JPH0752700Y2 - Bobbin thread cutting device for sewing machine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION This invention relates to a heavy-duty sewing machine that uses a very thick or tough thread that forms a lock stitch by knotting a lower thread and an upper thread. Between the lower thread of the lower thread and the upper end surface of the shuttle after the lower thread of the lower thread is electrically cut by the lower thread cutting member and electrically cut by the lower thread cutting member. The present invention relates to a lower thread cutting device of a sewing machine.

[0002]

2. Description of the Related Art At present, a sewing machine is provided with a thread trimming device for automatically 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 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. Has been.

However, when an extremely thick yarn or a tough yarn is used, the blade portions of the fixed blade and the movable blade are worn and the sharpness is deteriorated. Focusing on such a problem, the applicant of the present application has previously disclosed in Japanese Utility Model Laid-Open No. 61-39088 that good cutting performance can be obtained by a thread cutting means using a hot wire member having a large electric resistance even for a very thick and tough thread. A bobbin thread trimming device for a lockstitch sewing machine capable of obtaining the above is disclosed.

That is, in FIG. 8, when the thread is cut after the sewing is finished, first, the lead wire 20 is energized, the piston / cylinder assembly 21 feeds the feed mechanism 22 in the arrow direction, and the lower thread 23 When the front portion 25 of the bobbin thread cutting plate 24 that has been brought to a high temperature is brought into contact with the bobbin thread, the bobbin thread 23 is burned out. Before the bobbin thread 23 is brought into contact with the front portion 25, the bobbin thread 23 is reeled out from the bobbin case 27 by the feeding plate 26 by a length required for the next sewing start, so that the bobbin thread 23 is burned out. At this time, the bobbin case 27 side bobbin thread is held on the projecting portion 28 of the feeding plate 26, and after being burnt out, the feed mechanism 22 is returned to its original position by the operation of the piston / cylinder assembly 21 to project. Part 28
The bobbin thread held above moves to the right of the bobbin case 27 so as to be prepared for the next sewing start, and the thread cutting of the bobbin thread 23 is completed.

A front member 29 is fixed to the lower thread cutting plate 24 and the feeding plate 26 in an electrically insulated state. Reference numeral 30 denotes a connecting plate, one end of which is fixed to the front member 29 and the other end of which is fixed to the rear member 31. The rear member 31 is provided with rollers 32 and 32 on both sides. The rollers 32 and 32 are side plates 33 and 3.
It is supported by the grooves 34, 34 provided in 3. The front member 29, the connecting plate 30, and the rear member 31 form the feed mechanism 22.

[0006]

However, in the above-mentioned conventional device, since the lower thread cannot be reliably held,
When it is used for thick material sewing, there is a problem that the upper and lower threads of the first and second stitches at the start of sewing cannot be knotted or the knotting position becomes unstable. This invention was made in view of the above-mentioned problems, and when the driving means acts on the thread cutting operation position, the lower thread feeding member feeds the lower thread of the cloth and the bobbin case and cuts the lower thread. The cut bobbin thread end is blown obliquely downward in the upper direction of the hook, and the lower end of the bobbin thread is clamped between the lower surface of the feeding member and the upper end surface of the hook by the action of the drive means on the retracted position. An object of the present invention is to provide a bobbin thread trimming device for a sewing machine which can surely knot the upper and lower threads of the first and second stitches at the start of sewing.

[0007]

The present invention comprises a high electric resistance element which is arranged in a horizontal direction with respect to a needle drop path between a needle plate and a shuttle and which generates a predetermined Joule heat when energized. A bobbin thread trimming member having a cutting member at its tip, and a thread hooking portion which is juxtaposed to the bobbin thread trimming member below the bobbin thread trimming member and delivers a bobbin thread length required for the next sewing start from the bobbin case. And a connecting member for integrally connecting the rear ends of the lower thread cutting member and the feeding member, and the lower thread cutting member and the lower thread cutting member which are always connected to the lower member. The leading end of the thread reeling member is at the retracted position with respect to the needle drop path, and the advancing / retreating drive means that acts on the thread cutting operation position when thread cutting and the bobbin thread reeling when the driving means acts on the thread cutting operation position. The dashi member uses the lower thread of the cloth and bobbin case. After the bobbin thread is cut off by the cutting member of the bobbin thread trimming member and the bobbin case is cut off, an air blowing means for blowing the bobbin thread end toward the upper part of the shuttle is provided. It is characterized in that the lower thread is clamped between the lower surface of the feeding member and the end surface of the shuttle due to the action from the cutting operation position to the retracted position.

