JP2000317178A - Thread cutting drive - Google Patents

Abstract

(57) Abstract: To reduce power consumption and reduce the size of an actuator applied as a drive source of a thread cutting drive device. SOLUTION: An actuator 1 is driven to engage a roller 52 with a cam surface 62 of a cam 6, and the roller 52 moves along the cam surface 62 to impart a desired movement to the moving knife 9 to perform thread trimming. In the thread cutting drive device, the cam 6 inserts the roller 52 between the cam surface 62 and the guide portion 63, in which the cam 6 is opposed to at least the maximum displacement position from the substantially displacement start position of the cam surface 62. Insertion opening 62
a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread trimmer driving device that uses a cam to drive a thread trimmer which cuts a thread in cooperation with a moving knife and a fixed knife.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional example of a thread cutting drive device. The solenoid 1P is a rod 11 that can appear and disappear in the directions of arrows A and B.
The rod 11P is immersed in the direction of arrow B by excitation. The rod 11P is connected to the lower end of the swing arm 3P via the relay link 2P, and a spring 12P is formed on the swing arm 3P so that the rod 11P projects.
Is provided, and the rod 11P is always pulled in the direction of arrow A by the spring 12P. The swing arm 3P is rotatably supported at its upper end by a swing shaft 101P on a sewing machine frame (not shown).
It has.

[0003] The lower shaft 4P is connected to a drive source (not shown) and is configured to rotate, and rotationally drives a disk cam 5P fixed to the lower shaft 4P. A cam surface 52P that is displaced in the left-right direction (arrows A and B directions) is formed on the left end surface 51P (arrow A direction side) of the disk cam 5P in the drawing.
By bringing the roller 31P into contact with the cam surface 52P, the roller 31P moves right and left following the displacement of the cam surface 52P, and the swing arm 3P swings about the swing shaft 101P.

FIG. 2B is a development view of the cam 5P. In FIG. 2B, the downward direction is the leftward direction in FIG.
Direction). When the cam 5P rotates, the cam surface 52
P moves in the direction indicated by arrow E. From the point a to the point b, there is no displacement because it is on the same plane as the end face 51P.
At point c, the displacement in the direction of arrow B is the largest. Conversely, after point c, the displacement gradually proceeds in the direction of arrow A. Then, it becomes the same plane as the end face 51P at the point d, and there is no displacement until the point a.

The lower part of the swing arm 3P is connected to a moving knife base 7P via a relay link 6P. The moving knife base 7P is rotatable about a knife base 200P by a moving knife shaft 102P. 3P swings to rotate in the directions of arrows C and D. The base end of the moving knife 8P is fixed to the moving knife table 7P,
When the moving knife 8P is turned in the direction of the arrows C and D, and the moving knife 8P is near the turning start point, the knife portion 81P at the tip of the moving knife 8P is moved to the knife base 200.
The contact is made with the knife portion 91P of the fixed knife 9P fixed to the scalpel.

Reference numeral 10P denotes a shuttle, and the moving knife 8P crosses over the shuttle 10P to catch the yarn. Next, the operation will be described. When the thread trimming signal is generated, the solenoid 1P is excited just before the sewing operation is completed and the lower shaft 4P is still rotating. As a result, the rod 11P sinks in the direction of the arrow B against the tensile force of the spring 12P, and the roller 31P moves the roller 31P to the cam surface 52P of the disc cam 5P.
Contact to. Since the roller 31P is always urged in the direction of the arrow B by the excitation of the solenoid 1P, even if the disk cam 5P is rotated by the rotation of the lower shaft 4P and the cam surface 52P is displaced, the roller 31P remains in the cam surface 52P. The swing arm 3P swings about the swing shaft 101P in synchronization with the displacement of the cam surface 52P.

When the disk cam 5P rotates and the roller 31P passes the point b of the cam surface 52P, the roller 31P moves to the cam surface 52a.
, And rapidly moves in the direction of arrow B, and the swing arm 3P is rotated counterclockwise about the swing shaft 101P. The swing of the swing arm 3P is performed by the moving knife table 7 via the relay link 6P.
The moving knife table 7P swings in the direction of arrow D about the moving knife shaft 102P, and is moved so as to cross the moving knife 8P over the shuttle 10P.

