JPH09239178A - Needle thread holding device for sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a needle thread holding device for a sewing machine, capable of ensuring inexpensiveness and reducing the occurrence of a noise. SOLUTION: This sewing machine is formed to vertically drive a needle bar 6 having a sewing needle 6a on the lower end thereof, perform a sewing process with needle thread (a) led through the sewing needle 6a and bobbin thread under a throat plate 60, and then cut thread under the throat plate 60 after a sewing process. In this case, the needle thread holding device is formed to have a thread holding member 20 positioned behind the end of the sewing needle 6a approximately at the position of top dead center, and a hook part 32a for catching the needle thread (a) drooping from the sewing needle 6a after cutting, respectively on the front end. The hook part 32a is formed out of a hook member 32 reciprocating between a waiting position behind the thread holding member 20 and a projection position under the sewing needle 6a approximately at the position of top dead center through the thread holding member 20, a motor 43 for driving the hook member 32, and power conversion mechanisms 32c, 33, 35 and 44 linked to a motor output shaft for causing one reciprocating motion of the hook member 62 per rotation of the output shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle thread holding device for a sewing machine, and more particularly, a thread end cut from a sewing needle and hanging from a sewing needle after sewing of embroidery or the like in the sewing machine is provided on a back portion of the sewing needle. The present invention relates to a needle thread holding device for holding the upper thread.

[0002]

2. Description of the Related Art An apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No. 59-59.
There is a technique disclosed in Japanese Patent Publication No. 211487/1990. In the device described in this publication, a thread holding member is provided in the lower part of the sewing machine head (needle bar case), and a thread hooking member is arranged at the back of the thread holding member. The thread hooking member is driven by a rotary solenoid to project directly below the sewing needle at the top dead center, and then slides from that position to the original standby position. By driving the rotary solenoid, the thread hooking member slides as described above, hooks the upper thread hanging from the sewing needle by thread cutting, and guides the thread end into the opening of the thread holding member. . As a result, the yarn end of the upper yarn is held by the yarn holding member.

[0003]

Since the rotary solenoid is used as the drive source of the thread hooking member in the above-mentioned device according to the prior art, it is used as a stopper member when the thread hooking member moves forward and backward. The collision noise is loud, which is one of the causes of noise generation of the sewing machine. Therefore, in order to eliminate such noise, a device has been proposed in which the thread hooking member is driven by a pulse motor. However, in order to drive the pulse motor, an expensive drive circuit is required and the cost becomes high. Especially, in the case of a sewing machine with a multi-head type, the drive circuits described above are required for the number of sewing machine heads. It is pointed out that there are difficulties that lead to a significant cost increase.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a thread holding device of a sewing machine which is inexpensive and can suppress noise generation to a small extent. With the goal.

[0005]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned problems and achieve an intended object, the present invention allows a needle bar having a sewing needle at its lower end to be driven up and down to pass the needle through the sewing needle. In the sewing machine in which the upper thread and the lower thread below the needle plate are sewn, and the thread is cut below the needle plate after the sewing is completed, the needle of the sewing needle at a substantially top dead center position It has a thread holding member arranged at a substantially rearward position and a hook portion for hooking an upper thread hanging from the sewing needle after the thread cutting, and the hook portion has a hook portion of the thread holding member. Between the standby position located on the back side and the protruding position located below the sewing needle at the substantially top dead center position,
A hook member adapted to reciprocate through the thread holding member, and a motor for driving the hook member,
It is characterized by comprising a power conversion mechanism which is connected to an output shaft of the motor and which causes the hook member to reciprocate once by one rotation of the output shaft. In this case, it is proposed that a drive circuit that supplies a drive current to the motor be provided with a limit switch that detects that the motor has made one revolution. Further, it is preferable that the limit switch is a contact switch having an actuator that operates by contact with a movable portion that is rotated by the motor. Further, the motor may be a synchronous motor. The power conversion mechanism includes at least a drive arm fixed to the output shaft of the motor, and a swing lever having a free end side connected to the hook member and swingably supported. It is proposed that the end side is connected to the swing lever, and the hook member is reciprocated once through the swing lever by one rotation of the drive arm.

