JP2002355481A - Sewing machine thread trimmer - Google Patents

Abstract

(57) [Problem] To prevent a thread trimming error when a thread trimming is performed after a cloth is fed backward by a last needle. A feed means (27) for feeding a cloth (30) in a forward or reverse direction, an inner pot (1) for accommodating a bobbin (21) wound with a lower thread (23), and a needle hole (31a) of a needle plate (31) rotating around the inner pot. A horizontal hook 32 having an outer hook 2 having a sword tip 2a for catching an upper thread through which a needle passed therethrough, a moving knife 4 having a catcher 4a for catching a lower thread and an upper thread, and a moving knife A fixed knife 5 for cutting the captured lower thread and upper thread in cooperation with a moving knife, and a thread cutting actuator 4 for connecting a lower shaft of the sewing machine to the moving knife.
3, a feed amount change actuator 44 for changing the feed amount by the feed means, and a feed amount change actuator for changing the feed amount of the cloth at the time of thread trimming, and driving the feed means in the forward direction by a predetermined feed amount. And a control means 40 for performing thread trimming by operating the sewing machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutter for a sewing machine, and more particularly to a thread cutter for a sewing machine having a horizontal shuttle.

[0002]

2. Description of the Related Art In a sewing machine having a horizontal shuttle, a thread cutting device that cuts an upper thread and a lower thread connected to a bobbin using a movable knife is conventionally known. A conventional example of such a thread cutting device will be described with reference to FIGS.

In this thread cutting device, a lower thread 23 pulled out from an inner shuttle 1 of a horizontal shuttle and an upper thread 22 caught by a sword tip 2a of an outer shuttle 2 and rotated around the inner shuttle 1 are held down by a looper 3 descending. The upper thread 22 and the lower thread 23 are pulled by the movable knife 4 and cut between the fixed knife 5 and the thread cutting links 6 and 7 for supporting the movable knife 4.
The movable knife 4 is put into a standby state by the engagement of the cutting roller 8 and the cutting plate 9 supported by the one thread cutting link 7. A disconnecting link 10 for engaging and disengaging the disconnecting roller 8 is connected to the disconnecting plate 9.

The inner shuttle 1 is rotatably placed on the race surface of the outer shuttle 2 and is prevented from rotating by a rotation restricting body (not shown) attached to the frame. Meanwhile, outer pot 2
Is horizontally rotated in synchronization with the lower shaft 18 by a screw gear (not shown) fixed to the lower shaft 18, and the tip of the needle 2 a captures the loop of the upper thread 22 formed on the needle. Accordingly, the upper thread 22 goes around the inner hook 1 and the tension generating member 1 of the inner hook 1
A seam is formed by being entangled with the lower thread 23 coming out of 2.

[0005] The movable knife 4 is pivotally attached to the other end of each of the thread cutting links 6, 7 whose one end is swingably supported by the machine frame 25. One of the thread cutting links 6 has a machine frame 2
5, a thread cutting link spring 15 for urging the movable knife 4 in the direction of the thread cutting cam 16 is hung. A cutting roller 8 and a thread cutting roller 17 are attached to an intermediate portion of the other thread cutting link 7 and a pivotal connection portion with the movable knife 4, respectively. The movable knife 4 moves the bobbin thread 2 when moving to the right.
A catching portion 4a for catching the upper thread 3 and the upper thread 22 and a blade portion 4b for engaging the fixed knife 5 and cutting the lower thread 23 and the upper thread 22 are integrated at a predetermined interval. Therefore, when the movable knife 4 moves to the right, the fixed knife 5 enters between the capturing portion 4a and the blade portion 4b.

The thread cutting cam 16 is fixed to the tip of the lower shaft 18, and the cam 16a is cut at a predetermined phase so that the movable knife 4 moves to the right and subsequently to the left.

An intermediate portion of the cut-off plate 9 is swingably supported by a machine frame 25 by a support shaft 19, a cam portion is formed at the tip, and the other end is connected to a cut-off link 10. I have. Then, the disconnecting plate 9 is used for the disconnecting link spring 2.
0 urges the cam portion 9a in the direction in which the cam portion 9a is cut off and rides on the roller 8, that is, in the counterclockwise direction.

