JPH0779896B2 - Zigzag sewing machine with thread tightening correction device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a needle thread adjusting device for preventing unevenness of a lower thread in a seam by a zigzag sewing machine.

(Problems to be solved by the prior art and the invention) The straight stitches in the lockstitch sewing machine include a normal stitch as shown in FIG. 21 and a hitch stitch as shown in FIG. As shown in FIG. 23, it is generally desired to sew with a normal stitch in which the seam is disturbed and the thread is not untwisted. The normal stitches and the hitch stitches are generated as shown in FIGS. 24 and 25. It depends on whether it falls to the side. Generally, when the bobbin thread of the rotating hook is in front of the bobbin thread withdrawal point when viewed from the front in the direction of sewing, that is, when the bobbin thread is on the left side of the needle, FIG.
If the lower thread comes to the rear side of the lower thread withdrawal point, that is, to the right side of the needle, the stitch becomes a normal stitch in the path like G, and the hitch stitch becomes in the path as shown in FIG. Therefore, generally, when the bobbin thread supply source is viewed from the front in the traveling direction of the sewing machine as shown in FIG. It is effective to feed the lower thread from the left side as shown in Fig. 26a,
Most sewing machines avoid hitch stitches by this method. However, in such a system, in zigzag sewing, a phenomenon occurs in which the lower thread is offset as shown in FIG. 27a.
This phenomenon is remarkable when the stitch pitch is small, and in order to eliminate this phenomenon and obtain a non-uniform stitch as shown in FIG. 27b, the bobbin thread withdrawal point is set to the amplitude of zigzag stitch as shown in FIG. 26b. Need to be set in the center of.

As described above, in order to prevent the bobbin thread from shifting to one side, the bobbin thread draw-out opening for the bobbin thread is different from straight stitching and zigzag stitching, and it is desirable to set the proper position. On the other hand, the applicant of the present invention, in Japanese Utility Model Laid-Open No. 56-23074, designs a moving member for moving and setting the bobbin thread drawing port to the left when straight sewing in a sewing machine with the bobbin thread drawing port at the center of amplitude. It is shown that it is connected to the selection portion and engages with the lower thread to guide leftward when the straight stitch is selected.

In the conventional example, the guide member is moved left and right by selecting the pattern and the guide member directly acts on the bobbin thread to guide the bobbin thread drawing port, so that the bobbin thread drawing port can be clearly switched. However, the moving member does not directly control the bobbin thread when releasing the bobbin thread when switching from the straight stitch to the zigzag stitch, and the bobbin thread return depends on the thread withdrawing action when forming the stitches. For this reason, thread dulling due to release of the bobbin thread at the time of switching is likely to occur, and when zigzag stitching is selected, the moving member remains in the thread removal path of the upper thread, so there is a problem in that its shape and finish are limited. there were.

Therefore, a bobbin thread feeding mechanism and an adjusting device for responding to the amplitude and position of the needle are required, and it is necessary to set the range within the narrow gap between the needle plate and the shuttle.
The structure is also complicated. It is also proposed that the needle thread supply amount is stored in advance together with the needle amplitude data and the feed data and adjusted for each needle, but it is adjusted in addition to the data necessary for pattern formation such as pattern sewing. There are drawbacks in that many storage means are required to store the amount, and the device for adjusting the supply amount for each needle becomes complicated.

(Means for Solving the Problems) The present invention addresses the prevention of the deviation of the lower thread by changing the upper thread supply amount by the upper thread retracting means driven by the amplitude movement of the needle when forming the seam. A needle that moves left and right and up and down, an upper thread catching means that cooperates with the needle to form a lock stitch, a balance that moves up and down in synchronization with the needle, and an upper shaft rotation phase detection Means, a first needle thread pressing device which is a thread tension adjusting means arranged between the needle thread supply source and the balance, and is arranged between the first upper thread pressing device and the balance. A second needle thread presser for intermittently pressing the needle thread, an upper thread guide body connected to the amplitude drive member of the needle on the upper thread path, and the guide body in cooperation with one side of the amplitude range. The upper thread retracting means is composed of an action body arranged to operate, and the control means of the second upper thread pressing device.