[0006]

According to the above construction, when the motor is rotated once, the hook member reciprocates once between the standby position and the projecting position, and the hook portion of the hook member hooks the upper thread hanging from the sewing needle. Pull it into the thread holding member. As a result, the thread end of the upper thread is held at the position of the thread holding member, that is, at the rear position of the sewing needle at the substantially top dead center position.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A needle thread holding device for a sewing machine according to the present invention will be described below with reference to the accompanying drawings, with reference to a preferred embodiment in which the needle thread holding device is applied to a multi-head multi-needle sewing machine. FIG. 1 shows one sewing machine head 2 in a multi-head multi-needle sewing machine as a front view, and FIG. 2 shows the sewing machine head 2 in a left side view. A plurality of the sewing machine heads 2 are provided on the front surface of the horizontally installed frame 1 at appropriate intervals in the lateral direction. Each sewing machine head 2
Comprises a sewing machine arm 3 fixed to the front surface of the frame 1 and a needle bar case 5 supported laterally slidably on the front surface thereof. A plurality of needle bars 6 (six in this example) having sewing needles 6a attached to the lower ends thereof are supported on the needle bar case 5 so as to be vertically movable, and a balance 7 corresponding to each needle bar.
(6 in total) are swingably supported. The needle bar 6
A cloth presser 8 is attached to each of them, and a through hole 8a through which the sewing needle 6a can pass is formed at the lower end of the cloth presser 8 (FIG. 5).

Each of the sewing machine arms 3 has a single elongated sewing machine spindle 10 which is commonly supported by the sewing machine arm 3 so as to be rotatable, and the sewing machine spindle 10 is provided with a needle bar in each sewing machine arm 3. The drive mechanisms of 6 and the balance 7 are linked. The needle bar 6 and the balance 7, which are selected by sliding the needle bar case 5, are driven via the respective drive mechanisms when the sewing machine main shaft 10 rotates in one direction. A needle plate 60 is disposed on a sewing machine table (not shown) below the sewing machine head 2, and a thread cutting device (also not shown) is installed below the needle plate 60. The sewing machine head 2 has a thread holding member 20 attached to the needle bar case 5 and a needle thread hooking device 21 attached to the sewing machine arm 3.
Is equipped with a needle thread holding device.

First, the thread holding member 20 has a receiving frame 24 formed by bending attachment portions 23 at both ends of a receiving portion 22 having a length substantially corresponding to the width of the needle bar case 5.
The cover plate 25 is attached to the receiving portion 22. This lid plate 2
5 has both ends fixed by screws 27 via spacers 26 and is parallel to the receiving portion 22. Receiving part 2
The flocked sheets 28 are individually attached to the upper surface of 2 and the lower surface of the cover plate 25, and face each other without any gap. Further, the rear edge portions of the receiving portion 22 and the lid plate 25 are
It is bent in such a direction as to be separated from each other, and is set so as not to obstruct the entry of a hook member described later. The thread holding member 20 configured as described above is fixed by attaching both attachment portions 23 to the brackets 29 fixed to the lower end portions of both side surfaces of the needle bar case 5, and is configured by the receiving portion 22 and the lid plate 25. The thread holding portion is located at the rear portion of the sewing needle 6a at the top dead center position, and the opening of the thread holding portion faces obliquely upward.

Next, the needle thread hooking device 21 will be described. The assembly base 30 of the present apparatus has a mounting portion 30a mounted on the left side surface of the sewing machine arm 3 and a support portion 30b formed by bending along the lower surface of the sewing machine arm 3. A guide plate 31 having a guide groove 31a in the front-back direction of the hook member 32 is fixed to the lower surface of the mounting portion 30b, and the hook member 3 is provided between the guide groove 31a and the lower surface of the support portion 30b.
2 is slidably supported only in the front-back direction. The hook member 32 has a hook portion 32a formed at the tip and an arm portion 32b formed near the rear end. A connecting portion 32c is bent and formed at an end portion of the arm portion 32b projecting from a side end portion of the guide plate 31. A connecting lever 33 is connected to the connecting portion 32c by a pin 34. The other end of the connecting lever 33 is connected by a pin 36 to a free end of a swing lever 35 that is swingably attached to a mounting portion 30a via a support shaft 37. The swing lever 35 is fitted to the support shaft 37, and the other end of the return spring 40 hooked at one end with the screw 38 of the mounting portion 30a is hooked. 5 is biased clockwise.

