JP3531524B2 - Sewing machine lower thread cutting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lower thread cutting device for a sewing machine, which is provided in a sewing machine and cuts a lower thread after forming a seam on a work cloth.

[0002]

2. Description of the Related Art Conventionally, as a lower thread cutting device of this kind, a lower thread cutting means such as scissors, which is disposed below a needle plate of a sewing machine and cuts a lower thread after forming a seam on a work cloth,
Those equipped are known. Further, this bobbin thread cutting device is provided with bobbin thread holding means for holding the bobbin thread at a predetermined position below the bobbin thread cutting position by the bobbin thread cutting means after the formation of the seam, so that the bobbin thread is stably cut. It may be possible to execute it.

[0003]

However, conventionally, it has not been considered to provide a structure corresponding to the lower thread holding means as a structure completely independent of the lower thread cutting means. Therefore, when power is transmitted to the bobbin thread cutting means and the bobbin thread holding means via a link mechanism or the like, the bobbin thread holding and the bobbin thread cutting are performed in parallel. Then, the bobbin thread is cut before the bobbin thread is completely held, and the operation of the bobbin thread holding means continues even during the bobbin thread cutting. Therefore, conventionally, the position where the bobbin thread is actually cut is not stable, and the end portion of the bobbin thread left on the back side of the work cloth is also lengthened or shortened. On the other hand, when the bobbin thread is cut after the formation of the seam, it is required to make the end of the bobbin thread left on the back side of the work cloth as short as possible in order not to impair the aesthetic appearance of the work cloth. Further, when the lower thread is held and the lower thread is cut in parallel in this way, the once held lower thread may be pulled out by the cutting operation. For this reason, conventionally, the bobbin thread could not be stably held, and when the next sewing was started, the bobbin thread could not be captured and the seam could not be formed.

Therefore, according to the present invention, the position where the lower thread is cut is stabilized, the end portion of the lower thread left on the back side of the work cloth is shortened favorably, and the lower thread is reliably secured for the next sewing. The purpose of the present invention is to provide a lower thread cutting device for a sewing machine that can be held.

[0005]

The invention according to claim 1 made in order to achieve the above object, is arranged below the needle plate of the sewing machine, and the lower thread is formed after the formation of the seam on the work cloth. A lower thread cutting means for cutting the lower thread, a lower thread holding means for holding the lower thread at a predetermined position below the lower thread cutting position by the lower thread cutting means, the lower thread cutting means and the lower thread cutting means. a lower thread cutting device of a sewing machine provided with a link mechanism for transmitting power to the lower thread holding means, the pressing
It is arranged above the work cloth, and the upper thread is cut after the seam is formed.
The upper thread cutting means for cutting and the upper thread disposed below the needle plate.
After the upper thread is cut by the upper thread cutting means, the cut upper thread
Under the work cloth with the end of the thread and the lower thread entwined with the upper thread
And pulling down the lower thread, and separating the lower thread by the lower thread
The link mechanism further drives the lower thread holding means to hold the lower thread before the lower thread is cut by the lower thread cutting means, The bobbin thread when the bobbin thread cutting means is driven after the thread holding means is stopped to cut the bobbin thread and the bobbin thread is held.
The drive amount of the holding means is changed by the separation amount changing means.
The feature is that it is constant regardless of the change in the amount .

According to the present invention thus constructed, the lower thread cutting means is disposed below the needle plate of the sewing machine and cuts the lower thread after the seam is formed on the work cloth, and the lower thread is cut after the seam is formed. Bobbin thread holding means for holding the bobbin thread at a predetermined position below the position where the bobbin thread is cut by the thread cutting means. The link mechanism that transmits power to the lower thread cutting means and the lower thread holding means drives the lower thread holding means to hold the lower thread before cutting the lower thread by the lower thread cutting means, and then holds the lower thread. After stopping the means, the lower thread cutting means is driven to cut the lower thread. As described above, in the present invention, the bobbin thread is held by driving the bobbin thread holding means before cutting the bobbin thread by the bobbin thread cutting means, so that the bobbin thread can be reliably held. Also,
Since the lower thread is cut by the lower thread cutting means after the lower thread holding means is stopped, the lower thread can be reliably cut at a stable position.

Therefore, in the present invention, the position where the bobbin thread is cut can be stabilized and the end portion of the bobbin thread left on the back side of the work cloth can be shortened satisfactorily. It is also possible to secure good. Further, in the present invention,
As the bobbin thread can be held securely as described above,
Next, when sewing is started, the lower thread can be properly captured and the seam can be reliably formed.

Further, as described above , the present invention is arranged above the work cloth and arranged below the needle plate, and needle thread cutting means for cutting the upper thread after forming the seam. After the upper thread is cut by the upper thread cutting means, a lower thread handle for pulling the end portion of the cut upper thread together with the lower thread entwined with the upper thread to the lower side of the work cloth, and the lower thread by the lower thread handle Further comprising a loosening amount changing means for changing the loosening amount, and the link mechanism changes the drive amount of the lower thread holding means when holding the lower thread to change the loosening amount by the loosening amount changing means. is constant regardless.

