JPH0779897B2 - Thread tension control device for button sewing cycle sewing machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread tension controller for controlling the needle thread tension during one sewing cycle in a cycle sewing machine for button sewing.

[Prior Art and its Problems] Generally, in a cycle sewing machine for sewing buttons, several needles immediately before the end of one sewing cycle are dropped into the same button sewing hole to form a knot of upper and lower threads, Moreover, by making these knots a hitch stitch, a so-called thread knot was formed to prevent the stitches from fraying after thread cutting. When the knot is formed by the balance between the upper thread tension and the lower thread tension, the thread knot is immersed in the cloth W as shown in FIG. 8 (a). However,
Normally, this type of sewing machine is provided with a thread trimming mechanism below the needle plate, and the movable blade of the thread trimming mechanism is activated immediately before the sewing operation is finished, and the upper thread and the lower thread are pulled out to the side, Since the cutting is performed between the fixed blade and the movable blade, the thread knot M may be pulled out to the lower surface of the cloth W by the pulling-out operation of the movable blade as shown in FIG. 8 (b).

In this way, when the thread knot M is exposed on the lower surface of the cloth W,
When the sewn product is used, the thread knot M comes into contact with a user or the like and is frayed, so that the button B frequently comes off.

The present invention has been made in view of the above problems, and provides a button sewing cycle sewing machine capable of obtaining a good button sewing state in which a thread knot is not exposed on the lower surface of a cloth even after a thread cutting operation. An object is to provide a thread tension control device.

[Means for Solving the Problems] A clutch mechanism that connects an upper shaft that moves up and down a sewing needle and a drive source that rotates the needle, and a clutch mechanism that rotates in conjunction with the rotation of the upper shaft and that rotation causes cloth and buttons. And a cloth feed cam for moving the holding body of the machine, and reciprocatingly moves in the first, second, and third stages during one sewing cycle in association with the upper shaft, and the rotation of the upper shaft is stopped according to each stage. A shut-off frame that controls the clutch mechanism so that the speed is low and high, and a first frame that is provided in a shortest needle thread supply path from a predetermined needle thread supply source to the sewing needle and that clamps an upper thread located in the path. Thread tension, a second thread tension provided in the shortest upper thread supply path extending from the first thread tension to the upper thread supply source, and clamping the upper thread in the same path, and a first thread of the blocking frame. In the second step, the upper thread clamping force by the first thread tension is relaxed. No. 1 clamping force reducing mechanism, a second thread tension reducing mechanism for reducing the upper thread clamping force due to the second thread tension in the first stage of the blocking frame, and the blocking frame from the third stage to the second stage. A needle thread withdrawing mechanism that causes the needle thread from the second thread tension to the sewing needle to deviate from the shortest needle thread path at the time of switching to the step,
It is equipped with.

[Operation] In the present invention, when the sewing operation approaches the end, the blocking frame is switched from the third stage to the second stage, and the low-speed sewing operation is started, the upper thread drawing mechanism is activated at the same time. Then, the upper thread is made to deviate from the shortest upper thread supply path, and the upper thread path length is increased. At this time, the first needle located on the needle side
In the thread tension of No. 2, the holding force of the upper thread is relaxed by the operation of the first pinching and relaxing mechanism, and in the second thread tension, the second pinching force relaxing mechanism is in the non-operating state. Therefore, the upper thread clamping force is in a steady state. Therefore, the needle thread side of the needle thread is pulled upward due to the increase in the needle thread path length. After that, the movable blade of the thread trimming mechanism pulls out the upper thread in synchronization with the end of the sewing operation, but at this time, the first and second clamping force relaxing mechanisms move together with the movement of the blocking frame to the first stage. Since the upper thread holding force of the two thread tensioners is alleviated, the upper thread pulled out by the movable blade is smoothly supplied from the supply source side. Therefore, the thread knot formed on the cloth is not pulled out to the lower surface, and a good sewing state can be obtained.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

In FIG. 1, reference numeral 10 denotes an upper shaft rotatably supported by a sewing machine frame (not shown), and one rotation of the upper shaft causes a sewing needle (not shown) to perform one lifting operation. Reference numeral 11 denotes a clutch mechanism, which can change the connection state between the upper shaft 10 and a drive pulley 11a as a drive source that is rotated by a sewing machine motor, whereby the rotation speed of the upper shaft 10 can be adjusted. Has become. Reference numeral 12 is a blocking cam fixed to one end of the upper shaft 10, and a locking groove 12a is formed in the end surface thereof.

