JP2002113278A - Sewing machine thread trimmer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a thread cutting device for a sewing machine which can prevent the occurrence of bird's nest. SOLUTION: A fixed knife 18 fixed to a lower portion of a needle plate,
A first thread trimming knife having an upper thread engaging hole 2a and movable to a needle drop position for catching the upper thread 8 and a cutting position for cutting the upper thread end 8F in cooperation with a fixed knife at the start of sewing. A thread trimming device for a sewing machine, comprising: a second thread trimming knife that moves to an upper and lower thread cutting position for cutting upper and lower threads after sewing in cooperation with a fixed knife.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thread cutting device for a sewing machine.

[0002]

2. Description of the Related Art As an apparatus for preventing a needle thread cut end remaining on a sewing machine needle which has been cut after completion of sewing from becoming a thread ball (bird's nest) at the start of the next sewing operation. A thread cutting device for cutting the upper thread cutting end remaining in the sewing needle at the start of the next sewing is conventionally known. As an example, the applicant has filed patent application 2000-11.
No. 3020 proposes a thread cutting device. This device includes a thread locking portion that locks the upper thread and a blade portion formed around the thread locking portion, and the device advances and retreats between the standby position and the needle thread catching position where the thread locking portion matches the needle drop position. With a thread catching knife,
A thread trimming knife that advances and retreats between the initial position and the cutting position beyond the needle thread catching position and cuts the thread in cooperation with the thread catching knife. The thread catching knife advances to the needle thread catching position before descending below the plate, and the thread cutting knife advances to the cutting position after the sewing machine needle rises above the needle plate.

[0003]

However, in the above-described thread cutting device, after the thread cutting operation with the first needle is completed, the thread catching knife at the needle thread catching position is prepared for thread cutting with the last needle. It was necessary to rotate and stop at the standby position.
Since the rotation of the thread catching knife is performed under the needle, during rotation, the needle must be temporarily stopped in order to avoid interference with the needle or the needle drive must be performed at an extremely low speed. This caused the operator to feel uncomfortable. In addition, the upper thread end after thread trimming at the start of sewing is a free end,
There was a drawback that it was not stable when forming the next seam, so that it was not a beautiful seam.

An object of the present invention is to provide a thread trimming device for a sewing machine which can prevent the occurrence of a bird's nest by a novel configuration. Another object of the present invention is to provide a thread trimming device for a sewing machine which can prevent the upper thread end after thread trimming at the start of sewing from becoming unstable at the time of forming the next seam and can provide a beautiful seam. It is in. Still another object of the present invention is to provide a thread trimming device for a sewing machine, which can reduce the working time.

[0005]

According to the present invention, there is provided a fixed knife fixed to a lower portion of a needle plate, a needle drop position having an upper thread engaging hole, and catching an upper thread. When,
A first thread trimming knife movable to a cutting position for cutting the upper thread end in cooperation with the fixed knife at the start of sewing, and upper and lower threads for cutting upper and lower threads after sewing in cooperation with the fixed knife A second thread trimming knife movable to a cutting position is provided.

At the start of sewing, one end of the upper thread cut by the first thread cutting knife and the fixed knife is clamped. The first thread trimming knife and the second thread trimming knife driven by the knife driving means are spaced apart by a predetermined amount. During the sewing operation, it is preferable that the first thread trimming knife is stopped at the cutting position, and the sewing needle moves up and down between the thread trimming knife and the second thread trimming knife. The first thread trimming knife and the second thread trimming knife can be formed integrally.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an embodiment of a thread trimming device for a sewing machine according to the present invention will be described with reference to FIGS. The thread trimming device includes a hole knife (first thread trimming knife) 2, a thread handling knife (second thread trimming knife) 4, and a fixed knife 18 fixed to a lower portion of a needle plate (not shown). The hole knife 2 has a needle thread engaging hole (blade portion) 2a formed at a tip end on a side facing the thread handling knife 4. The needle thread engaging hole 2a has both a function of catching the needle thread (needle thread) 8 and a function of a blade part for cutting the upper thread end in cooperation with the fixed knife 18. The thread handling knife 4 has a thread handling portion 4a formed at the end opposite to the hole knife 2, and the upper and lower threads 8, 1 guided by the thread handling portion 4a.
4 is formed with a blade portion 4b for cutting in cooperation with the fixed knife 18. The blade 18a at the tip of the fixed knife 18 comes into contact with the blade 2a when the hole knife 2 rotates to the cutting position, and the blade 4a rotates when the threading knife 4 rotates to the upper and lower thread cutting positions.
b.