Further, the disk cam 5P is rotated to rotate the roller 31P.
Reaches the point c, the swing of the moving knife 8P in the direction of the arrow D ends. When the roller 31P passes the point c, the roller 31P follows the cam surface 51a and gradually moves in the direction of arrow A, thereby rotating the swing arm 3P clockwise about the swing shaft 101P. Then, the moving knife table 7P is swung in the direction of arrow C about the moving knife shaft 102P, and the moving knife 8P is moved back to the rotation start point position across the shuttle 10P.

At this time, the moving knife 8P captures the upper thread and the lower thread on the shuttle 10P, and cuts both the captured threads with the female portion 81P of the moving knife 8P and the female portion 91P of the fixed knife 9P.

[0010]

In the conventional thread cutting drive device, the solenoid 1P must always be energized at the time of thread cutting so that the roller 31P is pressed against the cam surface 52 in order to drive the moving knife 8P. There was a problem of consuming a lot of power. In addition, since the solenoid 1P is always energized, the roller 31P is constantly pressed against the cam surface 52P. Therefore, when the roller 31P moves from the point c to the point d, the cam 5P causes the roller 31P to move. It has to be pushed back, so that the rotation of the cam 5P is hindered and the return timing of the moving knife 8P is delayed, which causes a problem that the thread cannot be captured.

Therefore, in order to solve such a problem, when the roller 31P comes to the point c, the solenoid 1P
In some cases, the power supply to the solenoid 1P is stopped to reduce the power consumption of the solenoid 1P and reduce the load on the cam 5P. However, even in such a device, it is necessary to energize the solenoid 1P at least up to the point c.
There was a problem of consuming a lot of power. Also, if the timing of stopping the current supply is early, the return timing of the moving knife 8P is advanced due to the tension of the spring 12P, which causes inconvenience such as not being able to catch the thread. Since the rotation of the cam 5P is delayed, the return timing of the moving knife 8P is delayed, and there is a problem that inconvenience such as not being able to catch the thread is caused.

Further, since the swing arm 3P having the roller 31P and the rod 11P are directly connected, the solenoid 1P
The stroke of the rod 11P, the roller 31P is the cam surface 5
It has to be set so as to reach the maximum displacement position of 2P, the stroke of the rod needs to be lengthened, and the size of the solenoid increases, which causes a problem that the size of the entire device increases.

The displacement of the cam surface 52P from point b (displacement start position) to point c (maximum displacement position) is determined by the cam surface 52P.
Since the configuration is such that the component rapidly rises from the end face 51P of the P, a large load is applied to each component involved in driving the moving knife, and there is a problem that the components are quickly consumed. In addition, the speed at which the moving knife traverses over the shuttle is increased, which has a problem that the yarn before cutting is adversely affected and stable thread cutting cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the power consumption and to perform a stable thread trimming without imposing a burden on the driving of a cam, and to reduce the size of a thread trimming drive source to make the apparatus compact. A drive device is provided. Another object of the present invention is to provide a thread cutting device that makes the initial movement of the moving knife gentler, thereby increasing the durability of each component involved in driving the moving knife and performing stable thread cutting.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a thread trimming means having a fixed knife and a moving knife moving with respect to the fixed knife, and driving the moving knife. A cam having a cam surface formed thereon, a roller arranged opposite to the cam surface, a link connecting the thread cutting means and the roller, and engaging the roller by moving the roller toward the cam surface An actuator that drives the actuator to engage the roller with the cam surface,
In a thread cutting drive device that performs thread trimming by imparting a desired motion to the moving knife by the roller moving along the cam surface, the cam has a guide portion disposed to face a part of the cam surface, And an insertion port for inserting the roller between the cam surface and the guide portion.

Then, by energizing the power source, the actuator is driven to insert the rollers toward the cam surface from the insertion opening, and when the rollers come between the cam surface and the guide portion, the energization to the actuator is stopped. Since the roller is guided by the guide portion, it also moves along the cam surface and transmits a desired motion to the moving knife via the connecting link. Thereby, thread trimming is performed by cooperation of the moving knife and the fixed knife.