Reference numeral 13 denotes a cam shaft which is interlocked with the upper shaft 10 via a worm gear 14 and a gear 15, and is rotated once when the upper shaft 10 is rotated by the number of stitches corresponding to one sewing cycle. Reference numeral 16 is a cloth feed cam fixed to the cam shaft 13. A cam groove 16a is formed in the cloth feed cam 16, and a holder (not shown) for holding the cloth W and the button B moves in accordance with the shape of the cam groove 16a, as shown in FIG. 7 (a). As described above, the needles are designed to drop into the adjacent button sewing holes Ba1 and Bb1 and Ba2 and Bb2. Further, notches 44a, 44b having the same shape are formed on the peripheral surface of the cloth feed cam 16 at positions symmetrical by 180 °.
Is projected.

17 is a speed control cam attached to the lower surface of the cloth feed cloth feed cam 16 by screws 18, 18, 18 as shown in FIG. 11,
As shown in FIG. 2, a high-speed portion 17a is formed on the peripheral surface thereof, and low-speed portions 17b1 and 17b2 which are slightly recessed inward are included in the low-speed portion 1a.
Groove-shaped blocking portions 17c formed between 7b1 and 17b2 are formed at two 180 ° symmetrical positions. Further, the cloth feed cam 16 has an arc-shaped long hole through which the screws 18, 18, 18 are inserted, and the phase with respect to the cloth feed cam 16 can be changed within the range of the long hole. There is.

Reference numeral 19 is a speed control link that rotates about a shaft 20, and at one end thereof, a roller 19a that follows the end face of the speed control cam 17 is provided. The speed control link 19 is formed by connecting members 21 and 22.
Is connected to the rotary shaft 23 via. Further, the rotation shaft 23 is connected to a startup pedal 24 via a chain 25 and a startup link.
One end of 26 is fixed to the rotary shaft 23.

Reference numeral 27 denotes a support shaft supported by a sewing machine frame (not shown), and a blocking frame 28 and a rotating plate 29 are rotatably supported on the support shaft 27. The rotating plate 29 is a rotating shaft via a connecting member 30.
It is connected to an arm body 23a fixed to 23 and is adapted to rotate around a support shaft 27 in conjunction with the rotation of the rotating shaft 23. By this rotation movement, the blocking frame 28 also supports the support shaft 27.
Rotate around.

On the other hand, the shutoff frame 28 is provided with a locking claw 28a and a clutch control arm 28b on the upper part thereof, and the clutch control arm 2
8b is the upper shaft 10 by the clutch mechanism 11 depending on the moving position.
And the drive pulley 11a are connected to each other to control the rotational speed of the upper shaft 10.

Further, the locking claw 28a is provided so as to face the end surface of the blocking cam 12 and engages with the locking groove 12a of the blocking cam 12 in a state where the blocking frame 28 rotates in the direction of arrow A, The shaft 10 can be locked at a predetermined rotation phase.

In the mechanism configured as described above, the blocking frame 28 moves in three steps during one sewing cycle.

That is, in the stopped state before the start of the sewing cycle,
As shown in FIG. 1, it is fitted in a groove-shaped stop portion 17c formed in the speed control cam 17. At this time, the blocking frame 28
Is located in the first stage, the clutch control arm 28b provided therein is located so as to disconnect the interlocking relationship between the upper shaft 10 and the drive clutch 11a, and the locking pawl 28a is engaged with the disconnecting cam 12. It engages with the stop groove 12a.

When the operator depresses the drive start pedal 24 in this state, the drive link 26 rotates about the rotating shaft 23 via the chain 25, and the speed control link 19 moves the shaft 2 via the connecting members 21 and 22.
The roller 19a rotates in the direction of arrow C around 0, and the roller 19a comes out of the locking groove 12a. On the other hand, the rotation of the rotating shaft 23 also rotates the arm 23a in the same direction, and pushes down the connecting member 30. As a result, the rotating plate 29 rotates about the support shaft 27 in the arrow B direction, and the blocking frame 28 also rotates in the B direction. This blocking frame 28
The rotation of the locking claw 28a and the clutch control arm 28b provided on the locking claw 28a disengages from the locking groove 12a of the cutoff cam 12, and the clutch control arm 28b moves to the drive pulley 11a and the upper shaft. Connect with 10. As a result, the upper shaft 10 rotates and the cloth feed cam 16 starts to rotate, so that the roller 19a of the speed control link 19 is joined to the low speed portion 17b2 of the speed control cam 17.

