JPH11137879A - Sewing machine control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely start sewing even without equipping a picker device, and to prevent a thread tail from remaining on the processed cloth. SOLUTION: In a sewing machine in which a thread take-up lever 5 is driven by a drive source 31 separated from a drive source 23 for a needle bar 3, in the beginning of sewing, control of the drive source 31 for the thread take-up lever 5 is made different from that during the sewing operation, and this controlled drive prevents an needle thread guided to a sewing needle 11 of the needlebar 3 from moving upstream according to the lowering of the needlebar 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a sewing machine that drives a balance with a drive source different from a needle bar. More specifically, the present invention relates to a method for controlling a balance independently by controlling the driving of the balance. The present invention relates to a control method of a sewing machine that can solve a trouble.

[0002]

2. Description of the Related Art A sewing machine having a needle bar jump mechanism can perform a skipping operation by controlling the needle bar to jump when the sewing machine stops. That is, the needle bar can be held at the top dead center position when the sewing machine stops, and the sewing needle provided at the lower end of the needle bar can be retracted to a high position. And there are various advantages for controlling various devices such as a thread cutting mechanism.

[0003] The needle bar jump mechanism is incorporated in a link mechanism between the needle bar and a drive unit including a cam driven by the main shaft of the sewing machine and a link. When the needle bar jump mechanism receives the jump control signal during the sewing operation, the needle bar jump mechanism operates to cut off the transmission of the driving force from the driving unit to the needle bar, and thus, although the driving unit is operating, The needle bar is held at the top dead center so that so-called jump stitching can be performed. By issuing a jump command immediately before the sewing machine stops, the sewing machine can be stopped with the needle bar jumping. This jump stop state will be described with reference to FIG. FIG. 5 shows the temporal movement of the needle bar and the balance in relation to the rotation angle of the main shaft of the sewing machine, and shows that the main shaft angle A is in a stopped state of the sewing machine. When the needle bar is stopped, if a jump command is issued immediately before the time point B when the needle bar finally reaches the top dead center, the drive unit (the sewing machine main shaft) of the needle bar continues to operate until the main shaft angle A is reached. The rod is kept at top dead center. In the stopped state of the sewing machine (spindle angle A), the balance is located substantially at the top dead center, as is apparent from FIG.

[0004]

When the sewing machine is started,
The drive of the needle bar moves as shown by the broken line in FIG. 5 by the rotation of the main shaft of the sewing machine. However, since the needle bar is in the jump state under the condition that the engagement with the drive is disconnected, the needle bar rises again. It stays at the top dead center until it re-engages with the incoming drive and releases the jump at the spindle angle C. This spindle angle C
Above, the needle bar is driven up and down by the drive. On the other hand, with respect to the balance, not only a sewing machine of a type driven by a spindle but also a sewing machine of a type driven by a drive source different from the spindle, the motion setting has been conventionally fixed. Accordingly, the balance starts to move at the same time as the sewing machine is started, and as shown in FIG.
At this time, even at the timing when the needle bar starts to descend, the balance is still in the process of ascending. This means that the thread passed through the sewing needle is pulled relatively upstream by the balance as the needle bar is lowered.

[0005] By the way, at the end of the previous sewing step, the upper thread is cut off and remains as it passes through the sewing needle. However, as described above, the upper thread passed through the sewing needle is pulled up by the balance to the upstream side. Therefore, if the thread tail left on the sewing needle by the thread trimming is short, the sewing needle is lowered with the needle bar. Even if the thread does not come off from the thread or the thread does not come off until the sewing needle is pierced by the workpiece, the upper thread may come off from the workpiece by the time the sewing machine moves to the second needle. In other words, a so-called sewing error occurs. Conventionally, in order to prevent such inconvenience, a so-called picker device is conventionally provided at the front portion of the shuttle, and the picker device is driven at the time of thread trimming, thereby increasing the length of the thread tail remaining on the sewing needle after thread trimming. I am trying to set it. But in this case,
This prevents a sewing error, but if the thread tail is too long, the thread tail may remain on the upper surface of the sewing object. I try to avoid it.

