JPH06165891A - Thread cutter - Google Patents

Abstract

(57) [Summary] [Purpose] Thread cutting in a sewing machine having a half-turn hook with a hook point for the inner hook between the needle drop position and the bobbin thread lead-out point, without causing defective cutting or reducing the sewing quality. Provide a device. [Structure] The spindle 3 is on the left rear side of the needle drop position O as seen from the operator, stands by with the thread separating portion 1a facing forward, and when the thread is separated, the upper thread of the cloth side and the lower thread are separated in this order. Moving knife 1
It comprises a fixed knife 2 which cooperates with the moving knife 1 to cut the cloth side upper thread and the lower thread.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting device in a sewing machine having a half-rotary hook having an inner hook point between a needle drop position and a bobbin thread leading point.

[0002]

2. Description of the Related Art Sewing machines having a half-turn hook (hereinafter referred to as a DB type half-turn hook) having a needle drop position between a bobbin bobbin thread deriving point and a center hook point are widely used. The cutting device is one in which the fulcrum of the moving knife is on the right front side of the needle drop position as seen from the operator, the moving knife stands by in front, and when moving the thread, the moving knife picks the bobbin thread and the upper thread in this order. . In this thread cutting device, the lower thread and the cloth side upper thread, which are inevitably determined from the structure of the shuttle, are aligned in a straight line with respect to the needle drop position O as shown in FIG. 7 (1). It is possible to minimize the respective displacement amounts of the bobbin thread and the cloth side upper thread due to the forward movement of the moving knife 1. The thread cutting is performed as shown in FIG.

The moving knife 1 is moved forward from the standby state shown in (1) as shown in (2), and is separated (the bobbin thread and the cloth side upper thread are moved by the forward movement of the moving knife before cutting the thread. The operation of leading the knife to the thread guide portion) is started. The upper thread is sufficiently drawn into the hook, and the tip of the loosening part of the moving knife can surely enter. And, as shown by the black arrow in (3),
The bobbin thread is dealt with. This lower thread handling amount is represented as a difference between the distance from the support shaft of the moving knife to the leading end of the handling section and the distance from the support shaft to the end of the handling section. A large force does not act on the loosened and bent bobbin thread other than the restoring force of the bobbin thread itself and the force due to the feeding of the sewing machine, but the bobbin thread can return sufficiently because the loosening amount is small. Next, as shown in (4), the cloth side upper thread is loosened. Compared with the bobbin thread, the upper thread has large behavior changes such as lifting of the balance and thread removal of the hook.
It is necessary to move in the direction of the arrow (1), but since this direction and the forward direction of the moving knife match, the smallest handling amount can be effectively given. As shown in (5), the moving knife retreats last, and the loosened cloth-side upper thread goes over the outer circumference of the moving portion of the moving knife and enters into the thread guide section. As shown in (6), the moving knife 1 starts the backward movement, and the thread is hooked on the thread guiding portion in the order of the cloth side upper thread and the lower thread, and as shown in (7),
The upper thread is pulled up by a balance and held so as to wind around the moving knife. And the lower thread is pulled out to the moving knife,
The required amount is paid out. At this time, the backward movement speed of the moving knife 1 is controlled so that the bobbin may not idle (excessive rotation) due to the bobbin thread withdrawing speed being too high and adversely affecting the start of the next sewing. The upper thread held by the moving knife 1 is the residual thread on the needle side after thread cutting. Finally, as shown in (8), the cloth side upper thread and the lower thread are cut. Since the cutting position is right beside the needle hole, the yarn end remaining on the back of the cloth F is short, and good quality can be secured. Then, by setting the moving knife 1 to an appropriate width and determining the shape of the hole 5 of the cauldron upper spring 4 and the thread cutting direction as described above, the needle thread upper end necessary and sufficient for the next sewing And each length of the lower thread end can be secured.

By the way, in a sewing machine having a DB type half-turn hook, a perfect stitch is formed when forward feeding (sending from left to right) and a hitch stitch is formed when feeding backward (sending from right to left). , Not suitable for automatic eight-sided sewing. On the other hand, there is also known a sewing machine including a half-turn hook (hereinafter referred to as a DP type half-turn hook) in which a middle hook sword tip is arranged between a needle drop position and a bobbin bobbin thread deriving point (Japanese Patent No. 99353). Although a perfect stitch is formed at the time of both forward and reverse feed, it is suitable for an eight-sided stitch automatic sewing machine, but it has not been widely used so far, and its thread cutting device has not been developed.