Therefore, even if the pedal 24 is released in this state, the speed control link 19 is held at the low speed position, and the shutoff frame 28 moves to the second position.
Held in the stage. Therefore, the clutch control arm 28b
Drive pulley 11a and upper shaft 10 so that upper shaft 10 rotates at low speed.
The connection state with is maintained and the sewing operation is performed at low speed.

This low-speed sewing operation is performed for several stitches from the start of sewing, and when the roller 19a rides on the high-speed portion 17a of the speed control cam 17 next,
Since the speed control link 19 is further rotated in the arrow C direction, the blocking frame 28 is further rotated in the arrow B direction in conjunction with this, and moves to the third stage.

By moving to this third stage, the clutch control arm 28
Since b connects the drive pulley 11a and the upper shaft 10 so that the upper shaft 10 rotates at high speed, the cloth feed cam 16 rotates at high speed and the sewing operation is performed at high speed. And the cloth feed cam 16 is 1/2
The roller 19a of the speed control link 19 rotates again to the low speed position (because it slightly rotates in the direction of the arrow D) before a few stitches to rotate, and accordingly the clutch control arm 28b returns to the second stage. And switch to low speed sewing. At this time, cloth W
The holding body that holds the button B stops moving in the left-right direction until then according to the shape of the engaging groove 16a of the cloth feed cam 16, so that the sewing needle drops into the same button sewing hole and the thread knot is tied. It is formed. Then, when the sewing for half of the time is completed, the roller 19a is fitted into the stop portion 17c, and the speed control link 19 rotates to the cutoff position (rotates in the D direction). As a result, the shut-off frame 28 returns to the first stage and the clutch control arm
28b cuts off the connection between the upper shaft 10 and the drive pulley 11a, and the locking claw 28a engages with the locking groove 12a of the blocking cam 12,
The upper shaft 10 is locked in a predetermined rotation phase.

As described above, in this embodiment, the shutoff frame 28 moves to the third stage during the 1/2 cycle along with the rotation of the speed control cam 17 to control the clutch mechanism 11 to rotate the upper shaft 10
It can be switched to three stages of stop, low speed rotation and high speed rotation.

By the above-described half-cycle sewing, for example, in the case of sewing four hole buttons, the two holes are sewn, so that the thread trimming mechanism (not shown) is used immediately before the half-cycle sewing operation is completed. Is disconnected. And
After that, the remaining two holes are sewn for half a cycle to complete the sewing of the four-hole button.

Next, the thread tension control device in this embodiment will be described with reference to FIGS.

In FIGS. 3 and 4, reference numeral 32 is a first thread tension member provided on the side surface of the sewing machine arm m. The thread tension member 32 is located in an upper thread supply path from an unillustrated upper thread supply source to a sewing needle and has a pair of thread tension plates 32a and 32b facing each other.
The thread tension discs 32a and 32b are urged so as to be joined to each other by the elastic force of a spring, and always clamp the upper thread I with a predetermined clamping force. By pressing the thread tension rod 32c provided in the section, it is possible to reduce the clamping force of the upper thread.

In addition, 33 is a mount provided on the upper surface of the sewing machine arm m, and 34
Is a second thread tension member fixed to this mount 33. This second thread tension is located at IR (see FIG. 6) in the shortest upper thread supply path from the first thread tension 32 to the upper thread supply source, and is always a pair of thread tensions opposite to each other. The upper thread I1 is held between the dishes 34a and 34b. Both thread tension plates
One of the thread tension discs 34b of 34a and 34b is supported by the shaft 34c, and the other thread tension disc 34b is constantly urged downward by a spring. Reference numeral 35 is a thread guide provided on the mount 33, and an upper thread insertion hole 35a through which the upper thread I1 is inserted is formed. The upper thread insertion hole 35a extends from the first thread tension member 32 to the second thread tension member 32.
It is located in the shortest upper thread supply route IR leading to the thread tension 34.