However, the setting of the length of the yarn tail by the picker device has a drawback in that it is generally difficult to adjust the length because it is greatly affected by the properties of the yarn. Further, since the picker device is provided at the front portion of the shuttle as described above, not only is it difficult to replace the bobbin thread in the shuttle, but also when the sewn article is a tubular article, In particular, there is a disadvantage that the effective sewing area cannot be increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned disadvantages inherent in the sewing machine according to the prior art described above, and it is an object of the present invention to reliably prevent a sewing error without providing a picker device. It is an object of the present invention to provide a method for controlling a sewing machine that can perform sewing and that does not cause thread tails to remain on the upper surface of a sewing object.

[0008]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned problems and appropriately achieve the intended object, a method for controlling a sewing machine according to the present invention comprises driving a balance by a drive source different from a drive source of a needle bar. In the sewing machine, the control of the drive source of the balance at the time of sewing is made different from the control during the sewing operation, and the sewing machine is guided by the controlled drive of the balance to the sewing needle provided on the needle bar. It is characterized in that the yarn is prevented from relatively moving upstream as the needle bar descends.

[0009]

When the needle bar is lowered at the time of sewing, the upper thread passed through the sewing needle provided on the needle bar is prevented from relatively moving in the upstream direction. This prevents the length of the thread tail of the upper thread remaining from becoming short. Therefore, an appropriate length of the upper thread can be secured on the lower surface of the sewing object by the needle drop of the first needle of the sewing start.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a control method of a sewing machine according to the present invention will be described with reference to the accompanying drawings, taking a preferred embodiment applied to a multi-needle sewing machine. In FIG. 1 showing a vertical section of the sewing machine head, reference numeral 1 designates a sewing machine arm fixed to the front surface of a sewing machine frame (not shown), and a support case 2 is provided on the front surface of the arm 1 in a lateral direction (in FIG. (Vertical direction). In the support case 2, a plurality of needle bars 3 are vertically movable at predetermined intervals in the sliding direction, and a balance 5 corresponding to each needle bar 3 is pivotally supported via a shaft 6 so as to be swingable. ing. A presser foot 7 is fitted to the lower end of each needle bar 3 so as to be movable up and down, and a presser foot spring 10 interposed between the upper end thereof and a needle bar holder 8 fixed near the center of the needle bar 3. As a result, the presser body 7 is elastically urged downward. The cloth presser 7 a formed at the lower end of the cloth presser 7 is located immediately below the sewing needle 11 detachably fixed to the lower end of the needle bar 3. As shown in FIG. 2, a through hole 7b that allows the sewing needle 11 to be inserted is formed in the cloth presser 7a. Each needle bar 3
1 shows a state in which the needle bar 3 is held at the top dead center position by the needle bar holder 8 abutting against the stopper 13 when the needle bar 3 is pressed by the spring elasticity of the holding spring 12 mounted on the upper end thereof. I have.

As shown in FIG. 1, a base needle bar 15 parallel to the needle bar 3 is disposed at the front end of the sewing machine arm 1. A support block 17 is provided on the base needle bar 15 so as to be vertically movable. ,
A driving member 16 functioning as a driving section of the needle bar 3 is supported. The driving member 16 is rotatably supported on the support block 17 around the base needle bar 15.
At the rear of the sewing machine arm 1, a drive lever 18 is
0, and the free end of a connecting lever 21 is pivotally supported by the support block 17 via a shaft 22. The other end of the connecting lever 21 is connected to the free end of the lever 18. It is pivotally supported via a pin 29. A sewing machine main shaft 23 is disposed laterally at the center of the sewing machine arm 1, and a drive cam 24 is eccentrically fixed to the sewing machine main shaft 23 and is located above the drive lever 18.
The driving cam 24 has a ring portion 25 of a connecting rod 25.
a is fitted outside, and a free end of the rod 25 is connected to an intermediate portion of the drive lever 18 via a shaft 26.