The movable knife 4 is normally in a standby state by the engagement of the detaching roller 8 and the detaching plate 9, but when cutting the upper thread 22 and the lower thread 23, a thread cutter (not shown) is used. By operating the actuator to move the disconnecting link 10 in the direction of the arrow, the disconnecting plate 9 is rotated clockwise, and the engagement with the disconnecting roller 8 is released. Thereafter, the sewing machine motor rotates, the lower shaft 18 and the thread cutting cam 16 also rotate, and stops after the thread cutting operation is performed.

Therefore, when the engagement between the cutting-off plate 9 and the cutting-off roller 8 is released, the movable knife 4 moves to the right by the force of the thread-cutting link spring 15, and the thread-cutting roller 17 moves the thread-cutting cam. 16 and moves right and left following the shape of the cam portion 16a.
Is captured by the capturing unit 4a and returns. And the blade part 4b
Is engaged with the fixed knife 5, the threads 22 and 23 are cut, and when the thread cutting roller 17 completely rides on the cam portion 16a of the thread cutting cam 16, the rotation of the lower shaft 18 is stopped.

[0010] The looper 3 is lowered by a looper operating portion (not shown) attached to the disconnecting link 10. Accordingly, when cutting the thread, the cut-off plate 9 comes off the cutting roller 8 and the thread cutting roller 17 comes down against the thread cutting cam 16 by the force of the thread cutting link spring 15 at the time of cutting the thread.

Next, the thread trimming operation will be described step by step with reference to FIGS. 6 shows a state before thread trimming, FIGS. 7 to 10 show the progress of the thread trimming operation, and FIG. 11 shows a state just before thread trimming.

First, in a state before the thread trimming, the looper 3 is raised in a direction away from the horizontal shuttle 32, and as shown in FIG. 6, a loop of the upper thread 22 formed by raising a needle (not shown). When the outer hook 2 rotates counterclockwise, the sword tip 2a of the outer hook 2 scoops, and the rotation of the outer hook 2 causes the loop of the upper thread 22 to be pulled, so that the loop starts to go around a predetermined path around the inner hook 1.

Next, when a thread trimming command is issued by a thread trimming switch (not shown) or the like, the phase is detected by a rotary shaft of the main motor or a shield plate of an upper shaft (not shown), and the thread trimming actuator is driven to drive the looper 3. The upper thread 22 and the lower thread 23 are pressed downward from the upper side by being lowered in the direction in contact with the horizontal shuttle 32 and pressed against the inner shuttle 1 of the horizontal shuttle 32. Then, the upper thread 2 circling a predetermined path around the inner pot 1
7 is in the state shown in FIG. 7, the movable knife 4 advances in the direction shown by arrow A in FIG. 7, and the upper thread 22 shown by P in FIG.
And the cloth (needle) -side upper thread 22b (not shown) and the cloth-side upper thread 22a are separated and advanced to the forward position.

Next, as shown in FIG. 9, when the movable knife 4 is located at the most advanced position, the loop of the upper thread 22 finishes turning around the inner shuttle 1 and "slack" occurs in the upper thread 22. . Then, in this state, the movable knife 4 starts retreating toward the retreat position as indicated by an arrow C in FIG.

Next, as shown in FIG.
The "slack" of the upper thread 22 is gradually reduced by the operation of returning to the retracted position and the operation of lifting the balance (not shown). Then, during the returning operation of the movable knife 4 to the retracted position, the lower thread 23 and the upper thread 22 pressed by the looper 3
Starts moving toward the retracted position together with the movable knife 4 by being caught by the concave portion 4h of the capturing portion 4a of the movable knife 4. Further, the returning operation of the movable knife 4 to the retracted position and the lifting operation of the balance (not shown) are combined, so that the upper thread 22 moves from right to left in FIG.

The cloth-side upper thread 22a is pulled toward the retracted position until the movable knife 4 reaches the cutting position immediately before the retracted position, and the state shown in FIG. 11 is obtained. Thereafter, the cloth-side upper thread 22a and the lower thread 23 are cut at a position where the blade portion 4b of the movable knife 4 contacts the fixed knife 5.

