JPH02213385A - Thread-cutting device for sewing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention includes a needle thread cutting mechanism that connects the sewing material and the thread hole of the needle above the throat plate, and a needle thread cutting mechanism that operates after cutting the needle thread and The present invention relates to a thread cutting device for a sewing machine, which is equipped with a bobbin thread cutting mechanism that pulls out and cuts the bobbin thread connected to the sewing material and the bobbin in a direction crossing the sewing path.

[Conventional technology]

Conventionally, after the needle and upper thread catcher work together to entangle the upper and lower threads to form a sticky joint in the material to be sewn, the upper and lower threads are moved above the throat plate and above the needle plate when the sewing machine is stopped, etc. There is a buttonhole sewing machine equipped with a separate cutting device, and the 10th
The figure shows the bobbin thread trimming mechanism viewed from the bottom of the sewing machine, where 1 is a needle plate supported on a needle plate stand 2, and 1a and 1b are needle holes and knife incision grooves formed through the needle plate 1. And throat plate stand 2
is supported by a sewing machine bed (not shown). Reference numeral 4 denotes a fixed knife fixed to one side of the lower surface of the throat plate stand 2 with a screw 3, and 5 is a thread letting out body that forms a thread letting out part 6 and whose base end is rotatably supported on the throat plate stand 2 with a stepped screw 7. A long hole portion 8 is provided which is long in the diagonal direction.

Reference numeral 9 denotes a movable knife which is equipped with a blade 9a corresponding to the fixed knife 4 and is rotatably supported on the lower surface of the throat plate base 2 by a stepped screw 10. It is loosely fitted into the hole 8, linked to the rotation of the feeding body 5, and activated with a predetermined time delay. Further, the blade 9a of the movable knife 9 is arranged below the thread letting-out portion 6 of the letting-out body 5, and is configured so that the thread letting-out portion 6 always lets out the bobbin thread, followed by the movable knife 9.

Reference numeral 12 has one end rotatably connected to the feeding body 5 by a stepped screw 13 through a link, and the other end is interlocked with a foot pedal operation mechanism.

In such a conventional lower thread cutting mechanism of a sewing machine, when sewing is completed, by pressing the foot pedal, the needle thread cutting unit 5 moves the fixed knife 4 before the movable knife 9 having the blade 9a.
After the bobbin thread is fed out by the required amount by the payout body 5, the fixed knife 4 and the movable knife 9 work together to cut the bobbin thread, and the pressure on the foot pedal is released. The movable knife 9 and the feeding body 5 are configured to be moved back to their original positions.

[Problem to be solved by the invention]

However, in the conventional sewing machine thread cutting device as mentioned above,
The cut end of the needle thread protrudes above the top surface of the material being sewn, reducing its commercial value.For this reason, in high-end products, the needle thread protruding above the surface of the material being sewn must be manually cut off after sewing, or the needle thread protruding above the surface of the material being sewn may be cut off or placed inside the material. The material must be pulled into the back side for processing, which reduces sewing efficiency.

Also, when the bobbin thread is pulled out, the thread tension on the boppin side may vary, especially when sewing thin fabrics, because the thread tension on the boppin side is weaker than the thread resistance at the sticky part of the upper and lower threads, and the bobbin thread on the boppin side may be unwound. Therefore, the adhesive part of the upper and lower threads is not pulled out to the back side of the fabric, and the cut needle thread remains protrudes to the front side of the fabric, making it unsightly and making it impossible to obtain good sewing quality. Therefore, if the pressure on the boppin side is strengthened, there are problems such as the lower thread breaking if the lower thread is thin.

The present invention is intended to eliminate the above problems.

[Means to solve the problem]

The thread cutting device of the sewing machine of the present invention includes a fixed knife fixed to the lower surface of the throat plate base having a needle hole, a base end rotatably supported on the lower surface of the throat plate base, and a distal end cooperating with the fixed knife. a movable knife rotating arm having a blade portion of a movable knife that cuts the bobbin thread extending into the needle hole; a bobbin thread retrieval plate rotatably supported by the movable knife rotating arm; When the lower thread holding means provided on the lower thread pulling plate for holding and pulling the lower thread after forming the stitches and the moving knife rotating arm rotate and the blade portion of the moving knife approaches the fixed knife, The lower thread holding means cooperates with the tip of the rotating knife rotating arm to hold the lower thread, and the blade of the moving knife cooperates with the fixed knife to cut the lower thread. 1 position, and a second position in which, when the blade of the moving knife returns from the stationary knife, the bobbin thread holding means separates from the tip of the movable knife rotating arm to release the bobbin thread; The present invention is characterized by comprising a mechanism for rotating the bobbin thread retrieval plate relative to the movable knife rotating arm between the two.

[For production]

In the thread cutting device of the sewing machine of the present invention, the bobbin thread pulling plate pulls the bobbin thread while holding the bobbin thread, and the tips of the fixed knife and the movable knife hold the bobbin thread, and then the movable knife and the fixed knife cooperate with each other. The bobbin thread is cut by the action, and even after the bobbin thread is cut, sewing begins while holding the bobbin thread, and after a few seconds, the bobbin thread is released.