36 is a thread adjusting lever rotatably mounted on the mount 33 by a support shaft 37. This thread adjustment lever
An upper thread insertion hole 36a1 for inserting the upper thread I1 is formed in one end portion 36a of 36, and the upper thread I1 laid from the thread guide 35 to the second thread tension member 34 is inserted therein. Has been done.
The other end 36b of the thread adjusting lever 36 is spring-loaded at one end.
By the urging force of the spring 38 hooked on 8a, it is always joined to the thread adjusting arm 39 fixed to the blocking frame 28. Therefore, when the blocking frame 28 moves in the first, second, and third stages, the thread adjusting lever 36 also rotates about the support shaft 37 in the first, second, and third stages. Also, the thread adjustment lever
When 36 is in the third stage, that is, at the time of high-speed sewing operation, the needle thread insertion hole 36a of the thread adjusting lever 36 is located in the needle thread supply route IR, and the upper thread insertion hole 35a of the thread guide 35 is They are facing each other. Further, 40 is an operating plate for opening and closing the thread tension disc, which is provided so as to project from the thread adjusting lever 36. The operating plate 40 is provided at a position facing the second thread tension discs 34a and 34b, and when the thread adjusting lever 36 moves from the third stage to the first stage, the thread tension disc 34a is moved. , 34b, and the plate thickness of one of the thread tension discs 34a is raised from the other thread tension disc 34b against the spring for biasing the tension tension disc 34a, whereby the thread tension disc The upper thread clamping force by the plates 34a, 34b is relaxed or released. Also, the first
In the steps other than the step of, the operating plate 40 is
It is designed to be removed from a, 34b. Incidentally, 33a is a stopper for locking the thread adjusting lever 36 in the first stage. As described above, the first clamping force relaxing mechanism is constituted by the members 32 to 39, and the needle thread drawing mechanism is constituted by the members 32 to 38.
K1 is configured.

Further, FIG. 5 shows a second thread tension reducing mechanism K2 for reducing the upper thread clamping force in the second thread tension 32.

In the figure, reference numeral 41 denotes a rotation shaft rotatably supported by a sewing machine frame (not shown), and a driven claw 42 is fixed to a tip end portion thereof. The driven pawl 42 is urged in the arrow a direction together with the rotary shaft 41 by a winding spring 43 wound around the rotary shaft 41, and the joint portion 42a thereof is always pressed against the end face of the cloth feed cam 16. ing. Then, when the joint portion 42a rides on the notches 44a and 44b provided on the outer peripheral surface thereof by the rotation of the cloth feed cam 16, the driven pawl 42 rotates in the direction of arrow b against the biasing force of the spring 43. It is adapted to move and rotate in the same direction as the rotating shaft 41. The notches 44a and 44b are usually provided at the sewing end position of the cloth feed cam 16, but the attachment positions can be slightly moved and adjusted as necessary. Reference numeral 45 is a link member whose one end is fixed to the rotation 41, and the other end is rotatably connected to one end of a plate floating bar 46. Further, one end of the thread tension rod 32c is in pressure contact with the side surface of the plate float bar 46, and the plate float bar 46 moves back and forth in the directions of the arrows c and d, so that one end of the thread tension bar 32c. The portion is adapted to be inserted into and removed from a concave portion 46a formed on the side surface of the dish floating rod 46 so that the clamping force of the thread tension member 32 can be switched between the clamping state and the relaxing state. That is, when one end of the thread tension rod 32c is fitted into the recess 46a in the protruding state, the thread tension plates 32a and 32b hold the upper thread with a constant force, and from this state, the plate floats. When the lever rod 46 moves in the direction of the arrow d, one end of the thread tension rod 32c comes out of the recess 46a and enters the retracted state, and one thread tension disc 32a is separated from the other thread tension disc 32b by a predetermined amount. The thread clamping force is alleviated. The members 41 to 46 constitute a second thread tension reducing mechanism K2. Reference numeral 47 in the drawing denotes a driven body which moves by being fitted in the cam groove 16a of the cloth feed cam 16, and a holding body (not shown) which holds the cloth W and the button B moves together with the driven body 47. .

The yarn tension control device in this embodiment is constructed as described above, and its operation will be described below.

When the breaking frame 28 is in the first stage and the sewing operation is stopped, the thread tension lever 36a is held at the position shown in FIG. 6 (a) by the thread adjusting arm 39 provided on the breaking frame 28. Therefore, the operating plate 40 is in a state of being inserted into the measuring thread tension discs 34a and 34b of the second thread tension 34. Therefore, the upper thread clamping force of both thread tension discs 34a, 34b is in a relaxed state.

On the other hand, in the first clamping force reducing mechanism K1, the driven pawl 42 rides on the notch 44a provided in the cloth feed cam 16 and the rotary shaft 41 moves with the arrow b.
Since the tray float bar 46 is rotated in the direction and the tray float bar 46 is moved in the direction of the arrow c, the thread tension rod 32c is the recess 46a of the tray float bar 46.
The upper thread is clamped by the thread tension trays 32a and 32b in a relaxed state.