[0017]

FIG. 12 is a view for explaining the problem of the above-described thread cutting device, and is a side view when the catching section 4a catches the cloth-side upper thread 22a and the lower thread 23. N is the forward direction of the cloth 30, and R is the reverse direction.
The bending point of the cloth side upper thread 22a and the lower thread 23 in the looper 3 is B, and the cloth 30 at the needle hole 31a when the cloth 30 is fed in the forward direction when sewing with the last needle before thread trimming. The bending point of the upper thread 22a and the lower thread 23 is A1, and the angle between the straight line connecting B and A1 and the vertical line is θ1. On the other hand, when the cloth 30 is fed in the reverse direction when sewing with the final needle before thread trimming, the bending points of the cloth side upper thread 22a and the lower thread 23 at the needle hole 31a are A2, B and A2. Assuming that the angle between the straight line connecting and the vertical line is θ2, θ2 is smaller than θ1, and therefore, the catching portion 4a of the movable knife 4 easily misses the yarn. During the thread cutting operation, the cloth feed amount is set to zero.

As described above, in the conventional thread cutting device, the cloth is fed backward by the last needle for sewing just before the thread cutting, and when the thread is cut thereafter, the cloth is fed forward by the last needle and then the thread is cut. There is a problem that a thread trimming error is more likely to occur than in the case of performing the cutting.

Accordingly, an object of the present invention is to provide a thread trimming device for a sewing machine which can prevent a thread trimming error when a thread is trimmed after the cloth has been reversely fed by a final needle.

[0020]

According to the present invention, there is provided, in accordance with the present invention, a feeding means for feeding a cloth in at least a forward direction or a reverse direction, a needle for vertically moving through an upper thread, and a lower thread. A horizontal hook having an inner hook for storing a wound bobbin, an outer hook having a point for a needle which rotates on the outer periphery of the inner hook and catches a needle thread inserted through a needle hole of a needle plate, and a lower hook; A thread cutting means for cutting the lower thread and the upper thread by a moving knife and a fixed knife having a catching portion for catching the thread and the upper thread, a feed amount changing actuator for changing a feed direction and a feed amount by the feed means, and a thread. Control means for changing the feed amount of the cloth by the feed amount changing actuator at the time of cutting, driving the feed means by a predetermined feed amount in the forward direction, and then operating the thread cutting means to perform thread cutting. A thread cutting device for a sewing machine is provided.

The predetermined amount is 1 regardless of the feed amount before thread trimming.
４4 mm. The control means preferably includes a determination means for determining that the last seam immediately before the thread is reverse feed at the time of thread trimming, and a feed means at the time of thread trimming only when the determination means determines that the last seam is reverse feed. For driving a predetermined feed amount in the forward direction.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The thread cutting device according to the present embodiment includes a needle plate 31 that supports a cloth 30, a needle 28 that is provided on a sewing machine head (not shown) disposed above the needle plate 31 and that vertically moves through the upper thread 22. The cloth 30 is disposed below the needle plate 31 and moves the cloth 30 at least in the forward direction (N direction) or the reverse direction (R direction).
Direction), a horizontal shuttle 32 arranged below the needle plate 31, a looper 3, a movable knife 4 and a fixed knife 5. The fixed knife 5 is fixed to a sewing machine frame (not shown).

The horizontal shuttle 32 is a bobbin 2 on which the lower thread 23 is wound.
1 and an upper thread 2 which rotates around the inner circumference of the inner hook 1 and into which the needle 28 passing through the needle hole 31a of the needle plate 31 is inserted.
An outer shuttle 2 having a sword tip 2a for capturing the outer hook 2 is provided.

The outer shuttle 2 is rotatably mounted, and the inner shuttle 1 is restricted from rotating by a rotation stopper (not shown) attached to the sewing machine frame. The looper 3 can be moved up and down by a drive mechanism (not shown). The looper 3 moves up and down to loosen and release the lower thread 23 at the time of sewing, and moves down and presses the inner hook 1 at the time of thread cutting.

The movable scalpel 4 includes a capturing section 4a, a blade section 4b,
The spacer 34 sandwiched between the capturing part 4a and the blade part 4b
(See FIG. 2), and can be moved in the direction of the arrow in FIG. 1 via the thread cutting cam 16 of the lower shaft 18 and the thread cutting links 6 and 7 shown in FIG. I have. The capturing section 4a has a recess 4h. The cloth side upper thread 22a and the lower thread 23 captured by the concave portion 4h of the capturing portion 4a are cut by the cooperation of the fixed knife 5 and the blade portion 4b.

