES), the CPU 91 drives the thread trimming solenoid 161 to perform thread trimming ( S45 ), stops the drive of the drive motor ( S47 ), and controls the drive of the cloth press motor 43 to make the press The foot 24 is raised (S49), and after that, the sewing process is completed.

As described above, the CPU 91 controls the drive of the thread tension motor 16 to move the upper thread 6 in the retracting direction by a predetermined amount based on the amount by which the upper thread 6 is passed through the eye of the needle 10A ( S39 ). The amount of the upper thread 6 remaining on the fabric 99 at the time of sewing is small. Therefore, the sewing machine 1 can prevent the upper thread 6 from being tangled and clumped under the cloth 99 at the start of sewing.

The CPU 91 controls the driving of the thread tension motor 16 a plurality of times at the start of sewing, so that the upper thread 6 moves in total by the upper thread retraction amount acquired in S3 in the total number of movements ( S39 ). The CPU 91 moves the upper thread 6 a plurality of times, so that the upper thread 6 is less likely to be detached from the eye 10A of the needle 10 , that is, thread detachment, than when the upper thread 6 is moved only once. Therefore, the sewing machine 1 can suppress the occurrence of thread breakage at the time of sewing.

When the upper axis angle is, for example, 330 degrees (S33: YES), the CPU 91 moves the upper thread 6 in the retracting direction (S39). The timing corresponding to the upper axis angle of 330 degrees is after the needle 10 pierces the cloth 99 for the first time and before the second piercing into the cloth. Thread loss is easily caused by friction between the upper thread 6 held in the eye 10A of the needle 10 that moves up and down and the cloth 99 . Since the timing of the movement of the upper thread 6 in the retracting direction is after the needle 10 pierces the cloth 99 for the first time, the sewing machine 1 can prevent the thread from falling off when the needle 10 pierces the cloth 99 for the first time.

When the automatic retraction mode is input by the operator (S7), while the thread take-up lever 51 is pulling up the upper thread 6 (S37: YES), the CPU 91 rotates the thread tension disc 69 (S39). The upper thread 6 is easily stretched during the lifting of the thread take-up lever, and therefore, the upper thread 6 is easier to move in the retracting direction. The sewing machine 1 can further suppress the occurrence of the upper thread 6 being tangled under the cloth 99 at the start of sewing.

The CPU 91 moves the upper thread 6 by a predetermined amount within the number of starting stitches acquired in S5 (S39). In the sewing machine 1 , the period for starting sewing can be limited according to the number of stitches input by the input unit 47 . Therefore, the sewing machine 1 can diversify the manner in which the upper thread 6 is moved by controlling the driving of the thread tension motor 16 .

The CPU 91 moves the upper thread 6 in the retracting direction at the upper thread retracting timing acquired in S13 (S39). The timing of moving the needle thread 6 by controlling the driving of the thread tension motor 16 changes according to the timing of input by the input unit 47 . Therefore, the sewing machine 1 can diversify the manner in which the upper thread 6 is moved by controlling the driving of the thread tension motor 16 .

The CPU 91 moves the upper thread 6 in the retracting direction by the amount of the upper thread retracting input by the input unit 47 (S39). The amount of movement by which the upper thread 6 is moved by controlling the driving of the thread tension motor 16 changes according to the amount of retraction of the upper thread input by the input unit 47 . Therefore, the sewing machine 1 can diversify the manner in which the upper thread 6 is moved by controlling the driving of the thread tension motor 16 .

The timing of the movement of the needle thread 6 in the supply direction ( S27 ) is before the start of the driving of the drive motor ( S29 ). That is, the CPU 91 moves the upper thread 6 in the feeding direction before the thread tension motor 16 moves the upper thread 6 in the retracting direction and before the needle 10 penetrates the cloth 99 for the first time. The upper thread 6 is moved in the feeding direction before the upper thread 6 is moved in the retracting direction by the thread tension motor 16 . Therefore, the sewing machine 1 can prevent the needle 10 from piercing the cloth 99 for the first time to prevent the needle 10A from being short of the upper thread 6, and can reliably suppress the thread coming off.

In the above description, the sewing mechanism 12 is an example of the sewing portion of the present invention. The thread tension motor 16 is an example of the drive unit of the present invention. The input unit 47 is an example of a stitch number input unit, a timing input unit, and a movement amount input unit of the present invention. The CPU 91 at the time of executing S39 is an example of the upper thread retracting portion of the present invention. The CPU 91 at the time of executing S37 is an example of the determination unit of the present invention. The CPU 91 at the time of executing S27 is an example of the needle thread supply unit of the present invention.

