JPH0817865B2 - Sewing machine thread cutting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a needle thread cutting mechanism which is connected to a thread hole of a material to be sewn above a needle plate, and an upper thread cutting mechanism which operates after the needle thread is cut and is located below a needle plate. The present invention relates to a thread cutting device of a sewing machine, which includes a lower thread cutting mechanism that draws a lower thread connected to a sewing machine and a bobbin in a direction intersecting the path and cuts the lower thread.

[Conventional technology]

Conventionally, after the upper and lower threads are entangled by the cooperation of the needle and the upper thread catching body to form a binding portion thereof in the sewn object, the upper and lower threads are sewn above and below the throat plate in connection with the stop of the sewing machine. There is a buttonhole overlock sewing machine with a device for cutting separately with
The drawing shows the bobbin thread cutting mechanism as seen from the bottom of the sewing machine. 1 is a needle plate supported on a needle plate base 2, and 1a and 1b are needle holes and knife cutting grooves formed through the needle plate 1. The needle plate base 2 is supported by a sewing machine bed (not shown). Reference numeral 4 is a fixed knife fixed to one side of the lower surface of the needle plate base 2 with a screw 3, and 5 is a feeding body which forms a thread feeding portion 6 and whose base end is rotatably supported on the needle plate base 2 by a step screw 7. Yes, the long hole portion 8 which is long in the oblique direction is provided.

Reference numeral 9 denotes a moving knife which has a blade 9a corresponding to the fixed knife 4 and which is rotatably supported on the lower surface of the needle plate base 2 by a step screw 10, and a pin 11 is provided at a swinging end of the feeding body 5. It is loosely fitted to the portion 8, interlocked with the rotation of the feeding body 5, and is operated with a predetermined time delay. Further, the blade 9a of the moving knife 9 is arranged below the yarn paying-out portion 6 of the paying-out body 5 so that the moving knife 9 always follows after the lower thread is paid out by the yarn paying-out portion 6.

Reference numeral 12 is a link, one end of which is rotatably connected to the feeding body 5 by a step screw 13, and the other end of which is interlocked with a foot pedal operating mechanism.

In such a conventional sewing machine, the bobbin thread cutting mechanism presses the foot pedal at the end of sewing, whereby the feeding body 5 after cutting the upper thread causes the fixed knife 4 to move before the moving knife 9 having the blade 9a.
And the lower thread is fed out by the feeding body 5 by a necessary amount, and then the lower thread is cut by the cooperation of the fixed knife 4 and the moving knife 9 to release the pressing of the foot pedal. Thus, the moving knife 9 and the feeding body 5 are configured to return to their original positions.

[Problems to be Solved by the Invention]

However, in the conventional thread cutting device for a sewing machine as described above, the cutting end of the upper thread projects above the upper surface of the sewn item, which lowers the commercial value. The thread must be manually cut or drawn into the sewing object or on the back side thereof to be processed, which reduces the sewing work efficiency.

Also, when the bobbin thread is unwound, the thread tension on the bobbin side is weak due to the thread resistance at the connecting part of the upper and lower threads due to the variation in thread tension on the bobbin side, especially when sewing thin materials, and the bobbin side bobbin thread is fed out. The upper and lower threads are not pulled out to the back side of the cloth,
The cut upper thread residue protrudes to the front side of the cloth and is unsightly, so that good sewn product quality cannot be obtained. Therefore, when the pressure on the bobbin side is increased, there is a problem in that, in the case of a thin bobbin thread, bobbin thread breakage occurs.

 The present invention eliminates the above problems.