(Operation) Until the top dead center position of the balance due to the rotation of the drive shaft, the second upper thread presser is kept in a pressed state and the seam is a strong pressing force by the first upper thread presser and the second upper thread presser. The second upper thread pressing device is released by releasing the second upper thread pressing device during a phase in which the needle hole of the needle descends to approximately the center of the cloth thickness from the phase immediately after the top dead center of the balance. Weak pressure with only the container,
On the needle position side for correction between these phases, the upper thread drawing is performed by the operation of the upper thread drawing means. During this time, by providing a balance having a modified thread squeeze curve in order not to cause thread slack due to the lowering of the balance, or by providing another thread retracting means for absorbing the thread slack, the thread is passed through the first upper thread presser. The upper thread is supplied from the source.

(Example) Next, the Example of this invention is described in detail with reference to drawings.

In FIG. 5, a needle bar 3 which is connected to a drive unit (not shown) and is connected to an upper shaft 2 to which rotation is transmitted is supported by a sewing machine frame 1 so as to be vertically movable. The needle bar 3 has a crank rod 9 rotatably connected to the shaft portion of a needle bar crank 8 fixed to one end of a crank 7 provided at the shaft end of an upper shaft 2 rotatably supported by the sewing machine frame 1. It is fixedly inserted through a needle bar holder 10 having a rotatable shaft portion at the other end, and is inserted through a needle bar support 11 at the upper and lower portions of the needle bar holder and supported so as to be vertically movable. The needle bar support is a shaft 12 fixed to the sewing machine frame 1.
It is mounted on the pedestal and its vertical movement is restricted, and it is supported so that it can only rotate. The other end of the needle bar support 11 is connected to one end of a connecting rod 13, and the other end of the connecting rod is an output shaft 14 of a stepping motor 14 for needle bar amplitude fixed to the sewing machine frame 1.
It is connected to a through a fixed arm 15 and a link 16.

The feed dog 19 is a horizontal feed arm driven by the upper shaft 2.
The amount of movement of the horizontal feed arm is fixed by adjusting the swing angle of the horizontal feed arm, and the swing angle adjusting member 22 is fixed to the shaft end of the adjusting shaft 23. The amount of transmission to the horizontal feed arm 21 is adjusted by rotating the moving angle adjusting member, and the feed adjustment stepping is fixed to the arm 24 fixed to the other end of the adjustment shaft 23 and the sewing machine frame 1. Motor 25
A crank 26 fixed to the output shaft of the is connected via a link 27.

In FIG. 5a, reference numeral 32 denotes a rotary plate fixed to the upper shaft 2, and a slit formed in the rotary plate and the sewing machine frame 1
The fixed photo interrupter 33 constitutes a device for detecting the rotational phase of the upper shaft 2.

Reference numeral 34 is a link type balance, which is connected to the upper shaft 2 via a link 35 and has the characteristic of the thread Yurme curve shown in FIG. 6a. belongs to. In FIG. 3, reference numeral 36 denotes a first needle thread presser, which is a thread tensioner having a known structure for applying a spring pressure between the pair of thread holding trays 36a and 36b as shown in FIG.

By rotating the thread tension dial 37 of the first needle thread presser, the pressing force on the pair of thread holding trays 36a, 36b is changed, and "auto" is set on the scale of the thread tension dial 37. The position of 37a is set, and the pressing force corresponding to the general cloth is applied by matching with the display 38 provided on the surface of the sewing machine frame 1. Note that this function may be performed by the second needle thread pressing device.

39 is a second needle thread presser, and is the first needle thread presser.
An intermittent pressing device which is arranged on the upper thread path between 36 and the balance 34 and which presses and releases the upper thread during one cycle of stitch formation.

The second needle thread pressing device has a structure as shown in FIG. 7, and a threaded portion 40a of a flanged screw 40 is screwed into a screw hole 1a formed in the sewing machine frame 1 and Hollow hole in screw shaft 40c
40a is opened.