Therefore, as in the case of a sewing machine having a DB type half-turn hook, a thread cutting device for separating the lower thread by the moving knife and then the upper thread is applied to this sewing machine. That is, in this thread cutting device, as shown in FIG. 7 (2), the spindle 3 of the moving knife 1 is on the left rear side of the needle drop position O as seen from the operator, and the moving knife stands by at the rear, and When the thread is separated, the moving knife 1 separates the lower thread and the upper thread in this order. In this thread cutting device, the bobbin thread and the cloth side upper thread, which are inevitably determined from the structure of the hook, are on the front side of the hole 5 of the large hook upper spring 4, and the DB type half rotary hook is used. Unlike a sewing machine that has this, it is not possible to simply align the needle drop position O with the straight line. Therefore, the displacement amounts of the bobbin thread and the cloth side upper thread due to the forward movement of the moving knife 1 cannot be minimized. The thread cutting is performed as shown in FIG.

The moving knife 1 moves forward from the standby position shown in (1) as shown in (2) and (3), and first the lower thread is loosened. Next, as shown in (4), the cloth side upper thread is separated, but the behavior of the upper thread is large due to pulling up of the balance, thread removal from the shuttle, etc., and the cloth side upper thread exists anywhere in the range of the arrow in FIG. 7 (2). Since it is not decided whether or not to perform it, it is necessary to increase the displacement amount of the cloth side upper thread. For this reason, the bobbin thread is also greatly loosened, and the large loosened bobbin thread with a weak restoring force remains as it is in the original bending state, as indicated by the * mark in (4). In the final retracted state shown in (5), the cloth-side upper thread that has been loosened by the thread take-up motion of the shuttle returns, but the lower thread still bends. Next, as shown in (6), the moving knife 1 starts the backward movement to hook the cloth-side upper thread and the lower thread in the thread handing portion in this order, but the return of the lower thread is often incomplete. In that case, defective cutting of the lower thread occurs (here, the thread hooked state is shown). After threading, as shown in (7), the upper thread is pulled up by the balance, and the lower thread is fed out by the backward movement of the moving knife 1. Then, as shown in (8), the moving knife 1 hands each thread and secures a necessary length to perform thread cutting, but since thread cutting is performed on the side opposite to the side where the lower thread exits, Compared with a thread cutting device of a sewing machine having a DB type half-turn hook, the bobbin case side bobbin thread length remains longer by the width of the moving knife.

[0007]

In the above-mentioned one in which the conventional type thread cutting device for separating the lower thread and then the upper thread is applied to the sewing machine having the DP type half-turn hook, The distance from the time when the cloth-side upper thread is loosened to the time when the cloth-side upper thread, which has a large behavior, is long, and it is necessary to increase the momentum of the moving knife 1, and the looseness of the lower thread physically increases. At times, the bobbin thread cannot be hung on the thread pulling section, resulting in frequent bobbin thread cutting defects. Further, as a result of the length of the bobbin thread being carried due to the relationship of the spindle position of the moving knife 1, the bobbin case side bobbin thread remaining length after thread cutting becomes long, and a bird's nest occurs at the start of the next sewing. , Reduce the sewing quality. Furthermore, the behavior given to the bobbin thread is large, it is large during threading and hand pulling, and idling (excessive rotation) of the bobbin is large, so that the sewing quality is deteriorated.

According to the present invention, there is provided a thread cutting device for a sewing machine having a half-rotary hook in which a middle hook hook point is provided between a needle drop position and a bobbin lower thread lead-out point, which does not cause defective cutting or deteriorate sewing quality. It is intended to be provided.

[0009]

In order to achieve the above object, in the yarn cutting device of the present invention, the spindle is located on the left rear side of the needle drop position as seen from the operator, and the yarn handling section is directed toward you. It consists of a moving knife that stands by and handles the cloth-side upper thread and the bobbin thread in that order, and a fixed knife that cooperates with the moving knife to cut the cloth-side upper thread and the bobbin thread.

[0010]

[Working] In the thread cutting device configured as described above, the cloth-side upper thread is loosened more than the lower thread, the lower thread does not behave well, and the upper thread is surely placed in the thread hooking position by the thread take-up of the shuttle. After returning, the bobbin thread and the cloth side upper thread are reliably hooked by the moving knife, and the bobbin thread and the cloth side upper thread are reliably cut. Further, the amount of bobbin thread handing is shortened due to the positional relationship of the support shaft of the moving knife.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the yarn cutting device of the present invention will be described with reference to FIGS. 1 to 4, 7 (3) and 8.

This thread cutting device has a half-rotary hook (DP type half-rotary hook: the inner hook rotates counterclockwise) in which a middle hook point is provided between the needle drop position and the bobbin lower thread leading point. A moving knife that is attached to a sewing machine that has a sewing machine, the spindle 3 is on the left rear side of the needle drop position O when seen from the operator, stands by with the thread separating section facing you, and separates the cloth side upper thread before the lower thread. 1 and a fixed knife 2 which cooperates with the moving knife 1 to cut the cloth side upper thread and the lower thread, and the upper thread and the lower thread are cut by the hole 5 of the cauldron upper spring 4 at the time of cutting. Controlled.