Reference numeral 33 in FIG. 2 denotes an anti-spin device, which is a movable knife 4 for cutting the upper thread and the lower thread of the sewing machine.
In order to prevent the bobbin bobbin 21 from rotating by inertia after the bobbin thread pull-out operation is completed.

Next, the control system of this embodiment will be described with reference to FIG.
A thread trimming switch 41 and a feed amount setting means 46 for thread trimming are connected to an input section of the control section 40 composed of the control section c. The feed amount setting means 46 is incorporated in an operation panel or the like (not shown) together with other setting switches, or is stored in a memory in a readable manner in advance for setting the feed amount at the time of thread trimming operation. This is for setting the feed amount for feeding the cloth 30 in the forward direction at the time of thread cutting.

An output section of the control section 40 is connected to a main motor 42 of the sewing machine, a thread cutting solenoid 43 for connecting the movable knife to the lower shaft, and a feed amount changing stepping motor 44. The thread cutting solenoid 43 is an actuator for moving the disconnection link 10 shown in FIG.
This is an actuator for changing the feed amount of 0. A phase detector 45 is further connected to an input section of the control section 40. The phase detector 45 is a sensor that detects the rotation angle of the rotation shaft of the main motor 42, but may use a sensor that detects the rotation angle of the upper shaft (not shown).

The basic drive mechanism of the looper 3 and the movable knife 4 of the thread cutting device according to the present embodiment is the same as that shown in FIG. 5, and will be briefly described with reference to FIGS. To explain, when the thread trimming switch 41 is turned on, the thread trimming solenoid 43 operates to connect the lower shaft 18 of the sewing machine and the movable knife 4, and the looper 3 descends to hold the upper thread 22 and the lower thread 23. Next, by driving the main motor 42 and rotating the lower shaft 18, the movable knife 4 operates to cut the upper thread 22 and the lower thread 23. The thread cutting operation described with reference to FIGS. 6 to 11 is the same as the thread cutting operation of the thread cutting device according to the present embodiment.

Next, the control by the control unit 40 will be described with reference to the timing chart of FIG. During sewing before thread trimming, a straight or zigzag pattern sewing selected by an operator is performed by a normal feed amount setting means (not shown) according to a desired feed amount. After this sewing is completed, in order to perform reverse stitching for the purpose of preventing seam fraying, the reverse feed direction is operated by operating a reverse stitch switch or a reverse stitch lever (not shown). A needle stitch is formed and stopped temporarily. Thereafter, when the operator turns on the thread trimming switch 41 or automatically outputs a thread trimming start signal according to the automatic reverse sewing program, the controller 40 controls the feed amount changing stepping motor regardless of the desired feed amount. A drive signal of a predetermined pulse is sent to 44, and a feed amount adjusting device (not shown) of the feed dog 27 is operated to control the feed amount to a feed amount set by the feed amount setting means 46, for example, a forward feed of 3 mm. I do. Next, the control unit 40 drives the main motor 42 to rotate the lower shaft to drive the feed dog 27 via a feed mechanism (not shown) to feed the cloth 30 in the forward direction by the set and controlled feed amount 3 mm. Next, the thread cutting solenoid 43 is operated to connect the lower shaft of the sewing machine to the movable knife 4 and lower the looper 3. As a result, the movable knife 4 is operated, and the cloth-side upper thread 22a and the lower thread 23 are pulled by the movable knife 4 and cut off with the fixed knife 5. Thread 22a,
After cutting 23, a drive signal of a predetermined pulse is sent from the control unit 40 to the feed amount changing stepping motor 44, and the feed amount of the feed dog 27 is returned to the original value.

In this embodiment, the cloth 30 is fed in the forward direction by a constant feed amount at the time of thread cutting, regardless of whether the feeding direction of the last needle immediately before thread cutting is forward or reverse. Since the post-cutting is performed, as shown in FIG.
The angle θ between the straight line connecting the bending point A of the cloth-side upper yarn 22a and the lower yarn 23 at the point a and the bending point B of the yarns 22a and 23 at the looper 3 and the vertical line is shown in FIG. Bending points A1 and B of thread at the time of thread trimming when the last needle immediately before trimming is forward feed
Is equal to the angle θ1 formed by the straight line connecting the vertical line and the vertical line, so that the yarn can be easily captured by the capture unit 4a, and the yarn cutting error hardly occurs.