Therefore, it is not necessary to energize the actuator up to the maximum displacement position of the cam surface, and the energization may be stopped if the roller is guided by the guide portion arranged near the displacement start position. Can be shortened, power consumption can be suppressed, and stable thread cutting can be realized without imposing a load on driving of the cam.

Further, the above-mentioned configuration is provided with a one-way power transmission mechanism for transmitting the power from the actuator only in the direction in which the rollers move toward the cam surface. Then, when the rollers are guided by the guide portion and the energization of the actuator is stopped, the actuator is returned to the state before driving, and only the rollers are guided by the guide portion and move in the maximum displacement direction.

Therefore, the actuator does not need a stroke for moving the roller to the maximum displacement position, and only needs to have a stroke for moving the roller to a position where the roller is guided by the guide portion. Therefore, the actuator can be downsized. As a result, the entire device can be reduced in size. In addition, a step portion having a displacement amount larger than at least the radius of the roller from the tip of the guide portion is provided in the cam surface of the insertion port in a predetermined section.

Then, when the actuator is driven to insert and move the roller toward the cam surface from the insertion port, the roller enters the step. Thereafter, the roller abuts on the distal end of the guide portion, but since the center of the roller is located in the direction of displacement relative to the distal end of the guide portion, the roller is guided by the guide portion and displacement starts. Therefore, the rollers can be reliably introduced between the cam surface and the guide portion, and the thread trimming can be reliably performed.

Further, a thread cutting means having a fixed knife and a moving knife moving with respect to the fixed knife, a cam having a cam surface for driving the moving knife, and a cam disposed to face the cam surface A roller, a connecting link for connecting the thread cutting means and the roller, and an actuator for moving the roller toward a cam surface to engage the roller. Engage the surface,
In a thread trimmer driving device that performs a thread trimmer by imparting a desired movement to a moving knife by a roller moving along a cam surface, a thread trimmer is performed in a direction in which the cam surface is displaced before a displacement start position of the cam surface. A step portion displaced to such an extent that operation is not affected is provided.

Then, the roller is inserted into the step by driving the actuator, and the moving knife is moved so as not to affect the thread cutting operation. The roller starts to be displaced toward the maximum displacement from the step portion and moves along the cam surface, whereby the moving knife is given a desired movement, and thread trimming is performed in cooperation with the fixed knife. Therefore, since the amount of displacement of the roller up to the maximum displacement can be reduced by the step portion, the inclination of the displacement from the displacement start position to the maximum displacement position can be made gentle, and the thread cutting motion of the moving knife can be reduced. By loosening, it is possible to enhance the durability of each part related to the driving of the moving knife and to surely perform the thread cutting.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic rear view of a thread cutting drive device according to the present invention. FIG. 2 (a)
FIG. 2 is a development view of a cam applied to the thread cutting drive device of FIG. 1. Reference numeral 1 denotes an electromagnetic solenoid as an actuator, which is fixed to a sewing machine frame (not shown) via a solenoid base 2 by fixing screws 2a, 2a. The electromagnetic solenoid 1 has arrows F and G with a predetermined stroke.
A rod head 12 is fixed to the tip of the rod 11 by fixing screws 12a.

A stepped screw 12b is provided at the tip of the rod head 12.
Is mounted, and the stepped screw 12b is loosely fitted into the elongated hole 31 formed at one end of the roller operating member 3 having a substantially L shape. The other end of the roller operating member 3 is rotatably supported by a rotation shaft 4a of a shaft support base 4 fixed to a sewing machine frame (not shown). An engaging portion 32 is formed at an intermediate portion of the longer piece of the roller operating member 3 and extends in a direction opposite to a direction in which the shorter piece extends. The surface 32a is formed.

Reference numeral 5 denotes a roller support link, the lower end of which is rotatably supported by the rotation shaft 4a of the shaft support base 4. An approximately 1/4 portion from the top of the roller support link 5 extends rightward, and an engagement pin 51 that can engage with the engagement surface 32a of the engagement portion 32 of the roller operating member 3 is provided on the extended portion. The engaging surface 3 of the engaging portion 32 of the roller operating member 3
2a engages and rotates in the direction of arrow I about the rotation shaft 4a. A roller 52 is provided on the opposite side of the engagement pin 51. The roller operating member 3 and the roller supporting member 5 constitute a one-way power transmission mechanism.