In the present invention, the upper thread cutting means arranged above the work cloth cuts the upper thread after the formation of the seam. Further, the bobbin thread separator arranged below the needle plate is a work cloth together with a bobbin thread entwined with the bobbin thread after cutting the bobbin thread by the bobbin thread cutting means. To the bottom of. Therefore, the end of the upper thread does not remain on the surface of the work cloth,
The aesthetics of the work cloth can be more favorably secured. Moreover, the loosening amount of the lower yarn due to the lower yarn handling can be changed by the loosening amount changing means. Therefore, even when the thickness of the work cloth, the thickness of the lower thread, or the like changes, the upper thread can be properly pulled out below the work cloth, and the appearance of the work cloth can be secured.

Further, in the present invention, the link mechanism makes the drive amount of the lower thread holding means for holding the lower thread constant regardless of the change in the loosening amount by the loosening amount changing means. Therefore, even when the loosening amount is changed, the bobbin thread holding means similarly holds the bobbin thread, and the bobbin thread holding means continues to operate while the bobbin thread cutting means cuts the bobbin thread. It is possible to favorably prevent the occurrence of a situation. Therefore,
The above-described effect is ensured regardless of whether or not the handling amount is changed by the handling amount changing means.

Therefore, according to the present invention, in addition to the above-mentioned effects, it is possible to surely prevent the end portion of the upper thread from remaining on the surface of the work cloth, so that the appearance of the work cloth can be more excellently secured. The effect occurs. The invention described in claim 2 is claim 1
In addition to the serial mounting of the arrangement, the position where the lower yarn holding means for holding the lower yarn is characterized in that it is fixed at a predetermined position of the needle plate near.

In the present invention, the position where the lower thread holding means holds the lower thread is fixed at a predetermined position near the needle plate, and the position does not change even during operation of the lower thread cutting device. For this reason,
The position where the lower thread is cut can be further stabilized, and the end portion of the lower thread left on the back side of the work cloth can be further shortened. Further, since the predetermined position is fixed near the throat plate, the bobbin thread can be captured very well when the next sewing is started.

[0013] Thus, in the present invention, in addition to the effect of the invention of claim 1 Symbol placement, the ends of the lower thread to be left on the back side of the workpiece cloth by better shorten the appearance of the work cloth more satisfactorily secured At the same time, the next time when sewing is started, the bobbin thread can be captured better and the stitch can be formed more reliably.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the appearance of a buttonhole sewing machine M to which the present invention is applied. In addition, this overhollow sewing machine M forms overhollow stitches 100 (see FIG. 12) on a work cloth W (see FIG. 13), cuts between the zigzag stitches 101 and 102 of the overhollow stitch 100, and presses the button. This is a buttonhole sewing machine for a so-called button hole that forms the hole 110.

As shown in FIG. 1, a buttonhole sewing machine M
Includes a sewing machine motor 2, a pedal 3 for starting or stopping the sewing machine motor 2, an operation panel 4 for inputting various data for forming a boring stitch 100 and a button hole 110. , And a control device 5 and the like for performing drive control of each unit described later.

The overhollow sewing machine M has a bed portion 6, a pedestal portion 7 and an arm portion 8, and as shown in FIG. 2, a sewing mechanism 10 for forming a overhollow stitch 100 on a work cloth W.
And a feed table 11 for feeding the work cloth W, and a feed table drive mechanism 12 for driving the feed table 11 in the cloth feed direction (see FIG. 3).
And the zigzag seam 10 of the overlaid seam 100 of the work cloth W
A cutter 13 that cuts between 1 and 102 to form a button hole 110 and a cutter driving mechanism (not shown) that drives the cutter 13 up and down are provided.

As shown in FIG. 2, the sewing mechanism 10 includes a needle bar 15 provided on the head 8a of the arm section 8, a sewing needle 16 detachably attached to the lower end of the needle bar 15, and a needle bar. 15
Needle-bar drive mechanism 1 that reciprocates up and down and swings left and right
7 (see FIG. 5) and a hook (not shown) that is provided in the bed portion 6 and cooperates with the sewing needle 16 to form a holed stitch. Then, by driving the sewing mechanism 10 while feeding the work cloth W by the feed table 11, it is possible to form the overlock stitch 100 shown in FIG. As shown in FIG. 12, the overhole stitch 100 has a left zigzag stitch 101 and a right zigzag stitch 102, and further has a front bartack stitch 103 at its front end and an inner bartack stitch at its rear end. 104 respectively. During normal sewing, part of the front bar-tacking stitches 103, the left zigzag stitch 101, the back bar-tacking stitch 104, and the right zigzag stitch 10 are made.
2. The seam is formed in the order of the remaining part of the front bar-tacking seam 103.

