JPS6037758B2 - Looper drive device for overlock sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a loose overlock sewing machine, and more particularly to a looper drive device for an overlock sewing machine for low speed sewing with a simple structure and high efficiency.

Conventionally, the looper drive device of a green overlock sewing machine for low-speed sewing uses an eccentric cam fixed to the main shaft, a link that performs a simple shearing motion, and a bevel gear, etc. It is not possible to perform arbitrary movements, such as speed change movements, and secondly, the mechanism becomes larger and more complex, and the number of parts for movement transmission increases, resulting in problems with accuracy errors in each part, making assembly and adjustment difficult. There was a drawback.

Third, because the above mechanism is adopted, the needle bar must be rotated in the fabric feeding direction in order for the looper to pass through the front of the needle at the needle's top dead center, and to pass through the back of the needle at the bottom dead center. Because of this, the needle is subjected to bending force from the fabric, and the needle is bent every time it penetrates the fabric, making it easy to break the needle.
There were drawbacks such as unstable thread ring capture conditions. Fourth, the conventional looper only moves in a parabolic manner in a plane perpendicular to the main axis direction perpendicular to the cloth feeding direction, so the looper moves forward when the needle is at its bottom dead center. When passing through the back surface, the needle interferes with the needle, generates noise, accelerates wear and damage of the needle and looper, and has the disadvantage that it is not possible to further increase the sewing speed. On the other hand, low-speed overlock sewing machines are mainly used by dressmakers, tailors,
Since it has been developed and sold to dressmaking schools and general households, it is required that the mechanism be as simple as possible and that it can be provided at a low price.

Therefore, the conventional mechanism as described above cannot fully meet such demands.

The present invention was invented as a result of intensive research and development in order to eliminate the drawbacks of the prior art described above.The present invention aims to provide a simple and compact mechanism, as well as to provide a looper with arbitrary movements, e.g. It can move with variable speed, prevent interference between the looper and the needle, and enable higher-speed sewing.The movement mechanism is located away from the lower part of the throat plate, and the needle is not required in conventional mechanisms. The inclination angle of the sewing machine can be freely adjusted, for example, it can be vertical like that of a general sewing machine, and other mechanisms such as a lockstitch mechanism can be incorporated in the lower part of the throat plate. An object of the present invention is to provide a looper drive device for some green overlock sewing machines.

In the looper drive device of the overlock sewing machine of the present invention, the looper with the bobbin thread advances and retreats from the side of the needle that moves up and down with the upper thread, drawing a curved figure-eight movement locus, and moves forward and backward from the front side of the needle. The feature is that the warp is executed by passing the upper and lower threads alternately through the back side, and in short, the looper shape is L.
The looper is formed into a mold shape, has a tip at its tip, attaches the bottom end to the end of the looper, and is installed in an L-shaped state, and the looper is arranged perpendicular to the direction in which the cloth is fed. a looper shaft that arranges the looper; a drive shaft (main shaft) that is arranged parallel to the looper shaft and is driven by a motor via a flywheel or the like to drive various mechanisms; an eccentric cam or a triangular cam and a grooved cam that causes the looper ball to rotate at a predetermined angle and reciprocate twice in the direction of the sea bream; and an eccentric cam or a triangular cam and a grooved cam that engage with the eccentric cam or the triangular cam and the grooved cam to transmit their movements. In order to do this, the looper is composed of the drive shaft and a driven member provided at a distance from the looper, and the looper is given the desired yarn tying function by the combined motion transmitted from the driven member.

A preferred embodiment of the present invention will be described in detail below based on the drawings.

In Figs. 1 to 3, the main body 1 of the green overlock sewing machine is shown by the phantom line, and the main body 1 has a rotating drive shaft/(main shaft) 2 for driving various mechanisms of the overlock sewing machine. It is freely installed.