A pair of thread holding trays 41 and 42 are fitted on the shaft portion 40c of the flanged screw 40. From the flange portion 40b of the flanged screw 40 to the shaft portion 4
A slit groove 40d is formed over the area 0c, and the thread holding tray 42 is provided with a rib 42a which has a shape as shown in FIG. 8 and fits into the slit groove. Is allowed. A spring 43 is arranged between the thread holding tray 42 and the collar portion 40b of the collared screw 40, and presses the thread holding trays 41 and 42 to apply a holding pressure between the trays. By rotating the flanged screw 40 by using the slit groove 40d, the flange portion 40b is axially moved by the screw portion 40a and the screw hole 1a, and the pressing force of the spring 43 is exerted. It can be adjusted. The collar portion 40b is integrated with the shaft portion 40c by the adhesive agent or the like after assembling the thread holding tray 42 and the spring 43.

A pin 44 is inserted into the hollow hole 40 of the flanged screw 40 so as to be movable back and forth. One end of the pin 44 is in contact with the rib 42a of the thread holding tray 42, and the other end is fixed to the sewing machine frame 1. It is in contact with the tip of the output shaft 45a of the solenoid 45.

The second needle thread pusher 39 and the phase detector 63 are connected via a central processing unit 64 as shown in FIG.

Reference numeral 46 is a thread drawing means, which is a hole portion 48a through which the upper thread 47 is inserted.
The guide body 48 and the acting body 49 are provided.

The guide body 48 is as shown in FIG.
A guide part 48c fixed to the needle bar support 11 at b and having a hole 48a projects from the opening of the machine frame 1 of the sewing machine.

The action body 49 is formed with an action portion 49a and a main body portion 49b arranged above and below the guide portion 48c of the guide body 48, and a step portion of a pair of stepped screws 50 is provided in an elongated hole 49c provided in the main body portion. Are fitted. The pair of step screws are fixed to the sewing machine frame 1, and the working body 49 is engaged with the step portion of the step screw 50,
It is movably supported in the arrangement direction of the step screw. A solenoid 51 fixed to the sewing machine frame 1 is provided at one end of the working body.
The output shaft 51a of the sewing machine is connected to the sewing machine frame 1 so that the output shaft 51a is urged in the direction of arrow A when there is no signal to the solenoid. A spring 52 is provided. The solenoid 51 is connected to a pattern selecting means (not shown).

By the operation of the solenoid, the action body 49 connected to the output shaft 51a is supported by the step screw 50 and moves left and right to move to the 10th position.
It is set at two positions shown in FIGS. That is, a indicates the left position (shown by the solid line in the figure) and the right position (shown by the dotted line in the figure) of the guide portion 48c of the guide body 48, and the action portion of the acting body 49.
49a shows an operating position (shown by a solid line in the figure) and an inactive position (shown by a dotted line in the figure) of 49a. When the action part 49a of the action body 49 is set to the inactive position of the dotted line position in the figure in FIGS. a and b, the guide portion 48c of the guide body 48 is set to the a or b position. The upper thread inserted into the hole 48a of the body 48 is in a non-acting state in which it does not touch the acting portion 49a as shown in FIG. 11c, and is a position at the time of forming a stitch like a straight stitch.

When the action portion 49a of the action body 49 is set to the action position shown by the solid line in the figure, the needle thread inserted into the hole portion 48a of the guide body 48 is the guide portion 48c of the guide body 48 in the left position. At the right position, which is not touched as shown in FIG. 11a, the upper thread is pulled in as shown in FIG. 11b.

Next, the control of the upper thread will be described with reference to FIGS. 1 and 6 to 8. FIG. 6 is a Yurume curve diagram,
The horizontal axis of FIG. 6 is the rotational phase of the upper shaft 2 where the needle top dead center phase θa detected by the rotational phase detector of the upper shaft 2 is 0 °.

Further, in the figure, a is a balance thread Yurme curve which changes according to the operation of the balance 34, C is an operation diagram of the second upper thread pressing device 39 which is an intermittent pressing device, and C1 is the operation thereof, and C2 is That is when it is inactive.