Reference numeral 6 denotes a disk cam, which is rotatably supported by a lower shaft (not shown) which rotates in conjunction with the operation of the sewing machine, and rotates with the operation of the sewing machine. A cam surface 62 that is displaced in the left-right direction (arrows H and I directions) is formed on the end face 61 of the disk cam 6 on the right side (arrow H direction side) in the drawing. Then, by moving the roller 32 along the cam surface 62, the roller supporting member 3 can be swung in the directions of arrows H and I around the rotation shaft 4a.

Here, the details of the cam 6 will be described.
In the present invention, the configuration of the cam described below is the most characteristic part different from the conventional one. FIG. 2A is a developed view of a cam applied to the thread cutting drive device of FIG.
In FIG. 2A, the lower side is the right side in FIG.
Direction). When the disk cam 6 rotates, the cam surface 6
2 moves in the direction indicated by arrow J.

Hereinafter, points different from the conventional cam will be mainly described. First, the shape from point a to point b (displacement start position) is different, and a step portion 62 a having a displacement L larger than the radius of the roller 52 is formed. Accordingly, the displacement amount of the roller 52 in the movement from the point b to the point c becomes (maximum displacement) -L, and the inclination of the cam surface 62 from the point b to the point c becomes gentler than the conventional one. That is, the rollers 62 gradually displace in the direction of arrow I. From the point c to the point d, from the point d to the point a, it is the same as the conventional one, and from the point c to the point d is a gentle slope gradually displaced in the direction of the arrow H, and from the point d to the point a. Until there is no displacement.

A guide portion 63 is formed on a part of the facing surface of the cam surface 62 from the point b to the point c at a constant interval through which the roller 52 passes. Is formed to be 0, and this tip 6
3a is located slightly to the right of point b. The end face 61 side between the left end of the step portion 62a and the tip portion 63a is an insertion port 62b into which the roller 52 first enters,
The end face 61 side between the right end of the guide portion 63 and point d of the guide face 62 is a discharge port 62c from which the rollers 52 are discharged.

As a result, first, the roller 52 is
2a, the roller 52 comes into contact with the tip 63a.
The tip portion 63a abuts below the center of the guide portion 63, and is guided between the cam surface 62a and the guide portion 63. Before that, the roller 52 moves between the cam surface 62a and the guide portion 63 until the guide portion 63 disappears. After that, roller 5
2 moves along the cam surface 62a as in the prior art.

At the upper end of the roller support member 5, a connecting link 7
Is rotatably connected to the lower end of the moving knife link 8 by a connecting shaft 7b. The connection link 7 includes a first connection link 71 and a second connection link 72, and a long hole 73 is formed on the left of the first connection link 71, and the second connection link 72 An elongated hole 74 is formed on the right side. Adjusting screws 73a, 74a are provided in the slots 73, 74.
Are provided, and the relative positions of the first connection link 71 and the second connection link 72 are changed to adjust the adjustment screws 73a, 73a.
By fixing at 4a, the length of the link 7 can be changed.

The upper end of the moving knife link 8 is fixed to a moving knife shaft 8a rotatably supported by a sewing machine frame (not shown). The base end of a moving knife 9 as a thread cutting means is fixed to the moving knife shaft 8a.
With the swing of the roller supporting member 3 by the rotation of the roller 10, the roller is rotated in the directions of arrows M and N via the connecting link 7, the moving knife link 8, and the moving knife shaft 8 a, and crosses over the shuttle 10 to catch the yarn.

Reference numeral 11 denotes a fixed knife as thread cutting means, which is fixed to a sewing machine frame (not shown) near the rotation start point of the tip of the moving knife 9 and has a knife portion of the moving knife 9a at the tip. Female part 1 that cuts the thread in cooperation with 9a
1a is formed. Next, regarding the operation of the present invention,
This will be described with reference to FIGS. 2 and 3A to 3C. 3 (a) to 3 (c) are operation explanatory diagrams showing the operation of the present invention, and the right side of FIG. 3 is a view similar to FIG. The left side shows the operation diagram in a plan view of the thread cutting means as viewed from the surface.