[0008]

In the present invention, the bobbin thread trimming member arranged in the horizontal direction with respect to the needle drop path between the needle plate and the shuttle and the bobbin thread trimming member below the bobbin thread trimming member are arranged next to each other. A connecting member for integrally connecting the rear end portion of the lower thread feeding member for feeding the lower thread necessary for the sewing start of the sewing machine is provided to be able to advance and retreat to the retracted position and the thread cutting position by the driving means, and the driving means is set to the thread cutting working position. When the lower thread reeling member reels out the lower thread of the cloth and the bobbin case when cut, and is cut by the cutting member,
The lower thread end from the cut bobbin case is blown obliquely downward toward the upper part of the shuttle, and the driving means acts on the retracted position to clamp the lower thread end between the lower surface of the feeding member and the end surface of the shuttle. This ensures the knots of the upper and lower threads of the first and second stitches of the next sewing.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a partially cutaway front view showing an essential part of this embodiment, and FIG. 2 is a plan view of the one shown in FIG. In each drawing, 1 is a needle attached to a needle bar that moves up and down in conjunction with the main shaft of the sewing machine, 2 is a needle hole 2a
A needle plate 3 having a vertical hook for cooperating with the needle 1 to form a seam, 4 is arranged in the horizontal direction with respect to the needle drop path between the needle plate 2 and the vertical hook 3, and its tip The lower thread cutting member is provided with a cutting member 4a having a high electric resistance in a substantially arc shape so as to surround the needle drop path. 5 are arranged side by side below the lower thread cutting member 4 in parallel with the lower thread cutting member 4, and a thread hooking portion 5a having a substantially circular arc shape is provided at the tip end thereof so as to surround the needle drop path. This is a bobbin thread delivering member that delivers a bobbin thread length required for the start of sewing. The thread hooking portion 5a is located slightly closer to the needle drop path side than the cutting member 4a.

On the other hand, the rear end portion of the bobbin thread cutting member 4 is fixed to the insulator 6 supported by the frame of the bed by screws and connected to the power source through the lead wires 4b and 4b. When the lower thread cutting member 4 is energized, the cutting member 4a generates a predetermined Joule heat, whereby the lower thread can be electrically cut. The rear end portion of the bobbin thread feeding member 5 is fixed in the central portion of the insulator 6 together with the connecting rod 7 by sandwiching the insulator 6 with screws 8 and nuts 9.

The insulator 6, the connecting rod 7, the screw 8, the nut 9 and the like form a connecting member. Further, the tip of the inverted L-shaped flat portion of the connecting rod 7 is a driving means 1 including an air cylinder or the like.
It is fixed to the movable body 10b fixed to the rod 10a of 0. This drive means can be moved back and forth between the thread cutting position and the retracted position. 11 is an air blower for cutting the lower thread by the cutting member 4a by energizing the lower thread cutting member 4 and then blowing the lower thread end from the cut bobbin case toward the upper part of the shuttle from obliquely below. It is an air nozzle as a means. The air nozzle 11 is connected to an air tank (not shown) via a hose 11a. Although the air blowing means 11 is fixed to the air cylinder 10 in the present embodiment, the air blowing means 11 is not limited to this and may be used in another place.

The operation of the bobbin thread trimmer in this embodiment constructed as described above will be described with reference to FIGS. FIG. 3 shows a state before the bobbin thread 12 is set and sewing is started, and the bobbin thread cutting member 4 and the bobbin thread feeding member 5 are in the retracted positions shown by the driving means. Next, after sewing is completed, the lower thread cutting member 4 is energized based on a thread trimming signal (not shown), and the driving means acts on the thread trimming operation position to cause the lower thread trimming member 4 and the lower thread feeding member 5 to operate. It moves in the direction of the arrow as shown in FIG. At this time, since the position of the thread hooking portion 5a of the bobbin thread delivering member 5 is located slightly on the needle drop path side from the cutting member 4a of the bobbin thread cutting member 4,
The thread hooking portion 5a feeds the bobbin thread 12 between the cloth and the bobbin case, and then the bobbin thread 12 is cut only by lightly contacting the cutting member 4a (since the melting temperature of the thread is lower than the temperature of the cutting member 4a). .

Immediately after the lower thread 12 is cut by the cutting member 4a, the air nozzle 11 draws air from the air tank (not shown) through the hose 11a to remove the lower thread 12 from the bobbin case as shown in FIG. It works so as to blow it obliquely downward toward the upper part of the shuttle 3. From the state shown in FIG. 5, the driving means is retracted to the retracted position and the lower thread 12 from the bobbin case is shown on the lower surface of the lower thread feeding member 5 and the end surface 3a of the shuttle 3 (flat portion of the housing) in FIG. To be pinched.