Next, the movement of each operating part and the yarn will be described.

First, the balance 34 moves up and down by the rotation of the upper shaft 2 and acts on the upper thread 47 to form a balance thread Yurume curve as indicated by a in FIG. In the second upper thread pressing device 39, the phase θ1 from the phase where the elongation of the upper thread almost disappears due to the lowering of the balance 34 to the top dead center of the balance.
Until then, a strong holding force T ₂ is applied by pressing the spring 43 as shown in FIG. 7, and in other phases, the solenoid 45 is operated to push the pin 44 in the direction of arrow G, Abut on one end of the pin. The thread holding plate
By acting on the rib 42a of 42, the yarn clamping plate is pushed up against the pressing force of the spring 43 to change the upper yarn clamping pressure. The changed clamping pressure T ₂ is determined by the moving position of the solenoid. In this embodiment, the case where the clamping pressure is released by the operation of the solenoid, that is, the case where the T ₂ value becomes 0 due to the movement will be described. In the needle top dead center phase indicated by the phase θa, the cloth feed is not performed as described above, and the second upper thread pressing device 39 is in the operation indicated by C1 and the thread catching trays 41 and 42. The upper thread 47 is held between them.

This state is maintained until the next balance top dead center phase θ1 due to the rotation of the upper shaft, while the balance 5 rises to absorb the yarn in the upper yarn path to reduce the amount of upper yarn slack and reduce the phase θ.
Set to a minimum of 1 and tighten the seams. The thread path of the upper thread at this time is as shown in FIG. 12 (a), and the thread guide 53 (point e) fixed to the sewing machine frame 1-the needle hole 17a (point b) -entanglement of the upper and lower threads in the cloth The needle thread between points 54 (point f) maintains tension.

After tightening the thread at the seam at the balance top dead center phase θ1, the second upper thread pressing device 39 releases the upper thread 47 between the sandwiching trays 41 and 42 when C2 is inoperative. Then, as the needle 17 descends, the cloth is fed until the phase θ2 when the needle hole 17a reaches the center of the cloth thickness, and the cloth feeding is completed at the phase θ2, and the second needle thread pressing device 9 moves to the C1 position. At the time of operation, the upper thread 47 between the holding plates 41 and 42 is pressed and held. This phase θ2 is as shown in FIG. 12B, and the needle hole 17a (point g) of the needle 17 is at the center of the cloth when the stitch is fed by the cloth feed amount m.

Therefore, between the phase θ1 and the phase θ2, the upper thread 47 corresponding to the feed amount m and the cloth thickness t shown in the figure is required, and the thread piece 55
If the upper thread between the seam and the seam is in a tensioned state,
Since the upper thread pressing device 39 has released the nipping, the upper thread pressing device 39 pulls it out from the thread piece 55, which is the supply source of the upper thread, by the cloth feeding, and the tension is applied by the first upper thread tension device to be supplied.

During the phase θ1 and the phase θ2, the thread balance of the balance thread does not cause thread distortion.

Therefore, the upper thread in the upper thread path between the upper thread supply phases between the phase θ1 and the phase θ2 is in a tensioned state, and the shortage of the upper thread 47 generated by the cloth feeding action is supplied. In the phase θ2 after the yarn is supplied, the second needle thread pressing device 39 is in the operation shown by C1 and the solenoid 45 is excited to press and hold the needle thread 47.

In addition, the supply amount W of the upper thread between the phase θ1 and the phase θ2 described above.
Is the amount of thread supplied from the completed state by tightening the thread before the phase θ1 to the time when the needle hole 2a of the phase θ2 descends to the center of the cloth. E in
It is the amount obtained by subtracting the yarn lengths indicated by e to h to f in Fig. 12 (a) from the yarn length indicated by g to f, and the amount is shown in Fig. 12 (b).
The amount of the upper thread necessary for forming the seam, which is a value obtained by adding the cloth thickness t to the feed amount m indicated by f to g in the middle, is P, and the yarn indicated by e to h to f in FIG. The thread length obtained by removing the thread lengths indicated by e to g in FIG. 12 (b) from the length is taken as the adjustment amount L, and the elongation of the upper thread given by the first thread tensioner 36 is k.
Then, the supply amount W between the phase θ1 and the phase θ2 can be expressed by the following equation.