When the looper 3 descends, the looper 3 comes into contact with the projection 33a of the anti-spin body 33, and the projection 3
3a is pushed down to the position shown by the solid line in FIG. In the anti-spin body 33, since both ends of the bearing 33c wound in a coil form a protruding portion 33a and a bobbin contact portion 33b, when the protruding portion 33a is pressed down, the bobbin contact portion 33b is not attached to the lower portion. An abutting force is applied to push the yarn bobbin 21 toward the side of the flange portion 21a. Since the bobbin 21 is provided with a frictional force due to the contact force, idling is prevented.

The embodiment of the thread trimming device for a sewing machine according to the present invention has been described above. However, the present invention is not limited to this embodiment and can be variously modified.

For example, in this embodiment, the feed amount after the thread trimming switch 41 is turned on is set to 3 mm.
Controlled, but other feed amounts are set to feed amount setting means 4 for thread trimming.
6 can be set. However, if the feed amount is too small, the effect of the present invention cannot be obtained. Therefore, a value larger than the diameter of the needle hole 31a is preferable, for example, 1 mm to 4 mm.

In the present embodiment, regardless of whether the feed direction of the cloth 30 by the feed dog 27 at the time of the last needle for sewing immediately before thread trimming is in the forward direction or the reverse direction, The specified amount of feed is sent, but the feed amount is forwarded in the forward direction only when the last seam immediately before thread trimming is formed by reverse feed, and the feed amount is set to 0 when the last seam is formed by forward feed. Can be. Therefore, a sewing direction detecting means for detecting a sewing direction, a sewing direction storing means for storing a previous sewing direction in relation to a signal of a transfer detector during sewing,
The discriminating means for discriminating that the immediately preceding sewing direction was formed by reverse feed at the time of thread trimming, and the feed means at the time of thread trimming by moving the feed means in the forward direction only when this discriminating means has determined that the last stitch was formed by reverse feed. Is provided with means for driving a predetermined feed amount. Specifically, the ROM 40b or the RAM 40 of the control unit 40
The program constituting the above means is stored in c. In the sewing machine which feeds the cloth with the cloth feed dog, the sewing direction is detected by detecting the operation of the reverse feed stitching switch by the CPU 40a or by using this lever operation detection switch when operating the known reverse feed lever. In this case, as a matter of course, if it is not determined that the last stitch is formed by reverse feed, the feed means is not driven at the time of thread trimming. (The feed amount may be set to 0.)

Further, in the present embodiment, the feed dog 27
Has shown an example in which the present invention is applied to a sewing machine that sends the cloth 30 in the forward direction or the reverse direction. However, the present invention can also be applied to a sewing machine that is arranged above the needle plate 31 and uses an XY feeder that sends the cloth 30 in the XY directions. That is, when a desired embroidery pattern is selected and the sewing machine is started, the sewing data (X
-Y feed data) to be sent to XY. At this time, the XY feed including the feed component in the same direction as the forward feed by the cloth feed dog is referred to as the normal feed, and the XY feed including the feed component in the reverse direction is referred to as the reverse feed for convenience. When the thread cut signal is output after the embroidery sewing is completed, the XY feed data is extracted from the sewing data of the final stitch of the formed embroidery pattern, and it is determined whether the feed direction is the normal feed direction or the reverse feed direction. If it is determined that the feed direction is the reverse feed direction, the XY feed of a predetermined feed amount in the forward direction and then the operation of the thread trimming device to perform the thread trimming can prevent the occurrence of a thread trimming error. Also, when the thread cut signal is included in the embroidery sewing data, the XY feed data is extracted from the sewing data of the final stitch of the formed embroidery pattern, and whether the feed direction is the normal feed direction or the reverse feed direction is determined. If it is determined that the feed direction is the reverse feed direction, the occurrence of a thread cut error can be prevented by operating the thread cut device after the XY feed has been performed for a predetermined feed amount in the forward direction.