The moving knife 1 is basically the same as the conventional one, and the length is changed by the thread cutting cam shown in FIG. 3 (the numbers correspond to the sequence numbers in FIG. 4 in the cutting operation described later). Direction, a thread cutting connecting rod 6, a thread cutting connecting arm 7 swingably supported by the machine frame, a thread cutting rod 8, a thread cutting lever L9 swingably supported by the machine frame, and an integrated unit thereof. It is possible to perform counterclockwise rotation (forward movement) and clockwise rotation (return movement) via the thread trimming lever S10 and the moving knife link 11 that have been set. That is, as will be described later, during the forward movement, the cloth side upper thread is first separated, and then the lower thread is separated. Further, at the time of returning, the lower thread, the cloth side upper thread, and the thread are cut.

As shown in FIG. 2, the names of the parts of the moving knife 1 are as follows: 1a is a thread handling section, 1a 'is a thread handling section tip, 1b is a thread handling section, 1b' is a thread handling section tip or a thread handling section. The end, 1c is a jaw, 1d is a thread cutting blade (a blade is formed at the front edge of a hole called an eyeball), 1e is a hole into which the spindle 3 is fitted, and 1f is a pivot of the moving knife link 11. Is a hole into which is fitted.

The fixed knife 2 is located above the moving knife 1,
The thread cutting blade at the tip is located slightly before the needle drop position.

The cauldron upper spring 4 is fixed to the upper side of the cauldron 12 of the DP type half-rotary cauldron, and a specially shaped thread controlling hole 5 is formed in the center thereof around the needle drop position O. There is.

The thread cutting operation of the thread cutting device having the above-described structure is performed as shown in FIG. In FIG. 4, F is a cloth, and 13 is a corner of the bobbin case.

The moving knife 1 moves forward from the standby position shown in (1) as shown in (2), (3) and (4), and the upper thread and the lower thread are inserted in this order. Then, as shown in (5), after the last retreat, the needle moves backward as shown in (6), and the lower thread and the cloth side upper thread are hooked in this order, and as shown in (7), the moving knife 1 is further moved. The bobbin thread is fed back and the upper thread is pulled up by pulling up the balance. As shown in (8), the moving knife 1 is further moved back to cut the cloth side upper thread and the lower thread.

In the yarn cutting device of the present invention, in contrast to the one shown in FIG. 6, since the cloth-side upper yarn is loosened more than the lower yarn, the lower yarn is not given a large behavior.
Since the upper thread is also reliably returned to the thread hooking position as shown in (6) by the thread take-up by the shuttle, the lower thread and the cloth side upper thread are reliably hooked, and no defective thread cutting occurs. Further, the direction of the moving knife 1 for thread cutting is the same as that shown in FIG. 5, and as shown by the solid line in FIG. 8, the length of the bobbin thread that is cut and remains on the corner 13 side of the bobbin case is It is shortened by L ₂ −L ₁ as compared with that of FIG. 6 shown by the chain line. That is, since the bobbin thread is not unwound more than necessary, the bobbin is prevented from idling and the deterioration of sewing quality can be prevented.

[0020]

Since the present invention is configured as described above, it has the following effects.

That is, in a sewing machine having a DP type half-turn hook, it is possible to obtain a thread cutting device having stable cutting performance without deterioration of sewing quality or defective cutting.

[Brief description of drawings]

FIG. 1 is a plan view of a yarn cutting device according to the present invention.

FIG. 2 is a plan view of a moving knife used in the yarn cutting device of the present invention.

FIG. 3 is an exploded view of a thread cutting cam used in the thread cutting device of the present invention.

FIG. 4 is a perspective view for explaining an operation of a sewing machine having a DP-type half-turn hook, in which a cloth side upper thread and a lower thread are sequentially cut to cut the thread.

FIG. 5 is a perspective view illustrating a thread cutting operation in a sewing machine having a DB type half-turn hook.

FIG. 6 is a perspective view for explaining the operation of the sewing machine having a DP type half-turn hook when the bobbin thread and the cloth side upper thread are separated in this order to cut the thread.

7 (1), (2), and (3) are views for explaining the loci of the moving knife in each thread cutting operation of FIGS. 5, 6, and 4, respectively.

FIG. 8 is a difference in bobbin case side bobbin length between when the cloth side upper thread and the bobbin thread are separated in that order, and when the bobbin case side bobbin thread is separated in the order in which the sewing machine has a DP type half-turn hook. It is a figure explaining.

[Explanation of symbols]

 1 Moving knife 1a Thread separating part of moving knife 2 Fixed knife 3 Spindle of moving knife 4 Cauldron upper spring 5 Cauldron upper spring hole O Needle drop position

Claims (1)

[Claims] 1. A movement in which a spindle is located on the left rear side of a needle drop position as seen from an operator, stands by with a thread separating section facing you, and at the time of thread separating, a cloth side upper thread and a lower thread are carried out in this order. A thread cutting device comprising a knife and a fixed knife that cooperates with the moving knife to cut the cloth side upper thread and the lower thread.