Next, the feed table 11 and the feed table drive mechanism 12 described above will be described. As shown in FIGS. 2 and 3, the feed table 11 is formed in a plate shape that is long in the front-rear direction, and its front end portion has
An elongated hole 11a for forming the overholstered seam 100 and the button hole 110 is formed. A pair of left and right guide plates 20 are fitted on the upper surface of the bed portion 6, and a feed base 11 is guided and supported between the guide plates 20 so as to be movable back and forth.

The feed base drive mechanism 12 includes a movable member 21 fixed to the lower surface of the rear end of the feed base 11, and a movable member 22 fixedly connected to the movable member 21 by a connecting rod 23 which is long in the front-rear direction. A stepping motor 24 that drives the movable member 22 back and forth by a mechanism described below is provided.

The connecting rod 23 extends through the left end portions (rear side in FIG. 3) of the movable members 21 and 22 and extends.
A pair of bearings 25 are provided on both sides of the front and rear of the sewing machine 1, 22 so as to be supported by the sewing machine frame so as to be movable back and forth. In addition, on the right side of the connecting rod 23, a long rod 26
Is fixedly provided, and the right end of the movable member 22 is guided and supported by the rod 26 via a bearing 22a so as to be movable back and forth.

A drive pulley 27 is fixed to the output shaft of the stepping motor 24, and a driven pulley (not shown) is fixedly provided on the sewing machine frame behind the drive pulley 27, and an endless belt 28 is provided on both pulleys. It has been passed over. When the above-mentioned movable member 22 is fixed to a part of the belt 28 and the stepping motor 24 is driven, the feed base 11 is driven back and forth together with the movable members 22 and 21.

By the way, the movable member 22 is connected to a rear end portion of a presser arm 30 having a front end portion to which a cloth presser 31 is attached so as to be rotatable about an axial center in the left-right direction. The presser foot 31 is moved up and down by a cloth presser drive mechanism 33 (see FIG. 4), which will be described later, due to engagement between the groove 30a formed on the front upper surface of the presser arm 30 and the rolling roller 32.
Connected to 5. Therefore, the presser foot 31 moves up and down integrally with the presser bar 35 in the up-down direction, and the groove 3 moves in the front-rear direction.
It is possible to move within the range of 0a. Further, the above-mentioned cutter driving mechanism is mainly configured by a cutter driving solenoid 39 (see FIG. 11), and the cutter 13 is screwed to the cutter holder 41 at the lower end of the cutter mounting shaft 40 which is vertically moved by the cutter driving mechanism. It is attached via 41a.

Next, as shown in FIG. 4, the presser foot drive mechanism 33 is provided with L-shaped link pieces 43 and 44 which can be swung about the axis in the left-right direction in the front and rear of the arm portion 8 and the presser bar. 35 and a link member 45 extending in the up-down direction that is pin-connected between the L-shaped link piece 43 on the front side and one end of the L-shaped link piece 43 on the front side.
A vertically long link member 46 pin-connected between one end of the mold link piece 44 and a link member 65 (see FIG. 6) described later.
And a long link member 47 which is pin-joined between the other ends of the L-shaped link pieces 43, 44. The link member 46 is provided with a pin 46a protruding therefrom.
At one end 48 of a cam 48 that swings about a horizontal axis
a is engaged. Further, the other end 48b of the cam 48 is engaged with a pin 49a which is circularly moved in the vertical plane by the stepping motor 49, and the rotation of the stepping motor 49 is converted into vertical movement of the link member 46 by this cam 48. can do.

Then, the vertical movement of the link member 46 is L
Type link piece 44, link member 47, L type link piece 43,
It is transmitted to the presser bar 35 via the link member 45 in order. For this reason, in the presser foot drive mechanism 33, the presser foot 31
According to the rotation angle of the stepping motor 49 to an arbitrary height between the cloth pressing position for pressing the work cloth W by the cloth pressing member 31 and the maximum rising position where the cloth pressing member 31 is lifted to the maximum. Can be made.

Next, FIG. 5 is a perspective view showing the structure of the needle bar drive mechanism 17. As shown in FIG. 5, in the needle bar drive mechanism 17, the above-mentioned needle bar 15 is supported by a needle bar base 51 provided on the arm 8 so as to be swingable in the vertical direction. A needle bar holder 52 is fixed to the needle bar 15 at a predetermined position.

