JP2002085877A - Sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewing machine which is advantageous for improving a sewing quality by suppressing the pullback phenomenon of a thread caused by the rising of a presser foot, reducing an empty loop or the like from pulling to a needle side and preventing a stitch skipping. SOLUTION: The sewing machine has a needle bar for vertically moving the needle, a presser bar having the presser foot, which is provided vertically movably on the frame of the sewing machine for pressing an object to be sewn by downward moving, a tread tension applying part for applying a tension to the thread passed through the needle, and a pressure thread tension releasing mechanism connected to the thread tension applying part and the pressing bar and performing operation to release thread tension in the thread tension applying part and operation to raise the presser foot. The pressure thread tension releasing mechanism is set to make start timing t1 to release the thread tension preceding to start timing t2 to raise the presser foot in the operation of a foot thread operating mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine having a presser foot for holding a sewing product.

[0002]

2. Description of the Related Art As a sewing machine, a needle bar for raising and lowering a needle,
A presser bar having a presser foot at a lower end portion which is provided on a sewing machine frame so as to be able to move up and down and presses a sewing product by descending, a thread tension applying portion for applying tension to a thread passed through a needle, a thread tension applying portion and a presser bar. Is known which has a presser lifting thread loosening mechanism connected to the pressurizing mechanism. By operating the presser lifting thread loosening mechanism, an operation of releasing the thread tension by releasing the thread holding by the thread tension applying unit and an operation of raising the presser foot are performed. The yarn tension applying section is described in JP-B-55-3493.
No. 5, JP-B-56-1340 and the like. However, these publications do not mention the relationship between the start timing of the lifting of the presser foot and the start timing of the release of the thread holding when operating the presser lifting thread loosening mechanism.

[0003]

Problems that occur in the above-mentioned prior art will be described with reference to FIGS. 8 and 9. FIG. In order to sew the next sewn product from the state in which the hollow ring portion 100 is formed, an operation of lifting the presser foot 17 to release the sewn product having the sewn empty ring portion 100, There is a case where an operation sequence such as an operation of setting between the upper surface of the plate 20 and the presser foot 17, an operation of lowering the presser foot 17 and pressing the next sewing product, and an operation of sewing is performed. FIG. 8 shows a state in which the yarn 21 in the path from the empty ring portion 100, one end of which is held by the presser foot 17, to the yarn tension applying portion 23 is extended by the action of the yarn tension applying portion 23. From the state shown in FIG. 9, the presser foot 17 rises in the direction of arrow A1, and the presser foot 17
When the holding of the empty ring portion 100 is released, the yarn 21 that has been stretched along the path from the empty ring portion 100 to the yarn tension applying portion 23 is moved in the direction of arrow C1 as shown in FIG. Since it is pulled back, the empty ring portion 100 existing on the upper surface of the needle plate 20 moves in the direction of the arrow E1 toward the lower side of the needle plate 20. Therefore, the end 100a of the hollow ring portion 100 is
Needle 1 which has entered the lower side of the needle plate 20 through the needle drop hole 20a
There is a possibility that it will be pulled into the vicinity of the fourth eye 14a. This tendency is greater as the yarn 21 has a higher elasticity, the stronger the pulling force of the yarn 21 in the direction of the arrow C1.

In such a case, when starting sewing of the next sewing product, an appropriate thread state may not be obtained due to the effect of the hollow ring portion 100 drawn into the lower side of the needle plate 20. For this reason, the point 50 (or the point of the shuttle) of the ring looper disposed below the needle plate 20 is not inserted into the loop portion 21x of the thread 21, and sewing failure occurs due to skipping, and the quality of the sewing product cannot be ensured. It will be.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and suppresses the yarn pullback phenomenon caused by the rise of the presser foot, suppresses the empty ring portion from being drawn into the vicinity of the eye of the needle, and prevents jumping. It is an object of the present invention to provide a sewing machine that is effective in preventing sewing and improving the quality of sewing products.

[0006]

A sewing machine according to the present invention comprises:
A needle bar that raises and lowers the needle, a presser bar that is provided on the sewing machine frame so as to be able to move up and down, and has a presser foot at a lower end portion that presses a sewing product by lowering, and a thread tension applying unit that applies tension to the thread passed through the needle. , A presser lifting thread loosening mechanism coupled to a thread tension applying section and a presser bar, and having a presser lifting thread loosening mechanism for performing an operation of releasing the thread holding in the thread tension applying section and an operation of raising the presser foot. Is characterized in that, when operating the presser lifting thread loosening mechanism, the start timing of the release of the thread holding by the thread tension applying section is set to precede the start timing of the lifting of the presser foot. It is.

