JPH078664A - Bobbin thread breakage-detecting method for sewing machine - Google Patents

Abstract

PURPOSE:To stop a sewing machine automatically by indirectly judging the breakage of a bobbin thread by measuring the consumption quantity of a needle thread at every specified period of time when detecting the breakage of the bobbin thread in a sewing process by a sewing machine. CONSTITUTION:A bobbin thread 2 is put in a loop of a needle thread 1, which is formed at the bottom dead center of a sewing machine needle, and a sewing motion is advanced, and the needle thread 1 is fed and consumed by an entanglement with the bobbin thread 2. At this time, if a breakage of the bobbin thread 2 generates, there is no entanglement of the needle thread 1 with the bobbin thread 2, and the needle thread 1 linearly runs on the surface of a cloth in the cloth advancing direction. For this reason, the consumption quantity of the needle thread 1 becomes smaller by a portion for the entanglement with the bobbin thread 2, and a difference in the consumption quantity of the needle thread 1 per a unit period of time is generated before and after a breakage of the bobbin thread 2. By utilizing this principle, the generation of a breakage of the bobbin thread 2 can be indirectly detected by monitoring the behavior of the needle thread 1 only. Therefore, by this detection, a sewing machine device can automatically be stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to bobbin thread breakage in a sewing machine.

[0002]

2. Description of the Related Art Various methods have been invented to detect the breakage of the upper thread, but for the breakage of the bobbin thread, the bobbin thread is usually placed in a shuttle and installed directly under a sewing machine needle. Perhaps because it was impossible to directly monitor and measure the behavior, an effective method for detecting bobbin thread breakage has not been invented yet.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for determining a bobbin thread breakage necessary for automatically stopping a sewing machine when a bobbin thread breakage occurs during sewing work. .

[0004]

[Means for Solving the Problems] In order to achieve the above-mentioned object, this method does not monitor the bobbin thread itself or catch the moment of occurrence of bobbin thread breakage.
The present invention has been completed, focusing on the fact that the consumption of the upper thread is reduced.

The principle of this method will be described with reference to the drawings.
In FIG. 1, since the sewing operation of the sewing machine is advanced by passing the bobbin thread 2 through the loop of the bobbin thread 1 formed at the bottom dead center of the sewing machine needle, the bobbin thread 1 is always entangled with the bobbin thread 2 for consumption. Being done.

When the bobbin thread breakage occurs, the upper thread 1 is not entangled with the lower thread 2 as shown in FIG. 2, so that the upper thread 1 travels linearly on the cloth surface in the cloth advancing direction. Therefore, the consumption amount of the upper thread 1 is too small by at least the amount of entanglement with the lower thread 2.

In the pattern sewing machine shown in FIG. 3, the upper thread 1 is consumed while drawing the locus of ABCDE while being entangled with the lower thread 2. However, when the lower thread is cut at point A, Becomes the locus of ACE, and therefore the consumption of the upper thread is significantly reduced as compared with the normal case.

Therefore, if the principle that the upper thread consumption amount per unit time before and after the bobbin thread breakage is different is utilized,
Occurrence of bobbin thread breakage can be detected by indirectly monitoring the behavior of only the upper thread.

[0009]

EXAMPLE An example will be described with reference to the drawings. In FIG. 4, a pulley 6 which is rotatable about a fixed shaft 5 attached to a frame 4 is provided, and a plurality of pulleys 6 are provided near the outer periphery of the pulley 6. If the pulley device with the detection hole 7 gargled and the hole detection sensor 8 provided opposite thereto is installed in the middle of the needle thread path and the needle thread 1 is wound around the outer circumference of the pulley 6, the movement of the needle thread 1 The rotational movement of the pulley 6 can be substituted, and the consumption amount of the upper thread 1 can be calculated from the number of sensor reactions and the external dimensions of the pulley 6.

An appropriate cycle time for measurement is selected, the amount of cloth movement within that time is set to L1, while the pulley device measures the upper thread consumption in the normal case without bobbin thread breakage and If L2 is set, a value L which is an intermediate value between L1 and L2 and which is close to L1 is set as a reference value for bobbin thread breakage determination.

After setting the above-mentioned reference value L, it is judged that the bobbin thread breaks when the measured value of the upper thread consumption at the end of each measurement cycle is L or less.

In the case of straight line sewing or thin material sewing, it is necessary to lengthen the cycle time in order to improve the detection accuracy. However, if the needle thread consumption such as pattern sewing is relatively large, the measurement cycle time may be set short. The detection accuracy is high.

In this pulley device, if the rotation of the pulley 6 is stopped, the upper thread breakage occurs. Therefore, if the stoppage of the pulley 6 is measured, not only the lower thread breakage but also the upper thread breakage can be detected at the same time.

[0014]

In the sewing work of the sewing machine, it is impossible to predict the occurrence of the upper thread and the lower thread in advance, and the frequency of thread breakage is higher than other troubles. The ability to automatically stop the sewing machine by detecting thread breakage and bobbin thread breakage can greatly contribute to automation and unmanned operation.

Since this method judges the bobbin thread breakage at regular intervals, it cannot be expected to stop at the moment the bobbin thread breakage occurs, but the bobbin thread is indirectly monitored by monitoring only the behavior of the bobbin thread. Since the break can be detected, it can be realized with a simple device at low cost.

[Brief description of drawings]

FIG. 1 is a relational diagram of an upper thread and a lower thread in a normal state.

FIG. 2 is a relationship diagram of an upper thread and a lower thread when a lower thread breakage occurs.

FIG. 3 is a needle thread locus diagram at the time of pattern sewing.

FIG. 4 is a pulley device according to an embodiment.

[Explanation of symbols]

 1 Upper thread 2 Lower thread 3 Target fabric 4 Frame 5 Fixed shaft 6 Pulley 7 Detection hole 8 Sensor

Claims (1)

[Claims] 1. A bobbin thread breakage in which a bobbin thread breakage is indirectly determined by measuring a consumption amount of a needle thread at a constant time when detecting a bobbin thread breakage in a sewing process of a sewing machine. Detection method