On the other hand, the other end 53b of the needle bar connecting rod 53, whose one end 53a moves circularly along a circle C in the vertical plane, has a corner piece 54.
It is connected to the needle bar holder 52 via. A guide groove 52a having a rectangular cross section in the left-right direction is formed on the side of the corner bar 54 of the needle bar holder 52, and the corner block 54 engages with the guide groove 52a so as to be movable in the left-right direction. Further, a corner piece 55 is provided on the opposite side of the other end 53b of the needle bar connecting rod 53 from the side where the corner piece 54 is provided. By engaging the square piece 55 with the vertical groove 56a of the needle bar continuous rod guide 56, the other end 53b of the needle bar continuous rod 53 is guided so as to be movable only in the vertical direction. Further, a flat needle bar guide 57 is fixed to the side surface of the needle bar base 51. The needle bar guide 57 is formed with an elongated hole 57a extending along the needle bar 15, and a projection 52b protruding from the side surface of the needle bar holder 52 is engaged with the elongated hole 57a. Further, at the lower end of the needle bar base 51, the rotation of the stepping motor 61 is an endless belt 6.
The tip of a swing lever 62 that swings by being transmitted via 1a is connected via a square piece 63.

In the needle bar drive mechanism 17 constructed as described above, the force applied to the needle bar connecting rod 53 from the upper shaft 64 which is rotationally driven by the sewing machine motor 2 is transmitted to the needle bar 15 via the angular piece 54. Therefore, the needle bar 15 can be moved up and down. Further, the force applied from the stepping motor 61 to the swing lever 62 is applied to the needle bar base 51 via the square top 63.
And the needle bar 15 can be swung left and right. Then, by swinging the needle bar 15 left and right in accordance with the vertical movement of the needle bar 15 and feeding the cloth through the feed base 11, it is possible to form the above-described overlock stitch 100 and the like. .

FIG. 6 is a left side view showing the structure in the vicinity of the lower end 46b of the link member 46 from the back side direction of FIG. As shown in FIG. 6, the lower end 46b of the link member 46 extends to the inside of the bed portion 6, and the lower end 46b is one end 6 of the link member 65 that is swingable about a horizontal axis 65a.
It is pin-coupled to 5b. A pin 65c is erected on the other end of the link member 65, and the pin 65c is a cam hole 67b of a cam plate 67 that is swingable about a shaft 67a in the left-right direction.
Is engaged with.

The cam hole 67b is formed in an arc shape centered on the shaft 65a in the section of the angle α from the lower end, and is formed so that the distance from the shaft 65a gradually increases in the section of the subsequent angle β. The upper part thereof is formed in an arc shape centered on the shaft 65a. Therefore, from the state in which the link member 46 moves up most and the presser foot 31 is present at the presser foot position (shown by the solid line in FIG. 6), the link member 46 slightly descends and the link member 65 swings in the section of the angle α. While moving, the cam plate 67 does not swing at all. Subsequently, the link member 46 further descends, and the link member 65 swings in the section of the angle β, while the cam plate 67 gradually swings in the counterclockwise direction in FIG. Further, even if the link member 65 further swings beyond the section of the angle β, the cam plate 67 does not swing at all.

The rear end 69a of the link member 69 is pin-connected to the upper end of the cam plate 67. This link member 69
Extends forward in parallel with the surface of the bed portion 6, and its tip 69b has link members 71, 7 as shown in FIG.
3 is connected to the lower thread cutting mechanism 70. Therefore, the link member 69 moves back and forth only during the period in which the link member 65 swings in the section of the angle β, whereby the driving force of the stepping motor 49 is transmitted to the bobbin thread cutting mechanism 70 described below.

FIG. 7 is a bottom view showing the structure of the lower thread cutting mechanism 70. As shown in FIG. 7, the bobbin thread cutting mechanism 70 is
Shafts 77a, 78a provided vertically on the lower surface of the needle plate 75,
Lever 79 swinging around 79a and 79a, bobbin thread handling 7
8 and a lower thread grip 79. In addition, bobbin thread handling 7
8 is composed of a support portion 80 in which a pin 80a is erected at the tip and a lower thread handling body 81 having a notch 81a at the tip, and a screw 82 is screwed through a slot (not shown) The threading main body 81 and the support portion 80 are connected so that the mounting angle can be finely adjusted in the swinging direction. Pin 8
0a is engaged with a cam hole 77b provided at the tip of the lever 77, and the lever 77 is pin-connected to the above-mentioned link member 73. Therefore, when the link member 69 swings back and forth as described above, the lever 77 and the bobbin thread separating 78
Swings around the shafts 77a and 78a. Further, the outer peripheral surface adjacent to the notch 81a at the tip of the lower thread handling body 81 is a cam surface 81b, and the pin 7 erected on the lower thread grip 79 is provided.
When the cam surface 81b comes into contact with 9b, the lower thread grip 79 swings clockwise in FIG.