The hole knife 2 and the thread handling knife 4 are screwed and fixed to a knife drive base 6 having a shuttle shaft (not shown) as a rotation axis. The female drive base 6 has a connection hole 6a for driving. The needle 10 passing through the needle thread 8 can move up and down, and passes through a needle hole 12 of a needle plate (not shown). The hole knife 2 and the thread handling knife 4 are spaced apart by a predetermined amount, and the needle 10 can move up and down between them during the sewing operation. FIG. 1 shows a state in which the hole knife 2 and the thread handling knife 4 are at the initial position. At this time, the blade portion 2 a of the hole knife 2 is arranged at a position matching the needle hole 12. A shuttle 16 having a lower thread 14 is provided at the center of rotation of the hole knife 2 and the thread handling knife 4. The threading knife 4 is provided with a threading portion 4a and a blade portion 4b. When the threading knife 4 rotates, the threading portion 4a and the blade portion 4b are connected to the needle hole 1a.
It is configured to pass through a position that matches 2.

The knife drive base 6 is connected to a controller 22 via a drive actuator 20 (for example, a stepping motor, a solenoid, etc.) connected to the connection hole 6a and an actuator drive circuit 21, and a program set in advance by the controller 22. It is configured to operate based on. The sewing machine motor 24 is connected to the controller 22 via a motor driver 26 and a motor rotation control circuit 28, and operates based on a program set in advance by the controller 22. The sewing machine motor 24 is provided with a rotation speed detecting device, a needle position detecting device, and a stitch number detecting device (not shown).
Sent to A lint removing device 32 is connected to the actuator drive circuit 21 via a drive actuator 30 such as an electromagnetic valve.
Is connected. The lint removal device 32 includes a compressed air generation unit, a negative pressure generation unit, and a lint container. In addition,
A pedal 34 is connected to the controller 22.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. In the figure, S1, S2,
.. Indicate the numbers of the processing order (steps). First, when the pedal 34 is depressed forward in S1, the knife drive base 6 rotates to move the hole knife 2 and the thread handling knife 4 to the initial positions. When it is confirmed in S2 that the sewing machine has moved to the initial position, the process proceeds to S3, where the sewing machine starts rotating, and the needle 10 starts lowering. Then, the needle 10 passes through the needle hole 12 of the needle plate and the blade portion 2 of the hole knife 2
penetrates a and reaches the bottom dead center before turning up. Thus, the needle thread 8 is captured by the hole knife 2. FIG. 1 described above shows a state where the needle 10 is raised. At this time, the needle thread 8 passed through the needle 10 passes through the needle hole 12 and the blade portion 2a, and is pulled out toward the shuttle 16 by the action of the shuttle 16.

Next, the needle 10 turns downward from the top dead center,
When the balance reaches the top dead center position in S4, the process proceeds to S5, where the driving actuator 20 is rotated by the operation of the driving actuator 20 based on the program, and the hole knife 2 is rotated in the B direction as shown in FIG. And move to the cutting position, S7
The needle thread 8 is cut by the fixed knife 18 and the blade 2a of the hole knife 2, and the needle-side cut end 8F is clamped between the hole knife 2 and the fixed knife 18. According to the present embodiment, since the needle thread 8 remaining on the needle 10 is cut at the time of starting sewing, occurrence of a bird's nest can be prevented. In addition, since one end 8F of the cut needle thread 8 is held, when the first stitch is formed, the cut end 8F of the needle thread is fixed to the fixed knife 18F.
And the hole scalpel 2, so that the stitch shape is stable. At the time of this cutting, the position of the hole knife 2 is set so that the lowered needle 10 and the tip of the hole knife 2 do not interfere with each other.

When the cutting of the needle thread 8 is completed, a thread waste processing operation is performed in S8. That is, the lint 8b of the cut needle thread 8 is blown off by the compressed air from the compressed air generation unit of the lint removal device 32, sucked by the negative pressure generation unit, collected in the lint container, and passed for a predetermined time. Later, the lint removing device 32 stops.