And an eccentric cam 3 for driving the looper is placed at the appropriate place on the drive shaft.
is fixed. The eccentric cam 3 is formed into a cylindrical shape, and is provided with a grooved cam 4 provided with a wavy groove 41 that rises and falls twice per rotation over its outer periphery. A first driven member 5 has an arm 53 on the outside and a roller 51 on the inside of the base 52.
However, by engaging the rollers 51 with the wavy grooves 41, the eccentric cam 3
There is a rotatable iron joint on the top. Arms extended outward 5
A second driven member 50 is pivotally attached to the end portion 65 of 3 by a pin 54. The second follower member 501 is formed into a link shape, and one end 56 is connected to the first follower member 5 by the pin 54, and the end 57 is fixed to the looper shaft 6 with iron.
The looper shaft 6 is rotatably and slidably mounted on the main body 1 with its marking line perpendicular to the direction in which the feeder 8 moves, that is, the direction in which the cloth is fed in the sewing machine. The drive shafts 2 are mounted in parallel. A looper 7 is disposed on the looper shaft 6 at an end 61 thereof facing the side surface of the needle 9 which is carried by the needle bar 11 and moves up and down. The looper 7 is formed in an L shape. The end surface 71 is fixed to the looper shaft end 61 with the L shape lying on its side, and the L shape is
A tip 72 is provided at the shaped tip, and a thread hole 70 is provided at the base of the tip. On the other hand, a flywheel 20 is fixed to one end of the drive shaft 2 and is driven by a motor (not shown) via a belt 21. Upper thread (needle tip) S
I is threaded through a thread hole 90 formed at the tip of the needle 9 via the thread tension device 12, thread guides 13 and 14, and thread guide 15 of the needle shank 11. Further, the lower thread (looper thread) S2 is passed through a thread hole 70 formed at the tip of the looper 7 via a thread guide 16, a thread tension device 17, and a thread guide 18. When the flywheel 20 is rotated by the motor, the drive shaft 2 rotates, and the needle bar 11 and therefore the needle 9 move up and down reciprocally through a needle bar drive mechanism (not shown). The eccentric cam 3 fixed to the eccentric cam 2 rotates, and naturally the grooved cam 4 integrally formed with the eccentric cam also rotates.

Then, the first driven member 5 moves on the eccentric cam 3 in all directions via the rollers 51 engaged with the grooves 41, and moves eccentrically, so that the second driven member 5, which is bent at the pin 54, 50 to transmit the motion. The second follower member receives the movement and rotates the looper shaft 6.
This means that a composite motion of reciprocating motion and rotation of a predetermined angle is given twice per rotation of the drive shaft. As a result, Loopa 7
The tip 72 of the needle 9 alternately moves forward and backward on the front and back sides of the needle 9, which moves up and down, to perform a curved movement as shown by the locus 1 in Fig. 5A, and cooperates with the needle 9 to form the stitch shown in Fig. 11. It is possible to achieve a loose stitch. This suturing action will be described later. As described above, the present invention provides a grooved cam 4 on the drive shaft 2.
An eccentric cam 3 integrally formed therewith is fixed, thereby moving a pair of driven members 5, 50, and transmitting the movement to a looper shaft 6 disposed in a direction perpendicular to the cloth feeding direction. Since a configuration is adopted in which the tip 72 of the L-shaped looper shaft 7 makes a predetermined movement, the looper drive mechanism from the drive ball 2 to the looper 7 has a pair of driven members arranged between two parallel shafts, as shown in the figure. It is extremely simple and can be summarized in a compact manner.

Moreover, as can be seen from the diagram, this looper drive mechanism is connected to the throat plate 8.
Since the sewing machine is constructed so as to avoid the lower part of the needle plate, other mechanisms can be incorporated into the space below the throat plate, which provides various possibilities for the future of this type of sewing machine. Note that FIG. 4 shows an embodiment in the case of a vertical needle bar, and according to the present invention, such a case is also possible. Therefore, the looper drive mechanism from the eccentric cam 3 and the grooved cam 4 to the looper 7 will be described in more detail.
As shown in FIGS. 1 to 6C, the grooved cam 4 has an eccentric outer circumference, and an endless wavy groove 4 is formed on the circumference of the cylinder that also serves as the eccentric cam 3.
1, and its waveform is made to rise and fall twice in one rotation of the cylinder.

For example, as shown in the developed diagram in Fig. 5B, the grooved cam rotation angle oo
The lowest value is set at 180o and the highest value is set at 90o and 2700o. Further, the integrally formed eccentric cam 3 has its maximum and minimum eccentricity advanced by an appropriate amount (5o in the figure) from the maximum value during vibration of the grooved cam 4, as shown in the developed diagram in FIG. 6B. By combining the movements shown in the above two diagrams, the looper 7 can be given a movement along a curved figure-eight locus as shown in FIG. 5A. The first driven member 5, which receives movement from the two cams, has a base 52 that completely covers the wavy grooves of the grooved cam 4, and is attached to the eccentric cam 3 formed of a cylinder around the outer circumference of the grooved cam 4. The drums are sounding solid.