Since W = P- (L + k) and the entanglement point of the upper and lower threads is at the center of the cloth, L + k is insufficient with respect to the required needle thread P, but L of this insufficiency is shown in FIG. As shown in (a), the offset amount n of the thread guide 53 with respect to the needle center i and the needle hole 17a at the dead center of the balance.
Is the individual value of the sewing machine determined by the height v of the sewing machine.
The amount k of elongation of the yarn is a value of a property that varies depending on the type of yarn and the amount of pressing force of the fine adjustment needle thread tensioner 6, and the compensation of the elongation will be described later. Therefore, unlike the conventional needle thread tension adjuster for adjusting the thread tension, the intermittent pressing device 9 is used.
While releasing the thread, a slight tension is applied to prevent the upper thread from flowing into the fine-adjustment upper thread tension device and thereafter, so that the difference in the amount of elongation of the thread between thread types is small and L The shortage amount indicated by can be handled approximately constant for each sewing machine. The correction of the shortage of the upper thread amount is delayed to the operation phase of the phase θ2 of the second upper thread pressing device 39 as shown in FIG.
The yarn amount of 2r can be additionally supplied by releasing the position of 2 to a position lower than the center position of the cloth thickness by a predetermined amount r. This predetermined amount r can be calculated, confirmed, and set in advance by 2r-L + k. With this modification, the amount of needle thread corresponding to the amount of stitches determined by the cloth feed amount and cloth thickness can be accurately supplied.

Next, the correction of the stretching operation at the time of forming a seam in this embodiment will be described.

FIG. 13 shows the relationship between the pressing force to the upper thread 47 and the elongation amount of the upper thread at the balance top dead center phase θ1 during the stitch formation cycle on the horizontal axis. The horizontal axis shows the pressing force to the upper thread. The vertical axis represents the amount of elongation of the upper thread that occurs when the balance is raised.
In the figure, A shows a large amount of elongation and the seam under the same thread tension condition, as shown in Fig. 14 (b). In the case of polyester filament yarn which tends to hang up, B in the figure shows a small amount of elongation and the seam has a 14th stitch under the same thread condition. The case of a cotton yarn that tends to hang down as shown in FIG.

The first needle thread presser 36 always provides a constant clamping force T ₁ during the sewing cycle, and the second needle thread presser 39 is the balance.
The spring 43 as shown in FIG. 5 is provided between the phase in which the elongation of the upper thread almost disappears due to the descending of 34 and the phase in which the balance reaches the top dead center.
A strong clamping force T ₂ is given by the pressing of, and is released by the operation of the solenoid in the other phases, and the T ₂ value becomes 0 due to the movement.

As shown in FIG. 13, in the conventional one in which the constant pressure T ₁ is applied only by the first needle thread pressing device 36, the needle thread acting on the thread tightening of the seam at the balance top dead center θ1 during the sewing cycle is not The polyester filament yarn will have an elongation of l ₃ , and the cotton yarn will have an elongation of l ₁ . When the balance is raised, the upper thread is supplied between the first upper thread presser 36 and the needle together with the thread tightening of the seam, but the amount of the upper thread supplied decreases due to the occurrence of elongation. The more stretch occurs, the more the seams are suspended. On the other hand, in this embodiment, the clamping pressure T ₁ by the first upper thread pressing device 36 and the clamping pressure T ₂ by the second upper thread pressing device 39 are applied at the balance top dead center phase θ1 during the sewing cycle. T-becomes possible to clamp the upper thread at nip pressure of _3, l ₄ as FIG. 13 is a polyester filament yarn shown in the upper thread acting on tensioning seam by increasing the balance in the a, the l ₂ in cotton Elongation will occur.