Next, proceeding to S9, the sewing machine enters a sewing operation as shown in FIG. 5, the sewing object is sent in the E direction, and the stitch D formed on the sewing object is also sent in the E direction. .
When the first seam D is formed, the cut end 8F of the needle thread 8 is formed.
Is stably held between the fixed knife 18 and the hole knife 2, so that the stitch shape is stable. When the workpiece is further fed in the direction E, the cut end 8F of the needle thread 8 is moved as shown in FIG.
Is pulled out and knotted with the lower thread 14 to form a seam D. Further, when the workpiece is fed in the direction E and the stitches D for a predetermined number of stitches are formed, the sewing machine stops and the needles 10 also stop.

As described above, according to the present embodiment, the hole knife 2 and the thread handling knife 4 are connected to each other both when the needle thread 8 is cut at the start of sewing and when the sewing operation is performed. ~
It stops at the same position as shown in FIG. In addition, as described above, the needle 1 that has been lowered when the needle thread 8 is cut at the start of sewing.
0 and the tip of the hole knife 2 do not interfere with each other. Therefore, after the thread trimming is completed, it is not necessary to temporarily stop the needle 10 or set the needle drive at an extremely low speed in order to avoid interference with the needle 10. Further, since it is not necessary to move the position of the hole knife 2 after the cutting of the needle thread 8, the working efficiency is improved and the operator does not feel uncomfortable.

When the sewing is completed, when the pedal 34 is depressed backward in S10, a sewing end thread trimming command is issued, and the knife drive table 6 is driven in S11 according to a predetermined program, as shown in FIG. The hole knife 2 and the thread handling knife 4 are further rotated in the direction B, and the thread handling portion 4a is divided into the loop G formed by the needle thread 8, and while rotating, one end of the needle thread 8 and the lower thread 14 are rotated. And guide it to the blade portion 4b. S
At 12 and S13, as shown in FIG.
And the hole knife 2 further rotates in the B direction, and the needle thread 8 and the bobbin thread 1
4 is sandwiched between the blade portion 4b of the thread handling knife 4 and the fixed knife 18 and cut.

By the above operation, as shown in FIG. 9, the needle thread 8 and the lower thread 14 are knotted to form a seam, and a seam having a small remaining length at the sewing start portion H can be obtained.

After the thread trimming at the end of sewing is completed in this way, the process proceeds to S14, where the knife drive base 6 is driven based on a predetermined program, and the hole knife 2 and the thread handling knife 4 are returned to the initial positions shown in FIG. Then, the sewing process is completed.

FIG. 10 shows a main part of a second embodiment of the thread trimming device for a sewing machine according to the present invention. This embodiment is based on the first
In this embodiment, the hole knife 2 and the thread handling knife 4 are integrally formed to form an integral knife 36, which is fixed to the knife drive base 6 for use. The integrated knife 36 has a hole knife 36a and a thread handling portion 36b at both ends, and the hole knife 36a corresponds to the hole knife 2 of the first embodiment.
b corresponds to the thread handling knife 4 of the first embodiment. Others are the same as in the first embodiment. Note that the knife drive table 6 may be omitted, and the integral knife 36 may be directly driven by the drive actuator 20.

FIG. 11 shows a main part of a third embodiment of the thread cutting device for a sewing machine according to the present invention. In this embodiment, the hole knife 2 and the thread handling knife 4 of the first embodiment are integrally formed as an integral knife 38.
To be used. The integral knife 38 has a hole knife 38a and a thread handling portion 38b at both ends thereof. The hole knife 38a corresponds to the hole knife 2 of the first embodiment, and the thread handling knife 3
8b corresponds to the thread handling knife 4 of the first embodiment. In the case of the first and second embodiments, the hole knife 2 (hole knife portion 36a) and the thread handling knife 4 (thread handling knife portion 36b) are arranged to face each other. In the case of the mode, the hole female portion 38a and the thread handling portion 38b are arranged in the forward direction. The rest is the same as in the first and second embodiments, and the knife drive table 6 may be omitted and the integral knife 38 may be directly driven by the drive actuator 20.

The operation of the third embodiment is performed based on the flow chart of FIG. 12, but is different from the flow charts of FIGS. Therefore, the description is omitted.

Although the present invention has been described based on the embodiment shown in the drawings, the present invention is not limited to this, and can be variously modified. For example, the hole knife 2 and the thread handling knife 4 rotate around the shuttle 16, but may move straight in the horizontal direction.