Therefore, as can be seen in the figure, the rod 51 provided inside the base 52 is always correctly engaged toward the cam axis, and rolls into contact with both side walls of the groove 41 without causing strain such as twisting, and the entire member 5 reciprocates in parallel with the cam axis x - phantom, and eccentrically moves due to the outer periphery of the eccentric cam 3. and the second
The movement is transmitted to the looper ball 6 via the driven member 50. As described above, the looper shaft 6 is rotatably and slidably mounted on the main body 1 perpendicular to the cloth feeding direction and parallel to the drive shaft 2.

The second driven member 501 fixed to the looper shaft has an end 56 extending toward the drive shaft 2 for connection with the first driven member 5. Thus, the second driven member 50 and the first driven member 5
rotates in parallel planes, and therefore can be easily connected by being pivoted by a pin 54 parallel to the looper axis, and the arms of the pair of connected support members 5, 50 are used as levers, the looper axis 6, and the drive shaft 2. is taken as a fixed node, and the distance between the axis ○ of the drive shaft 2 and the center of the driven member base 52 attached to the eccentric cam 3 is taken as the crank, and a lever crank mechanism with a modified 4-decoration link is formed as a driving element, and from this, the looper shaft is rotated, and the entire lever crank mechanism is moved by the grooved cam 4 to cause the looper shaft to reciprocate, and the resultant motion is transmitted to the looper 7, causing the looper to perform a three-dimensional circular arc motion. In addition, as shown in FIG. 14, the second driven member 50 fixed to the looper shaft 6 is a U-shaped arm,
It may be pivoted to this via a pin 54 with the first driven portion 5 provided on the drive shaft 2 interposed therebetween.

Further, as shown in FIG. 15, a triangular cam 3a is provided on the drive shaft 2, and a two-pronged cam follower 50a as a second driven portion fixedly installed on the louver shaft 6 is engaged with the triangular cam 3a. Therefore, the swinging motion of the looper 7 may be provided with variable speed. Next, the operation of the present invention will be explained.

As the flywheel 20 rotates, the drive shaft 2 moves in the direction of the arrow h.
The integrally formed grooved cam and eccentric cam 3 also rotate in the same direction.

Therefore, the rollers 51 of the first driven member 5 that engage with the cam groove 41
slides along the groove 41, and the first driven member 5 is transmitted to the looper shaft 6 via the second driven member 50, and moves the shaft 6 along the axis x-x of the drive shaft 2 (Fig. 5A). do. At the same time, the base portion 52 of the driven member 5 makes a biased zero movement according to the biased D cam 3, and this is also transmitted to the looper shaft 6 via the second driven member 50, causing the shaft 6 to rotate. The looper 7 at the end of the looper shaft that is operated by these movements will be explained again with reference to FIGS. 5A to 8B. When the two cams, the grooved cam 4 and the eccentric cam 3, start rotating from 00, the eccentric cam 3 causes the looper 7 to move. first spreads upward, and the tip 72 rises in an arc. At the same time, the looper 7 is moved from the side by the grooved cam 4 toward the needle movement trajectory Y--Y (FIG. 5A). As a result, the two movements are combined, and the looper tip 72 advances toward the needle and retreats along a trajectory as shown in Figure 5A. Now, in this embodiment, when the eccentric cam 3 rotates to 850 degrees, the tip 72
The swing (arc movement) reaches the top dead center, but since the feed (forward and backward movement) of the tip 72 by the grooved cam 4 reaches its maximum point at 900, it does not reach the maximum yet and reaches 900 before turning back and swinging. When the plane was slightly below top dead center, it began to move backwards.
When the eccentric cam 3 rotates to 2650 degrees, the swing reaches the bottom dead center. At this time, the feed by the grooved cam 4 is still 270
Since the maximum point of o has not been reached, I do not turn back, but this time I move back when the swing is slightly above bottom dead center. In other words, the tip 72 follows a curved figure-eight locus and makes a three-dimensional circular arc movement within the cylindrical surface as shown in FIG. I will explain the above-mentioned movement while actually sewing it.