The connecting rod 25, the driving lever 18,
A drive mechanism for the needle bar 3 is constituted by a link group consisting of the connection lever 21. When the drive cam 24 is rotated in one direction by driving the sewing machine main shaft 23, the support block 17 is moved to the base needle bar via the link group. 15 is reciprocated up and down. Since the driving member 16 also moves up and down with the vertical movement of the support block 17, the engaging pin 8a protruding from the rear surface of the needle bar holder 8 is fitted into the engaging groove 16a formed on the front surface of the driving member 16. When the driving members 16
At the same time, the needle bar 3 is driven up and down. A jump control device (not shown) is provided at a side position of the base needle bar 15, and when a jump command is received, the driving member 16 is moved to the position shown in FIG.
When the drive member 16 is rotated in the circumferential direction of the base needle 15 at the time when it reaches the substantially top dead center position indicated by the imaginary line, the engagement groove 16a is disengaged from the engagement pin 8a. Function. Accordingly, when a jump command is issued from the jump control device and the engaging pin 8a is disengaged from the driving member 16, the needle bar 3 is held at the top dead center position by the elasticity of the holding spring 12, and the jump command is released. After that, when the driving member 16 reaches the top dead center, the engagement groove 16a is fitted to the engagement pin 8a, so that the vertical drive of the needle bar is restarted.

As shown in FIG. 1, a balance driving mechanism 30 is provided above the sewing machine arm 1. The balance driving mechanism 30 includes a pulse motor 31 fixed to the sewing machine arm 1, a motor lever 32 fixed to a rotating shaft 31 a of the motor, and a balance driving lever swingably supported on the sewing machine arm 1 via a shaft 35. 33, a connecting lever 34 for connecting an intermediate portion of the balance driving lever 33 to the motor lever 32. A roller 36 is supported at the free end of the balance driving lever 33, and the roller 3
6 is fitted in a fitting groove 5 a formed in the base end of the balance 5. Then, the pulse motor 31 is driven to drive the motor lever 3
By swinging the balance 2, the balance 5 swings up and down as shown by the solid and imaginary lines in FIG.

As described above, FIG. 1 shows a state in which the sewing machine is stopped. In this state, the balance 5 is waiting at the top dead center position shown by a solid line. When the sewing machine stops, the drive member 16 of the needle bar 3 stops at a position slightly lower than the top dead center position, as is apparent from the timing chart of FIG. 3, a timing S indicates a stop position of the sewing machine spindle 23, and a broken line h indicates a movement locus of the driving member 16. When the sewing machine (the sewing machine main shaft 23) stops, a jump command is issued immediately before the stop, whereby the state is maintained while reaching the top dead center immediately before the stop as described above, and the state shown in FIG. It has become. In the stopped state, the needle bar 3 is selected by sliding the support case 2, and the engagement pin 8 a of the selected predetermined needle bar 3 is inserted into the engagement groove 16 a of the driving member 16. The fitting groove 5a in the balance 5 corresponding to the needle bar 3 is engaged with the roller 36 of the balance driving lever 33, respectively, so that the balance can be driven.

A thread trimming device (both not shown) is provided below the needle plate below the sewing machine arm 1, and when the sewing operation is completed, the upper thread is cut automatically or by an instruction from the operator. It is. Thereafter, the thread processing device 38 (see FIG. 1) installed on the lower surface of the sewing machine arm 1 is operated, and the upper thread processing is executed by the hook 40 provided on the thread processing device 38. The hook 40 performs a retreating operation immediately after advancing toward the lower side of the sewing needle 11, and a gap between the thread hooking members 41, 41 arranged in the middle of the movement path is formed by the hook tip. Reciprocate. And after sewing the thread, sewing needle 1
The upper thread a hanging from 1 is caught by the hook 40 by the operation of the hook 40 and pulled rearward, and the thread tail is hooked on the thread hooking member 41 as shown in FIGS. In addition, between the thread hook members 41, 41, an appropriate resistance is given to the upper thread a to hold it.