〔Example〕

The present invention will be explained in detail below with reference to the drawings.

Figure 1 shows a buttonhole sewing machine (hereinafter referred to as the sewing machine)
FIG. 2 is a bottom view of the thread trimming device of FIG.

20 is equipped with a moving knife blade 2Qa corresponding to the fixed knife 4 and a moving knife tip 20b at the tip, and the other base end is rotatably supported on the lower surface of the throat plate base 2 by a step screw 10. The movable knife rotating arm 21 is an L-shaped bobbin thread pulling plate whose base is rotatably supported on the distal end side of the movable knife rotating arm 20 with a stepped screw 21a. A bobbin thread letting-out portion 21b is formed at the tip of one arm, and a pin 21C is provided protruding from the tip of the other arm.

Reference numeral 22 denotes a drive plate (hereinafter referred to as a stopper) that engages with the pin 21c, and the stopper 22 can be slightly adjusted in position using a long hole and a screw. 23 is a driving means for displacing the bobbin thread pulling plate 21 (details will be described later, but opening the bobbin thread letting-out portion 21b of the bobbin thread pulling plate 21 in a scissor-like manner relative to the tip 20b of the moving knife); A protrusion 2 rotatably supported on the frame by a screw 24a
4b, a link 25 whose one end is connected to the lever 24, and a stepped screw 26a to freely rotate the throat plate base 2.
an L-shaped drive lever 26 that is supported by the lever 2 and has one arm that engages with the pin 21c and an arm that connects to the other end of the link 25;
4 and a spring 27 that is always biased in the direction of the arrow.

Further, 28 is a link whose one end is rotatably connected to the movable 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, 33 is the object to be sewn, and 34 and 35 are supported by supports fixed to a frame (not shown), and are operated in conjunction with the operation of a pedal (not shown). Upper thread trimmers 36, which are arranged opposite to each other, are supported on the support body and cooperate with the upper thread trimmers 34 and 35 to cut the upper thread 31.
After cutting the upper thread 31, the upper thread 31 is held between the upper thread 31 and the upper thread 31 during the next sewing start count, and the upper thread 31 is cut before the lower thread 32 is cut. There is. Note that 37 is a bopin case.

The present invention has the above configuration, and its operation will be explained next. 1st
The figure is a bottom view of the thread cutting device showing the end of one cycle of sewing of the sewing machine. In this state, the tip 20b of the moving knife and the bobbin thread unwinding portion 21b of the bobbin thread retrieval plate 21 are opened in the shape of scissors. . When the foot pedal is operated while the sewing machine is stopped, the needle thread 31 is cut in cooperation with the needle thread trimming knives 34 and 35, and the needle thread trimming knife 35 is cut in conjunction with this operation. The needle thread 31 is held between the upper surface and the lower surface of the holding body 36, resulting in the state shown in FIG.

Next, the lever 30 interlocks with the pedal operation mechanism and rotates in the direction of the arrow shown when pulling the bobbin thread in FIG. When pressed, it is rotated counterclockwise around the step screw 10. Therefore, the bobbin thread letting out part 21b of the bobbin thread pulling plate 21 moves in a scissor-like direction toward the tip 20b of the movable knife while letting out the amount of bobbin thread necessary for the next stitch from the boppin case, and fixes it. Becomes closer to Female 4. Therefore, as shown in FIG. 7, the bobbin thread 32 is pulled out between the workpiece 33 and the boppin case 37 in a direction crossing the path thereof, and the joint between the needle thread 31 and the bobbin thread 32 is pulled out to the back side of the fabric. At the same time, the tip 20b of the movable knife and the bobbin thread reeling-out portion 21b of the bobbin thread pulling plate 21 close in a scissor-like manner to remove the thread 3.
2 to provide resistance (first position).

Next, as shown at the end of the bobbin thread trimming in FIG.
The pin 21c of No. 1 engages with the stopper 22, whereby the bobbin thread pulling plate 21 is rotated clockwise relative to the moving knife rotating arm 20, and at the 6th position, the blade portion 20a of the moving knife and the fixed knife are rotated. 4 cuts the bobbin thread 32, and the bobbin thread letting-out portion 21b of one arm of the bobbin thread retrieval plate 21 and the tip 20b of the movable knife of the movable knife rotating arm 20 further close into a scissor-like shape. The lower thread 32 is now held.

Next, when the operation of the foot pedal is released and the sewing machine is started, the next time sewing begins will be 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 movable knife rotating arm 20 rotates clockwise around the step screw 10, and the blade portion 20a of the movable knife moves toward the fixed knife 4. However, the lower thread 32 is held between the lower thread pulling plate 21 and the tip 20b of the moving knife.