[0007] According to the sewing machine of the present invention, the presser lifting thread loosening mechanism is arranged so that the timing of starting the release of the thread holding is made earlier than the timing of starting the lifting of the presser foot when operating the presser lifting thread loosening mechanism. Is set. For this reason, the start of the release of the thread holding precedes the start of the lifting of the presser foot. As a result, even when the yarn between the empty ring portion and the yarn tension applying portion is stretched, the start of the release of the yarn holding precedes the start of the rise of the presser foot as described above, The thread pullback phenomenon caused by the lifting of the presser foot is reduced. Therefore, it is reduced that the empty ring portion is drawn into the vicinity of the eye of the needle due to the yarn pullback phenomenon.

As an example of the presser lifting thread loosening mechanism, a configuration using a presser lifting lever that is manually rotated by a user is given as an example.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described with reference to FIGS. As shown in FIG. 1, the sewing machine according to the present embodiment is operated by a housing 12 having a bed housing 10 and an arm housing 11, and a driving source provided in the housing 12.
A needle bar 16 for raising and lowering the needle 4 and a presser bar 19 provided at a lower end of the presser foot 17 which is provided so as to be able to move up and down and presses a sewing material such as a fabric by descending. Further, as shown in FIG. 2, the sewing machine includes a thread tension applying section 23 for applying tension to the thread 21 attached to the needle 14, a thread tension applying section 23, and a presser bar 19.
And a presser thread loosening mechanism 25 that operates in conjunction with. As shown in FIG. 3, the thread tension applying section 23
3a, a thread gripping plate (1) 23b urged by a spring 23a
And a thread gripping dish (2) 2 facing the thread gripping dish (1) 23b
3c and a thread loosening operating portion 45 for elastically contracting the spring 23a. The thread 14 is formed by the thread gripping plate (1) 23b and the thread gripping plate (2) 23c urged by the spring 23a.
, A tension is applied to the yarn 14. When the thread loosening operation section 45 moves in the direction of the arrow W1 (see FIG. 3), the thread gripping plate (1) 23 resists the spring 23a of the thread tension applying section 23.
b moves in the same direction, the thread gripping action of the thread gripping tray (1) 23b and the thread gripping tray (2) 23c is released, and the tension of the thread is released.

As shown in FIG. 2, a pressing foot 17 is provided at the lower end of a pressing rod 19 disposed along the vertical direction.
7x attached. A holding member 27 for regulating the rotation of the holding rod 19 is provided at an intermediate portion of the holding rod 19 with a screw 27x.
It is fixed by. A driving member 29 is attached to the upper end of the holding rod 19 with a screw 29x. At an intermediate portion of the presser bar 19, a pressing spring 31 for exerting a function of pressing a sewing product is attached. The presser lifting shaft 33 is disposed in a direction substantially perpendicular to the presser bar 19, that is, in a lateral direction. The presser lifting shaft 33 is rotatably supported by the housing 12 so as to be rotatable around the center axis of the presser lifting shaft 33. A thread loosening shaft 35 is arranged along the presser lifting shaft 33 so as to be movable in the longitudinal direction of the loosening shaft 35. At one end of the presser lifting shaft 33, a presser lifting cam 37 for generating a lifting function for the driving member 29 of the presser bar 19 is provided. A thread loosening cam 39 for generating a drive to the thread loosening shaft 35 is fixed to the other end side of the presser lifting shaft 33 by a screw (not shown).
A presser-lifting lever 41 for performing a presser-lifting operation is integrally attached to the other end of the presser-lifting shaft 33. The presser lifting thread loosening mechanism 25 includes a presser lifting lever 41, a presser lifting shaft 33, a presser lifting cam 37, and a thread loosening cam 39.

The lifting lever 41 is manually operated by the user.
Is rotated in one direction or the other around the center axis of the presser lifting shaft 33, the presser lifting shaft 33 rotates about its central axis, and the presser lifting cam 37 is the same as the presser lifting shaft 33. The drive member 29 is raised and lowered by rotating in the direction, whereby the presser bar 19 and thus the presser foot 17 are raised and lowered.

When the lifting lever 41 is rotated in one direction or the other direction, the lifting shaft 33 is moved as described above.
Rotates about its central axis, so that the presser
, The thread loosening cam 39 is rotated, the thread loosening shaft 35 moves in the longitudinal direction of the thread loosening shaft 35 by the convex cam portion 39c of the thread loosening cam 39, and is further connected to the thread loosening shaft 35. The thread loosening drive plate 43 moves in the same direction, and the thread loosening drive plate 4
The thread loosening operation part 45 connected to 3 moves in the same direction. When the thread loosening operating section 45 moves in this manner, as can be understood from FIG. 3, the thread loosening operating section 45 elastically contracts the spring 23a in the thread tension applying section 23 in the thread holding release direction (the direction of the arrow W1). In order to make the thread grasping dish (1) 2
3b, the thread holding action of the thread gripping plate (2) 23c is released, and as a result, the yarn gripping plate (1) 23 of the thread tension applying unit 23 is released.
b, the holding of the yarn 21 by the yarn gripping plate (2) 23c is released.