Here, when the pedal 24 is depressed to move the blocking frame 28 to the second stage and the low speed operation is started, the thread adjusting lever 39 is driven and the thread adjusting lever 36 is moved to the state shown in FIG. 6 (a). To clockwise, and is held at the second stage shown in FIG. 6 (b). As a result, the operating plate 40 separates from between the thread tension discs 34a, 34b, and the upper thread I1 is clamped by the both thread tension discs 34a, 34b with a stronger clamping force than in the first step. In this second stage, the driven claw in the second clamping force relaxing mechanism K2
Since 42 is still riding on the notch 44a, the upper thread clamping force by the thread tension discs 32a and 32b is the same as in the first stage.

After the low speed sewing operation is completed, the high speed part 17 of the speed control cam 17
When the roller 19a rides on a, the blocking frame 28 moves to the third stage, and the high-speed sewing operation is started, the thread adjusting lever 36
6a further rotates clockwise from the state shown in FIG. 6 (b) and is held at the position shown in FIG. 6 (c). At this time, since the upper thread insertion hole 36a1 formed at the one end 36a of the thread adjusting lever 36 faces the upper thread insertion hole 35a of the thread guide 35, the first thread tension member 34 reaches the second thread tension member 32. The upper thread I1 coincides with the shortest upper thread supply route IR. In addition, the second thread tension 34 is set to the upper thread I1.
Is being held with a steady clamping force. Further, in the first thread tension member 32, the driven claw 42 is disengaged from the notch 44a, the rotary shaft 41 rotates in the arrow a direction, and the dish floating bar 46 moves in the arrow d direction. 32c fits into the recess 46a and is in a protruding state, and the upper thread clamping force by both thread tension discs 32a, 32b is clamped by a constant clamping force stronger than in the second stage. Therefore, the upper thread
Appropriate tension is generated in I1, and the knot with the lower thread I2 is formed in the cloth W.

After this, the half-cycle sewing operation is approaching the end and
a comes into contact with the low speed portion 17a of the speed control cam 17 and the shutoff frame 28
Returns to the second stage, and when the sewing speed changes to a low speed, the thread adjusting lever 36 moves from the state of FIG. 6 (b) to the state of FIG. 6 (c) again according to the thread tension arm 39, Upper thread insertion hole
Since 36a deviates from the shortest upper thread supply route IR, the upper thread I1 is pulled out to the side and the upper thread supply route between the two thread tensions 32, 34 increases. At this time, the second thread tension member 34 is still clamped by the upper thread I1 steady clamping force, but in the first thread tension factor 32, the driven claw 42 rides on the notch 44b, so the upper thread clamping force is in a relaxed state. Has become. Therefore, the upper thread I1 corresponding to the increase of the upper thread supply path is fed from the needle side, and the upper thread tension is greatly increased. As a result, as shown in FIG. 7, the needle thread I1 formed in this low speed sewing operation is
The knot between the lower thread I2 and the lower thread I2, that is, the thread knot M, is pulled out to the upper surface of the cloth W.

After this, at the same time when the half-cycle sewing operation is completed, the movable blade of the thread trimming mechanism pulls out both the threads I1 and I2 and cuts between them and the fixed blade. At this time, the first and second thread tension As described above, since the upper thread clamping force of 32 and 34 is in the relaxed state, the upper blade I1 of the upper thread is smoothly pulled out from the upper thread supply source side in the thread pulling operation by the movable blade. Therefore, the upper thread on the stitch side is not pulled out, and the thread knot M is held on the upper surface of the cloth W. In some cases,
It is conceivable that the thread on the cloth side is pulled out to some extent, but even in that case, the thread knot M is only submerged in the cloth W,
It is not pulled out to the lower surface of the cloth W.

As described above, when the thread knot M is formed on the upper surface of the cloth W, the thread knot M is covered with the button B and the cloth W, so that the user does not come into direct contact with the user when wearing the cloth knot and the fray occurs. The rate is greatly reduced.

In the above embodiment, the second clamping force reducing means is operated by the rotation of the cloth feed cam 16 that interlocks the blocking frame 28, but it may be directly linked to the operation of the blocking frame 28. However, the present invention is not limited to the above embodiment.