Green stitching involves crossing the looper at the bottom dead center and top dead center of the needle, catching the upper thread (needle thread) with the looper when the needle rises from the bottom dead center, and lowering it with the needle when the needle descends from the top dead center. Sewing is constructed by capturing a thread (looper thread), twisting the captured upper and lower threads, and sewing them one after another. In the case of the present invention as well, both the upper and lower yarns are reliably captured by the looper drive device described above, and defects such as skipped stitches and the like can be completely eliminated. That is, Fig. 7 shows the locus drawn by the tip of the looper, and the curve lo on the left side of the figure matches the phase of the displacement of the looper axis in Fig. 5A with the phase of the rotation angle of the looper in Fig. 6A. In this case, the tip of the looper simply reciprocates around the same point on the cylindrical surface C as shown by the arrow. ”
Point Uo indicates the position where the tip of the looper intersects with the needle at its top dead center, and Lo also indicates the intersecting layer at its bottom dead center. The radius r of the cylindrical surface C is the distance between the center of the looper pith 6 and the tip of the looper tip 72. At the top dead center of the needle, the action of the looper tip 72 turning toward the back of the needle is from one point Uo to a point DUO, which is the dead center of both circular arc movement and reciprocating linear movement.
It is obtained by multiplying the rotation angle of the radius r by the radius r, and can also be obtained by the curve lo. However, at the needle bottom dead center, the looper tip 72 and the needle 9 intersect with each other in the reciprocating stroke at the same point Lo, so the radial deviation of the looper tip 72 in the reciprocating stroke cannot be obtained, and the needle 9 in the forward stroke of the looper tip 72 cannot be obtained. Interference with the needle 9 is unavoidable, as shown in Figure 8A.
is bent due to interference. On the other hand, curve 1 is obtained by slightly advancing the phase of the circular arc motion of the looper tip 72 relative to the phase of the reciprocating linear motion, and as shown by the arrow, it draws different trajectories when descending and when ascending.

and the point U where the looper tip 72 intersects the needle at the needle top dead center,
From there, the looper tip 72 moves further forward and wraps around toward the back side of the needle 9, reaching the top dead center DU of the arc movement. During this time, the radius r rotates by an angle ■u, and reu=B becomes the amount of wraparound, and the triangle for needle penetration shown in FIG. 10 is formed to be large. On the other hand, the point where the looper tip 72 intersects with the needle 9 at the bottom dead center is point L when the looper tip 72 moves forward, and can be located away from the back of the needle 9, and when it intersects with the needle 9 when moving backward. passes through the point -. Therefore, a deviation CL in the radius r direction occurs between the points L and L2 by an amount corresponding to the rotation angle @L of the radius r, and as a result, the looper tip 72 separates from the back surface of the needle 9 when moving forward as shown in FIG. 8B. Interference is prevented by passing through the needle, and when retracting, it becomes possible to approach the needle 9 and enter the hollowed out portion. In this process, the bobbin thread S2 passed through the thread hole 70 at the tip of the sword is passed between the needle side opening of the thread hole 70 and the needle plate 8.
A small triangular gap is formed between the edges of 0 and 0. Then, the needle 9 descends from the top dead center, passes through this triangular gap, enters the hole in the needle plate, and the bobbin thread S2 is captured by the needle 9. In this case, in the conventional mechanism, the triangular gap becomes extremely small as in SA, causing skipped stitches. However, in the present invention, as described above, the looper 7 is actuated by the combined action of swing (arc movement) and feed (forward and backward movement), so the looper tip 7
2 passes through the needle 9 and then wraps around toward the back of the needle. Furthermore, since the swinging phase is earlier than the feeding phase, the swinging reaches its top dead center before the feeding reaches the turning point, and the above-mentioned curve becomes stronger. Therefore, the needle side opening of the thread hole 700 of the looper moves closer to the needle side, and the inside of the triangular gap of the bobbin thread becomes larger as shown in SB, making it easier for the needle 9 to pass through, and the capture of the bobbin thread S2 by the needle 9 becomes easier. become certain. When the needle 9 reaches the bottom dead center, the tip 72 of the looper passes forward to the back of the needle 9, retreats from the turning point, and captures the upper thread SI attached to the needle 9. However, in the conventional mechanism, when the looper retreats, In order to securely capture the thread, the looper passing through the back surface of the needle 9 during the forward movement is forced to do so at the expense of slightly interfering with the back surface of the needle (column 0.3 &) as shown in Figure 8A. As a result, there were drawbacks such as noise generation and wear on the tip of the sword.

