JPH07102270B2 - Needle thread cutting device for sewing machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a needle thread cutting device for cutting an upper thread connected to a material to be sewn after finishing a sewing operation, and particularly to a very thick thread having high strength. The present invention relates to a needle thread cutting device suitable for a sewing machine.

[Prior Art] Currently, a sewing machine is provided with a thread trimming device that automatically performs thread trimming after a sewing operation is completed. The thread trimming device includes a plate-shaped fixed blade provided on the side of the ascending / descending path of the sewing needle and a movable blade that overlaps with the upper surface of the fixed blade, and is interlocked with the end of the sewing operation. It is generally known that the movable blade is moved forward so as to traverse the ascending / descending path to capture the thread, and then the backward movement of the movable blade pulls out the captured thread to the side and shears it with the fixed blade. ing.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional thread cutting device, since the thread is sheared by the joining operation of the movable blade and the fixed blade, so to speak, the fixed blade and the movable blade are inevitable. The sword part wears and the sharpness decreases.

This is particularly remarkable when extremely thick yarns or yarns with high strength are used. For example, in recent years, in the sewing of airbags mounted on automobiles and the like, threads that are extremely thick and have excellent strength are used as compared with the threads used for sewing clothes, and conventional threads are used for cutting such threads. When a cutting device is used, the fixed blade and the movable blade deteriorate in a very short time, and it is necessary to frequently replace them with a new one.In some cases, the fixed blade and the movable blade remain uncut. Sometimes it was inserted between the and, resulting in poor cutting.

Focusing on this another problem, the applicant of the present application has previously filed Japanese Patent Application No.
No. 139220 (No. 3-76575, Jitsukaihei) discloses a needle thread cutting device for a sewing machine that can obtain good cutting performance even with tough threads and very thick threads by means of thread cutting means using heat rays. However, the yarn clamping means and the yarn cutting means each require different drive sources, which complicates the configuration and makes it difficult to set the drive timing.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a needle thread cutting device having a simple structure and easy timing adjustment.

[Structure of Invention]

An upper thread cutting device according to the present invention has upper thread cutting means for nipping and cutting an upper thread between a sewing needle and a material to be sewn. The upper thread cutting means is fixed to a fixing member and this fixing member. An upper thread clamping mechanism including a movable member that opens and closes the upper thread to clamp the upper thread, a fusing member that is provided below the movable member, that interlocks with the movable member, and generates Joule heat when energized, and is connected to the upper thread clamping mechanism. One driving means for moving the upper thread clamping mechanism from the original position to the upper thread fusing position, and an upper thread clamping mechanism for moving the upper thread clamping mechanism from the original position to the upper thread fusing position in conjunction with the driving by the driving means. The open / close mechanism is configured to open and close the upper thread in a direction intersecting with the upper thread when the upper thread is moved from the fusing position to the original position.

[Action]

In this invention, the sewing operation by the sewing machine is completed,
The needle rises. The driving mechanism operates the opening / closing mechanism to open the upper thread clamping mechanism and moves the upper thread from the original position to the upper thread clamping / fusing position. When the movable member of the upper thread clamping mechanism reaches the upper thread clamping and fusing position, the upper thread clamping mechanism is closed by the driving means via the opening / closing mechanism and moves from the upper thread clamping and fusing position to the original position. Therefore, the upper thread is fused by the fusing member provided below the movable member. Further, when the closing operation is continued, the needle thread holding mechanism holds and holds the thread ball having a diameter larger than the diameter of the upper thread formed at the tip of the upper thread due to the fusing, by engaging the thread ball. Then, the upper thread holding mechanism holds the upper thread in the original position until the start of the next sewing operation.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view of the needle thread cutting means A according to the present invention.

In the figure, 1 is composed of a movable member 1a and a fixed member 1b,
It is a needle thread clamping mechanism in which both ends thereof are oppositely joined.

The movable member 1a is a long shaft support having rising portions at both ends.
1a2 and a base portion 1a1 extending to the shaft supporting portion 1a2, and the shaft supporting portion 1a2 is rotatably supported on the mounting base 3 (openable and closable with respect to the fixing member 1b) by a shaft supporting pin 1p. There is.