[Means for solving the problem]

A thread cutting device of a sewing machine of the present invention includes an upper thread cutting mechanism capable of cutting an upper thread connected to a thread hole of a sewing object and a needle above the needle plate and holding a thread end connected to the thread hole of the needle, and a needle plate. A sewing machine provided with a lower thread cutting mechanism for cutting a lower thread connected to a sewing object and a bobbin below with a fixed knife fixed to the lower surface of the needle plate base and a moving knife rotatably supported. In the thread cutting device of No. 1, the bobbin thread cutting mechanism includes a moving knife rotating arm having one end rotatably supported by the needle plate base and a moving knife at the other end, and the moving knife rotating arm. Revolving means for imparting reciprocating motion and rotatably supported on the other end side of the moving knife rotating arm to perform opening and closing operations in cooperation with the moving knife, and to the sewing object and bobbin. A lower thread drag plate having a feeding portion that engages a continuous lower thread and draws out a predetermined amount of the lower thread, and is fixed to the lower surface of the needle plate. A drive plate that engages with the bobbin thread drawing plate at the time of forward movement of the arm and controls the closing operation of the arm, and after returning the moving knife rotating arm, engages with the bobbin thread drawing plate in synchronization with the sewing machine main shaft, Drive means for imparting an opening operation to the bobbin thread drawing plate,
It is characterized by having.

[Work]

In the thread cutting device of the present invention, the bobbin thread bobbin holds the bobbin thread while holding the bobbin thread, and cooperates with the moving knife and the fixed knife while holding the bobbin thread at the tips of the fixed knife and the moving knife. The bobbin thread is cut with, and after the bobbin thread is cut, sewing is started with the bobbin thread held, and the bobbin thread is released after a few stitches.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a bottom view of a thread trimming device of a buttonhole overedging machine (hereinafter referred to as a sewing machine) as seen from the bottom of the sewing machine.
The same or corresponding parts as those of the conventional example are designated by the same reference numerals, and the present invention will be described below.

20 is provided with a blade portion 20a of a moving knife corresponding to the fixed knife 4 and a tip 20b of the moving knife on the tip portion, and the other base end is the needle plate base 2
A moving knife rotating arm rotatably supported by the step screw 10 on the lower surface of the
21 is a step screw 21 whose base is on the tip side of the moving knife rotating arm 20.
It is an L-shaped bobbin thread bobbin rotatably supported by a,
At the tip of one arm of this bobbin thread guide plate 21,
21b is formed, and a pin 21c is projectingly provided on the tip of the other arm.

Reference numeral 22 is a drive plate (hereinafter referred to as a stopper) that engages with the pin 21c, and the position of the stopper 22 can be slightly adjusted by using an elongated hole and a screw. Reference numeral 23 is a driving means for displacing the bobbin thread drawing plate 21 (the bobbin thread delivering portion 21b of the bobbin thread drawing plate 21 is opened in a scissor shape with respect to the tip 20b of the moving knife, which will be described later in detail). A lever 24 having a protrusion 24b rotatably supported by the frame by 24a
And a link 25, one end of which is connected to the lever 24, and a step screw 26a
An L-shaped drive lever 26 rotatably supported by the needle plate base 2 and having one arm engaging the pin 21c and an arm connecting to the other end of the link 25, and one end fixed to the frame. It is composed of a spring 27 whose other end is fixed to the lever 24 and constantly biased in the arrow direction.

Further, 28 is a link whose one end is rotatably connected to the moving knife rotating arm 20 by a step screw 13, and the other end is connected to one end of a lever 30 rotatably supported by the frame by a step screw 29. .
The other end of the lever 30 is connected to a pedal operating mechanism of a foot pedal (not shown).

In FIG. 6, 31 is the upper thread of the sewing machine, 32 is the lower thread,
Numeral 33 is a sewn object, 34 and 35 are needle thread cutting knives which are arranged opposite to each other and are supported by a support body fixed to a frame (not shown) and operate in relation to pedal operation (not shown), and 36 are thread supported by the support body and After cutting the upper thread 31 in cooperation with the cutting knife 34 and 35,
The upper thread 31 is sandwiched between several needles at the beginning of the next sewing, and the upper thread 31 is cut before the lower thread 32 is cut. Incidentally, 37 is a bobbin case.