In the case where the second upper thread pressing device 39 is opened after the balance top dead center, as shown in FIG. 13, the clamping pressure is T ₁ by only the first upper thread pressing device 36, and the elongation of the thread is not the polyester filament thread. l ₃ and l ₁ for cotton thread, so the solenoid 45
The upper thread 47 becomes an extension l ₃ , l ₁ immediately after top dead center with respect to an extension l ₄ , l ₂ at the top dead center of the balance by the action of, and this difference l ₄ −l ₃ , l ₂ − l The _one- minute pre-feed of the stitches will be performed from the needle thread tension regulator 36 in the needle thread path between the stitches.

L ₄ -l l ₂ is more of polyester filament yarn having the characteristics of l ₄ -l ₃ by it is to set the value of T ₂ as larger than l ₂ -l ₁ of ₃ -l ₁ of this difference Since a larger amount of the upper thread than the cotton thread having the above characteristic is supplied into the upper thread path after the first upper thread pressing device 36, the elongation characteristic of the sewing thread can be corrected.

Make sure that T ₂ is equal to the difference between l ₃ and l ₁
The most accurate correction is made by setting the value. The operating phase of the second needle thread pressing device 39 is detected by the upper shaft phase detecting device, and the solenoid 45 is operated.
Is to operate.

In addition to the yarn supplying action, the correction of the supplying amount with respect to the needle amplitude position according to the present invention is performed as follows.

That is, since the guide body 48 is structured to be moved in conjunction with the amplitude position of the needle bar 3 as described above, the balance is dead on the balance at any of the left and right needle drop positions for forming zigzag stitches. In the point phase θ1, the position is as shown in FIG. 11 (a), and the phase at which the needle penetrates the cloth differs depending on the amplitude position. At the left needle drop position, the position shown in FIG. 11 (b) is set at the right needle drop position. The position is as shown in FIG. 11 (c).

Therefore, at the left needle drop position, the yarn winding corresponding to the bending of the needle thread 47 shown in FIGS. 11 (b) d-e-f is performed, but in this phase, the pressing on the needle thread is released and weak as shown in FIG. Due to the upper thread tension, this upper thread portion is supplied from the thread piece side, and more upper thread is supplied as compared with the right needle drop position shown in FIG. 11 (c), and FIG. The zigzag seam in which the bobbin thread is biased to one side as shown in Fig. 27) is a seam corrected as shown in Fig. 27 (b).

The solenoid 51 is a known pattern selecting means shown in FIG.
56 is electrically connected to the solenoid so that the action body 49 is located at the action position shown by the solid line in FIG. 10 in response to the selection of the pattern for correcting the deviation of the bobbin thread.
The solenoid 51 is controlled so that the working pair 49 is located at the non-acting position shown by the dotted line in FIG. 10 in response to the selection of a pattern in which the bobbin thread deviation is not corrected, for example, a pattern such as a straight stitch is controlled. Control and respond.

In this embodiment, as the correction means, the guide body 48 is fixed to the needle bar support 11, and the working body 49 is solenoid driven.However, as shown in FIG. The action of the guide body 48 is fixed to the needle bar 3 and the needle bar thread guide 5
7. The action of the action body 49 may be performed by arranging the action on the thread hook 58 fixed to the sewing machine frame 1 as shown in FIG. 15 and operating by the amplitude of the needle.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In the present embodiment, as shown in FIG. 16, a thread tension dial 37 is provided on the upper thread path from the top 55 to the needle hole 17a of the needle, and the upper thread is clamped between the pair of thread clamping trays 36a, 36b. A first needle thread presser 36 which is a known thread tensioner for applying tension
The second upper thread pressing device 39 of the first embodiment, the correcting means of the first embodiment, and the well-known balance 134 for the upper thread Yulmi curve.
And a third upper thread presser having a structure similar to that of the second upper thread presser 39 and intermittently applying an upper thread tension weaker than that of the second upper thread presser to the upper thread. 59 and are arranged.

Next, the operation of each needle thread pressing device and the feeding of the needle thread will be described.

In FIG. 17, a is a balance upper thread Yurume curve, C is an operation diagram of the second upper thread presser, D is an operation diagram of the third upper thread presser, and C1 And D1 are in operation (ie, when pressed), and C2 and D2 are in operation (ie, open).

