JPH07155489A - Rotary thread cutting device for sewing machine - Google Patents

Abstract

PURPOSE:To property and surely select the thread to cut and the thread not to cut, and cut the thread to cut. CONSTITUTION:This device has a thread catching member 11 moved along a circular reciprocating route and a thread cutting knife 12 having a thread cutting edge part, and the thread catching member 11 is reciprocated according a prescribed thread cutting command, to select, at its returning, the thread to cut and the thread not to cut from a plurality of threads laid extending from a sewing machine hook to a throat plate NB by a protruding thread selecting part formed on the top end. The selected thread is caught by recessed thread catching parts formed on both side positions of the thread selecting part, and the thread to cut is touched by the edge part of the knife 12 and cut. On the other hand, a holding plate 21 which is touched by the thread selecting part of the thread catching member when a needle thread loop is released from the hook is supported by a sewing machine frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suspended between a needle plate and a sewing machine hook by a thread catching member and a thread cutting knife which move along an arcuate reciprocating path set below the needle plate. The present invention relates to a rotary thread cutting device for a sewing machine, which selects a plurality of threads (needle thread, upper thread, lower thread) and cuts the upper thread and the lower thread.

[0002]

2. Description of the Related Art At present, various thread trimming devices provided for sewing machines have been proposed. However, in a lock stitch sewing machine, etc., in which a needle thread and a bobbin thread are knotted to form a seam, a thread cutting device is provided below the needle plate. The one in which the lower thread and the upper thread are cut is generally used. In addition, this type of thread cutting device is roughly classified into a horizontal type and a rotary type according to the moving direction of a thread catching member that catches a thread to be cut. In the rotary type, the shape of the member is slightly more complicated than the horizontal type, which has a flat plate shape because the thread catching member and the thread trimming knife have a curved shape, but the sewing needle insertion hole in the needle plate Since the upper thread and the lower thread can be cut in the vicinity of, there is an advantage that the remaining thread connected to the cloth can be shortened as compared with the horizontal type.

A conventional rotary type thread trimming device and its peripheral structure will be described below with reference to FIGS. 4 to 7. First, the peripheral structure will be described with reference to FIG. In the figure, reference numeral 1 denotes a lower sewing machine shaft provided in the sewing machine bed, which is adapted to rotate in synchronization with a sewing machine main shaft (not shown) for raising and lowering the sewing needle N. Reference numeral 2 denotes a sewing machine hook held on the sewing machine lower shaft 1. The sewing machine hook 2 is composed of an outer hook 3 which rotates integrally with the lower shaft 1 of the sewing machine, and an inner hook 4 which is rotatably supported in the outer hook 3, in which a lower thread is wound. The unillustrated lower thread bobbin mounted is the bobbin case 5.
It is rotatably supported via. An engaging portion 6a of an inner hook stopping member 6 fixed in the sewing machine bed is engaged with the front portion of the inner hook 4, so that the inner hook 4 can be prevented from rotating by this engaging portion 6a. It has become. Further, a sword tip 3a, a cam plate 3b, and a runway retainer 3c are provided on the outer peripheral portion of the outer hook 3.

On the other hand, FIGS. 5 to 7 are views showing a conventional rotary type thread trimming device provided around the sewing machine hook 2. As shown in FIG.
This rotary type thread trimming device includes a thread catching knife 11 and a thread trimming knife 12, and both knifes 11 and 12 are attached to the lower shaft 1 by a driving force of a driving means (not shown) which operates according to a predetermined thread trimming command. Each holder 1b fixed to the loosely fitted metal 1a
Is reciprocated along a reciprocating movement path on an arc centered on the lower shaft 1. That is, the thread catching knife 11 fixed to one of the holders is provided with a thread trimming position (one-dot chain line in FIG. 5) from one side part (left side part in the figure) of the outer hook to the uppermost part of the outer hook. The thread trimming knife 12 fixed to the other holder takes a moving path to reach the thread cutting position shown in FIG. 5) from the other side (right side in the figure) of the outer hook (indicated by a chain line in FIG. 5). (Shown) to move along a reciprocating movement route.

