JPH0975573A - Automatic thread cutting device of sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the feed performance of a sewing machine with feed teeth by constructing a device so that a slide plate is passed through under the normal path for needle and bobbin threads when moving forward, and the captures the needle and bobbin threads to guide them to the action locus of a movable blade and cut them when moving backward. SOLUTION: In an automatic thread cutting device of sewing machine, a fixed blade 10 is fixed to a thread cutting base plate 9 mounted on a base body 1, and a movable blade 2 and a slide plate 4 are incorporated to form a movable blade unit 40 via a spacer with the same width as the fixed blade 10. The movable blade unit 40 is supported by the thread cutting base plate 9 with the movable blade 2 and fixed blade 10 placed within the movable blade unit so that the movable blade unit can oscillate freely. With a thread cutting drive mechanism of a thread cutting mechanism 32. the slide plate 4 is passed through under the normal path for needle and bobbin threads 36 and 38 when the movable blade unit 40 moves forward, and the slide plate 4 captures the needle and bobbin threads 36 and 38 to guide them to the action locus of the movable blade 2 and cut the needle and bobbin threads 36 and 38 when moving backward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic thread cutting device for a sewing machine using a horizontal hook.

[0002]

2. Description of the Related Art Conventionally, an automatic thread trimming device for a sewing machine using a horizontal shuttle has been disclosed in Japanese Utility Model Laid-Open No. 146874/1990, Japanese Patent Laid-Open No. 3-1.
As shown in Japanese Patent Application No. 09095 and Japanese Unexamined Patent Publication No. 6-339592, it is necessary to provide a device having a thread pressing function for guiding the upper and lower threads to be cut into the movement trajectory of the movable knife.

The reason for this is that in a sewing machine using a horizontal hook, the upper thread passing above the hook and the lower thread pulled out from the hook are substantially horizontal along the lower surface of the needle plate toward the needle plate needle hole. This is because the upper and lower threads do not intersect with the locus of movement of the movable knife located below the needle plate and the upper and lower threads to be cut cannot be captured without the thread pressing function.

On the other hand, a sewing machine provided with a lower thread feeding lever for improving the sewing condition can be used as a "thread presser", but the thread feeding operation is different from the thread cutting operation. At the time of thread cutting, a switching device for switching the function is required.

Further, when the bobbin thread delivering lever is provided, it is necessary to provide it between the needle hole and the shuttle. Either the interval between the upper needle hole and the shuttle should be widened, or the feed dog in front of the needle hole should be provided. I have to shorten it. Further, in this case, it is difficult to provide the front tooth located particularly before the needle hole.
In the former case, the amount of needle thread required for the hook increases and the sewing condition deteriorates. In the latter case, the feed efficiency at the start of sewing decreases.

[0006]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide an automatic thread trimming device for a sewing machine, which uses a horizontal hook to cut upper and lower threads in cooperation with a movable knife and a fixed knife. An object of the present invention is to provide an automatic thread trimming device for a sewing machine that does not require the provision of a device having a thread holding function and does not sacrifice the original feeding performance of a sewing machine having front teeth.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention is directed to a sewing machine which uses a horizontal shuttle and cuts upper and lower threads by the cooperation of a movable knife and a fixed knife. In the automatic thread trimming device, the automatic thread trimming device includes a fixed knife fixed to a thread trimming base plate of a base body, a movable knife unit including a movable knife and a slide plate integrated with the movable knife through a spacer. The movable knife unit is slidably supported with respect to the thread cutting base plate of the base body with the fixed knife interposed therebetween, and the movable knife unit is moved forward by an external operation for thread cutting. The slide plate passes below the upper and lower yarns, captures the upper and lower yarns when returning, and cuts the upper and lower yarns in cooperation with the movable knife and the fixed knife.