The correction of the difference in the elongation characteristics is the same as that of the first embodiment, and therefore will be omitted.

Regarding the thread pulling action of the above-mentioned needle thread correcting means in the present embodiment, as shown in FIG. 16, it is arranged between the second needle thread pressing device 39 and the third needle thread pressing device 59. The body 149 is fixed to one end of a lever body 60 that is rotatably supported by the sewing machine frame 1, and the other end of the lever body is the other end of the upper shaft 2.
It is arranged on a cam 61 which is fixed to the cam 61, and is always biased by a spring means 62 so as to come into contact with the cam 61. At the end of the lever body 60, the output shaft of the solenoid 151 fixed to the sewing machine frame 1 is always opposed with a proper gap.

One end of the working body 149 is provided with an opening 149a, and the distal end of a guide body 148 fixed to the needle bar support 11 enters the opening so as to enter the opening.

A guide hole 148a is provided at the tip of the guide body 148, and the guide hole is formed in the opening 149a of the acting body 149 as shown in FIGS. 19 and 20 with respect to the swing of the needle 17. Appear and disappear.

The action body 149 is driven by the rotation of the upper shaft 2 and operates in accordance with the phase. At the balance top dead center phase θ1,
The position a shown by the solid line in FIG. 19 is reached, and at the phase θ2 in which the needle hole 17a of the needle 17 reaches approximately the center of the cloth thickness, the position b is indicated by the dotted chain line in FIG. 19, and the guide body 148 is left and right for forming zigzag stitches. In either case of the needle drop position, the position is the position shown in Fig. 19 (a) in the balance dead center phase θ1, the phase in which the needle penetrates the cloth differs depending on the amplitude position, and the position in the left needle drop position is
At the position shown in Fig. 19B, the right needle drop position becomes the position shown in Fig. 19C.

Therefore, at the left needle drop position, when the phase θ1 changes to the phase θ2, the acting body 149 shifts from the position shown in FIG. 19a to the position shown in FIG. 19b, and the guide body 148 moves from the position shown in FIG. 19
It moves to the position shown in the drawing and the yarn winding for the bending shown in FIGS.

In this phase, as shown in FIG. 17, the pressing of the upper thread by the second upper thread presser 39 is released, and the weak upper thread pressing force by the first upper thread presser 36 causes the thread winding Is the upper thread supply from the thread piece side.

On the other hand, in the right needle drop position, when the phase θ1 changes to the phase θ2, the acting body 149 changes from the position shown in FIG. 19a to the position shown in FIG. 19b, and the guide body 148 moves from the position shown in FIG. It becomes the position shown in Fig. (C) and the yarn cannot be bent as shown by the dotted line in Fig. 20.

Therefore, in zigzag stitching, more needle thread is supplied on the left needle drop position side than on the right needle drop position, and the zigzag stitch, which has a tendency for the bobbin thread to deviate as shown in FIG. 27a, is corrected as shown in FIG. 27b. With seams.

The solenoid 151 is also electrically connected to the pattern selecting means 56 as in the first embodiment, and the output of the solenoid 151 is selected in response to the selection of the pattern for which the lower thread deviation is to be corrected. The shaft is controlled so as not to abut against the lever body 60, and the solenoid 151 is excited to select a pattern for which correction of the bobbin thread deviation shown in FIG. 19c is not performed, for example, pattern selection such as straight stitching. The output shaft is pushed out in the direction of arrow B to rotate the lever body 60 in the direction of arrow B, and
The nine openings 149a are located as shown in FIG. 19c.