Then, the base portion 1a1 is positioned so as to be located below the mounting base 3 as it is separated from the mounting base 3, and has a substantially cross-section. It has a shape.

The fixing member 1b also has a cross-sectional shape similar to that of the base portion 1a1 and one end thereof is fixed to the mounting base 3.

Reference numeral 2 is a cutting member fixed to the lower surface of the base 1a1 and has a U-shape as shown in FIG.
The side edge of 1a1 is projected to the lower surface of the side edge of the fixing member 1b.

The mount 3 is connected to the tip of the piston P of the cylinder S and moves back and forth in the arrow direction in accordance with the operation of the piston P.

Reference numeral 4 denotes a fixed base attached to the end of the cylinder S, and a locking spring 6 is fixed to one end and a stopper 7 is fixed to the other end.

Further, the locking portion 7a at the tip of the stopper 7 and the rising end portion (upper side in the figure) of the shaft supporting portion 1a2 constitute a regulating means for setting the closing timing of the movable member 1a.

The locking spring 6 is urged and engaged with one rising end portion (front side in the drawing) of the shaft supporting portion 1a2 of the movable member 1a to hold it at a predetermined position.

Here, the opening / closing mechanism is formed by the shaft supporting portion 1a2, the locking spring 6 and the stopper 7.

Reference numeral 5 is a pressing spring fixed to the mounting base 3, which is the shaft support portion.
Engage with the lower surface of 1a2 and press it upward to urge the shaft support 1
It is designed to prevent a2 from moving.

The needle thread cutting means A configured as described above is attached to the lower portion of the sewing machine head M as shown in FIG.

In the figure, A1 is a support plate for fixing the upper thread cutting means A to the sewing machine M, and A2 is a clamp fitting for rotatably elastically supporting the end of the cylinder S.

Further, C is a needle thread feeding means, which is composed of an engaging member 8 and a cylinder 8a as a forward / backward driving means of the engaging member 8, and is attached to the side surface of the sewing machine head M so that the engaging member 8 projects. The upper thread 9 between the balance and the needle N is laterally (left in the figure)
It is refracted to and is fed out from the yarn supply source side.

Further, B is a guide means for guiding the movement of the upper thread cutting means A between the original position and the cutting position, and is constituted by a guide plate 10 having an inclined hole 10a.

An engaging element (not shown) of the needle thread holding mechanism 1 is fitted in the inclined hole 10a, and the movement path of the needle thread holding mechanism 1 due to expansion and contraction of the cylinder S is regulated like an arrow.

The operation of the embodiment under the above-mentioned structure will be described with reference to FIGS.

2 and 4 are a side view and a plan view of the needle thread cutting means A with the needle thread holding mechanism 1 in the closed position in the original position.

First, when sewing is completed, the cylinder of the thread feeding means C is
The engagement member 8 is projected by 8a and the thread is tensioned between the needle N and the material to be sewn.

Next, as the piston P of the cylinder S extends to the left in the direction of the arrow, the mounting base 3 including the needle thread clamping mechanism 1 also starts moving to the left.

At this time, since one rising end (downward in the figure) of the shaft supporting portion 1a2 of the movable member 1a is engaged with the locking spring 6, the movable member 1a rotates counterclockwise about the shaft pin 1p. Then, the other rising end (upper side in the figure) of the shaft support 1a2 is fixed to the fixing member 1.
The rotation is stopped when it comes into contact with the end 1b1 of b, and the movable member 1a in the needle thread holding mechanism 1 moves the needle thread 9 against the fixed member 1b.
It will be opened in between.