Reference numeral 13 is a hook thread retainer having a rod shape. The hook thread presser 13 is adapted to be inserted into and removed from the through hole 5a formed in the front surface of the bobbin case 5 by a solenoid (not shown) which operates in response to a thread cutting command.
When inserted into a, the bobbin case 5 comes into contact with the bobbin thread bobbin accommodated in the bobbin case 5 to give resistance to the rotation of the bobbin bobbin, and prevents excessive rotation of the bobbin thread bobbin at the time of thread cutting. It is designed to secure the remaining length of the needle thread after the thread is cut by cutting the thread path.

In such a structure, the sewing machine main shaft rotates and the sewing needle N and the sewing machine hook 2 start a known stitch forming operation. That is, the ascending / descending movement of the sewing needle N and the rotating movement of the outer hook 3 are started, and the sword tip 3a is moved to the sewing needle N.
Of the upper thread loop IL formed below the needle plate NB at the time of rising
And the upper thread loop IL is moved along the periphery of the sewing machine hook 2. Therefore, when the thread trimming command signal is issued, the hook thread presser 13 is inserted into the through hole 5a of the bobbin case 5, so that the upper thread I1 passing through the front surface side of the bobbin case 5 is wound around the hook thread presser 13. While moving around the inner hook 4, the needle thread loop IL is removed from the blade tip 3a at the time when the blade tip 3a makes one full turn, is once delivered to the track retainer 3c opposite to this, and is further removed from there. After that, the thread is cut by a thread cutting operation described later.

On the other hand, in the thread trimming device, when the thread trimming command signal is received, the upper thread loop IL begins to pass around the inner shuttle 4, and at the same time, the thread catching knife 11 is located at the lateral position (initial position) of the sewing machine shuttle 2. From the sewing machine hook to the cloth, and the needle thread I1 hung between the needle plate NB and the cloth and the needle thread Ia hung between the sewing needle N and the cloth. From among the lower thread I2, as shown in FIG. 7A, the upper thread I1, the lower thread I2 to be cut, and the needle thread Ia not selected are selected and captured. This selection is performed by the tip of the thread catching knife 11.

That is, at the tip of the thread catching knife 11,
As shown in FIG. 7, two recesses 11a and 11b are notched to form a thread splitting portion 11c at the tip, and this thread splitting portion 11c is the upper thread loop I.
The upper thread I which is the thread to be cut by entering into L
1 and the lower thread I2 have one recess (cutting thread catching portion) 11a
And the other needle thread Ia is caught by the other recess (non-cutting thread catching section) 11b.

Then, a thread catching knife 11 that catches each thread
Is near the uppermost position of the sewing machine hook 2 (at the time of passing slightly)
The upper thread I1 and the lower thread I2, which are vertically overlapped with the cutting thread catching section 11a of the thread catching knife 11, are cut by the blade section 12a of the thread cutting knife 12. At this time, the non-cutting thread catching portion 11b is the blade portion 1 of the thread cutting knife 12.
Since it passes through the side of 2a, the needle thread Ia captured here does not join with the blade portion 12a of the thread cutting knife 12 and is not cut.

As described above, in the rotary type thread cutting device described above, after the upper thread I1 and the lower thread I2 to be cut and the needle thread Ia which should not be cut are selected by the thread catching knife,
The upper thread I1 and the lower thread I near the needle drop hole NBa of the needle plate NB.
Since 2 is cut, it is possible to prevent a long residual thread from being formed on the cloth. Moreover, since the upper thread loop IL is cut while being wound around the hook thread presser 13, a sufficient length can be obtained for the remaining thread formed on the needle N, and the needle thread Ia is sewn at the start of the next sewing. There is no possibility of pulling out from the N needle thread insertion hole Na.

[0011]

However, in the above-mentioned rotary type thread trimming device, the yarn catching state by the yarn catching knife 11 may be disturbed and a proper cutting state may not be obtained, resulting in lack of stability. There was a problem. This is
Especially, it is remarkable in the Tetoron yarn which is easy to slip.
The disorder of the yarn catching state occurs when a yarn that should not be cut is wound around the yarn catching portion for cutting due to a temporary slack that occurs in the upper yarn loop when the upper yarn loop exits from the sewing machine hook 2. .