In the present invention, as described above, the looper operation is a combination of swing and feed, and in the case of the bottom dead center, as shown in Figure 5A, the retreat position of the feed is delayed and its trajectory rises above the bottom dead center of the swing. Follow. Therefore, as a result of utilizing this characteristic, the looper tip 72 passes away from the back surface of the needle 9 during forward feeding, and
It passes in contact with the back surface of the needle 9 only when retracting, ensuring that the needle thread SI passed through the needle 9 is captured by the looper tip 72, thereby preventing damage to the looper. Furthermore, since these movements are performed by the grooved cam and the eccentric cam 3, good movement can be achieved by paying attention to the settings of these cams. Next, the 12th A
A clutch mechanism for preventing the movement of the looper shaft 6 from being transmitted to the looper 7 as necessary will be explained with reference to FIGS.

In FIG. 12A, the looper 7 has its arm shaft 75 screwed into the screw 1.
00' is fixed to the clutch arm 110, and the clutch arm 110 is loosely attached to the louver shaft 6, and is restrained in the direction of the looper shaft 6 by a collar 65 and a collar 120 (fixed to the looper shaft 6 with a screw 130). There is. A hole 66 is provided in the looper shaft 6, into which a spring 140 and a ball 150 are pushed, and a clutch member 170 is rotatably attached to the looper shaft 6 by a pin 160. The clutch member 170 includes a knob portion 171, an engaging portion 172, and a cam portion 17.
3 is formed, and the cam portion 173 is pressed from the pole 15. On the other hand, the engaging portion 172 engages with a groove 111 formed in the clutch arm 110 to connect the looper shaft 9 and the looper 7. In Figure 12A, looper 7
is connected to the looper shaft 6 to perform the edge warping, and the clutch member 170 is pressed in the direction of the rebound gauge by the pawl 150 to maintain engagement with the groove 111.

In FIG. 12B, the knob portion 171 is rotated clockwise to remove the engaging portion 172 from the groove 111, and the clutch member 1
70, the cam part 173 is pressed by the ball 150',
held in the released position. Therefore, the looper shaft 6 and the looper 7 are free, and the movement of the looper shaft 6 is not transmitted to the looper 7. At this time, lock stitching can be performed by moving the lock stitching device, for example. Next, referring to the effects of the present invention, first of all, since the looper shaft is disposed with its axis perpendicular to the cloth feeding direction and parallel to the drive shaft, the looper shaft can be moved by the cam mechanism, and the transmission mechanism The looper is a simple L-shaped one bent at right angles, and the bottom end of the L-shape is fixed to the tip of the looper shaft, and a tip is formed at the tip. With the L-shape facing toward the side of the needle and the L-shape sideways, the looper is moved in circular arc motion and forward and backward reciprocating motions, so the space in which the looper moves is much smaller than in conventional mechanisms.
It's a small space, and the lower part of the throat plate is empty.

It is also possible to incorporate other mechanisms into the empty space, and since the looper is located on the side of the needle and moves in an arc and reciprocates, it does not utilize the nascent angle of the needle as in conventional mechanisms.
Even if the needle moves in the vertical direction, it can be installed without affecting the effectiveness. Therefore, it will be possible in the future to provide a hook mechanism for lockstitching in the empty space so that the lockstitch can be used for both loose overlocking and lockstitching.
In addition, since the mechanism of the present invention has a simple structure when implemented, it is easy to ensure accuracy. Moreover, in the looper drive device of the present invention,
The looper is moved in a circular arc and reciprocated twice in the direction of the central axis of the circular movement for each circular movement, and the looper is driven by a three-dimensional circular arc movement that is a combination of these movements.
At the needle top dead center, the needle can easily and reliably capture the bobbin thread, preventing skipped stitches, and at the needle bottom dead center, interference between the looper tip and the needle is prevented, reducing noise and enabling higher speed operation. This has the effect of preventing damage to the needle and looper.