[0037]

According to the present invention, there are provided a feeding means for feeding a cloth at least in a forward or reverse direction, a needle for inserting an upper thread and moving up and down, and an inner pot for accommodating a bobbin wound with a lower thread. A horizontal hook having an outer hook having a sword point for capturing the upper thread through which the needle passing through the needle hole of the inner hook is rotated and having a needle passing through the needle hole of the inner hook, and a catching section which catches the lower thread and the upper thread is provided. A moving knife driven by the lower shaft of the sewing machine, a fixed knife that cuts the lower thread and the upper thread captured by the moving knife in cooperation with the moving knife, and a thread cutting actuator that connects the lower shaft of the sewing machine and the moving knife A feed amount changing actuator for changing the feed amount by the feed means,
At the time of thread trimming, the feed amount of the cloth is changed by the feed amount changing actuator, and the feed means is driven in the forward direction by a predetermined feed amount.
Since there is provided control means for performing thread trimming by operating the thread trimming actuator, it is possible to prevent thread trimming mistakes when thread trimming is performed after the cloth has been reversely fed with the last needle. When the predetermined amount is set to 1 to 4 mm, it is possible to more effectively prevent a thread trimming error.

The control means includes a discriminating means for discriminating that the last seam immediately before the thread is reversely fed at the time of thread trimming, and a feed means for the time of thread trimming only when this discriminating means determines that the last seam is the reverse feed. When a means for driving the means in the forward direction by a predetermined feed amount is provided, it is possible to more efficiently prevent a thread trimming error.

[Brief description of the drawings]

FIG. 1 is a plan view of a thread cutting device according to the present embodiment.

FIG. 2 is a cross-sectional view of the thread cutting device according to the present embodiment.

FIG. 3 is a block diagram of a thread cutting device according to the present embodiment.

FIG. 4 is a timing chart of the thread cutting device according to the embodiment.

FIG. 5 is a plan view showing a basic configuration of the thread cutting device.

FIG. 6 is a plan view showing a state before thread trimming of the thread trimming device.

FIG. 7 is a plan view showing a state immediately after the start of thread trimming of the thread trimming device.

FIG. 8 is a side view showing a state immediately after the start of the thread cutting of the thread cutting device.

FIG. 9 is a plan view showing a state where the moving knife of the thread cutting device has moved to the most advanced position.

FIG. 10 is a plan view showing a state in which the moving knife of the thread cutting device captures a thread.

FIG. 11 is a plan view showing a state immediately before thread trimming of the thread trimming device.

FIG. 12 is a side view showing a state where the moving knife of the thread cutting device captures a thread.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner shuttle 2 Outer shuttle 2a Sword point 4 Movable knife 4a Capture part 5 Fixed knife 21 Bobbin 22 Upper thread 23 Lower thread 27 Feed dog (feed means) 28 Needle 30 Cloth 31 Needle plate 31a Needle hole 32 Horizontal hook 40 Control part 43 Thread Cutting solenoid 44 Feed amount change stepping motor

Claims (3)

[Claims] 1. A feeding means for feeding a cloth at least in a forward or reverse direction, a needle which moves up and down through an upper thread, an inner pot for storing a bobbin wound with a lower thread, and an outer periphery of the inner pot. A horizontal hook having an outer hook having a blade point for capturing a needle thread which is rotated and passed through a needle hole of a needle plate, and a moving knife and a fixed knife having a catch portion for catching a lower thread and an upper thread. By means of this, a thread trimming means for cutting the lower thread and the upper thread, a feed amount changing actuator for changing the feed direction and the feed amount by the feed means, After driving the means in the forward direction by a predetermined feed amount,
A thread trimming device for a sewing machine, comprising: control means for operating thread trimming means to perform thread trimming. 2. The thread trimming device for a sewing machine according to claim 1, wherein the predetermined amount is 1 to 4 mm. 3. The control means comprises: a discriminating means for discriminating that the last seam immediately before the thread is reverse feed at the time of thread trimming; and a discriminating means for discriminating that the last seam is reverse feed at the time of thread trimming. 3. The thread trimming device for a sewing machine according to claim 1, further comprising: means for driving a feed means in a forward direction by a predetermined feed amount.