According to the present invention, it is necessary to provide a device having a thread holding function in an automatic thread cutting device of a sewing machine configured to use a horizontal shuttle to cut upper and lower threads by cooperation of a movable knife and a fixed knife. Therefore, it is possible to provide an automatic thread trimming device for a sewing machine that does not sacrifice the original feeding performance of a sewing machine having front teeth.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(1) Structure of Thread Cutting Mechanism The thread cutting mechanism 32 has a thread catching portion a of the slide plate 4 which is integrated with the movable knife 2 when the movable knife 2 moves forward in FIG. As shown in FIG. 3, the upper thread 36 of the upper thread passing through the inner hook 34 and the lower thread 3 pulled out from the inner hook 34.
These upper and lower yarns 36 and 38 pass while being scooped from below, and when the movable knife 2 is moved back to the left in the figure, it is caught by the yarn catching portion a of the slide plate 4 and these The upper and lower threads are blade parts v formed near the tip of the fixed knife 10.
Of the upper and lower threads of the movable knife 2 and the upper and lower threads of the movable knife 2 are guided to the upper surface of the blade u of the movable knife 2, and the upper and lower threads of the movable knife 2 are cut in cooperation with the fixed knife 10. is there.

The configuration of the thread cutting mechanism 32 will be described in detail with reference to FIG. In the figure, the movable knife 2,
The spacer 3 and the slide plate 4 are laminated in this order and integrated by the caulking pin 5, and these constitute the movable knife unit 40. A bush 6 having an elongated hole A is fixed near the left end of the slide plate 4. The knife guide 7 and the knife guide 8 are respectively screwed to the thread cutting base plate 9 (hereinafter, base plate 9), and the base end portions thereof are screwed to the base plate 9 via the knife guide 7 to slide plate 4 and the movable knife. The movable knife unit 40 is guided in the width direction and the vertical direction together with the fixed knife 10 interposed between the movable knife unit 40 and the movable knife unit 40.

The slide plate 4 is formed so as to be bent substantially vertically to the side near the tip thereof, and when the movable knife unit 40 moves forward, the upper and lower threads are raised to a position higher than the path during normal sewing. Slanted portion a1 and second slanted portion a2 that captures and guides the upper and lower yarns when the movable knife unit 40 retreats.
Is formed and is connected to the second inclined portion a2, and guides the upper and lower yarns so as to pass below the blade portion v of the fixed knife 10 when the movable knife unit 40 retreats. A guide groove portion J is formed.

The height of the slide plate 4 near the apex of the thread catching portion a is such a height that it can enter the escape groove W formed on the lower surface of the needle plate 31 and move in the escape groove. Therefore, when the movable knife unit 40 returns, the upper and lower threads 3
The yarns 6 and 38 are reliably captured by the second inclined portion a2 of the yarn capturing portion a, and are guided to the guide groove portion J of the slide plate 4 that is continuous with this. Further, since it is configured in this way, the feed dog 46 can be provided with the front tooth 47, and the original feed performance of the sewing machine having the front tooth is not sacrificed.

A guide bending portion s inclined upward is formed near the tip of the fixed knife 10, and the movable knife unit 40 is provided.
The upper and lower threads 36 and 38 guided in the guide groove J of the slide plate 4 are guided to the lower surface of the blade portion v near the tip of the fixed knife 10 when returning. The base plate 9 is fixed to the base body 1, and the shaft b is fixed to the lower surface side of the base plate 9,
An arcuate groove C centered on the axis b is formed in the base plate 9.

(2) Thread Cutting Drive Mechanism Next, the thread cutting drive mechanism 42 for driving the thread cutting mechanism 32 will be described mainly with reference to FIGS. 2 and 4 to 6.

The knife driving arm 11 is rotatably supported by an axis b, and pins L and D are provided on two L-shaped arm portions, respectively.
Are fixed. The pin d is inserted in the elongated hole A of the bush 6. The link 12 is provided with a hole F and a hole G whose forming directions are different by 90 degrees, and the pin F of the female driving arm 11 is provided in the hole F.
Is inserted, and the pin j of the cam driven plate 20 fixed to the cam driven arm 18 of the thread trimming drive mechanism 42 described later is inserted into the hole G.

When the link 12 is moved by the pin j through the hole G in the direction of arrow D in FIG. 2, the movable knife unit 40 is moved through the pin e, the knife driving arm 11, the pin d and the elongated hole A of the bush 6. When the link 12 is moved forward and the pin j is moved in the direction of arrow E in FIG. 2 through the hole G, the movable knife unit 40 is returned to the opposite direction, and thread trimming is performed between them. It has become. Details of the thread cutting operation will be described later.