Further, the needle thread withdrawing mechanism is not limited to the one using the thread adjusting lever 36 as in the above embodiment, but may have another structure. For example, a second thread tensioner is provided so as to be able to move between the upper thread supply path and a position deviating from the upper thread supply path, and a moving means such as a solenoid is connected to the thread tensioner so that the third stage of the cutoff frame can be achieved. To the second stage is detected by a microswitch or other detecting means, and the solenoid is driven by the detection signal to cause the second thread tension to deviate from the upper thread supply path. However, the present invention is not limited to the above embodiment.

[Effects of the Invention] As described above, according to the thread tension control device for the button sewing cycle sewing machine of the present invention, the upper thread withdrawal is performed at the time when the high-speed sewing operation is switched to the low-speed sewing operation for thread knotting. The mechanism allows the needle thread to be inserted into the sewing needle to be pulled up, and the needle thread clamping force due to the thread tension is alleviated during thread cutting operation, so the thread knot is reliably prevented from being pulled out to the bottom surface of the cloth. can do.
Therefore, when using the product, the knot does not come into direct contact with the user, and it is possible to significantly reduce the occurrence of fraying of the knot and the resulting drop-off of buttons. It is possible to improve.

[Brief description of drawings]

FIG. 1 is a perspective view showing a drive system mechanism of a cycle sewing machine in an embodiment of the present invention, FIG. 2 is a plan view showing a speed control cam of the one shown in FIG. 1, and FIG. 3 is a thread in the same embodiment. FIG. 4 is a perspective view showing the first and second thread tensions of the tension control device and the first clamping force relaxing mechanism, FIG. 4 is a side view of the first clamping force relaxing mechanism shown in FIG. 3, and FIG. FIG. 6 is a perspective view showing a second holding force relaxing mechanism of the thread tension control device in the embodiment, and FIGS. 6 (a), 6 (b) and 6 (c) are plan views showing the operating state of the one shown in FIG. FIG. 7 is a vertical sectional side view showing a button sewing state by a button sewing cycle sewing machine according to the embodiment, and FIGS. 8A and 8B are vertical side views showing a button sewing state by a conventional button sewing cycle sewing machine. It is a figure. In the figure, 10 ... Upper shaft 11 ... Clutch mechanism 16 ... Cloth feed cam 28 ... Breaking frame 32 ... First thread tension 34 ... Second thread tension K1 ... First clamping force relief mechanism K2 …… Second clamping force relief mechanism I1 …… Upper thread I2 …… Lower thread IR …… Shortest upper thread path

Claims (3)

[Claims] 1. A clutch mechanism for connecting an upper shaft for raising and lowering a sewing needle and a drive source for rotating the upper shaft, and a clutch mechanism for rotating in conjunction with the rotation of the upper shaft, and the rotation of the rotating mechanism for holding cloth and buttons. And a cloth feed cam that moves the upper shaft and the upper shaft, reciprocatingly moves in three steps, first, second and third, during one sewing cycle, and the rotation of the upper shaft stops at a low speed according to each step. , A shut-off frame for controlling the clutch mechanism so that the speed is high, and a first needle thread provided in a shortest needle thread supply path from a predetermined needle thread supply source to the sewing needle, and for nipping an upper thread positioned in the path. Of the thread tension, a second thread tension provided in the shortest upper thread supply path from the first thread tension to the upper thread supply source, and holding the upper thread in the same path, and a second thread tension of the blocking frame. In the first and second stages, the first
A first pinching force easing mechanism for easing the upper thread pinching force due to the second thread tension, and a second thread tension easing mechanism for easing the upper thread pinching force due to the second thread tension in the first stage of the blocking frame. An upper thread withdrawing mechanism that causes the upper thread from the second thread tension to the sewing needle to deviate from the shortest upper thread path when the blocking frame is switched from the third step to the second step. A thread tension controller for a button sewing cycle sewing machine, which is characterized by: 2. A needle thread withdrawing mechanism includes a lever body that moves in three steps in conjunction with a blocking frame, and the lever body comprises:
It is characterized in that it has an upper thread insertion portion for laterally diverging the upper thread in the shortest upper thread supply path from the second thread tension to the sewing needle at the time of moving from the third step to the second step. A thread tension control device for a button sewing cycle sewing machine according to claim 1. 3. A needle thread withdrawing mechanism, wherein a second thread tension which is movable to a predetermined position deviating from the needle thread feeding path and a time point when the interruption frame is switched from the third stage to the second stage. 2. The thread tension control device for a button sewing cycle sewing machine according to claim 1, further comprising thread tension moving means for moving the second thread tension from the upper thread supply path.