For example, as described above, the runway retainer 3 is attached to the outer hook 3.
In the sewing machine in which c is formed, there is a moment when the upper thread loop IL delivered to the runway retainer 3c is pulled out by the thread catching knife 11 moving toward the cutting position (see FIG. 7).
(See (a)), at that moment, the upper thread loop is temporarily loosened T
As a result, the slack T caused the needle thread Ia to go over the front end portion of the thread dividing section 11c and wrap around to the cutting thread catching section 11a as shown in FIG. 7B.
When the needle thread Ia wraps around the cutting thread catching portion 11a, the three upper threads I1, the needle thread Ia, and the lower thread I2 are cut, and the needle thread Ia connected to the sewing needle N becomes shorter. The problem occurs that the upper thread is pulled out from the sewing needle N at the start of the next sewing operation.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a thread cutting device for a sewing machine capable of properly selecting a yarn to be cut and a yarn not to be cut and surely cutting the yarn. For the purpose of provision.

[0014]

SUMMARY OF THE INVENTION According to the present invention, in a sewing machine in which an upper thread and a lower thread are knotted by the cooperation of a sewing needle and a sewing machine hook to form a stitch, an arc-shaped reciprocating path is provided. A thread catching member that moves along and a thread cutting knife provided with a thread cutting blade are provided, and the thread catching member is reciprocally moved in response to a predetermined thread cutting command, and the tip end portion thereof moves forward. By the formed convex thread dividing section, a plurality of threads that are hung from the sewing machine hook over the sewing needle are sorted into threads to be cut and threads not to be cut, and the selected threads are separated. The thread to be cut is caught by the concave thread catching portions formed on both sides of the sewing machine so that the thread to be cut is joined to the blade portion of the thread trimming knife for cutting, and the upper thread loop is pulled out from the sewing machine hook. Holding plate to be joined to the yarn splitting portion of the yarn catching member at the time of It is obtained by supporting the sewing machine frame.

[0015]

According to the present invention, even if the upper thread loop is loosened when it is removed from the sewing machine hook, the sewing machine frame supports the thread dividing section for selecting the thread to be cut and the thread not to be cut. Since the holding plate is joined, the yarn that should not be cut wraps around into the catching part of the yarn that should be cut, and the proper yarn catching state initially selected by the yarn splitting part is held until the cutting is completed. . Therefore, the three threads are not cut at the same time.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described with reference to FIGS.
It will be explained based on. It should be noted that the same or corresponding parts as those described in the above-mentioned prior art are designated by the same reference numerals, and the detailed description thereof will be omitted. The rotary type thread trimming device of the sewing machine in this embodiment has a thread catching knife 1 as a thread catching member having the same structure and operation as those shown in the prior art.
1 and a thread trimming knife 12 (however, the blade portion of the thread trimming knife of the embodiment is an upper knife having a blade on the upper portion), and the same construction is provided in the sewing machine hook as its peripheral construction. -It works.

However, in this embodiment, a holding plate that can be joined to the yarn catching member 11 is provided, and this point is significantly different from that shown in the above-mentioned prior art, whereby the thread cutting performance is improved. It can be greatly improved. In the figure, 21 indicates the above-mentioned holding plate. The holding plate 21 is formed of a thin flexible member, and an attachment portion 21a formed at one end thereof has an inner hook stopper member 6 held by the sewing machine frame to prevent the inner hook 4 from rotating. It is fixed together with the inner hook stopper member 6 by the set screw 22 and forms a cantilever spring as a whole. Further, the holding plate 21 is integrally formed with a curved portion 21b which is curved in an arc shape along the movement path of the thread catching member 11 and the attachment portion 21a, and the tip portion 21b1 of the curved portion 21b serves as a sewing needle. It is set to the non-interference position.

In this embodiment thus constructed, when the thread cutting command is inputted, the thread catching member 11
Starts the forward movement from the initial position set to the side of the outer hook 3 toward the cutting position as in the conventional case, and the upper thread I1 and the lower thread I2 to be cut are cut in the middle by the thread catching portion 11a. The needle catching portions 11b respectively catch the needle threads Ia that should not be cut. At this time, the upper thread loop is in a state of being passed from the sword tip 3a to the runway retainer 3c, but after that, the upper thread loop IL is caught by the thread catching member 11 and pushed out to the thread cutting position. As in the case of FIG. 7 (a) described above, the slack is temporarily generated by withdrawing from the track retainer 3c.