Two studs 41 are attached to the mounting portion 30a.
And the synchronous motor 43 is fixed by these studs 41 in a state of being floated from the mounting portion 30a. This motor 43 is an alternating current with a constant frequency.
When a commercial power source (for example, 100 V at 50 Hz) is supplied, the internal drive shaft rotates at a constant speed, and the output shaft 43a rotates via a built-in reduction mechanism. Output shaft 43
A drive arm 44 is fixed to a, and a roller 45 is supported at the free end of the drive arm 44. The drive arm 44 is rotationally driven at the front position of the swing lever 35 in FIG.
The return spring 40 elastically abuts the peripheral surface of the roller 45 on the roller 45. The drive arm 44, the connecting lever 33, the swing lever 35, and the connecting portion 32c of the hook member 32 constitute a power converting mechanism.

The drive arm 44 is driven to rotate counterclockwise in FIG. 5, and the upper edge 35a of the swing lever 35 is pushed downward by the roller 45 in accordance with the rotation, whereby the swing lever 35 returns. It swings counterclockwise against the biasing force of the spring 40. Along with this, the hook member 32 is slidably driven in the protruding direction via the connecting lever 33, and when the roller 45 of the drive arm 44 is at the top dead center position, as shown in FIG. 35 is the uppermost position, and the hook member 32 is most retracted to the standby position. Further, as shown in FIG. 5B, when the straight line connecting the centers of the roller 45 and the output shaft 43a and the upper edge 35a of the swing lever 35 are orthogonal to each other, the swing lever 35 is at the lowest position. With
The hook member 32 projects most and is located at the projecting position. Therefore, the driving arm 44 rotates 360 ° counterclockwise from the position shown in FIG.
2 will make one reciprocating motion.

Next, a mechanism for rotating the drive arm 44 by 360 ° and stopping it will be described. A support case 50 is attached to the front surface of the attachment portion 30a above the drive arm 44, and a limit switch 51 and a slide switch 52 are supported by the support case 50. The limit switch 51 is a C contact type switch, and when the actuator 51a is in the free state shown in FIG. 5B, the A contact is in the ON state, and the drive arm 44
When the actuator 51a is at the position shown in FIG. 5A (this position is hereinafter referred to as "origin position"), the actuator 51a is pushed by the free end of the drive arm 44 to open the A contact.
When it is turned off, the B contact is closed (turned on).

FIG. 7 shows a circuit configuration for supplying a drive current to the synchronous motor 43. The synchronous motor 43 is connected to a commercial AC power source 53 of 100 V at 50 Hz, for example, via the limit switch 51, the slide switch 52, and two switch circuits 54 and 55. Each of the switch circuits 54 and 55 is composed of an electronic device such as a monostable multivibrator, and one switch circuit 54 is closed (ON) only for a predetermined time when the needle thread processing signal is input. The other switch circuit 55 is closed (ON) at the same time when the one switch circuit 54 is closed (ON), and the one switch circuit 5 is closed.
Even after 4 is opened (OFF), the closed (ON) state is continuously maintained, and after a predetermined time elapses, it is opened (OFF). The slide switch 52 is for manually inactivating the synchronous motor 43 regardless of the presence or absence of the needle thread processing signal. This switch 52
Is normally in the closed (ON) state.