The lower shaft 13 has a lower shaft 13 as shown in FIG.
A guide pin 14 is driven into a hole formed at a right angle to the longitudinal direction of the. The thread cutting cam 15 has a fitting hole to be fitted to the lower shaft 13 and a long groove N to be engaged with the guide pin 14 as shown in the figure. The thread cutting cam 15 rotates integrally with the lower shaft 13. In addition, it is slidable in the axial direction with respect to the lower shaft 13.

The thread cutting cam 15 is pressed leftward in FIGS. 4 and 5 by a compression coil spring 16 arranged between the thread cutting cam 15 and the thrust ring 17, and the thread cutting cam 15 is normally operated.
The right end surface of the long groove N is brought into contact with the pin 14.

Further, as shown in FIG. 6, the thread trimming cam 15 has a cam groove in its operating state for driving the knife indicated by phase section X1 and a cam groove for not driving the knife indicated by phase section X2 of equal diameter. A groove H is formed. The cam follower arm 18 is rotatably supported on the base body 1 by a shaft 19, and a pin i engageable with the cam groove H is fixed thereto.
Cam follower plate 2 integrated with cam follower arm 18 by screws
The pin j of 0 is fitted in the hole G of the link 12 of the thread cutting drive mechanism 42.

(3) Thread Cutting Cam Switching Mechanism Next, the thread cutting cam switching mechanism 44 for switching the thread cutting cam 15 between the inoperative state and the operating state will be described with reference to FIG. In the figure, a pin k is fixed to a base plate 22 fixed to the base body 1, and a claw g formed at the tip of a switching arm 21 rotatably supported by the pin k is a thread cutting cam 15 It is located on the left side of the. The conversion arm 23 is rotatably attached to the base body 1 via a shaft 24, and a pin n and a pin p are fixed to the L-shaped arm, respectively.

The connecting rod 25 connects the pin m of the switching arm 21 and the pin n of the converting arm 23. The solenoid 26 is fixed to the base body 1 via a mounting plate 27, and the plunger q of the solenoid 26 and the pin p of the conversion arm 23 are connected by a link 28.

(4) Description of Operation The thread cutting operation will be described with reference to the motion diagram related to the operation of the thread cutting device shown in FIG. 12 and the related drawings. In the motion diagram of FIG. 12, the upper axis phase of 280 degrees to 40 degrees corresponds to the phase section X1 of FIG. 6 in the drive range of the movable knife 2, and the upper axis phase of 4 degrees.
0 degrees to 280 degrees corresponds to the phase section X2 in the figure.

When an external operation for thread trimming is performed before the upper shaft phase is 100 degrees for thread trimming, the solenoid 26 becomes O when the upper axis phase is near 100 degrees because of the circuit configuration.
When the external operation for thread cutting is performed in the range of N and the upper shaft phase is in the range of 100 degrees to 200 degrees, the solenoid 26 is turned ON in the upper shaft phase and the thread cutting operation is performed by the thread cutting mechanism 32. When thread cutting is completed, the sewing machine stops and the solenoid 26 turns off.

Now, the solenoid 26 is turned on by an external operation.
Then, the thread cutting cam 15 is moved to the right in FIG. 7 by the claw g of the switching arm 21 via the thread cutting cam switching mechanism 44. At this time, since the thread trimming cam 15 is in the range of the phase section X2 with respect to the pin i of the cam follower arm 18 and the pin i faces the cam groove of the cam groove H of equal diameter, the pin i is in the cam groove H can be engaged.

In this state, after the lower shaft 13 continues to rotate and the pin i follows the phase section X1 of the thread cutting cam 15,
The sewing machine rotates up to around 50 degrees to 70 degrees of the upper axis phase and stops. During this time, the movable knife 2 moves forward from the original position shown in FIG. 8 to the position shown in FIG.
When returning to the same original position as in FIG. 8 shown in FIG. 1, the upper and lower threads are cut in cooperation with the fixed knife 10.