Furthermore, by adopting a clutch mechanism to prevent the movement of the looper shaft from being transmitted to the looper as necessary, when used in conjunction with a lockstitch sewing machine, the looper can be stopped during lockstitching. This has the effect of reducing noise and ensuring safety. In summary, according to the present invention, the intended purpose has been achieved and its effects are remarkable.
It has many advantages in terms of its properties and structure, and its value is enormous.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view of an overlock sewing machine incorporating a looper drive device showing an embodiment of the present invention, Fig. 2 is a front view of the main parts related to the looper of the sewing machine, and Fig. 3 shows an inclined needle bar. Fig. 4 is a side view of the main parts related to the looper of the same sewing machine adopted, Fig. 4 is a side view of the same side as Fig. 3 in which a vertical needle bar is adopted, and Fig. 5A is an explanation of the figure-of-eight movement locus of the looper by the looper drive mechanism of the present invention. Fig. 5B is an expanded diagram of the grooved cam of the embodiment of the present invention, Fig. 5C is a side view of the grooved cam, Fig. 6A is an explanatory diagram of the looper arc movement of the embodiment of the invention, and Fig. 6B is the eccentricity of the embodiment. cam development diagram,
Fig. 6C is a front view of the eccentric cam, Fig. 7 is an explanatory diagram of the locus of the looper tip due to the cylindrical surface, Fig. 8A is an explanatory diagram showing interference with the looper needle of the follower device, and Fig. 8B is an explanatory diagram of the looper needle in the device of the present invention. A similar explanatory view, FIG. 9, is a cross-sectional side view of the integrally formed grooved cam, eccentric cam, and the first driven member in which the grooved cam is engaged with the eccentric cam 3, and the grooved cam is engaged with the first driven member. Fig. 10 is an explanatory diagram of the intersecting state of the looper tip with the needle and the formation of the bobbin thread gap according to the present invention;
12A and 12B are longitudinal sectional views of a looper clutch mechanism, FIG. 13 is a perspective view of the looper, and FIGS. 14 and 15 are another embodiment of the looper driving element of the present invention. 2... Drive koji, 3... Eccentric cam, 4... Groove cam, 4
1... Cam groove, 5... First driven member, 51
......Colo, 54...Connecting pin, 50...
...Second driven member, 6...Looper ball, 7...
...Roopa, 72. ...Sword tip, 8...Feed money, 80... Throat plate, 9... Needle, SI...
Upper thread, S2... Lower thread, 20... First wheel, 11...
needle. Figure 1 Figure 2 Figure 3 Figure 4 Figure 14 Figure 15 Figure 5A Figure 5B Figure 5C Figure 6A Figure 6B Figure 6C Figure 7 Figure 8A Figure 8B Figure 9 Figure 10 Figure 11 Figure 12A Figure 12B Figure 13

Claims (1)

[Scope of Claims] 1. A looper shaft provided perpendicularly to the cloth feeding direction and rotatable and slidable on the sewing machine frame, a looper attached to the end of the looper shaft, and arranged parallel to the looper shaft. a drive shaft driven by a motor, an eccentric cam provided on the drive shaft that gives the looper shaft a predetermined oscillation in one rotation in synchronization with the up and down movement of the needle, and an eccentric cam that makes two reciprocating movements in the axial direction. and a driven member provided between the drive shaft and the looper shaft for engaging the eccentric cam and the groove cam and transmitting their motion. looper drive device. 2. A looper shaft provided perpendicular to the cloth feeding direction and rotatable and slidable on the sewing machine frame, a looper attached to the end of the looper shaft, and a looper shaft arranged parallel to the looper shaft and driven by a motor. a drive shaft, a triangular cam provided on the drive shaft and giving the looper shaft a predetermined rocking angle in synchronization with the vertical movement of the needle in one rotation; and a groove cam giving the looper shaft two reciprocating movements in the axial direction; A looper drive device for an overedge sewing machine, comprising: a driven member provided between the drive shaft and the looper shaft for engaging the eccentric cam and the grooved cam and transmitting their motion. 3. A looper shaft provided perpendicular to the cloth feeding direction and rotatable and slidable on the sewing machine frame, a looper attached to the end of the looper shaft, and a looper shaft arranged parallel to the looper shaft and driven by a motor. a drive shaft; a cam provided on the drive shaft that causes the looper shaft to swing at a predetermined angle in synchronization with the vertical movement of the needle; and a grooved cam that causes the looper shaft to reciprocate twice in the axial direction; a driven member provided between the drive shaft and the looper shaft for engaging the cam and the grooved cam and transmitting their motion, and a clutch for preventing the motion of the looper shaft from being transmitted to the looper, if necessary. A looper drive device for an overlock sewing machine, characterized by comprising a mechanism.