[0022]

According to the sewing machine thread trimming device of the present invention,
With a fixed knife fixed to the lower part of the needle plate and a needle thread engagement hole,
A first movable position between a needle drop position for capturing the upper thread and a cutting position for cutting the upper thread end in cooperation with the fixed knife at the start of sewing;
A thread trimming knife, and a second thread trimming knife that can move to an upper and lower thread cutting position for cutting the upper and lower threads after sewing in cooperation with the fixed knife, so that the upper thread that causes bird nests is provided. The cut end can be cut at the start of sewing, and the occurrence of a bird's nest can be prevented.

At the start of sewing, if one end of the upper thread cut by the first thread cutting knife and the fixed knife is clamped, the cut end of the needle thread is formed when the first stitch is formed. ,
Since it is held between the fixed knife and the first thread trimming knife, a stable stitch shape is obtained.

When the first thread trimming knife and the second thread trimming knife driven by the knife driving means are arranged at a predetermined distance from each other, the distance between the first thread trimming knife and the second thread trimming knife can be reduced. Can be used as a sewing space for the needle to move up and down during sewing.

During the sewing operation, the first thread trimmer is stopped at the cutting position, and if the needle moves up and down between the thread trimmer and the second thread trimmer, the upper thread is moved at the cutting position. After cutting the needle, stop the needle temporarily to avoid interference with the needle,
There is no need to make the needle drive extremely slow. Furthermore, since it is not necessary to move the position of the first thread cutting knife after cutting the needle thread, the working efficiency is improved and the operator does not feel uncomfortable.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which a hole knife and a thread handling knife of a first embodiment of a thread cutting device of the sewing machine of the present invention are at an initial position.

FIG. 2 is a control block diagram according to the first embodiment.

FIG. 3 is a flowchart of an operation according to the first embodiment.

FIG. 4 is a perspective view of the first embodiment when the needle thread is cut by the hole knife at the start of sewing.

FIG. 5 is a perspective view of the first embodiment at the time of starting a sewing operation.

FIG. 6 is a perspective view of the sewing operation according to the first embodiment during continuation of the sewing operation.

FIG. 7 is a perspective view showing a state in which the thread handling knife is moving toward the upper and lower thread cutting positions after the sewing operation of the first embodiment is completed.

FIG. 8 is a perspective view of the first embodiment when the upper and lower threads are cut by the thread handling knife after the completion of sewing.

FIG. 9 is a perspective view of a seam obtained according to the first embodiment.

FIG. 10 is a perspective view of a main part of a second embodiment of the thread trimming device of the sewing machine of the present invention.

FIG. 11 is a perspective view of a main part of a third embodiment of the thread trimming device of the sewing machine of the present invention.

FIG. 12 is a flowchart illustrating the operation of the third embodiment.

[Explanation of symbols]

 2 hole knife (first thread cutting knife) 4 thread handling knife (second thread cutting knife) 6 knife drive stand 8 needle thread (upper thread) 8F cutting end 14 lower thread 18 fixed knife 36, 38 one-piece knife

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3B150 AA02 CB03 CE01 CE17 CE23 CE27 FH02 FH03 FH07 FH09 FH11 FH15 JA02 JA11 LA53 LB02 NA48 NA71 NB16 NC02 NC11 QA06 QA07

Claims (5)

[Claims] 1. A fixed knife fixed to a lower portion of a needle plate, a needle dropping position having an upper thread engaging hole for catching an upper thread, and an upper thread end cooperating with the fixed knife at the start of sewing. A first thread trimming knife movable to a cutting position for cutting, and a second thread trimming knife movable to an upper and lower thread cutting position for cutting upper and lower threads after sewing in cooperation with the fixed knife. Sewing machine thread trimming device. 2. The sewing machine according to claim 1, wherein at the start of sewing, one end of the upper thread cut by the first thread trimming knife and the fixed knife is clamped. Thread cutting device. 3. The thread trimming device for a sewing machine according to claim 1, wherein the first thread trimming knife and the second thread trimming knife driven by knife driving means are arranged apart from each other by a predetermined distance. A thread trimming device for a sewing machine. 4. The sewing machine according to claim 3, wherein the first thread trimming knife is stopped at the cutting position during the sewing operation, and the sewing machine needle is connected to the thread trimming knife and the second thread trimming knife. A thread cutting device for a sewing machine, which moves up and down between the sewing machines. 5. The thread trimming device for a sewing machine according to claim 3, wherein said first thread trimming knife and said second thread trimming knife are formed integrally.