FIG. 7 is a left side view showing only the main part in the state shown in FIG. 6 (a). In this way, since the lower thread 12 is clamped at a predetermined position between the lower thread feeding member 5 and the end surface 3a of the shuttle 3, the upper and lower threads of the first and second stitches at the start of the next sewing are sewn. The nodule becomes reliable and the nodule becomes stable. In the above embodiment, the cutting member 4a and the thread hooking portion 5
Although it has been described that a is formed in a substantially arc shape so as to surround the needle drop path, it is not limited to the arc shape, and various shapes may be used.

[0015]

As described above, in the bobbin thread trimming device of the present invention, the bobbin thread feeding member feeds the bobbin thread between the cloth and the bobbin case when the driving means operates in the thread trimming operation position. After the bobbin thread is electrically cut at this timing, the cut bobbin thread end is blown obliquely downward from the upper direction of the shuttle so that the drive means is actuated to the retreat position to move the bobbin thread end to the bobbin thread end. Since the lower surface of the feeding member and the end surface of the hook are both clamped, it is possible to easily thread even a very thick or tough thread especially when sewing thick materials, and it is possible to always clamp the lower thread at a predetermined position. The upper and lower knots of the first and second stitches at the start of sewing are secured, and the knots are stabilized.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an essential part of an embodiment of the present invention.

FIG. 2 is a plan view of the apparatus shown in FIG. 1 except for a needle plate and the like.

FIG. 3 is an explanatory view showing a state before setting a lower thread and starting sewing, (a) is a front view and (b) is a plan view.

FIG. 4 is an explanatory view showing a state in which the bobbin thread trimming member is energized and the driving means has acted on the thread trimming operation position after the completion of sewing, (a) is a front view, and (b) is a plan view.

FIG. 5 is an explanatory view showing a state in which after the cutting member cuts the lower thread between the cloth and the bobbin case, the cut lower thread is blown toward the upper portion of the hook from below.
(A) is a front view and (b) is a plan view.

FIG. 6 is an explanatory view showing a state in which the driving means is retracted to the retracted position and the lower thread from the bobbin case is clamped between the lower surface of the lower thread feeding member and the upper portion of the shuttle, and (a) is a front view. ,
(B) is a plan view.

FIG. 7 is a left side view of what is shown in FIG. 6 (a).

FIG. 8 is a front view showing a conventional bobbin thread cutting device of a lockstitch sewing machine.

[Explanation of symbols]

 1 needle 2 needle plate 3 hook 4 bobbin thread cutting member 4a cutting member 5 bobbin thread feeding member 5a thread hooking portion 6 insulator 7 connecting rod 8 screw 9 nut 10 driving means (air cylinder) 11 air nozzle 12 bobbin thread

Claims (1)

[Scope of utility model registration request] 1. A vertically reciprocating needle, a lower thread bobbin wound with a lower thread, a bobbin case for rotatably holding the lower thread bobbin, and a vertical movement of the needle. Rotate,
In a lockstitch sewing machine provided with a vertical hook for connecting a lower thread drawn out from the bobbin case and an upper thread inserted in a needle, the needle thread is arranged in a horizontal direction with respect to a needle drop path between the needle plate and the hook. From a bobbin case, a bobbin thread cutting member having a cutting member made of a high electric resistance body for generating a predetermined Joule heat when energized is provided at a tip portion thereof, and a bobbin thread cutting member arranged below the bobbin thread cutting member in parallel. A bobbin thread delivering member having a thread hooking portion for delivering a bobbin thread length required for the next sewing start, and a connection for integrally connecting the respective rear end portions of the bobbin thread cutting member and the bobbin thread delivering member. A member and the connecting member, and the tip ends of the bobbin thread cutting member and the bobbin thread feeding member are always in the retracted position with respect to the needle drop path, and can be moved back and forth to act in the thread cutting operation position during thread cutting. Driving means and thread cutting device When the bobbin thread feeding member reels out the bobbin thread between the cloth and the bobbin case when the bobbin case is actuated at the moving position, and the bobbin thread is cut by the cutting member of the bobbin thread cutting member, the bobbin thread end from the cut bobbin case is removed. An air blow-out means for blowing the air toward the upper part of the hook, and holding the lower thread between the lower surface of the feeding member and the end surface of the hook by the action of the driving means from the thread cutting operation position to the retracted position. A bobbin thread cutting device for sewing machines.