Like the well-known overlock stitch sewing machine, the needle plate 75 is inserted with an elongated needle hole 75a in the left-right direction (the swinging direction of the needle bar base 51) and the tip of the cutter 13 when the button hole is formed. A cutter hole 75b is formed. Further, on the lower surface of the needle plate 75, a concave portion 75c is formed which includes the periphery of the needle hole 75a and the cutter hole 75b and constitutes a moving space for the scissors 83 described below. Scissors 83
The bobbin thread fixing blade 85 fixed to the lever 77 and the bobbin thread movable blade 87 swinging around the pin 85a provided upright on the bobbin thread fixing blade 85 are provided. The thread movable blade 87 is held in pressure contact with a clasp 89 and a disc spring (not shown). At the front side (left side in FIG. 7) end edge of the bobbin thread movable blade 87, left and right protrusions 87a,
87b is formed, and as will be described later, the inner wall surface on the front side of the recessed portion 75c is a cam surface 75d that abuts on the protruding portions 87a and 87b and swings the lower thread movable blade 87.

Further, a hook 79 is provided at the tip of the lower thread grip 79.
c is formed, and a lower thread gripping spring 91 is fixed to the lower surface of the needle plate 75 so as to come into pressure contact with the lower surface of the lower thread grip 79.
The lower thread gripping spring 91 is composed of a leaf spring having a notch 91a on the front side and, as described later, cooperates with the hook 79c to grip the lower thread S (see FIG. 13).

As shown in the perspective view of FIG. 8 (A) and the top view of FIG. 8 (B), the upper thread movable blade 95 cuts the upper thread T (see FIG. 13) near the cloth presser 31. An upper thread cutting mechanism 99 is provided. Power is transmitted to the upper thread movable blade 95 from the above-mentioned link member 47 (FIG. 4) through a link mechanism (not shown), and as shown in FIG. 8B, the upper thread movable blade 95 is Hole portion 31a formed in 31
The upper thread T that connects the work cloth W and the sewing needle 16 through this is cut. In the needle thread movable blade 95, the link member 65 has the above-mentioned angle α.
The operation is finished while moving the section (Fig. 6), and the upper thread T is cut during this period.

As will be described later, when the overlock stitch machine M forms the overlock stitch 100 and the overlock stitch machine M is stopped, the stepping motor 49 rotates in the direction of pushing down the link member 46. Then, accordingly, the link member 65 swings in the counterclockwise direction in FIG. 6 in the section of the angle α, and the needle thread T is cut during this. Subsequently, the link member 65 swings in the counterclockwise direction in FIG. 6 in the section of the angle β, during which the bobbin thread S is cut as described below. When the link member 46 is further pushed down and the link member 65 further swings in the counterclockwise direction in FIG. 6, the thread trimming operation or the like is not executed during this time, and the presser foot 31 according to the lowering of the link member 46.
Only the ascent of is performed.

Here, the link member 65 swings counterclockwise in the section of the angle β, and accordingly the link member 69.
The operation of the bobbin thread cutting mechanism 70 when the retreat is performed will be described.
First, during sewing of the overholstered stitch 100, the link member 69 is disposed at the most advanced position, and the bobbin thread cutting mechanism 70 is provided.
The respective members are disposed at the positions shown in FIG.

The link member 65 swings in the section of the angle β,
As the link member 69 moves backward, the lever 77 is moved to the position shown in FIG.
Rocks in the clockwise direction at. Since the cam hole 77b of the lever 77 is configured to push the pin 80a forward in the initial stage of this swinging, at this time, the bobbin thread handling 7
8 also swings clockwise in FIG. Then, the notch 81a of the lower thread handling body 81 catches the lower thread S connecting the work cloth W and the shuttle (not shown) through the needle hole 75a and pulls it in the swinging direction. Thereby, as will be described later, the end Ta of the upper thread T cut by the upper thread cutting mechanism 99 is pulled out below the work cloth W together with the lower thread S entangled in the upper thread T. The lower thread handling 78 causes the lower thread S to be hooked on the hook 79c of the lower thread grip 79.

When the lever 77 is further swung, and the bobbin thread separating member 78 is further swung accordingly, as shown in FIG. 9A, the cam surface 81b of the bobbin thread separating main body 81 is moved to the lower thread gripping 79. It abuts the pin 79b. When the bobbin thread handling 78 further swings, as shown in FIG.
By pushing b backward, the lower thread grip 79 swings clockwise in FIG. In addition, the lower thread handling 78 is shown in FIG.
When the pin 80a swings to the position shown in (B), the pin 80a engages with a portion of the cam hole 77b formed in an arc shape centered on the shaft 77a. Therefore, even if the lever 77 swings further, the lower thread handling 78 does not swing. The surface 81c of the lower thread handling body 81 that follows the cam surface 81b is formed in an arc shape centered on the shaft 78a. Therefore, after the bobbin thread grip 79 has swung to the position shown in FIG. 9B, the position of the bobbin thread grip 79 does not change even if the bobbin thread handling 78 may rock further. Therefore, even if the attachment angle between the support portion 80 and the bobbin thread separating main body 81 is adjusted by the screw 82 and the bobbin thread separating amount by the bobbin thread separating 78 is changed,
The drive amount and operation timing of the lower thread grip 79 do not change.