After the movable knife 2 reciprocates to cut the upper and lower threads, the solenoid 26 is turned off and the thread cutting cam 15
Is driven by the compression coil spring 16 by the cam follower arm 18
Pin i comes out of the cam groove of the thread trimming cam 15 in the phase section X2, and returns to the inactive position on the left side.

In the present embodiment, the width of the cam groove in the phase section X2 in which the engagement and disengagement with the pin i of the cam follower arm 18 is performed is larger than the width of the cam groove in the phase section X1 for operating the thread cutting mechanism 32. . The reason for this is that the engagement and disengagement of the cam groove and the pin i of the cam driven arm 18 can be smoothly performed in the phase section X2.

If the widths of the cam grooves in the phase section X1 and the phase section X2 are the same, the cam follower arm 18 in the phase section X2.
Not only does it not smoothly engage with the pin i of the cam follower arm 18 at the phase section X2 due to friction of the cam follower arm 18 and each mechanism connected thereto after the thread cutting is completed. Friction occurs between the side surface of the cam groove,
In order to return the thread cutting cam 15 to the inoperative position, it is necessary to increase the biasing force of the compression coil spring 16, and when the pin i of the cam driven arm 18 is engaged with the cam groove of the phase section X2, the solenoid is used. It is not preferable because the suction force of 26 must be increased.

The cam follower arm 18 is formed with a tongue piece r which is arranged at a non-acting position of the thread cutting cam 15 on the outer peripheral surface of the thread cutting cam 15 with a minute gap. The tongue pieces r face each other with a width smaller than the sliding amount of the thread cutting cam 15,
During normal operation when the thread trimming cam 15 is in the inoperative position, the operation of the cam follower arm 18 is restricted to prevent the movable knife 2 from moving.

When the movable knife unit 40 moves forward from FIG. 8 to FIG. 9, the thread catching portion a of the slide plate 4 integrated with the movable knife 2 passes through the inner hook 34 as shown in FIG. The upper thread 36 of the upper thread and the lower thread 38 pulled out from the inner hook pass through while scooping these upper and lower threads.

The height of the slide plate 4 in the vicinity of the apex of the thread catching portion a is such that it can be moved into the escape groove W formed in the lower surface of the needle plate 31 as shown in FIG. Since the upper and lower yarns 36 and 38 are reliably caught by the second inclined portion a2 of the yarn catching portion a when the movable knife unit 40 is returned, the upper and lower yarns 36 and 38 are guided to the guide groove portion J of the slide plate 4 which is continuous with this. To be done.

When the movable knife unit 40 is returned to the position shown in FIG. 11 which is the same as FIG. 8 through FIGS. 9 to 10,
These upper and lower threads 36, 38 are guided in the guide groove portion J of the slide plate 4 as described above, and the guide bent portion s inclined upward is formed near the tip of the fixed knife 10 as described above. The upper and lower threads guided in the guide groove portion J of the slide plate 4 when the movable knife unit 40 is moved back are guided by the guide bending portion s to the lower surface of the blade portion v formed at the tip of the fixed knife 10, and then. These upper and lower yarns are guided to the upper surface of the blade portion u of the movable knife 2 and the upper and lower yarns are cut in cooperation with the fixed knife 10 by the subsequent return movement of the movable knife 2.

[0034]

As described above, according to the present invention, in the automatic thread trimming device of the sewing machine, which is configured to cut the upper and lower threads by the cooperation of the movable knife and the fixed knife by using the horizontal hook, the thread pressing function is provided. Since it is not necessary to provide a device having a sewing machine, it is possible to provide an automatic thread trimming device for a sewing machine that does not sacrifice the original feeding performance of a sewing machine having front teeth.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of a thread cutting device.

FIG. 2 is an exploded perspective view showing a part of a thread cutting mechanism and a thread cutting driving mechanism.

FIG. 3 is a cross-sectional view showing the relationship between the upper and lower threads and the thread cutting mechanism.

FIG. 4 is a plan view showing a main part of a thread trimming drive mechanism.

5 is a view on arrow K in FIG.

FIG. 6 is a view on arrow L in FIG.

FIG. 7 is a view of the thread cutting cam drive mechanism as viewed in the direction of arrow M in FIG.

FIG. 8 is a view showing an inoperative state of the thread trimming mechanism.