In the present embodiment, the presser lifting thread releasing mechanism 25 adjusts the start timing t1 of releasing the thread holding in the thread tension applying section 23 at the time of operating the presser lifting thread releasing mechanism 25. It is set so as to precede the rising start timing t2. Further description is made with reference to FIG. FIG. 4 shows this timing relationship. The horizontal axis in FIG. 4 indicates the operation angle of the presser lifting lever 41 in which the presser lifting lever 41 is rotated, one of the vertical axes in FIG. 4 indicates the amount of elevation of the presser foot 17, and the other vertical axis in FIG. The characteristic line S2 shows the amount of lifting of the presser foot 17 from the lowest position without the cloth and the thread of the presser foot 17, and the characteristic line S1 shows the amount of holding and releasing the yarn in the yarn tension applying section 23. 23 shows the thread holding and releasing amount. As shown by the characteristic line S1 in FIG. 4, the release of the thread holding starts when the operation angle of the presser lifting lever 41 is θ1, and the release of the thread holding is completed when the operation angle of the presser lifting lever 41 is θ4. The characteristic line S in FIG.
As shown in FIG. 2, the operation angle of the presser lifting lever 41 is θ3 to
The lifting of the presser foot 17 is started at θ4, and the raising of the presser foot 17 ends when the operation angle of the presser lifting lever 41 is θ9. If there is a cloth or thread under the presser foot 17, the rising of the presser foot 17 is shifted to the thickness θ9 of the cloth or thread. Thus, in the present embodiment, the start timing t1 of the release of the thread holding is ahead of the start timing t2 of the lifting of the presser foot 17 by θ. As shown by the characteristic line S2 in FIG. 4, the rising change rate of the presser foot 17 is α1 in the initial rising and middle stages of the presser foot 17, the ascending end of the presser foot 17 is α2, and α1> α2. Set in a relationship. The reason is as follows. That is,
The fact that the start timing t1 of the release of the thread holding is ahead of the start timing t2 of the ascent of the presser foot 17 by θ means that the presser foot 17 is earlier than the start timing t1 of the release of the thread holding.
Means that the start timing t2 of the rise of. On the other hand, it is necessary to secure the absolute value of the amount by which the presser foot 17 is raised. In order to cope with this, the rising change rate α1 of the presser foot 17 in the initial rising and middle stages is set to be higher than the rising change rate α2 of the lifting end, and the start timing t2 of the lifting of the presser foot 17 is delayed. , Presser foot 1
The absolute value of the rise amount of 7 is secured.

In this embodiment, as shown in FIG. 4, the end of the release of the thread holding and the initial rise of the presser foot 17 are overlapped by θX in order to limit the mechanism and shorten the operation time. . Thus, the end of releasing the thread holding and the presser foot 1
Even if the rise of 7 overlaps in time, the presser foot 17
At the timing t2 of the start of the rise, the release of the thread holding is almost completed, and there is no problem.

FIG. 7 shows the relationship between the timing of releasing the thread holding and the timing of raising the presser foot 17 according to the prior art. The vertical and horizontal axes in FIG. 7 correspond to the vertical and horizontal axes in FIG. According to the prior art, as shown in FIG. 7, the start timing of the thread holding and releasing is delayed by θY from the start timing of the lifting of the presser foot 17. That is, since the lifting of the presser foot 17 is started earlier than the start of the thread holding and releasing, the holding of the thread is released as the presser foot 17 is raised, and a thread pull-in phenomenon occurs.

In chain stitching, cover hem stitching, and the like, it is necessary to form an empty ring at the end of sewing. In this embodiment, as in the prior art, the sewing foot is raised by raising the presser foot 17 in the direction of the arrow A1 in order to sew the next sewing product from the state in which the hollow ring portion 100 is formed as shown in FIG. An operation of releasing the already sewn product, an operation of setting the next sewn product between the upper surface of the needle plate 20 and the presser foot 17, an operation of lowering the presser foot 17 and pressing the next sewn product, an operation of sewing, and the like The operation order may be performed. In this embodiment, as described above, the start timing of the release of the thread holding precedes the start timing of the lifting of the presser foot 17.

In FIG. 5, tension is generated in the yarn portion 21c of the yarn 21 between the hollow ring portion 100, one end of which is held by the presser foot 17, and the yarn tension applying portion 23, and the yarn 21 is stretched. When the presser foot 17 rises in the direction of arrow A1, the thread 21 is originally pulled back in the direction of arrow C1 due to the rise of the presser foot 17, but in this embodiment, Since the start timing of the release of the holding of the thread precedes the start timing of the lifting of the presser foot 17, the amount of the yarn corresponding to the tension is compensated by the supply of the yarn from the yarn spool, and as a result, the yarn 21 in the direction of arrow C1 is obtained. Return is suppressed. Therefore, the empty ring portion 10
The zero end 100a is prevented from being pulled into the vicinity of the eye hole 14a of the needle 14 inserted into the needle drop hole 20a of the needle plate 20.