In this way, when the bobbin thread grip 79 swings to the position shown in FIG. 9 (B), the bobbin thread handling 78 is shown in FIG. 10 (A).
As shown by omitting, the hook 79c is arranged at a position where the hook 79c bites a predetermined amount along the upper surface of the notch 91a of the lower thread gripping spring 91. Therefore, the lower thread S is reliably held between the hook 79c and the notch 91a.

At this time, the protruding portion 87b of the lower thread movable blade 87 contacts the cam surface 75d, so that the scissors 8
3 begins to close. Then, when the pin 80a reaches the end of the cam hole 77b and the swing of the lever 77 stops (which coincides with the time when the link member 65 swings in the section of the angle β and the backward movement of the link member 69 stops). As shown in FIG. 10B, the tips of the lower thread movable blade 87 and the lower thread fixed blade 85 are completely overlapped with each other, and the lower thread S stretched between the work cloth W and the hook 79c is scissors 83. Has finished cutting.

On the other hand, when the presser foot 31 is lowered and the sewing of the overhole stitch 100 is started again, the link member 69
Moves forward and the lever 77 returns to the position shown in FIG. At this time, the protruding portion 87a of the lower thread movable blade 87 contacts the cam surface 75d, so that the scissors 83 also return to the open state as shown in FIG.

When the bobbin thread grip 79 starts sewing and the feed table 11 starts moving, the bobbin thread grip 79 operates via a link mechanism (not shown) on the pin 79d protruding rearward. Is transmitted, and thereby returns to the position shown in FIG. For this reason, the bobbin thread S is held between the hook 79c and the notch 91a at the start of the next sewing, so that the formation of the seam at the start of sewing can be favorably performed. Moreover, the lower thread S is provided between the hook 79c and the notch 91a.
10A, the scissors 83 do not block the path from the needle hole 75a to the hook 79c and do not apply any force to the bobbin thread S, as shown in FIG. For this reason,
The lower thread S can be held extremely reliably by the lower thread grip 79 and the lower thread grip spring 91. Therefore, the bobbin thread S can be captured very well at the start of the next sewing, and the seam can be reliably formed. In addition, the overlock stitch machine M
Then, after securely holding the lower thread S in this way, scissors 8
Since the cutting is performed by 3, the lower thread S can be reliably cut at a stable position, and the appearance of the work cloth W can be ensured as described later.

Next, the structure of the control system of this overhole sewing machine M will be described. As shown in FIG. 11, the control device 5 is composed of a microcomputer having CPU 5a, ROM 5b, and RAM 5c as main parts, and further, an input for inputting a signal corresponding to the operation state of the pedal 3 and a signal from the operation panel 4. A drive signal is output to the interface 5d, the sewing machine motor 2, the stepping motor 24, the stepping motor 49, the stepping motor 61, and the cutter driving solenoid 39 via a drive circuit (not shown), and the operation panel 4 also controls the display state and the like. An output interface 5e for outputting a signal is provided, and these are connected by a bus 5f.

In the boring stitch sewing machine M thus constructed, various data such as width and pitch relating to the boring stitch 100 are set on the operation panel 4 and then the pedal 3 is pressed.
When is depressed, the control device 5 executes the program stored in the ROM 5b to pierce the work cloth W with the boring stitch 10
Form 0. That is, based on the data input from the operation panel 4, the data of the needle drop points forming the overlock stitch 100 is created, and the sewing machine motor 2, the stepping motors 24 and 61 are formed to form the stitches at the needle drop points.
Drive.

FIG. 12 is an explanatory diagram showing the data of the needle drop points used by the overlock stitch sewing machine M. This data is data including the needle drop points of 113 needles from the needle drop points P1 to P113. Based on this data, the controller 5 causes the sewing machine motor 2, the stepping motors 24 and 61 to
When is driven, stitches are formed in the order of the needle drop points P1, P2, ..., Part of the front bar-tacking stitch 103, the left zigzag stitch 101, the back bar-tacking stitch 104, and the right zigzag stitch 10
2. The sewing is performed in the order of the remaining part of the front bar-tacking seam 103. Further, at a predetermined time during sewing of the right zigzag stitch 102 or at the end of sewing of the right zigzag stitch 102, the control device 5 drives the cutter driving solenoid 39 to cause the cutter 1 to move.
3 forms the buttonhole 110. Then, after the formation of the overholstered stitch 100, the control device 5 drives the stepping motor 49 as described above to drive the link member 4.
6 is lowered, the upper thread cutting mechanism 99 is driven, the lower thread cutting mechanism 70 is driven, and the presser foot 31 is raised.