As a result of this slack, in the conventional device, as shown in FIG. 7 (b), the upper thread loop passed over the thread splitting portion 11c, but this inconvenience occurred. In the example, the holding plate 21 is joined to the tip of the thread dividing section 11c of the thread catching member 11 immediately before the upper thread loop IL is pulled out from the runway retainer 3c, so that it is once caught by the catching sections 11a and 11b. It is completely prevented that the spun yarn moves to a different catch. In other words, each yarn undergoes the cutting operation while maintaining the proper yarn catching state initially selected by the yarn dividing section 11c, and only the upper yarn I1 and the lower yarn I2 to be cut are surely cut.

In the above embodiment, the holding plate 21
Although the description has been made by taking the case where the tool is fixed to the sewing machine frame together with the inner hook stopping member 6, the holding plate 21 is screwed to the inner hook stopping member 6 and supported by the sewing machine frame through the inner hook stopping member 6. It is also possible. It is also possible to fix the holding plate 21 to other members fixed to the machine frame of the sewing machine,
Furthermore, the holding plate 21 may be movably held by a sewing machine frame. For example, the holding plate may be fixed to the lower surface of the thread trimming knife, moved together with the thread trimming knife, and brought into contact with or separated from the thread catching member.

In the sewing machine hook, the runway holder 3 is attached to the outer hook.
Although there are some which are not provided with c, when a thick thread is used in such a sewing machine hook, the thread that is pulled out from the outer hook has no action and its behavior is unstable. Therefore, the yarn may move from the catching portion of the yarn catching member. Therefore, the present invention is also effective for a sewing machine provided with a sewing machine hook that is not provided with the track retainer 3c.

[0022]

As described above, according to the present invention, the yarn catching member that moves along the arcuate path makes it possible to distinguish the yarn for cutting from the yarn suspended from the needle plate to the sewing machine hook. The thread for cutting is selected and captured, and the thread for cutting is cut in cooperation with the thread cutting knife, and the thread catching member separates the thread when the upper thread loop is removed from the sewing machine hook. Since the holding plate is joined to the portion, even if looseness is temporarily formed in the upper thread loop when the needle thread is removed from the sewing machine hook, the looseness does not disturb the thread catching state and always cuts. Only the power thread can be reliably cut, and stable cutting performance can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged front view of essential parts showing an embodiment according to the present invention.

FIG. 2 is a perspective view of an essential part of what is shown in FIG.

3 is a plan view of what is shown in FIG. 2. FIG.

FIG. 4 is a perspective view showing a peripheral configuration of a rotary thread cutting device.

FIG. 5 is an explanatory front view showing a conventional rotary type thread cutting device.

FIG. 6 is an enlarged front view of the main part of what is shown in FIG.

FIG. 7 is a plan view showing a thread catching state in a conventional thread trimming device, FIG. 7 (a) shows a state at a moment when an upper thread loop is pulled out from a track pressing member by a thread catching member, and FIG. The states in which the yarn is disturbed by the yarns are shown.

[Explanation of symbols]

 N Sewing needle NB Needle plate I1 Upper thread IL Upper thread loop I2 Lower thread 2 Sewing machine hook 3 Outer hook 4 Inner hook 11 Thread catching member 11a Thread catching section 11b Thread catching section 11c Thread splitting section 12 Thread trimming knife 21 Holding plate

Claims (1)

[Claims] 1. A sewing needle that moves up and down, and a sewing machine that rotates in synchronism with the lifting movement of the sewing needle cooperate with an upper thread that is inserted into the sewing needle and a lower thread that is fed from the sewing machine. In a knitting machine, a thread catching member that moves along a circular arc-shaped reciprocating movement path from a side part of a sewing machine hook to a predetermined thread cutting position from a side part to a top part, and a thread cutting blade. A thread trimming knife provided with a portion, the thread catching member is reciprocally moved in response to a predetermined thread trimming command, and a convex thread dividing portion formed at the tip of the thread moving member moves the sewing machine from the sewing machine hook. A plurality of threads hung over the sewing needle are selected into a thread for cutting and a thread for non-cutting, and the selected threads are formed by concave thread catching portions formed on both sides of the thread dividing portion. Capture and join the thread for cutting to the blade of the thread trimming knife. A rotary plate of the sewing machine, characterized in that a holding plate that is joined to the thread dividing portion of the thread catching member is supported by the sewing machine frame immediately before the upper thread loop is pulled out from the sewing machine hook while being cut. Thread trimming device.