KR20080106850A - Thread-cutting driving device of sewing machine - Google Patents

Abstract

A thread-cutting driving device of sewing machine is provided to prevent the thread-cutting driving device of sewing machine from being stopped when a roller goes in gear with the edge section of the entrance of the cam groove or the thread-cutting driving device of sewing machine from being damaged by a mechanical load. A thread-cutting driving device of sewing machine comprises a driving mes(14), a driving shaft(11), a cam(12), a detection unit, a roller, an actuator and a control unit. The driving mes cuts the thread. A drive motor rotates a driving shaft. The cam is rotatable by the driving shaft and a cam groove(12c) operating the driving mes. The detection unit detects a rotation angle. The roller is connected to the driving mes. The actuator moves the roller in order to become inserted in the cam groove. The control unit rotates the cam. The control unit again rotates to the cam after operating the actuator.

Description

Thread cutting operation device of sewing machine {THREAD-CUTTING DRIVING DEVICE OF SEWING MACHINE}

The present invention relates to a thread cutting operation device of a sewing machine for cutting a thread by operating a movable blade along a cam which rotates in association with a drive shaft.

Conventionally, as the above-mentioned thread cutting operation device, for example, as described in Patent Literature 1, a cam having a predetermined cam groove and provided to a drive shaft on a lower shaft of a sewing machine, a roller disposed to face the cam groove, and a roller And an actuator for moving the shaft to engage or space the cam groove, and engage the roller with the cam groove by an actuator when cutting the thread, and move the movable scalpel along the cam groove of the cam rotating in conjunction with the drive shaft. A thread cutting actuator for driving is known.

FIG. 6 shows a part of the configuration of the yarn cutting operation device 100 disclosed in Patent Document 1. As shown in FIG.

The thread cutting operation device 100 includes a groove cam 101 rotatably supported by a drive shaft (not shown), a roller 102 installed to be engaged with or detached from the groove portion 101a of the groove cam 101. In addition, the roller 102 is provided to be in contact with and separated from each other, and is provided with an actuating member 103 for entering the roller 102 from the opening 101b of the groove portion 101a by the driving of the actuator 104. do. In addition, the roller 102 is connected to a movable blade not shown.

The actuator 104 is driven and controlled by a control device (not shown). When an operator operates a thread cutting operation member such as a pedal, the plunger portion 104a of the actuator 104 moves upward in FIG. 6. As a result, the actuating member 103 rotates about the axis 103a and pushes the roller 102 to the left side of FIG. 6 to move it toward the opening 101b of the groove cam 101. At this time, the groove cam 101 is rotated together with the drive shaft, and the roller located inward of the groove cam 101 from the opening 101b is inside the groove 101a by the edge portion 101c of the groove cam 101. Guided to the engaging portion with the groove (101a). Thereafter, the roller 102 reciprocates in the direction along the substantially axial direction of the groove cam 101 in accordance with the shape of the groove portion 101a, whereby the movable blade connected to the roller 102 reciprocates and is fixed (not shown). Work with the scalpel to cut the sewing thread.

[Patent Document 1] Japanese Patent Laid-Open No. 2000-317178

In the conventional thread cutting operation apparatus 100, when the roller 102 pushed by the actuating member 103 collides with the groove wall 101d of the groove cam 101, the roller 102 is caused by the impact. It bounces largely (bound), collides with the actuating member 103 and collides with the groove cam 101 again, and is gradually converged. At this time, while repeating the bounding, the home cam 101 is already rotating, and the relative position of the collided roller 102 and the home cam 101 changes. For this reason, the roller 102 which splatters outward from the groove part 101a collides with the outer surface of the edge part 101c, and may be caught between the edge part 101c and the actuating member 103, and such a case may be engaged. Even if the movable blade does not operate, there was a problem that the thread cutting operation device 100 itself is impossible to operate. In addition, at this time, there is a problem in that the thread cutting operation device 100 is broken, such as a large mechanical load is generated in each part is broken by the action member 103 and the like.

An object of the present invention is to enable reliable thread cutting operation and to prevent trouble such as breakage.

