JPH0131176Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a fabric edge detection device for a sewing machine, and particularly to one that uses ultrasonic waves as a detection medium.

[Prior art] When stitching along the outer periphery of a polygonal workpiece, such as pocket stitching, on the inside of the polygonal workpiece, it is necessary to temporarily stop the sewing machine at a corner (fabric edge) of the workpiece. ,
In order to automate this process, the sewing machine is equipped with a fabric edge detection device.

Some of the detection media of this fabric edge detection device use ultrasonic waves, and changes in the thickness (fabric edge) of the material to be sewn, such as whether the material has become thinner from two layers to one layer, can be detected by the amount of ultrasound transmitted. It was determined by the changes.

[Problems to be Solved by the Invention] The above-mentioned determination can be made more easily and accurately as the change in the amount of transmission is larger, or in other words, the larger the change in the amount of attenuation is.

However, when ultrasonic waves are transmitted through the same object to be sewn, ultrasonic waves with a relatively high frequency have a property that the amount of attenuation is larger than that with a relatively low frequency. This relational expression is shown below.

A (dB) = 27.3FNT/C where F is frequency, N is acoustic loss, and T is thickness.

Furthermore, from the above equation, even if ultrasonic waves of the same frequency are transmitted, the amount of attenuation will be greater when used on thick materials such as denim than when transmitted on thin materials such as jersey. In the case of thick objects to be sewn, the number of transmitted ultrasonic waves decreases, and there is a problem that the transmission of ultrasonic waves cannot be detected when two layers are stacked.

That is, when ultrasonic waves of a high frequency are transmitted to a thin object to be sewn, the amount of attenuation of the ultrasonic waves due to the height of the frequency increases, making it easier to determine changes in thickness.

Furthermore, when ultrasonic waves of a low frequency are transmitted to a thin material to be sewn, the amount of attenuation of the ultrasonic waves decreases, making it difficult to distinguish changes in thickness.

On the other hand, when transmitting high frequency ultrasonic waves to a thick material, the amount of attenuation of the ultrasonic waves due to the thickness increases, and this also overlaps with the fact that the ultrasonic waves have a high frequency, so the amount of attenuation becomes too large and the ultrasonic waves becomes impermeable.

In addition, when transmitting low-frequency ultrasonic waves to a thick material to be sewn, the number of ultrasonic waves transmitted increases due to the reduction in attenuation due to the low frequency, and the amount of attenuation due to the thick material increases from 2 layers to 1 layer. Makes it easy to distinguish thickness changes from sheet to sheet.

The present invention improves the performance of a fabric edge detection device using ultrasonic waves by utilizing the above-mentioned properties.
By making it possible to adjust the ultrasonic oscillation frequency to be lower than that for thin materials, the thickness of two layers and one layer can be easily adjusted, regardless of the thickness of one layer of the material. It is an object of the present invention to provide a fabric edge detection device for a sewing machine that can accurately determine changes (fabric edges).

[Means for Solving the Problems] This invention includes a transmitting means disposed on the machine frame so as to be able to transmit ultrasonic waves to the material to be sewn on the fabric feeding path before the needle in the fabric feeding direction; a receiving means arranged on a machine frame so as to be able to receive the ultrasonic waves transmitted through the sewing material and emitting a reception signal; a starting means capable of generating two or more different oscillation frequencies of the ultrasonic waves in the transmitting means; A control means for controlling the electrical actuation means of the sewing machine mechanism in relation to a received signal of the means, and a control means for controlling the electrical actuation means of the sewing machine mechanism in relation to a received signal of the means, and for switching the transmission frequency of the ultrasonic wave to low or high depending on the thickness or thinness of the workpiece of different thicknesses. The present invention proposes a cloth edge detection device for a sewing machine, characterized by comprising a switching means.

[Example] Next, an example of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes a sewing machine head, in which a workpiece W ₁ of clothing body cloth is placed on a throat plate 4 attached to a table 3 so as to pass under the presser foot 2;
The workpiece _W2, which is a piece of pocket cloth, is inserted between the workpiece _W1 and the presser foot 2 such that the rear edge S is located further back than the presser foot 2 in the cloth feeding direction.

5 is a transmitter that transmits ultrasonic waves, and presser foot 2
It is fixed to the sewing machine head 1 so as to face the needle plate in front of the sewing machine in the cloth feeding direction. A receiver 6 receives the ultrasonic waves emitted from the transmitter 5 through a hole 4a provided in the throat plate 4 and emits a received signal, and is fixed to a sewing machine frame (not shown).

FIG. 2 is a block diagram showing the control circuit of the above embodiment, where 7 is a drive circuit for the oscillator 5, and 8 is a block diagram showing the control circuit of the above embodiment.
This is an analog switch that switches between an oscillation circuit 9 that oscillates at 750 KHz and an oscillation circuit 10 that oscillates at 250 KHz, and is operated by a command issued by the CPU 11 after reading the frequency changeover switch 8a, and constitutes a starting means 12.

13 is a preamplifier that amplifies the received signal from the receiver 6, 14 is an attenuator, 15 is a main amplifier, 16 is a detector, 17 is an A/D converter,
The attenuator 14 is adjusted by a command from the CPU 11, the output data is stored in the RAM 18, and the electrical actuation device 20 of the sewing machine mechanism is controlled in accordance with the sewing material discrimination program stored in the ROM 19. Configure.

Next, the operation of the above embodiment will be described. The sewing machine operator checks the thickness of a piece of material to be sewn and sets the frequency changeover switch 8a to either the thick material side or the thin material side.
When the CPU 11 is a thick object, it switches the analog switch 8 to the 250KHz oscillation circuit 10 side, and when it is a thin object, it switches it to the 750KHz oscillation circuit 9 side, turns on the drive circuit 7, and sends each ultrasonic wave from the transmitter. Send.

As the sewing progresses, the objects W ₁ and W ₂ are fed in sequence, and when the rear end S of the object W ₂ reaches the receiver 6,
The amount of ultrasound transmitted to the receiver 6 changes,
The CPU 11 determines this as fabric edge detection and controls the electrical actuation device of the sewing machine mechanism.

In the above embodiment, the sewing machine operator switches the ultrasonic frequency depending on the thickness of the material to be sewn, but the ultrasonic frequency is electrically connected to a well-known fabric thickness detection device, and the ultrasonic frequency is outputted from the fabric thickness detection device. It is also possible to automate this frequency switching by having the CPU read the cloth thickness signal.

[Effects of the invention] The structure and operation of the invention are as described above, and by switching the transmission frequency of ultrasonic waves according to the thickness of the upper and lower pieces of sewing material, Since the change in the amount of sound wave transmission can be increased, there is an effect that cloth edge detection becomes more accurate.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a state in which a fabric edge detection device of a sewing machine is attached to the head of the sewing machine, and FIG. 2 is a control block diagram. 5... Ultrasonic transmitter, 6... Ultrasonic receiver.

Claims (1)

[Scope of Claim for Utility Model Registration] A transmitting means disposed on a machine frame so as to be able to transmit ultrasonic waves to a workpiece on the cloth feeding path before the needle in the cloth feeding direction; a receiving means arranged on the frame of the machine so as to be able to receive sound waves and emitting a reception signal; and a receiving means for emitting a received signal;
a starting means capable of generating the different frequencies as described above; a control means for controlling the electrical actuating means of the sewing machine mechanism in relation to the received signal of the receiving means; A fabric edge detection device for a sewing machine, comprising: switching means for switching the transmission frequency of ultrasonic waves to low or high depending on the thinness of the fabric.