JP2000197786A - Method for detecting skipping stitch at seam in sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect skipping stitches at seams in sewing. SOLUTION: In this sewing machine, an upper yarn 5 scooped up by a bayonet 3 of a shuttle body 2 during one up-and-down movement of a sewing needle 1 is looped and passed once through the shuttle body 2, while a surface-side yarn portion 7 of the looped upper yarn 5 traverses the surface 9 of a bobbin case 8 stored in the shuttle body 2. A photoelectric detector which is sensitive to a reflected light detects in noncontact relation whether the traversed surface- side yarn portion is present or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stitch skipping detection method for detecting a so-called skipped stitch in which a stitch is not formed without tangling an upper thread and a lower thread in sewing of a sewing machine.

[0002]

2. Description of the Related Art Sewing of a sewing machine is performed by forming a seam by tangling an upper thread and a lower thread as required. More specifically, a sewing needle with a needle thread penetrates through the fabric, protrudes to the lower side of the fabric, and then moves upward, but when the sewing needle that has reached the bottom dead center moves upward, the needle thread sags and loops. Is formed. At the same time, while the sewing machine needle is rotating in conjunction with the vertical movement of the sewing machine needle, the needle thread in the loop is scooped at the point where the sewing machine needle is slightly raised. Then, the inner pinwheel rotates, and the balance sharply rises at a position where the point of the sword is slightly past the bottom dead center.
The middle sword is removed from the tip and pulled up. As a result, the lower thread coming out of the bobbin case and reaching the fabric is entangled with the upper thread to form one seam.

[0003] The sewing is performed in this manner. However, due to the inconsistency of the vertical movement of the sewing machine needle and the timing of the rotation of the hook, the tension of the thread, and the like, the hook of the hook does not scoop the loop. In some cases, stitches in which a stitch is not formed over one or several stitches may occur.

As means for detecting such skipping, a skipping detection method disclosed in, for example, JP-A-52-72656 is provided.

[0005] This detection method focuses on the fact that the needle thread caught by the sword of the middle stitch during a single vertical movement of the sewing machine needle forms a loop and passes through the middle stitch once. The presence or absence of the upper thread passing through the kama is detected by a thread passage detector. The yarn passage detector has an operating lever whose tip is in contact with the side wall of the inner hook to form a contact, and when the upper thread forms a loop and passes through the inner hook, the upper thread connects the contact. They are configured to be separated from each other, an electrical change generated by the separation of the contacts is extracted as a detection signal, and the presence or absence of skip is determined based on the detection signal.

[0006]

However, in the case of the contact type detection method, when the contacts are separated, the upper thread passing through the loop in a loop pushes up the contacts. The seam shape is likely to be abnormal due to a change in the tension of the upper thread every time the contact is opened. Such an abnormality in the shape of the seam is not preferable in terms of sewing. For example, in the case of sewing a product requiring high safety such as an airbag or a seat belt, there is a problem that the reliability of the sewing cannot be obtained. was there.

[0007] The present invention has been developed in view of the above-mentioned problems, and the needle thread, which has been scooped by a sword with a middle hook, forms a loop during one vertical movement of the sewing needle. Once passing through the kama, the front side yarn portion of the looped yarn is focused on the movement path of the upper thread that crosses the surface of the bobbin case in which the inner loop is housed, and An object of the present invention is to solve the above-described problem on the basis of non-contact detection of the presence or absence of a thread crossing the surface of a bobbin case.

[0008]

In order to solve the above-mentioned problems, the present invention employs the following means. That is, the method for detecting stitch skipping in the sewing machine according to the present invention (hereinafter referred to as skipping stitch detection method) is a method in which a needle thread caught with a middle sword is looped during one vertical movement of a sewing needle. And passes through the inside of the bobbin case once, at which time the front side thread portion of the looped upper thread crosses the surface of the bobbin case accommodated in the inside of the bobbin case. It is characterized in that the presence or absence of a thread portion is detected in a non-contact manner by a photoelectric detector sensitive to reflected light.

As the photoelectric detector, it is preferable to use a color difference photoelectric detector capable of distinguishing the color of the yarn by comparing with the color of the surface of the bobbin case.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The skip skip detection method according to the present invention includes:
As shown in FIGS. 1 to 4, during one vertical movement of the sewing machine needle 1, the needle thread 5 scooped by the tip 3 of the middle stitch 2 forms a loop and passes through the middle stitch 2 once. At this time, it is configured to pay attention to a movement path of the upper thread, in which the front thread portion 7 of the upper thread 5 that has formed the loop crosses the surface 9 of the bobbin case 8 in which the inner thread is housed. , This front side thread part 7
Is detected in a non-contact manner by the photoelectric detector 10 shown in FIG. 5 which is sensitive to reflected light. Hereinafter, this will be described in detail by taking as an example a case where the inside shell 2 makes a half-turn movement.

FIG. 1 shows a sewing machine needle 1 with a needle thread 5 protruding downward through a cloth 11, and the loop formed when the sewing machine needle moves upward from a bottom dead center. This indicates a state where the sword 3 has been dropped.