The present invention is not limited to the above-described embodiments. The sewing machine 1 may also be a lockstitch sewing machine, a buttonhole sewing machine, a home sewing machine, an embroidery sewing machine, or the like. The sewing machine 1 may be a sewing machine in which the shuttle mechanism 40 is omitted, such as a circular stitch sewing machine. After the execution of the thread trimming ( S45 ), the CPU 91 may drive the drive motor, and the sewing may be continued while the stitches 98 are formed on the cloth 99 . In this case, the sewing that is started after the thread trimming has been performed is the starting seam.

The CPU 91 may acquire the upper thread retraction amount not based on the detection result of the input unit 47 but by reading the upper thread retraction amount previously stored in the storage device 94 ( S3 ). The timing for retracting the upper thread input by the input unit 47 may be after the needle 10 pierces the cloth 99 for the second time. In this case, when the second stitch 98 is formed, the CPU 91 may move the upper thread 6 in the retracting direction several times in succession ( S39 ).

The upper thread retraction timing input by the input unit 47 may be a timing other than the thread take-up period. In this case, the sewing machine 1 can also suppress the possibility of the thread coming off when the thread take-up lever 51 is pulled up. The number of starting stitches input by the input unit 47 may be one stitch or three or more stitches. When the operator's input is the automatic retraction mode ( S9 : YES), the CPU 91 may retract the upper thread 6 when it is determined in S37 that the thread take-up lever is not being lifted ( S39 ).

When the CPU 91 retracts the upper thread 6 in S39 in the set retraction mode, it may not retract by the amount obtained by dividing the upper thread retraction amount acquired in S3 by the number of times the upper thread retraction acquired in S11. When the number of times of the upper thread retraction acquired in S11 is two or more, the sewing machine 1 may individually set the amount of the upper thread retraction. In the automatic retraction mode, when the CPU 91 retracts the upper thread 6 in S39 , it may not retract by the amount obtained by dividing the upper thread retraction amount acquired in S3 by the number of starting stitches acquired in S5 . When the number of starting stitches acquired in S5 is two or more, the sewing machine 1 may individually set the upper thread retraction amount.

Claims (8)

1. A sewing machine (1) has:

a sewing part (12) having a needle bar (11) to which a needle (10) is attached, the needle bar being capable of moving up and down, the sewing part being capable of sewing a fabric (99) with the needle moving up and down;

a wire clamping mechanism (60) having: a thread take-up reel (69) around which the upper thread (6) is wound; and a drive unit (16) for rotating the thread clamping disk, wherein the thread clamping mechanism adjusts the supply amount of the surface thread to the needle by the rotation of the thread clamping disk;

a sewing control part (91) for sewing the cloth by controlling the sewing part; and

a thread adjusting control part for controlling the drive part to control the supply amount of the upper thread to the needle when the sewing control part controls the sewing of the cloth,

the sewing machine is characterized in that the sewing machine is provided with a sewing machine,

the thread adjusting control unit has a thread take-up control unit that controls the drive unit to move the upper thread in a take-up direction, which is a reverse direction of a feeding direction in which the upper thread is fed to the needle, by a predetermined amount based on an amount of the upper thread threaded on the needle when the sewing control unit controls the sewing of the fabric.

2. The sewing machine of claim 1,

when the sewing control part controls the sewing of the cloth, the thread withdrawing control part controls the driving part for a plurality of times to make the upper thread move for the specified amount under the movement of the plurality of times.

3. Sewing machine as in claim 1 or 2,

the thread take-up control section moves the upper thread in the take-up direction at least once after the needle pierces the fabric for the first time from the start of sewing by the sewing control section and before the needle pierces the fabric for the second time.

4. Sewing machine as in claim 1 or 2,

the sewing part is provided with a thread take-up lever (51) which lifts the upper thread by moving up and down synchronously with the up and down movement of the needle bar,

the thread adjusting control part has a judging part for judging whether the take-up lever is lifting the upper thread,

the thread take-up control section moves the upper thread when the judgment section judges that the thread take-up lever is lifting up the upper thread.

5. Sewing machine as in claim 1 or 2,

the sewing machine has a needle number input part (47) for inputting the number of needles for limiting the sewing by the control of the sewing control part,

the thread take-up control section moves the upper thread by the predetermined amount within the needle count input by the needle count input section.

6. Sewing machine as in claim 1 or 2,

the sewing machine has a timing input part for inputting the timing of the upper thread moving by the thread take-up control part,

the thread retracting control section moves the upper thread in the retracting direction at the timing input by the timing input section.

7. Sewing machine as in claim 1 or 2,

the sewing machine has a movement amount input part, which can input the specified amount,

the thread retraction control unit moves the upper thread by the predetermined amount input by the movement amount input unit.

8. Sewing machine as in claim 1 or 2,

the thread adjusting control part has a thread supplying control part which makes the upper thread move to the supplying direction before the thread withdrawing control part makes the upper thread move and before the needle penetrates the cloth for the first time,

the thread take-up control section moves the upper thread by the predetermined amount after the needle pierces the fabric for the first time.

Images