In other words, from the state where the presser foot 17 holds the empty ring portion 100 as shown in FIG. 5, the presser foot 17 rises in the direction of arrow A1 as shown in FIG. When the holding is released, the start timing of the release of the thread holding precedes the start timing of the lifting of the presser foot 17. Therefore, when the presser foot 17 starts to rise in the direction of arrow A1, the tension of the thread 21 held by the thread tension applying unit 23 has already been released.

As a result, when the presser foot 17 rises in the direction of arrow A1 to start releasing the holding of the empty ring portion 100, it is stretched from the seam of the empty ring portion 100 to the thread tension applying portion 23. The return of the thread 21 which has been performed is compensated for by the thread supply from the thread spool side.
As can be understood from the related art, unlike the related art, it is reduced that the end 100a of the empty ring portion is pulled in the direction of the arrow E1 to the vicinity of the eye hole 14a of the needle 14 inserted into the needle drop hole 20a of the needle plate 20. You. Even when the yarn 21 has high elasticity, the end 100a of the empty ring portion is less likely to be pulled in the direction of the arrow E1.

Therefore, as can be understood from FIG. 6, when starting the sewing of the next sewing product, an appropriate thread state is obtained, and the point 50 (or the hook of the shuttle) of the ring looper arranged below the needle plate 20 is obtained. The tip of the sword is reliably inserted into the loop portion 21x of the thread 14. As a result, it is possible to suppress the occurrence of skipping, which has conventionally occurred, prevent poor sewing, and ensure the quality of sewing products.

In addition, the present invention is not limited to the embodiment described above and shown in the drawings, but can be implemented with appropriate modifications without departing from the scope of the invention. Some of the words and phrases described in the examples can be described in the claims.

[0022]

According to the sewing machine of the present invention, the presser lifting thread releasing mechanism is set so that the start timing of the release of the thread holding is set earlier than the start timing of the lifting of the presser foot. The release precedes the lifting of the presser foot. As a result, even when tension is generated in the yarn from the empty ring portion to the yarn tension applying portion and the yarn is being stretched, the yarn pullback starts because the yarn release start timing precedes. Thus, the sewing portion such as the empty ring portion is less likely to be drawn into the vicinity of the eye of the needle. For this reason, at the beginning of sewing of the next sewing product, the occurrence of skipping is suppressed, and the quality of sewing products is improved.

[Brief description of the drawings]

FIG. 1 is an overall view of a sewing machine.

FIG. 2 is a perspective view of a main part of the sewing machine.

FIG. 3 is a configuration diagram schematically illustrating an internal structure of a yarn tension applying unit.

FIG. 4 is a graph showing a relationship between an operation angle of a presser lifting lever, an amount of lifting of a presser foot, and an amount of thread holding and releasing.

FIG. 5 is a view for explaining a state in which a presser foot presses an empty ring portion while inserting a needle into a needle drop hole of a needle plate;

FIG. 6 is a diagram illustrating an operation state when a presser foot that presses an empty ring portion is raised.

FIG. 7 shows the operation angle of the presser lifting lever according to the related art;
It is a graph which shows the relationship between the presser foot raising amount and the thread holding release amount.

FIG. 8 is a view for explaining a state in which a presser foot presses an empty ring portion according to the related art.

FIG. 9 is a diagram illustrating an operation state when a presser foot that presses an empty ring portion is raised according to the related art.

[Explanation of symbols]

In the drawing, 14 is a needle, 17 is a presser foot, 19 is a presser bar, 2
1 is a thread, 23 is a thread tension applying section, 25 is a presser lifting thread loosening mechanism, 33 is a presser lifting shaft, 35 is a thread loosening shaft, 39 is a thread loosening cam, and 41 is a presser lifting lever.

Claims (1)

[Claims] 1. A needle bar for raising and lowering a needle, a presser bar provided at a lower end of the sewing machine frame so as to be able to move up and down and pressing a sewing product by lowering, and applying tension to the thread passed through the needle. A presser lifting thread loosening mechanism that is connected to the thread tension applying section and the presser bar and performs an operation of releasing the thread holding in the thread tension applying section and an operation of raising the presser foot. In the sewing machine having the above, the presser lifting thread release mechanism is set so that the start timing of releasing the thread holding is earlier than the start timing of the lifting of the presser foot when operating the presser lifting thread release mechanism. A sewing machine characterized by the following.