FIG. 9 is a diagram showing a forward end state of the thread trimming mechanism.

FIG. 10 is a view showing a state in the middle of returning of the thread trimming mechanism.

FIG. 11 is a view showing a returning end state of the thread trimming mechanism.

FIG. 12 Motion diagram related to thread trimming device

[Explanation of symbols]

 1 Base Main Body 2 Movable Female 3 Spacer 4 Slide Plate 9 Thread Cutting Base Plate 10 Fixed Female 11 Female Driving Arm 12 Link 13 Lower Shaft 15 Thread Cutting Cam 18 Cam Follower Arm 20 Cam Follower Plate 32 Thread Cutting Mechanism 33 Horizontal Knife 35 Needle Plate Needle hole 36 Upper thread 38 Lower thread 42 Thread cutting drive mechanism 40 Movable knife unit 44 Thread cutting cam switching mechanism H Cam groove J Guide groove part a Thread catching part a1 First inclined part a2 Second inclined part i Cam Follower arm Pin s Guide bending part v Fixed knife blade

Claims (4)

[Claims] 1. A fixed knife provided in a base main body of a sewing machine using a horizontal shuttle and fixed to a predetermined position with respect to the base main body, and a thread cutting drive for cutting a thread in cooperation with the fixed knife. A movable knife that is driven by a mechanism, and a needle thread that is pulled out from the needle plate needle hole that is guided to a position that intersects the movement trajectory of the movable knife at the end of sewing work by the sewing machine and that passes through the upper side of the shuttle; In an automatic thread trimming device of a sewing machine that cuts an upper and lower thread consisting of a lower thread drawn from a needle plate and reaching a needle hole by reciprocating movement of a movable knife, the fixed knife is fixed to a thread cutting base plate attached to the base body. Is
The movable knife is integrated with a slide plate to form a movable knife unit via a spacer for the thickness of the fixed knife, and the movable knife unit slides on the thread cutting base plate with the movable fixed knife interposed therebetween. The slide plate is movably supported, and when the movable knife unit is moved forward by the thread trimming drive mechanism during the thread trimming operation, the slide plate passes below the normal path of the upper and lower threads, and the upper and lower threads are moved during the backward movement. An automatic thread cutting device for a sewing machine, characterized in that the upper and lower threads are cut by capturing and guiding the moving knife within the movement locus of the movable knife. 2. The slide plate of the movable knife unit includes:
A first slanted portion which rises to the side near the tip thereof at a substantially right angle and raises the upper and lower threads to a position higher than the path during normal sewing when the movable knife unit moves forward;
And a guide groove is formed so as to be connected to the second slanted portion, and a return groove of the movable knife unit is formed. The automatic sewing machine according to claim 1, wherein the upper and lower threads are sometimes caught by the second inclined portion, and then guided by the guide groove portion and guided near the lower portion of the blade portion of the fixed knife. Thread trimming device. 3. A thread in which the thread cutting drive mechanism is switched between an operating position and a non-operating position on the lower shaft by a thread cutting cam switching mechanism, and a cam groove which engages with a pin of a cam driven arm in the operating position is formed. The thread trimmer includes a cutting cam, a cam follower plate integrated with the cam follower arm, and a knife driving arm that is reciprocally rotated by a link to the cam follower plate to reciprocally rotate the thread trimming mechanism. The cam is provided with a cam groove in a cam phase section X1 for operating the thread cutting mechanism to perform thread cutting in its operating state, and a cam groove in a phase section X2 connected to the cam groove and not operating the thread cutting mechanism. The width of the cam groove in the section X2 is made wider than the width of the cam groove in the phase section X1, so that the engagement of the pin of the cam driven arm with the cam groove in the phase section X2 is surely performed. Automatic thread trimming for sewing machine according to Item 1. Apparatus. 4. A guide bending portion inclined upward is formed in the vicinity of the tip of the fixed knife, and the upper and lower threads guided by the guide bending portion in the guide groove portion of the slide plate when the movable knife unit is returned. 3. The automatic thread trimming device for a sewing machine according to claim 2, wherein the thread guide is guided to the lower surface of the blade of the fixed knife.