The present invention is configured as described above, and the operation will be described below. FIG. 1 is a bottom view of the thread trimming device showing the completion of sewing of one cycle of the sewing machine. In this state, the tip 20b of the moving knife and the bobbin thread feeding portion 21b of the bobbin thread drawing plate 21 open in a scissor shape. ing. When the foot pedal is operated while the sewing machine is stopped, the upper thread 31 is cut in cooperation with the upper thread trimming knives 34 and 35, and the needle thread trimming knife 35 moves forward and backward. The upper thread 31 is sandwiched between the upper surface and the lower surface of the sandwiching body 36, and the state shown in FIG. 6 is obtained.

Next, the lever 30 interlocks with the pedal operating mechanism to pivot in the direction of the arrow shown when bobbin threading in FIG. 2 moves the link 28 in the direction of the arrow to move the moving knife pivot arm 20 via the step screw 13. It is pressed so that it rotates counterclockwise about the step screw 10. Therefore, the lower thread feeding portion 21b of the lower thread winding plate 21 is
The bobbin thread amount required for the next stitch is fed out from the bobbin case and dragged to move in a scissor-like closing direction with respect to the distal end 20b of the moving knife to come close to the fixed knife 4. Therefore, as shown in FIG. 7, the lower thread 32 is pulled out in the direction intersecting with the route between the sewing object 33 and the bobbin case 37 and the upper thread is pulled out.
Pull out the connecting portion between 31 and the bobbin thread 32 to the back side of the cloth, and close the tip 20b of the moving knife and the bobbin thread feeding part 21b of the bobbin thread drawing plate 21 like scissors to hold the bobbin thread 32 and give resistance. Becomes (first position).

Next, as shown in FIG. 3 at the end of bobbin thread trimming, the moving knife rotating arm 20 further rotates counterclockwise to move the bobbin thread drawing plate 21.
21c of the lower knife is engaged with the stopper 22, whereby the lower thread drawing plate 21 is rotated clockwise relative to the moving knife rotating arm 20, and at that position, the blade portion 20a of the moving knife and the fixed knife 4 are moved. The lower thread 32 is cut in cooperation with the lower thread feeding portion 21b of one arm of the lower thread drawing plate 21 and the tip 20b of the moving knife of the moving knife rotating arm 20.
Further closes like scissors and holds the lower thread 32 in the meantime.

Next, when the operation of the foot pedal is released and the sewing machine starts, the next sewing starts as shown in FIG.

That is, when the lever 30 returns in the direction of the arrow and the link 28 moves in the direction of the arrow, the moving knife rotating arm 20 rotates clockwise around the step screw 10, and the blade portion 20a of the moving knife moves the fixed knife 4 to the fixed knife 4.
A bobbin thread 32 is held between the bobbin thread drawing plate 21 and the tip 20b of the moving knife, although the bobbin thread 32 is separated from the bobbin thread.

On the other hand, the drive cam starts to push up the protrusion 24b by one cycle of rotation of the main cam provided with the drive cam provided on the lower surface of the sewing machine bed which is decelerated in conjunction with the main shaft (not shown). Then, since the lever 24 rotates clockwise around the step screw 24a, the link 25 moves in the arrow direction, and the L-shaped drive lever 26 rotates one arm around the step screw 26a in the arrow direction. Then, as shown in FIG.
It comes closer to the direction of the pin 21c.

FIG. 8 shows a state in which the bobbin thread 32 at the start of sewing is held by the tip 20b of the moving knife and the bobbin thread feeding portion 21b of the bobbin thread drag plate 21.