FIG. 8 is a timing chart showing the relationship between the rotation angle of the drive arm 44 and the respective states of the switch 51, the switch circuits 54 and 55, and the synchronous motor 43. In FIG. 8, the drive arm 4
The state where 4 is at the origin position is 0 °. When the drive arm 44 is at the origin position, the switch circuit 54,
55 are both open (OFF) and switch 5
Regarding No. 1, since the actuator 51a is pressed by the drive arm 44 as described above, the B contact is in the closed (ON) state. Now, when the needle thread processing signal is input to the switch circuit 54, the switch circuits 54 and 55 are both closed (ON), whereby current is supplied to the motor 43 via the switch circuit 54 and the drive arm 44 is moved. Rotation starts counterclockwise from the state shown in FIG. The free end of the drive arm 44 is separated from the actuator 51a of the switch 51, so that the switch 5
In No. 1, the A contact is closed (ON), and after a lapse of some time thereafter, the switch circuit 54 is opened (OFF). Therefore, after the switch 51 is switched, electric current is supplied to the motor 43 via the switch circuit 55.

When the drive arm 44 is rotated 360 ° and returned to the original position by the rotation of the motor 43, the actuator 51a of the switch 51 is pressed by the drive arm 44 as shown in FIG. 5 (a). The A contact of the switch 51 is opened (OFF), whereby the current supply to the motor 43 is stopped and the motor 43 is stopped. After a short time, the switch circuit 5
5 becomes open (OFF) and returns to the original state. By the series of operations described above, the hook member 32 projects from the standby position to the projecting position, and returns from the projecting position to the standby position.

Next, the procedure for processing the upper thread will be described with reference to FIG. The upper thread processing signal is issued immediately after the thread trimming is automatically executed when the sewing of the predetermined unit is completed during the automatic operation. Further, even when the sewing machine is intentionally stopped in the middle of sewing and a thread trimming command is manually issued, this needle thread processing signal is issued after execution of thread trimming. FIG. 6A shows a state where the needle bar 6 is returned to the top dead center position after the thread cutting is executed, and the end of the cut upper thread a is still in the needle plate 6.
0 under the needle plate 60 through the needle hole 60a, and the upper thread a
Hangs substantially vertically from the through hole 8a of the cloth presser 8, and the hook member 32 is in the standby position. Now, when the upper thread processing signal is output, the hook member 32 starts to project as described above, and the hook portion 32a at the tip thereof passes through between the receiving portion 22 of the thread holding member 20 and the lid plate 25 and advances. To do. Then, as shown in FIG. 6 (a), when the hook member 32 reaches the projecting position, the hanging upper thread a has the hook portion 32a.
It will be in the state of getting inside. Then hook member 3
2 starts returning to the standby position, and the upper thread a
Is hooked on the hook portion 32a and pulled backward.

As shown in FIG. 6A, when the hook member 32 returns to the standby position, the upper thread a is held between the receiving portion 22 and the cover plate 25, and the upper thread a The thread tail is retracted and held at the rear position of the sewing needle 6a. When the needle bar case 5 is slid for the subsequent needle bar selection operation, the thread holding member 20 is fixed to the needle bar case 5 and slides together with the needle bar case. On the other hand, the needle thread hooking device 21 is fixed to the sewing machine arm and is immovable, and therefore the hook member 32 is also immovable. Therefore, the needle thread a caught on the hook portion 32a of the hook member 32 slides on the needle bar case 5. 6C, the thread tail of the upper thread a hangs down from the receiving section 22, and the upper thread is still released from the hook section 32a. The state of being held by the holding member 20 is maintained.

According to the structure of this embodiment, so-called stoppers at the standby position and the projecting position of the hook member 32 are unnecessary, and therefore, no stopper sound is generated at the standby position and the projecting position during operation, which is extremely advantageous. Works quietly. Further, since the hook member 32 is driven to reciprocate only once by rotating the output shaft of the synchronous motor 43 once in a single direction, an expensive drive circuit such as a pulse motor drive is not required and the manufacturing cost is suppressed. It is possible.