On the other hand, the drive cam begins to push up the protrusion 24b due to one cycle of rotation of the main cam, which is provided with a drive cam provided on the lower surface of the sewing machine bed and is decelerated in conjunction with a main shaft (not shown). Then, the lever 24 rotates clockwise around the shoulder screw 24a, so the link 25 moves in the direction of the arrow, and one arm of the L-shaped drive lever 26 rotates in the direction of the arrow around the shoulder screw 26a. Then, as shown in FIG. 4, it approaches the pin 21C of the bobbin thread pulling plate 21.

Figure 8 shows that the bobbin thread 32 at the beginning of sewing is at the tip 20b of the moving knife.
A state in which the thread is held by the lower thread pulling-out portion 21b of the lower thread pulling plate 21 is shown.

Next, after a few seconds have elapsed since the start of sewing, the drive lever 26 rotates further, and one arm of the drive lever 26 moves toward the bobbin thread pulling plate 2.
Push up pin 21c of No. 1. Therefore, the tip 2 of the moving scalpel
0b and the bobbin thread unwinding portion 21b of the bobbin thread pulling plate 21 are opened like scissors to release the bobbin thread 32 (second position), and the bobbin thread pulling plate 21 further rotates as shown in FIG. 9, the sewing is performed as shown in FIG. 9, and the sewing returns to the state shown in FIG. 1 when the sewing is completed.

In addition, in the above description, the holding means is formed by the lower thread letting-out portion 21b of the lower thread pulling plate 21, the moving knife rotating arm 20, the pin 21c1 of the lower thread pulling plate 21, the stopper 22, and the driving means 2.
It forms a mechanism that causes displacement at 3rd grade. Note that the movable knife rotating arm 20 and the driving means 23 may be configured using solenoids, air cylinders, etc., with their respective timings aligned.

〔Effect of the invention〕

In the device of the present invention, the bobbin thread 32 is drawn while being held by the movable knife blade 20a of the movable knife rotating arm 20 and the bobbin thread pulling plate 21, so that the bobbin thread 32 is not affected by the idle rotation of the boppin. Since the sticky contact points 31 and 32 are reliably drawn out to the back side of the cloth, there is no remaining needle thread, and it is possible to obtain good sewing quality without having to manually cut off the needle thread protruding from the upper surface of the workpiece.

In addition, since the tip 20b of the moving knife and the lower thread feeding portion 21b of the lower thread pulling plate 21 hold the lower thread 32 even after the lower thread is cut, the upper and lower threads 31 and 32 are securely attached at the beginning of sewing. This has the advantage of eliminating the needle thread coming out at the beginning of sewing.

9... Stacking, 20... Moving knife rotating arm, 20a...
・Blade of moving knife, 20b... Tip of moving knife, 21...
・Lower thread retrieval plate, 21b...Lower thread unwinding part, 21c
... Pin, 22 ... Drive plate (stopper), 24.3
0...Lever, 24b...Protrusion, 25.28...
Link, 26... Drive lever, 27... Spring, 31
... Upper thread, 32 ... Lower thread, 33 ... Material to be sewn, 34
゜35... Needle thread trimming knife, 36... Holding body, 37...
...Bopin case.

[Brief explanation of the drawing]

1 to 5 are bottom views of the thread cutting device of the sewing machine of the present invention,
6 to 9 are longitudinal cross-sectional views of the main parts thereof, and FIG. 10 is a bottom view of the needle thread trimming device of a conventional sewing machine. 1... Throat plate, 2... Throat plate stand, 4... Fixed knife, 1
0.13.21a, 24a, 26a, 2-day criminal plot drawing A7

Claims (2)

[Claims] (1) A fixed scalpel fixed to the lower surface of the throat plate base having a needle hole, a base end rotatably supported on the lower surface of the throat plate base, and a distal end that cooperates with the fixed knife to form the needle hole. A movable knife rotating arm equipped with a movable knife blade for cutting the bobbin thread extending from the movable knife, a bobbin thread pulling plate rotatably supported by the movable knife rotating arm, When the lower thread holding means provided on the lower thread pulling plate for holding and pulling the lower thread and the rotating arm of the moving knife rotate and the blade of the moving knife approaches the fixed knife, the lower thread holding means a first position in which the movable knife cooperates with the tip of the rotating arm to hold the bobbin thread, and the blade of the movable knife cooperates with the stationary knife to cut the bobbin thread; When the knife blade returns from the fixed knife, the bobbin thread is pulled between a second position where the bobbin thread holding means separates from the tip of the movable knife rotating arm and releases the bobbin thread. A thread cutting device for a sewing machine, comprising a mechanism for rotating a plate relative to the rotating arm of the moving knife. (2) The bobbin thread pulling plate has an L-shape with a thread feeding portion formed at the tip of one arm and a pin at the tip of the other arm, and the bobbin thread pulling plate is connected to the movable knife. The sewing machine thread according to claim 1, wherein the mechanism for rotating the rotating arm relative to the rotating arm includes a drive plate provided near the fixed knife, and a drive lever provided on the opposite side of the drive plate via the pin. Cutting device.