Invention of Claim 1 is the movable blade 14 which cut | disconnects a thread, the drive shaft 11 which rotates in cooperation with a drive motor, and the cam groove 12c which can be rotated by the said drive shaft, and drives the said movable blade. A cam 12 formed therein, a detection means 3 for detecting a rotation angle of the cam, and a roller 13 which is movable so as to be engaged with or spaced apart from the cam groove, and which is connected to the movable blade; A thread cutting device of a sewing machine having an actuator for moving the roller to be engaged with the cam groove at a time, the rotation angle of the cam which rotates the cam and allows the roller to enter the cam groove is detected. And controlling means for controlling the drive motor and the actuator to stop the rotation of the cam when detected by the motor and to rotate the cam again after actuating the actuator. It characterized.

The detecting means is for detecting the rotation angle of the cam, and may be provided in the drive motor or the drive shaft.

The drive shaft is for rotating the cam, and may be a lower shaft or an upper shaft of the sewing machine, or an independent shaft connected thereto.

In addition, the cam may be directly fixed to a drive shaft such as a lower shaft or an upper shaft, or may be fixed to a rotating shaft that cooperates with these drive shafts.

The drive motor is for rotating the drive shaft may be a sewing machine motor or may be a unique motor for thread cutting only.

In the invention according to claim 2, in the sewing machine according to claim 1, the control means controls the drive motor so that the cam rotates at a predetermined low rotational speed when the cam is rotated again. It is done.

In addition, "the predetermined low rotational speed" of Claim 2 is a rotational speed lower than the rotational speed of the cam before rotation of the said cam stops, and the roller which enters through the inlet of a cam groove continues after passing the said inlet. The rotational speed of the cam so that it can be guided to the cam groove properly.

According to the invention as set forth in claim 1, when the rotational angle of the cam is detected by the detecting means at the position where the inlet of the cam groove can enter the roller, the control means controls the drive motor to be temporarily stopped. That is, as the cam rotation pauses, it is possible to earn a time for the bound of the roller to converge. Therefore, the roller is engaged with the edge portion near the inlet of the cam groove to prevent the device from being stopped or the device is damaged by the mechanical load at that time, and it is possible to reliably perform the thread cutting operation, thereby ensuring the reliability and durability of the sewing machine. This is further improved.

In addition, the control means stops the driving of the motor when the rotation angle of the cam that allows the roller to enter the cam groove is detected by the detecting means, and drives the motor again after the roller enters the inlet by the driving of the actuator. . As a result, it is not necessary to strictly control the drive timing of the actuator with respect to the rotation angle of the cam, that is, the angle at which the roller can enter the inlet of the cam groove, thereby significantly reducing the malfunction caused by the timing shift. . In other words, the roller moving by the actuator can enter the inlet of the cam groove more reliably. Therefore, the thread cutting operation can be more reliably performed, and the reliability of the sewing machine is significantly improved.

According to the invention of claim 2, after the cam is temporarily suspended, the cam starts to rotate at a predetermined low rotational speed. Thus, even if the waiting time of the cam is insufficient as the time before the bound of the roller converges, the time until the bound of the roller converges can be obtained as the cam rotates at a low rotational speed after the waiting time. That is, as the roller is bound, the roller is protruded to the outside of the cam groove and the thread cutting of the thread cutting device becomes poor, or the thread cutting device stops due to the engagement between the roller and the edge. Can be prevented. Thus, a more reliable and durable sewing machine can be provided.

(Overall Configuration of One Embodiment of the Present Invention)

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the sewing machine 1 according to one embodiment of the present invention, when a signal for instructing thread cutting is generated, for example, by an operator operating a thread cutting switch, the thread cutting operating device 10 operates to cooperate with the movable blade and the fixed blade. The thread is cut automatically.

As shown in Fig. 1 and Fig. 2, the sewing machine 1 is a sewing machine motor 2 as a driving motor for rotating an upper shaft (not shown) provided in the extending installation direction of the sewing machine arm portion, and is installed on the upper shaft or the sewing machine motor. Drive as encoder 3 as detection means for detecting the rotational angle of the shaft, lower shaft 11 as drive shaft connected to rotate in synchronization with the upper axis, and various operations of the sewing machine including thread cutting operation. The apparatus 4 is provided.

When the sewing machine motor 2 is driven by the control of the drive device 4, the upper shaft rotates to operate a well-known needle bar swing mechanism. In addition, the lower shaft 11 rotates in association with the rotation of the upper shaft, and a known drum mechanism and a transfer mechanism operate. At this time, the rotation angle of the upper shaft is detected by the encoder 3 and output to the drive device 4. In addition, since the upper shaft and the lower shaft 11 are interlocked at a constant rotation ratio, the rotation of the cam 12 described later fixed to the lower shaft 11 and the lower shaft 11 from the rotation angle of the upper shaft detected by the encoder 3. The angle can also be detected.