Here, as shown in FIG. 12, in the data of the needle drop point used in the overlock stitch machine M, the penultimate needle drop point P112 is arranged at the left end of the overhollow stitch 100. The last needle drop point P113 is arranged in the vicinity thereof. Therefore, in the overlock stitch sewing machine M, the length of the end portion of the lower thread S left on the back side of the work cloth W can be shortened as follows.

As described above, in the overlock stitch sewing machine M, after the upper thread T is cut by the upper thread cutting mechanism 99, the end Ta of the cut upper thread T is processed by the lower thread separating unit 78 together with the lower thread S. The cloth W is pulled out below. For this reason,
As schematically shown in FIG. 13 (A), when the upper thread T is cut, the end Ta projects from the needle drop point P113 to the surface of the work cloth W.
As schematically shown in (B), the end portion Ta is pulled out below the work cloth W together with the lower thread S. Therefore, the needle drop point P11
No seam is finally formed in 3 and the last seam is the penultimate needle drop point P112. Then, the scissors 83 cut the lower thread S stretched between the needle drop point P112 and the hook 79c.

Since the needle drop point P112 is disposed at the left end of the overholstered stitch 100 in the hole stitching sewing machine M, the bobbin thread S stretched between the work cloth W and the hook 79c is provided.
Is shortened, and in turn, the length of the end portion of the lower thread S left on the back side of the work cloth W after cutting is also shortened. Moreover, as described above, the end Ta of the needle thread T does not remain on the surface of the work cloth W. Therefore, in the hole stitching sewing machine M, the aesthetic appearance of the work cloth W in which the hole stitches 100 are formed can be favorably ensured. Further, in the overlock stitch sewing machine M, the mounting angle of the support portion 80 and the bobbin thread separating main body 81 can be adjusted by the screw 82, and the separation amount of the bobbin thread S by the bobbin thread separating 78 can be changed. Therefore, the thickness of the work cloth W and the lower thread S
Even if the thickness of the cloth changes, the upper thread T can be satisfactorily processed with the work cloth W
It is possible to secure the aesthetic appearance of the work cloth W by pulling the work cloth W downward.

In the overlock stitch machine M, as described above, the lower thread S is held by the lower thread grip 79 before the lower thread S is cut by the scissors 83, and the lower thread grip 79 is stopped. Since cutting with scissors 83 from
The bobbin thread S can be surely cut at a stable position. Moreover, as described above, even if the loosening amount of the lower thread S is changed, the drive amount of the lower thread grip 79 does not change, and the lower thread S can be held similarly. Further, the lower thread grip 79
Does not move while the lower thread S is being cut by the scissors 83, and the lower thread S
The holding position of is fixed at a predetermined position near the needle plate 75. Therefore, the above holding can be reliably performed, whereby the end portion of the lower thread S left on the back side of the work cloth W can be shortened more favorably, and the appearance of the work cloth W can be more favorably secured.

Further, since the holding position is fixed to the sewing start side near the needle plate 75, the bobbin thread S can be captured better when the next sewing is started, and the stitch is formed more reliably. can do. Further, as shown in FIG. 9 (B) and FIG. 10 (A), after the lower thread grip 79 holds the lower thread S, the lower thread separation 7 is performed by the shape of the cam hole 77b.
The swing of 8 stops. Therefore, the lower thread handling 78 does not pull out the held lower thread S from the lower thread grip 79, and the above holding can be performed more reliably.

If the groove 79e shown in FIG. 14 is provided at the portion where the hook 79c of the lower thread grip 79 is provided, the lower thread S is held better and the cutting of the lower thread S is further stabilized. At the same time, it is possible to more reliably capture the lower thread S at the start of the next sewing. That is, without the groove 79e, as shown in FIG. 15 (A), the lower thread S may be disengaged from between the lower thread grip 79 and the lower thread grip spring 91, but the groove 79e is provided. In this case, as shown in FIG. 15B, the lower thread S is reliably held between the groove 79e and the lower thread gripping spring 91. Therefore, the bobbin thread S is not pulled out at the time of cutting the bobbin thread S, etc., and the bobbin thread S can be surely captured to form a stitch when the next sewing is started.

In the embodiment described above, the scissors 83 serve as the lower thread cutting means, the lower thread grip 79 and the lower thread grip spring 91 serve as the lower thread holding means, and the lower thread separating means 7 from the link member 65.
The mechanism up to 8 corresponds to the link mechanism, and the screw 82 corresponds to the loosening amount changing means. Further, the present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the scope of the present invention. For example, the link mechanism that drives the scissors 83, the bobbin thread grip 79, and the bobbin thread separating 78 may individually transmit power from separate stepping motors. However, in the above embodiment, the scissors 83, the lower thread grip 79,
And the lower thread handling 78 are driven by a common link mechanism,
Moreover, since the lower thread handling 78 is part of the link mechanism by providing the cam surface 81b, the configuration is extremely simplified and synchronization control is not required, and the manufacturing cost can be reduced favorably. . Further, the present invention can be similarly applied to various sewing machines other than the overlock stitch sewing machine.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a buttonhole sewing machine to which the present invention is applied.