At the initial position where the thread trimming is not performed, as shown in FIG. 3 (a), in each part of the apparatus, the rod 11 is in a protruding state, and the roller 32 is moved rightward of the end face 61 of the cam 6. The moving knife 9 is located off the hook 10. When the thread cutting signal is generated, electricity is supplied to the electromagnetic solenoid 1 from a power source (not shown) to the electromagnetic solenoid 1 just before the sewing operation is completed and the lower shaft (not shown) is still rotating. The head 12 is immersed in the direction of the arrow G, and the roller operating member 3 is rotated counterclockwise around the rotation shaft 4a via the stepped screw 12b and the elongated hole 31. Thereby, the engaging surface 32a of the engaging portion 32 of the roller operating member 3 moves the engaging pin 51 of the roller supporting member 5 to the left (arrow I).
Direction), the roller supporting member 5 is rotated counterclockwise about the rotation shaft 4a, and the roller 52 is pressed against the step portion 62a of the cam surface 62 (FIG. 3B, right side). At this time, the connecting link 7 connected to the upper end of the roller supporting member 3
Is moved to the left (in the direction of arrow I), the moving knife link 8 to which the multiple ends of the connecting link 7 are connected is the moving knife shaft 8a.
To rotate the moving knife 9 fixed to the moving knife shaft 8a in the N direction to advance to a position slightly over the end of the shuttle 10 (FIG. 3 (b) left).

At this time, the amount by which the moving knife 9 advances onto the shuttle 10 is determined by the amount of displacement of the step portion 62a. However, the moving knife 9 is positioned so as not to hinder the subsequent thread trimming operation. Set to. The timing for inserting the roller 52 into the step portion 62a may be any time as long as the roller 52 is pressed against the step portion 62a.
In the present invention, the position is set to an intermediate position between the points a and b shown in FIG.

Subsequently, when the cam 6 rotates, the roller 52 becomes b
At a point slightly past the point, it comes into contact with the distal end portion 63a of the guide portion 63. At this time, since the center of the roller 52 is located above the distal end 63a, the roller 52 rides on the guide 63 from the distal end 63a. After that, the roller 52
Guided by the cam surface 62 and the guide portion 63. The supply of electric power to the electromagnetic solenoid 1 is stopped when the roller 52 rides on the distal end portion 63a of the guide portion 63, the rod 11 enters the initial position, and the roller operating member 3 is returned to the initial position. However, since the roller 52 is guided by the cam surface 62 and the guide portion 63a, the roller 52 moves along the cam surface 62, and the thread cutting operation is continued.

Then, the roller 52 is gradually displaced from the point b to reach the point c (the maximum displacement position) (FIG. 3C). As described above, the rod 11 of the electromagnetic solenoid 1 is already immersed, and the roller operating member 3 returns to the initial position,
The engagement surface 32a and the engagement pin 51 are separated from each other. Also,
The moving knife 9 has moved to the position where the rotation in the N direction is greatest as shown in the left part of FIG.

Further, when the cam 6 rotates and the roller 52 passes the point c, the roller 52 gradually moves in the direction in which the amount of displacement decreases, that is, the roller supporting member 5 moves around the rotation shaft 4a. The connecting knife 7 is gradually rotated clockwise to move the connecting link 7 in the direction indicated by the arrow H, whereby the moving knife 9 is rotated in the M direction. The thread is caught by the reciprocating operation of the moving knife 9, and further, the moving knife 9 moves backward and the knife section 9 of the moving knife 9 is moved.
a and the fixed knife 11a cut the thread.

Without departing from the gist of the present invention,
It goes without saying that various changes are possible. For example, in the present invention, the guide portion is formed even after passing the point c (maximum displacement position). However, after the point c, the roller 52 moves along the cam surface 62. , C may not be provided before point c.

[0040]

According to the present invention, the actuator is driven to engage the roller with the cam surface, and the roller moves along the cam surface to impart a desired movement to the moving knife to perform thread trimming. In the thread cutting drive device, the cam is provided with a guide portion arranged to face a part of the cam surface, and an insertion port for inserting a roller between the cam surface and the guide portion. It is not necessary to energize the actuator up to the maximum displacement position of the cam surface, and the energization may be stopped if the roller is guided by the guide portion arranged near the displacement start position. It is possible to reduce the power consumption, suppress power consumption, and realize stable thread trimming without imposing a load on driving of the cam.