(Thread cutting device)

Next, the thread cutting operation device 10 will be described in detail.

As shown in FIG. 1, the thread cutting operation device 10 is provided on the cam 12 that is installed on the lower shaft 11 and rotates according to the rotation of the lower shaft 11, and the cam groove 12c formed on the cam 12. The roller 13 is installed so as to move in a direction substantially along the installation direction of the lower shaft 11 by engaging, and is connected to the roller 13 through a connecting link 15, and is interlocked with the movement of the roller 13. The movable blade 14 which rotates to a predetermined direction, and the air cylinder 16 which presses and moves the roller 13 toward the cam 12 are provided.

The cylindrical cam 12 is fixed to and supported by the lower shaft 11 concentrically. That is, the cam 12 rotates integrally with the lower shaft 11. In addition, since the encoder 3 can detect the rotation angle of the lower shaft 11 as described above, the rotation angle of the cam 12 provided on the lower shaft 11 can be detected. On the outer circumferential surface 12a of the cam 12, a cam groove 12c in which the roller 13 can be engaged is formed. The cam groove 12c is formed to be displaced in the axial direction so as to reciprocate the movable scalpel 14 in accordance with the rotation of the cam 12.

The roller 13 is supported at the predetermined position toward the end face 12b of the cam 12 by the roller support member 13a. Moreover, the roller support member 13a is supported so that rotation is possible centering on the rotation point 13b provided in the sewing machine frame which is not shown in figure. Thereby, the roller 13 reciprocates in the rotation range of the roller support member 13a.

In addition, an outlet 12h is formed in the cam groove 12c, and the roller 13 moved along the cam groove 12c from the outlet 12h is guided to the outside of the cam groove 12c, and the roller 13 ) Is returned to the standby position (the position shown in FIG. 1).

When the lower shaft 11 rotates, the cam 12 also rotates, and the roller 13 moves along the cam groove 12c in a direction almost along the longitudinal direction of the lower shaft 11. The movement of the roller 13 rotates the movable knife 14 through the connecting link 15.

The movable scalpel 14 in which the concave hook portion 14a is provided at the distal end is provided to reciprocate between a drum (not shown) and the needle plate. The movable scalpel 14 hooks and captures the upper thread and the lower thread drawn out below the needle plate by the hook portion 14a in the forward (downward) direction of rotation. In addition, the movable blade 14 is retracted (upward in Fig. 1) to rotate in contact with a fixed blade (not shown) installed at a predetermined position below the needle plate to cut the upper thread and the lower thread. Therefore, the fixed blade and the movable blade 14 function as "thread cutting means". In addition, the upper thread which the hook part 14a of the movable blade 14 hangs may be any one or more of the loops of the upper thread formed below the needle plate.

In addition, the movable blade 14 is most advanced when the roller is in the position of the highest displacement position 12g of the cam groove 12c, and the movable blade 14 is in a state of capturing the upper thread and the lower thread. Thereafter, the movable knife 14 retreats by the movement until the roller 13 returns from the outlet 12h to the standby position, and the captured thread is cut. In addition, when the roller 13 is not engaged with the cam groove 12c, the movable knife 14 is provided so that it may stand by in a position which does not interfere with the sewing operation of the sewing machine 1. As shown in FIG.

(Structure of engagement between roller and cam groove)

Next, the structure in which the roller 13 moves to engage the cam groove 12c will be described in detail.

The air cylinder 16 has at least a plunger portion 16a provided so that its front end faces the end face 12b of the cam 12 with the roller 13 and the drive portion 16b for driving the plunger portion 16a. Have When the plunger part 16a is driven by the drive part 16b, it moves to expand and contract from the drive part 16b. Moreover, the drive of the drive part 16b is controlled by the drive device 4 mentioned above. At this time, the plunger portion 16a at the time of non-operation of the air cylinder 16 is waiting at the position near the cam 12, and when the plunger portion 16a is driven by the drive of the drive portion 16b, the roller 13 In contact, the roller 13 is pushed toward the cam 12, and the roller 13 is moved. Therefore, the air cylinder 16 functions as an "actuator."