FIG. 2 is a right side view showing a main configuration of a sewing mechanism of the sewing machine.

FIG. 3 is a perspective view showing a configuration of a feed carriage driving mechanism of the sewing machine.

FIG. 4 is a right side view showing a configuration of a presser foot drive mechanism of the sewing machine.

FIG. 5 is a perspective view showing a configuration of a needle bar drive mechanism of the sewing machine.

FIG. 6 is a left side view showing a configuration of a connecting portion between the lower thread cutting mechanism of the sewing machine and the cloth pressing drive mechanism.

FIG. 7 is a bottom view showing the configuration of the lower thread cutting mechanism.

FIG. 8 is a perspective view and a top view showing the configuration of the needle thread cutting mechanism of the sewing machine.

FIG. 9 is an explanatory diagram illustrating an operation related to holding the lower thread of the lower thread cutting mechanism.

FIG. 10 is an explanatory diagram illustrating an operation relating to bobbin thread cutting of the bobbin thread cutting mechanism.

FIG. 11 is a block diagram showing a configuration of a control system of the sewing machine.

FIG. 12 is an explanatory diagram showing data of needle drop points used by the sewing machine.

FIG. 13 is an explanatory diagram schematically showing the effect of lower thread handling of the sewing machine.

FIG. 14 is a bottom view and an arrow A view showing a more desirable form of the bobbin thread grip of the sewing machine.

FIG. 15 is an explanatory view showing the effect of the bobbin thread gripping.

[Explanation of symbols]

2 ... Sewing machine motor 3 ... Pedal 4 ... Operation panel
5 ... Control device 10 ... Sewing mechanism 15 ... Needle bar 16 ... Sewing needle 1
7 ... Needle bar drive mechanism 24, 49, 61 ... Stepping motor 33 ... Cloth pressing drive mechanism 45, 46, 47, 65, 69, 71, 73 ... Link member 67 ... Cam plate 70 ... Lower thread cutting mechanism 75 ... Needle plate 75a ... Needle hole 77 ... Lever 78 ... Lower thread separating 79 ... Lower thread gripping 82 ... Screws 83 ... Scissors 91 ... Lower thread gripping spring 99 ... Upper thread cutting mechanism 1
00 ... holling stitch M ... holling sewing machine S ... bottom thread T ... upper thread W ... work cloth

Front Page Continuation (72) Inventor Takashi Kondo 15-1 Naesehiro-cho, Mizuho-ku, Nagoya, Aichi Brother Industries, Ltd. (72) Inventor Atsushi Kamano 15-1 Naeshiro-cho, Mizuho-ku, Nagoya-shi, Aichi Brother Industries Ltd. In-company (72) Inventor Yukio Nishida 15-1 Naeshiro-cho, Mizuho-ku, Nagoya, Aichi Brother Industries, Ltd. (56) Reference JP-A-7-289765 (JP, A) JP-A-2-213385 (JP , A) JP-A-4-164491 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D05B 65/02 D05B 65/06

Claims (2)

(57) [Claims] 1. A bobbin thread cutting means which is disposed below a needle plate of a sewing machine and which cuts a bobbin thread after forming a seam on a work cloth, and a bobbin thread cutting means for cutting the bobbin thread by the bobbin thread cutting means after the seam is formed. A bobbin thread cutting device for a sewing machine, comprising: a bobbin thread holding means for holding a bobbin thread at a predetermined position below a cutting point; and a link mechanism for transmitting power to the bobbin thread cutting means and the bobbin thread holding means. Is placed above the work cloth, and is
Upper thread cutting means for cutting the thread, and upper thread cutting means arranged above the needle plate and cut by the upper thread cutting means.
After cutting the thread, the end of the cut upper thread is entangled with the upper thread.
Lower thread handling that pulls down the work cloth together with the lower thread
And a loosening amount changing hand for changing the loosening amount of the lower yarn by the lower yarn handling.
Further comprising a stage, and the link mechanism, after holding the bobbin thread by driving the lower thread holding means prior to the cutting of the lower thread by the lower thread cutting means, after having stopped the lower thread holding means Drive the above bobbin thread cutting means to cut the bobbin thread and hold the bobbin thread.
The drive amount of the lower thread holding means is changed by the loosening amount changing means.
A bobbin thread cutting device for a sewing machine, wherein the bobbin thread cutting device keeps a constant amount regardless of the change of the loosening amount . Wherein a position where the lower yarn holding means for holding the lower yarn, the lower thread cutting device according to claim 1 Symbol placement of the sewing machine, characterized in that it is fixed at a predetermined position of the needle plate near.