Further, in this embodiment, the synchronous motor 4 is
The limit switch 51 is used in the start / stop circuit of No. 3 as a switch for detecting the position of the output shaft 43a (driving arm 44). That is, although the drive arm 44 has an advantage of always returning to the origin position even if the operation is repeated, the time required for the output shaft to rotate once if the frequency of the alternating current to be supplied is determined because of its function. Since it is constant, it is not always necessary to provide the switch 51. That is, when receiving the needle thread processing signal,
A timer switch that supplies a current to the synchronous motor 43 while the drive arm 44 makes only one rotation may be used. In this case, the switch 54 as shown in this embodiment is used.
55 may also be unnecessary. Although the limit switch 51 is adopted as the switch for detecting the position of the drive arm, an optical switch or a magnetic switch may be used instead of the limit switch 51.

[0021]

As described above, according to the needle thread holding device of the sewing machine of the present invention, the hook member is reciprocated once by the simple control of rotating the motor once in a single direction. This eliminates the need for the stopper member at the standby position and the protruding position of the hook member. Therefore, the sewing machine can be operated extremely quietly without generating a stopper sound. Further, since the drive circuit of the motor can be made extremely simple, the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a front view of a sewing machine head in which a needle thread holding device of a sewing machine according to the present invention is preferably implemented.

FIG. 2 is a side view of the sewing machine head shown in FIG.

FIG. 3 is an exploded perspective view of a needle thread hooking device.

FIG. 4 is an exploded perspective view of a needle thread holding member.

FIG. 5 is an operation explanatory view of the upper thread hooking device.

FIG. 6 is an explanatory diagram of a thread hooking operation by a hook member.

FIG. 7 is a schematic configuration diagram of a circuit that drives a motor.

FIG. 8 is a timing chart showing the operation timing of the motor.

[Explanation of symbols]

 6 Needle bar 6a Sewing needle 20 Thread holding member 32 Hook member 32a Hook part 43 Synchronous motor (motor) 60 Needle plate a Upper thread 32c Connection part ... Power conversion mechanism 33 Connection lever ... Power conversion mechanism 35 Swing lever ... Power conversion Mechanism 44 Drive arm ... Power conversion mechanism

Claims (5)

[Claims] 1. A needle thread passed through the sewing needle (6a) by driving a needle bar (6) having a sewing needle (6a) at the lower end up and down.
(a) and the lower thread below the needle plate (60) are sewn, and the thread is cut below the needle plate (60) after the sewing is completed. A thread holding member (20) arranged substantially rearward of the needle tip of the sewing needle (6a), and a needle thread hanging from the sewing needle (6a) after the thread cutting.
It has a hook part (32a) for hooking (a) at its tip, and the hook part (32a) is at a standby position located on the back side of the thread holding member (20) and at a substantially top dead center position. Between the protruding position located at the lower part of the sewing needle (6a), the thread holding member (2
(0) Hook member designed to reciprocate through
(32), a motor (43) for driving the hook member (32), and an output shaft of the motor (43), and the hook member (32) reciprocates once by one rotation of the output shaft. A needle thread holding device for a sewing machine, characterized in that it is configured with a power conversion mechanism (32c, 33, 35, 44). 2. The sewing machine according to claim 1, wherein a limit switch (51) for detecting that the motor (43) makes one revolution is provided in a drive circuit for supplying a drive current to the motor (43). Upper thread holding device. 3. The needle thread holding machine for a sewing machine according to claim 2, wherein the limit switch (51) is a contact switch having an actuator (51a) which is operated by contact with a movable part rotated by the motor (43). apparatus. 4. The needle thread holding device for a sewing machine according to claim 1, wherein the motor (43) is a synchronous motor. 5. The power conversion mechanism comprises a drive arm (44) fixed to an output shaft of the motor (43), a free end side of which is connected to the hook member (32), and is swingably supported. A drive lever (35) and at least the drive arm.
The free end side of (44) is connected to the swing lever (35), and the swing lever (35) is rotated by one rotation of the drive arm (44).
The upper thread holding device for a sewing machine according to any one of claims 1 to 4, wherein the hook member (32) is reciprocated once through the needle.