3 is an explanatory diagram showing a cam groove 12c formed in the cam 12.

As shown in FIG. 3, the cam groove 12 has an inlet 12d for the roller 13 to slide into the cam groove 12c at a boundary position between the outer circumferential surface 12a of the cam 12 and the end face 12b. Is formed. The air cylinder 16 is disposed on the end face 12b of which the inlet 12d is formed with respect to the cam 12, and during non-cutting, the plunger portion 16a of the air cylinder 16 and the cam ( The roller 13 is arrange | positioned and installed between the end surfaces 12b of 12).

In FIG. 4, when the lower shaft 11 rotates by the drive of the sewing machine motor 2, as the cam 12 rotates, the rotation angle position of the cam groove 12c with respect to the roller 13 changes relative. At this time, when the inlet 12d of the cam groove 12c is in a position parallel to the roller 13, the sewing machine motor 2 is controlled to stop by the drive device 4 described later, so that the lower shaft 11 and the cam 12 are stopped. ) Rotation stops. That is, the cam 12 stops in a state where the inlet 12d of the cam groove 12c is located at the side of the roller 13. In addition, the upper shaft angle at which the inlet 12c and the roller 13 are in parallel with each other is constant, and the sewing machine motor 2 is arranged so that the inlet 12c and the roller 13 coincide by detecting the upper shaft angle with the encoder 3. Control is made.

Next, the air cylinder 16 is driven under the control of the drive device 4, and moves rapidly so that the plunger portion 16a extends toward the cam 12. As a result, as shown in Fig. 4A, the roller 13 moves toward the inlet 12d of the cam groove 12c, and the roller 13 collides with the wall surface 12e of the cam groove 12c. The roller 13 springs (bounds) by the impact at the time of such a collision. At this time, since the plunger 16a of the air cylinder 16 is still in the extended state, the roller 13 hits the tip of the plunger 16a and returns to the inside of the cam groove 12c from the inlet 12d again. do. At this time, even if the roller 13 is further bound, it returns to the cam groove 12c by the plunger 16a again. By repeating this, the bound motion of the roller 13 converges gradually.

While the bound motion of the roller 13 is converged, the sewing machine motor 2 is stopped by the control of the driving device, so that the inlet 12d of the cam groove 12c is held at the opposite position of the plunger 16. As a result, the bound motion of the roller 13 is surely converged.

Thereafter, the lower shaft 11 is restarted by the drive device 4 at a predetermined low rotational speed (for example, 170 [rpm]). The cam 12 rotates by this, and the rotation angle position of the cam groove 12c with respect to the roller 13 changes. Therefore, as shown in Fig. 4B, the roller 13 is led to the inside of the cam groove 12c by the edge 12f formed at the end of the inlet 12d of the cam groove 12c. It moves along the shape of the groove 12c. In this way, the movable scalpel 14 connected through the roller 13 and the connecting link 15 rotates as the roller 13 moves, and the upper and lower threads are captured to slide the fixed scalpel to slide the fixed scalpel. Do it.

In addition, the plunger 16a of the air cylinder 16 continues the extended position (position shown in Fig. 4 (a)) until the roller 13 is introduced into the cam groove 12a by the edge 12f. It is controlled by the drive device 4 so as to hold. That is, the plunger 16a of the air cylinder 16 elastically presses the roller 13 toward the cam 12 by air pressure. When the cam 12 rotates until the cam groove 12c is at the position shown in Fig. 4B, the air cylinder 16 is operated and the plunger 16a is contracted so as to be drawn into the driving portion 16a. Move.

(Drive mechanism)

Next, the part regarding the control of the thread cutting operation apparatus 10 among the functions of the drive apparatus 4 is demonstrated in detail using the flowchart of FIG.

The drive device 4 is electrically connected to an unshown thread cutting switch provided at a predetermined position of the sewing machine 1. For example, when sewing is finished and the sewing machine motor 2 is stopped at a predetermined needle upper position, when the thread cutting switch is operated by an operator (step S1: YES), the driving device 4 is threaded. The thread cutting is performed by controlling the driving of each part of the cutting operation device 10.

Specifically, the drive device 4 first drives the sewing machine motor 2 (step S2) to rotate the lower shaft 11 to rotate the cam 12. At this time, by the output of the encoder 3, the drive device 4 detects the rotation angle position of the cam 12, that is, the rotation angle position of the cam groove 12c. When the cam 12 is rotated (step S3: YES) until the inlet 12d of the cam groove 12c is located on the side of the roller 13 (state shown in Fig. 4A) (step S3: YES), 4) stops the sewing machine motor (step S4).