As shown in FIG. 17, the thread balance Yurme curve a1 of the present embodiment against the thread pulling action by the movement of the guide body 148 is a conventional one different from that of the first embodiment, and the balance dead Between the point position θ1 and the phase θ2 where the needle hole is located approximately in the center of the cloth thickness, the thread slack as shown by the dotted line with respect to the solid line in FIG. 6 has the thread slack effect of the balance as shown in FIG. Therefore, when the guide body 148 is actuated to draw in the upper thread and the left needle drop position, the effect of drawing the upper thread from the thread piece side by the amount of withdrawal is offset by the thread squeeze of the balance, so that the thread is pulled out from the thread piece. Therefore, it is impossible to supply the yarn corresponding to the deviation of the lower yarn piece of the present invention. Therefore, in this embodiment, as shown in FIG. 17, the phase θ1 in which the second needle thread pressing device 39 is released is set.
At the subsequent phase θ3, the third upper thread presser 59 is operated to clamp the upper thread and operate so that the thread squeeze action caused by the lowering of the balance 134 does not affect the thread pull-in of the upper thread correcting means. It is a thing.

(Effect) As described above, according to the present invention, the supply amount of the upper thread is adjusted in accordance with the amplitude position in accordance with the deviation phenomenon of the lower thread of the zigzag stitch which varies depending on the needle drop position in the amplitude range of the needle. Since it can be supplied and increased in a weak state, the bias can be prevented without imposing a load on each mechanism.

Further, by using the structure for this purpose, it is possible to supply the upper thread corresponding to the elongation characteristics which differ depending on the type of the upper thread.

[Brief description of drawings]

The drawings relate to the embodiment of the present invention, FIG. 1 is an explanatory view of the flow of the operation of the correction mechanism, FIG. 2 is an explanatory view of the control structure, FIG. 3 is an external view of the sewing machine, and FIG. 4 is the first upper thread. FIG. 5 is a perspective view of the pressing device, FIG. 5 is an explanatory diagram of the drive mechanism, FIG. 6 is a yarn Yurume curve diagram, FIG. 7 is an explanatory diagram of the second needle thread pressing device, and FIG. 8 is a perspective view of the holding plate. FIG. 9 is a perspective view of the upper thread drawing means, FIG. 10 is an explanatory view of the drawing state of the upper thread drawing means, FIG. 11 is an operation explanatory view of the upper thread drawing means, and FIG. FIG. 13 is an explanatory diagram of elongation correction, FIG. 14 is an explanatory diagram of upper and lower thread entanglement positions, and FIG.
FIG. 16 is an explanatory view of another embodiment of the needle thread drawing means, FIG. 16 is an external view of the sewing machine of the second embodiment, FIG.
18 is a perspective view of the upper thread drawing means, FIG. 19 is an operation explanatory view of the upper thread drawing means, FIG. 20 is an explanatory view of a drawing state of the upper thread drawing means, FIG. 21 is a normal stitch explanatory view, FIG. 22 Is an explanatory view of a hitch stitch, FIG. 23 is an explanatory view of disorder of a seam, 24
The figure is a normal stitch generation process explanatory diagram, Fig. 25 is a hitch stitch generation process explanatory diagram, Fig. 26 is an explanatory diagram of bobbin thread draw-out points and seams, and Fig. 27 is an explanatory diagram of zigzag stitch bottom thread deviation. 11 is a needle bar support made of an amplitude driving member, 17 is a needle,
34 is a balance, 36 is a first upper thread pressing device, 39 is a second upper thread pressing device, 48 is an upper thread guiding body, 49 is an acting body, 55 is a thread piece as a source of the upper thread, and 63 is a phase. It is a detection means.

Claims (2)

[Claims] 1. A needle that moves left and right and up and down, an upper thread catching means that cooperates with the needle to form a lock stitch, a balance that moves up and down in synchronization with the needle, and an upper shaft rotational phase. Detection means,
A first upper thread pressing device, which is a tension adjusting means for the thread, arranged between the upper thread supply source and the balance, and an upper thread intermittently arranged between the upper thread pressing device and the balance. A second needle thread pressing device that presses the needle thread, an upper thread guide body connected to the amplitude drive member of the needle on the upper thread path, and arranged so as to work in cooperation with the guide body on one side of the amplitude range. A zigzag sewing machine with a thread tightness compensating device, which comprises an upper thread drawing means composed of an acting body and a control means of the second upper thread pressing device. 2. A switching means for switching the working body of the upper thread drawing means to a two-state position of operating and non-operating is connected to the pattern selecting means. Zigzag sewing machine with thread tightening correction device.