Next, in the state where several stitches have passed from the start of sewing, the drive lever 26 is further rotated, and one arm of the drive lever 26 is moved to the lower thread drawing plate 21.
Push up the pin 21c of. Therefore, the tip 20b of the moving knife and the bobbin thread delivering portion 21b of the bobbin thread drawing plate 21 are opened like scissors to release the bobbin thread 32 (second position), and the bobbin thread drawing plate 21 is further rotated. It moves and becomes as shown in FIG.
Sewing is performed as shown in the figure, and the sewing machine returns to the original state when the sewing in FIG. 1 is completed.

Further, in the above description, the lower thread feeding portion 21b of the lower thread winding plate 21 forms a holding means, and the moving knife rotating arm 20, the pin 21c of the lower thread winding plate 21, the stopper 22, the driving means 23, etc. It forms a mechanism for displacement. It should be noted that the moving knife rotating arm 20 and the driving means 23 may be configured with solenoids, air cylinders, or the like at the same timing.

〔The invention's effect〕

In the device of the present invention, the bobbin thread 32 is struck while being held by the blade portion 20a of the moving knife of the moving knife rotating arm 20 and the bobbin thread drawing plate 21, so that the upper and lower threads are not affected by the idle rotation of the bobbin. Since the connection points 31 and 32 are reliably pulled out to the back side of the cloth, there is no needle thread remaining, and it is possible to obtain good sewn product quality without the need to manually cut off the needle thread projecting on the upper surface of the workpiece.

Further, since the tip 20b of the moving knife and the bobbin thread feeding portion 21b of the bobbin thread drawing plate 21 retain the bobbin thread 32 even after the bobbin thread is cut, the upper thread and the lower thread 31, 32 are surely connected at the start of sewing, There is an advantage that the upper thread loss at the start of sewing is eliminated.

[Brief description of drawings]

1 to 5 are bottom views of the thread cutting device for mimin of the present invention,
6 to 9 are longitudinal sectional views of the main part thereof, and FIG. 10 is a bottom view of a lower thread cutting device of a conventional sewing machine. 1 ... Needle plate, 2 ... Needle plate base, 4 ... Fixed knife, 10, 13, 21
a, 24a, 26a, 29 …… Step screw, 20 …… Moving knife rotating arm, 20a…
… Blade of moving knife, 20b …… Tip of moving knife, 21… Lower thread drag plate, 21b… Lower thread feeding section, 21c… Pin, 22 ……
Drive plate (stopper), 24, 30 …… Lever, 24b …… Protrusion,
25, 28 …… Link, 26 …… Drive lever, 27 …… Spring, 31
...... Upper thread, 32 …… Lower thread, 33 …… Sewn object, 34,35 …… Upper thread trimming knife, 36 …… Clamping body, 37 …… Bobbin case.

Claims (1)

[Claims] 1. A needle thread cutting mechanism (34, 35, 36) capable of cutting an upper thread connected to a thread hole of a sewing object and a needle above a needle plate and holding a thread end connected to the thread hole of a needle. A bobbin thread cutting mechanism that cuts a bobbin thread connected to the sewing object and the bobbin below the needle plate by a fixed knife (3) fixed to the lower surface of the needle board base and a moving knife rotatably supported. In the thread cutting device of the sewing machine, the bobbin thread cutting mechanism has one end rotatably supported by the needle plate base (2) and the other end having a moving knife rotating arm ( 20), rotating means for imparting reciprocating motion to the moving knife rotating arm (20), and rotatably supported on the other end side of the moving knife rotating arm (20) so as to cooperate with the moving knife. The lower thread drag plate (21) having a feeding portion that engages with the lower thread connected to the workpiece and the bobbin and draws out a predetermined amount of the lower thread, and the lower needle plate. Is fixed to the moving knife times Doude (20)
After returning the drive plate (22) that engages with the bobbin thread drawing plate (21) and controls the closing motion of the bobbin thread moving plate (21) and the moving knife rotating arm (20), the lower part is synchronized with the sewing machine main shaft. A thread cutting device for a sewing machine, comprising: a drive means (23) which engages with the thread dragging plate (21) and gives an opening operation to the lower thread dragging plate (21).