Next, the operation of the preferred embodiment of the present invention will be described. When starting the sewing machine in the stopped state,
As shown in the timing chart, the balance 5 is kept stopped until the timing T when the needle bar 3 starts to descend,
When the timing T is reached, the pulse motor 31
Is driven to lower the balance 5. At this time, the thread tail of the upper thread a is displayed on the balance 5 by the lowering of the needle bar 3.
A descending control is provided to make the movement so as not to fall off from 1,41. 2A shows an enlarged view of the lower end portion of the needle bar 3 in FIG. 1, and FIG. 2B shows a state where the needle bar 5 is slightly lowered. 2 (a) and 2 (b), as the needle bar 3 is lowered, the thread hook 41, the eye hole (not shown) of the sewing needle 11, and the thread path 43 are connected. The thread path is increasing. Accordingly, when the needle bar 3 is lowered, the thread tail of the upper thread a becomes the thread hooking member 41,
In order to prevent the thread from dropping off from 41, it is necessary to supply the increased amount of the yarn path from the upstream side, and the lowering control of the balance 5 is performed so that this supply is appropriately performed.

Next, after the balance 5 has been lowered to a predetermined height H in FIG. 3, the lowering drive of the balance 5 is stopped, and thereafter the balance 5 is driven up by the motion during normal sewing. However, after the needle dropping of the first needle is completed, the operation shifts to driving in a normal motion. As mentioned above,
After the lowering drive of the balance 5 is stopped, the upper thread a is no longer supplied from the upstream side, so that the lower thread of the needle bar 5 causes the thread tail of the upper thread a to resist the resistance of the thread hooking members 41, 41. And fall off. Until the needle bar 5 further moves down to reach the bottom dead center, the upper thread a relatively moves upstream with respect to the sewing needle 5, and the length of the upper thread a remaining downstream of the sewing needle 5 decreases. When the needle drop of the first needle is completed, the upper thread a of an appropriate length remains on the lower surface of the sewing object. For this reason, the entanglement with the lower thread is surely formed by the needle drop of the second needle, and a sewing error unlike the conventional sewing machine does not occur.

Regarding the upper thread a remaining on the lower surface of the sewing object due to the needle drop of the first needle, the length of the thread tail varies depending on the sewing object, the properties of the upper thread a, and the like, as shown in FIG. The height H at which the downward drive of the balance 3 is stopped can be adjusted. By the control at the time of sewing described above,
The picker device described in the section of the prior art is unnecessary, but when sewing is performed depending on the properties of the upper thread a or by applying a large tension to the upper thread a, the picker device is left on the sewing needle 11 after the thread cutting. The tail length of the upper thread a may not be a normal length as shown in FIGS. In such a case, a special drive control of the balance 5 may be performed even at the time of thread trimming. That is, in FIG. 4, the thread trimming operation is performed near the timing C, but the lifting operation of the balance 5 is completed earlier as indicated by the two-dot chain line in FIG. The yarn tail length of the yarn a can also be appropriately secured.

In this embodiment, the pulse motor 31 is used as a drive source for driving the balance 5, but another type of motor such as a servo motor may be used instead of the pulse motor.

[0020]

As described above, according to the method for controlling a sewing machine according to the present invention, the needle thread having the appropriate length can be left on the lower surface of the sewing object by the needle drop of the first needle for sewing. Therefore, stitches are formed reliably by the second stitches. Therefore, there is a beneficial effect that occurrence of sewing error is prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal section of a sewing machine head in which a control method according to the present invention is suitably performed.

FIG. 2 is a partially enlarged view of the sewing head shown in FIG.

FIG. 3 is a timing chart for explaining the motion of the balance at the time of sewing.

FIG. 4 is a timing chart for explaining the motion of the balance at the time of thread cutting.

FIG. 5 is a timing chart of a balance and a needle bar in the conventional device.

[Explanation of symbols]

 3 Needle bar 5 Balance 11 Sewing needle 23 Sewing machine spindle (drive source) 31 Pulse motor (drive source) a Upper thread

Claims (1)

[Claims] 1. A sewing machine in which a balance (5) is driven by a drive source (31) different from a drive source (23) of a needle bar (3), wherein the balance (5) is driven during sewing. The control of the source (31) is made different from the control during the sewing operation, and the needle thread (a) guided to the sewing needle (11) provided on the needle bar (3) by the controlled drive of the balance (5). ) Is prevented from moving relatively upstream with the lowering of the needle bar (3).