Next, the drive device 4 operates the air cylinder 16 to control the plunger 16a to extend toward the cam 12 (step S5). As a result, the roller 13 is pushed toward the inlet 12d of the cam groove 12c as described above. Thereafter, the driving device 4 drives the sewing machine motor 2 at a low speed after maintaining the stationary state for a predetermined time, so that the lower shaft 11 and the cam 12 have a low rotational speed (for example, 170 [rpm]). Control to rotate (step S6).

In addition, it is preferable that the stop time required for the stroke from the stop of the sewing machine motor 2 to the low rotation is a short time (for example, about 100 [ms]). Further, the stop time is preferably set so that the time until the bound converges, for example, when the roller 13 is bound to the wall surface 12e is empirically obtained.

Thereafter, when the cam 12 is rotated until the roller 13 is introduced into the cam groove 12c by the edge 12f (state shown in Fig. 4 (b)) (step S7: YES), the drive device (4) controls the air cylinder 16 so that the plunger 16a contracts and moves toward the drive unit 16b (step S8).

Thereafter, the drive device 4 drives the sewing machine motor 2 at a normal cutting drive speed (step S9), and the rotation angle at which the cam groove 12c of the cam 12 is engaged with the roller 13 is engaged. As long as it is a position, the lower shaft 11 and the cam 12 are rotated (step S10: YES). In this way, the movable blade 14 is rotated in accordance with the movement of the roller 13 to perform the thread cutting operation as described above. When the roller 13 comes out of the outlet 12h of the cam groove 12c and reaches the rotation angle position of the cam 12 where the engagement between the roller 13 and the cam groove 12c is eliminated (step S10: NO), the driving device 4 stops the sewing machine motor 2 (step S11). The processing of the drive unit 4 is thus completed.

(Operational effect by the sewing machine of the above embodiment)

According to the above embodiment, when the inlet 12c of the cam groove 12 is detected by the encoder 3 and the rotation angle of the cam 2, which allows the roller 13 to enter, the driving device 4 is a sewing machine motor. Control to wait (2). Thereby, even when the roller 13 is bound by the reaction which collided with the wall surface 12e of the cam groove 12c, since the sewing machine motor 2 is controlled to wait temporarily, the roller 13 is a cam groove 12c. As the cam 12 rotates while protruding outward, the possibility that the roller 13 is not introduced into the cam groove 12c may be reduced. That is, as the rotation of the cam 12 is paused by the temporary waiting of the sewing machine motor 2, the time until the bound of the roller 13 converges can be earned. Therefore, as the roller 13 is taken out without being introduced into the cam groove 12c, it is possible to solve the problem that the movable scalpel 14 does not operate and thread cutting is not performed. In addition, as the roller 13 is engaged with the edge 12f of the cam groove 12c, the thread cutting actuator 10 is stopped, or the thread cutting actuator 10 is broken by the mechanical load at that time. The problem can be solved. Therefore, the sewing machine 1 provided with the thread cutting operation device 10 which operates more reliably can be provided, and the reliability and durability of a sewing machine are improved more.

In addition, since the plunger 16 of the air cylinder 16 is in the extended position (position shown in FIG. 4 (a)) until the roller 13 is introduced into the cam groove 12c by the edge 12f. Even when the roller 13 is moved out of the cam groove 12c by the reaction that collides with the wall surface 12e of the cam groove 12c, the roller 13 collides with the plunger 16 and the cam groove 12c. It is braked to be located inward from the inlet of. Therefore, it is possible to provide the sewing machine 1 having the thread cutting operation device 10 that operates more reliably, further improving the reliability and durability of the sewing machine.

Furthermore, in addition to the above-described effects, after the sewing machine motor 2 is paused, the sewing machine motor 2 is again turned on after the roller 13 enters the inlet 12d by the driving of the air cylinder 16. Drive it. Thereby, it is possible to strictly control the driving timing of the air cylinder 16 with respect to the angle of rotation of the cam 12, that is, the angle at which the roller 13 can enter the inlet 12d of the cam groove 12c. There is no need, and the malfunction caused by the timing shift can be greatly alleviated. That is, the roller 13 moving by the drive of the air cylinder 16 can enter the inlet 12d of the cam groove 12c more reliably. Accordingly, the sewing machine 1 having the thread cutting operation device 10 that operates more reliably can be provided, and the reliability of the sewing machine is significantly improved.