FIG. 2 shows a state in which the upper thread 5 has been scooped by the blade 3 and the inner thread 2 continues to rotate clockwise (arrow), and the front thread of the upper thread 5 in a loop is shown. The part 7 has moved from the state shown by the dashed line in FIG. 2 to the state shown by the solid line so as to cross the surface 9 of the bobbin case 8 accommodated in the inner bridge 2.

Then, while continuing the clockwise rotation,
Fig. 2 shows the state in which the point 3 is slightly past the bottom dead center (Fig. 3).
The rotation of the inner shaft 2 is continued as shown by the arrow in FIG. The state of the front-side thread portion 7 immediately before the inner hook 2 is moved to the reverse rotation is shown by a dashed line in FIG. Sewing needle 1 in conjunction with the rotation
Is raised, and the feed blade feeds the fabric for one stitch while the sewing machine needle is raised. The balance (not shown) ascends rapidly when the sling 2 shifts to the reverse rotation, and the upper thread 5 which has been looped into the state shown by the solid line through the state shown by the two-dot chain line in FIG. The sword is removed from the sword tip 3 and raised. As a result, the lower thread 13 coming out of the bobbin case 9 and reaching the fabric 11 is entangled with the upper thread 5 to form one seam 14 (FIG. 4).

The inverted spine 2 returns to the initial state as shown by the dashed line in FIG. 4 and repeats the same operation as described above.

The photoelectric detector 10 is arranged so as to irradiate light at an angle of about 45 degrees with respect to the rotation axis of the inner shell 2, as shown in FIG. The presence / absence of the front side thread portion 7 of the upper thread crossing the surface 12 is detected. The photoelectric detector 10 irradiates light from the light projecting portion 15 toward the front side thread portion 7 of the upper thread 5 (FIG. 2), receives the light reflected by the front side thread portion 7 at the light receiving portion, The front-side yarn portion 7 is detected by a detection unit responsive to the reflected light, and the presence or absence of the front-side yarn portion that crosses is determined.

It is preferable that the photoelectric detector 10 is configured as a color difference photoelectric detector capable of discriminating the color of the yarn by comparing with the color of the surface 12 of the bobbin case 9. For example, a keyence CZ-41 photoelectric detector can be suitably used. In such a configuration, even if the color of the upper thread and the color of the surface of the bobbin case are similar to each other, the difference in the property of the reflected light is compared with the case where the color is simply determined based on the presence or absence of the reflected light. Because it can be accurately identified by color components,
The presence / absence of the front side yarn portion that crosses can be determined with high sensitivity.

In the above description, the case in which the inner hook makes a half-rotational movement has been described. However, even when the inner hook makes a full-rotational movement, the method for detecting the upper thread crossing the bobbin case surface is as described above. The same is true.

[0018]

The present invention has the following excellent effects. In the method for detecting skipped stitches according to the present invention, during one vertical movement of the sewing machine needle, the needle thread scooped by the sword of the inside stitch passes through the inside of the stitch once in a loop. In a sewing machine in which the front side thread portion of the upper thread that has formed the loop crosses the surface of the bobbin case in which the inner thread is stuck, the presence or absence of this front side thread portion is detected by a photoelectric detector that responds to reflected light. Therefore, the presence or absence of the upper thread passing through the inside of the loop in a loop can be reliably detected without contact.

Therefore, unlike the case of the above-mentioned conventional contact-type detection method, there is no resistance due to the opening of the contacts, so that reliable sewing can be performed without instability of the seam. Therefore, even when sewing a product requiring high safety such as an airbag or a seat belt, the sewing can be performed safely and reliably.

In particular, when a color difference photoelectric detector capable of distinguishing the color of the yarn by comparing it with the color of the surface of the bobbin case is used as the photoelectric detector, the presence or absence of the upper thread crossing the surface of the bobbin case can be determined with high accuracy. Will be able to detect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a state in which a loop is scooped with a sledge point.

FIG. 2 is an explanatory view showing a state in which a front side thread portion of an upper thread crosses the surface of a bobbin case.

FIG. 3 is an explanatory diagram showing a state in which a looped upper thread comes off from a middle hook.

FIG. 4 is an explanatory view showing a stitch formed by tangling a lower thread with an upper thread;

FIG. 5 is an explanatory diagram showing an arrangement state of a photoelectric detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sewing needle 2 Nakagama 3 Sword point 5 Needle thread 6 Loop 7 Front thread part 8 Bobbin case 9 Bobbin case surface 10 Photoelectric detector

Claims (2)

[Claims] 1. A needle thread which has been scooped by a sword of a middle stitch forms a loop during one vertical movement of a sewing machine needle and passes through the middle stitch once. In a sewing machine in which the front side thread portion of the upper thread has crossed the surface of the bobbin case in which the inner thread is stuck, the presence / absence of the front side thread portion that crosses is determined without contact by a photoelectric detector sensitive to reflected light. A stitch skipping detection method for a sewing machine. 2. The method according to claim 1, wherein the photoelectric detector is a color difference photoelectric detector capable of distinguishing a thread color by comparing a color of a thread with a surface color of the bobbin case.