When the operation during this period is shown in FIG. 2, as the cylinder S extends, the needle thread cutting means A is guided from the original position by the guide means B and moves to the lower left in the figure, and the needle thread holding mechanism is , The fixing member 1b located below the presser foot K with the needle thread 9 interposed therebetween.
The movable member 1a1 is open. (See FIG. 5) Next, that is, in the state of FIG. 5, when the piston P still extends, the locking portion 7a at the tip of the stopper 7 and the movable member
The movable member 1a rotates clockwise about the shaft pin 1p because one of the rising ends of the shaft supporting portion 1a1 (upper side in the drawing) of the la 1a engages with each other. After contacting the upper thread 9, the movable member 1a sandwiches the upper thread 9a between the movable member 1a and the fixed member 1b, and at the same time when the apex of the cutting member 2 contacts the upper thread 9, the cutting member 2 is energized. The upper thread 9 is cut between the work clamp K and the work W due to the Joule heat generated at the apex.

A timer is set in advance so that this energization is started at the above timing according to the operation timing of the air cylinder S.

Then, the operator can adjust the timing back and forth according to the thickness of the thread and the like.

After that, the needle thread holding mechanism 1 in a state of holding the end portion of the cut needle thread 9 on the needle N side is contracted by the piston P of the cylinder S, and the operation reverse to the above-described process causes the needle thread holding mechanism 1 to move as shown in FIG. Return to the original position shown.

During this time, as the upper thread catching mechanism 1 retreats, the engaging member 8 of the upper thread feeding means C also returns to the original position, and when the next sewing process is started, the upper thread end held by the upper thread catching mechanism 1 becomes Needle N
Is removed by the action of. After that, the above operation is repeated.

In this embodiment, as shown in FIG. 3, the cutting member 2 has an apex that abuts the needle thread, and thus, the apex is in very small size.
By energizing, this part instantly glows red and a quick cutting operation is possible, but since it has a U-shape as a whole, "sagging" can be caused by repeated contact with the upper thread. The durability is remarkably improved without any occurrence.

[Effects of the Invention] Since the mechanism having the function of holding and fusing the upper thread is integrally integrated and the driving is performed by a single driving source, the timing of each function can be easily adjusted. In addition, an upper thread cutting device having a small number of parts and having durability is realized, and high-strength upper thread or extra-thick upper thread can be efficiently melted, and the quality of sewing products and the sewing efficiency are improved.

Furthermore, because a thread ball is formed at the tip of the melted upper thread,
Since the upper thread is clamped by the clamping member and the thread ball is hooked between the clamping members, the upper thread does not easily fall out between the clamping members. Further, since the upper thread is clamped, the upper thread is not pulled under the cloth in the next sewing operation, the bird's nest is prevented, and the appearance of the stitch at the beginning of pulling is not impaired.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a needle thread cutting means according to an embodiment of the present invention, and FIG. 2 is a side view of a sewing machine provided with a needle thread cutting device according to an embodiment of the present invention. 3 is a plan view of the cutting member, FIG. 4 is a plan view of the needle thread cutting means in which the needle thread holding mechanism is in a closed state, and FIG. 5 is a process in which the needle thread holding mechanism is closed to open and then closed. FIG. 3 is a plan view of the upper thread cutting means showing In the figure, A ... upper thread cutting means B ... guiding means C ... upper thread feeding means S ... cylinder (driving means) 1a ... movable member (upper thread clamping mechanism) 1b ... fixed member (upper thread clamping mechanism) ) 2 ... Cutting member

Claims (1)

[Claims] 1. A needle thread cutting device for a sewing machine, which cuts an upper thread from a sewing needle to a material to be sewn after completion of a sewing operation, wherein the upper thread is clamped and cut between the sewing needle and the material to be sewn. The upper thread cutting means has a thread cutting means, and the upper thread cutting means includes a fixed member and a movable member that opens and closes the fixed member and holds the upper thread, and a movable member provided below the movable member. The fusing member that interlocks and generates Joule heat by energization, one driving means that is connected to the upper thread clamping mechanism and moves the upper thread clamping mechanism from the original position to the upper thread fusing position, and in conjunction with the drive by the driving means. When the upper thread clamp mechanism is moved from the original position to the upper thread fusing position, the upper thread clamp mechanism is opened, and when it is moved from the upper thread fusing position to the original position, the upper thread clamp mechanism is closed to open and close in the direction crossing the upper thread. Opening and closing mechanism A needle thread cutting device for a sewing machine, which performs thread cutting and holding of the needle thread at the same time by the driving source.