Also, since the actuator is provided with a one-way power transmission mechanism for transmitting only the power in the direction in which the rollers move toward the cam surface, the actuator moves the rollers to the maximum displacement position. There is no need for a stroke for moving, and it is sufficient if there is a stroke for moving the roller to a position where the roller is guided by the guide portion. Therefore, the size of the actuator can be reduced, and thus the entire device can be reduced in size.

Further, since a step portion having a displacement larger than at least the radius of the roller from the tip of the guide portion is provided in the cam surface of the insertion port in a predetermined section, it is ensured that the roller is introduced between the cam surface and the guide portion. Thread cutting can be performed reliably. Further, in a thread trimmer driving device that drives an actuator to engage a roller with a cam surface, and the roller moves along the cam surface to impart a desired motion to a moving knife and perform thread trimming, Before the displacement start position, a step is provided in the direction in which the cam surface is displaced so as not to affect the thread cutting operation, so that the amount of displacement up to the maximum displacement of the roller can be reduced by the step. So you can
It is possible to make the slope of the displacement from the displacement start position to the maximum displacement position gentler, make the thread cutting movement of the moving knife gentler, improve the durability of each part related to the driving of the moving knife, and cut the thread. It can be performed reliably.

[Brief description of the drawings]

FIG. 1 is a schematic rear view of a thread cutting drive device to which the present invention is applied.

FIG. 2 is a development view of a cam applied to the thread cutting drive device. (A) A development view of a cam applied to the thread cutting drive device of the present invention. (B) A development view of a cam applied to a conventional thread cutting drive device.

FIG. 3 is an operation explanatory diagram illustrating the operation of the thread cutting drive device of the present invention. (A) When the roller is before displacement. (B) When the roller is inside the step. (C) When the rollers are at maximum displacement.

FIG. 4 is a plan view of a conventional thread cutting drive device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic solenoid 1a Rod 3 Roller operation member (one-way power transmission mechanism) 32 Engagement part 32a Engagement surface 4 Shaft support base 4a Rotary shaft 5 Roller support member (one-way power transmission mechanism) 51 Engagement pin 52 Roller 6 Cam Reference numeral 61 End surface 62 Cam surface 62a Step portion 62b Insertion port 62c Discharge port 63 Guide portion 63a Tip 7 Connecting link 8 Moving knife link 8a Moving knife shaft 9 Moving knife (thread cutting means) 9a Female section 10 Hook 91 Fixed knife (thread cutting) Means) 91a female part

Claims (4)

[Claims] 1. A thread cutting means comprising a fixed knife and a moving knife moving with respect to the fixed knife, a cam having a cam surface for driving the moving knife, and a cam disposed to face the cam surface. A roller, a connecting link for connecting the thread cutting means and the roller, and an actuator for moving the roller toward a cam surface to engage with the roller. In the thread cutting drive device that engages with the surface and imparts a desired movement to the moving knife by moving the roller along the cam surface to perform thread trimming, the cam may be substantially displaced from a displacement start position of the cam surface. A thread cutting drive device comprising: a guide portion that is disposed to face at least up to a maximum displacement position; and an insertion port for inserting the roller between the cam surface and the guide portion. 2. The thread cutting drive according to claim 1, further comprising a one-way power transmission mechanism for transmitting the power from the actuator only in the direction in which the rollers move toward the cam surface. apparatus. 3. The thread cutting drive device according to claim 1, wherein a step portion having a displacement amount larger than at least the radius of the roller from a tip of the guide portion is provided in a predetermined area on a cam surface of the insertion port. . 4. A thread cutting means comprising a fixed knife and a moving knife moving with respect to the fixed knife, a cam having a cam surface for driving the moving knife, and a cam disposed to face the cam surface. A roller, a connecting link for connecting the thread cutting means and the roller, and an actuator for moving the roller toward a cam surface to engage with the roller. In a thread trimmer driving device that engages with the surface and applies a desired motion to the moving knife by the roller moving along the cam surface to perform thread trimming, the cam surface is positioned before the displacement start position of the cam surface. A thread cutting drive device comprising a step portion displaced in a direction in which the thread cutting operation is not affected.