In addition, since the time required for the stroke from the stop of the sewing machine motor 2 to the low rotation is a short time (for example, about 100 [ms]), the thread cutting operation of the thread cutting operation device 10 is lukewarm due to the stop. I rarely feel that. Therefore, the sewing machine 1 equipped with the thread cutting operation device 10 which operates more reliably without impairing the comfort by automatic thread cutting can be provided, and the reliability of the sewing machine is further improved.

Moreover, after the roller 13 enters from the inlet 12d of the cam groove 12c, the drive of the sewing machine motor 2 is started at a predetermined low rotational speed (for example, 170 [rpm]). Thus, even if the waiting time of the sewing machine motor 2 is insufficient as the time until the bound of the roller 13 converges, the sewing machine motor 2 is driven at the low rotation described above after the waiting time, so that the roller 13 ), You can buy the time before the bounds converge. That is, as the roller 13 is bound, as the roller 13 protrudes outward of the cam groove 12c, the thread cutting of the thread cutting operation device 10 becomes poor, or the roller 13 and the edge 12f Can be prevented more effectively by the low rotation as described above. Therefore, the sewing machine 1 with higher reliability and durability can be provided.

(Etc)

In addition, although the sewing machine 1 has a drum mechanism in the above-mentioned embodiment, it may be a sewing machine which forms needle stitches by the sewing machine without a drum mechanism, for example, a looper.

In addition, although the sewing thread is cut by the cooperation of the movable knife and the fixed knife, it may be applied to a thread cutting device for cutting the sewing thread only by the movable knife.

In addition, each part can also be changed in the range which does not deviate from the characteristic of the structure described in embodiment mentioned above. For example, the instruction for cutting the thread by the thread cutting switch may be an input of a thread cutting instruction through the touch panel display, or may be a thread cutting command incorporated in a sewing program of a sewing machine to sew using sewing data.

In addition, the predetermined low rotational speed (for example, 170 [rpm]) mentioned above and the time (for example, about 100 [ms]) which are required for the stroke from the stop of the sewing machine motor 2 to low rotation are an example, and the said numerical value is the last. Needless to say, it is not limited to.

In addition, although the air cylinder 16 was used as an actuator in embodiment mentioned above, if the same function can be implement | achieved, other structures (for example, a solenoid etc.) may be sufficient.

1 is a perspective view showing the main configuration of a thread cutting device of a sewing machine.

2 is a block diagram showing a relationship between a driving device of a sewing machine and its connecting device.

3 is an explanatory diagram showing a cam groove formed in the cam.

It is explanatory drawing which shows the relationship of the transition of the rotation angle position of a cam groove, and the position between a roller and the plunger part of an air cylinder. 4 (a) shows a state in which the roller moves from the inlet of the cam groove to the inside of the cam groove by the plunger portion. 4 (b) shows a state in which the roller is introduced into the cam groove by the edge of the cam groove.

5 is a flowchart showing a thread cutting control process by the driving apparatus.

It is explanatory drawing which shows a part of structure of the conventional thread cutting device.

              Explanation of symbols on the main parts of the drawings

2: sewing machine motor 3: encoder

10: thread cutting device 11: lower axis

12: Cam 12c: Cam Home

13: roller 14: movable blade

16: air cylinder

Claims (2)

Movable scalpel for cutting thread, A drive shaft rotating in conjunction with the drive motor, A cam rotatable by the drive shaft and having a cam groove for driving the movable blade; Detecting means for detecting a rotation angle of the cam; A roller coupled to the cam groove so as to be engaged or spaced apart and connected to the movable scalpel; A thread cutting operation device of a sewing machine having an actuator for moving the roller to be engaged with the cam groove when actuated, Rotate the cam and stop the rotation of the cam when the rotation angle of the cam into which the roller enters the cam groove is detected by the detecting means, and then rotate the cam again after actuating the actuator. Thread cutting operation device of the sewing machine characterized in that it comprises a control means for controlling the drive motor and the actuator. The method of claim 1, And said control means controls said drive motor such that said cam rotates at a predetermined low rotational speed when said cam is rotated again.

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