JPS6038155B2 - Sewing machine fabric thickness detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fabric thickness detection device for a sewing machine that detects the thickness of a workpiece such as fabric moving to a sewing section of a sewing machine and generates a detection signal, and in particular, relates to a fabric thickness detection device that uses ultrasonic waves. The object of the present invention is to detect cloth thickness without being influenced by external environment such as dust or light.

An embodiment of the present invention will be described with reference to the drawings. In a positioning machine near the sewing machine general section in the cloth feeding direction, the cloth W is
A transmitter 2 which faces the upper surface of the moving throat plate 1 at a distance and generates ultrasonic waves downward and has a well-known configuration, and a cloth W adjacent to the transmitter that is located on the throat plate 1 or on the throat plate 1. A receiver 3 having a well-known configuration and capable of receiving the reflected ultrasonic waves from the transmitter 2 and converting them into electric quantities is fixed to the machine frame.

Next, to explain the electric circuit of this embodiment, NM is an astable multipipulator (eye excitation oscillation circuit) that acts in conjunction with the starting operation of a sewing machine pedal (not shown) and oscillates pulses of a constant period; A monostable multipiper that generates a pulse for a fixed time from the rise of the pulse of the self-excited oscillation circuit NM, UO oscillates an ultrasonic wave of, for example, 2 HZ while the pulse of the monostable multi MM is generated, and sends it from the oscillator 2. This is a pump excitation oscillator circuit that generates an electric current. AM is an amplification circuit, AA is a rectifier circuit that full-wave rectifies the alternating current wave generated by receiver 3, BF is a bandpass filter that removes the nozzles other than the obi castle near 2rohi 2 from the rectified wave, and GI is a gate circuit that inputs the signals from the monostable multi-MM and the filter BF and passes through and outputs the signal from the filter BF between pulse generation of the monostable multi-MM, and PW is the ultrasonic wave of 2 days from the output of the gate circuit GI. This is a detection circuit that selects and outputs only square waves. G2 is a NAND gate circuit that inputs the detection circuit PW and monostable multi-MM,
1 is an inverter, and the OS is a constant cycle (k<unstable multi-N
An oscillation circuit G3 generates a reference pulse with a period of M), and G3 inputs signals from the gate G2 and the oscillation circuit OS.
This is a gate circuit that passes and outputs the reference pulse from the oscillation circuit OS between the second pulse generation. CT is a binary counter that counts the output of the gate circuit G3 and generates a 4-bit output. When the count output is "011", the thickness of three layers of cloth W on the throat plate 1 is "1001"'' means the thickness of two layers, ''110 times means the thickness of one sheet,
“For 111r, it is set empirically in advance so that the output is when the thickness of zero, that is, the top surface of the throat plate is detected.
When it becomes "1111", the gate circuit G3 is cut off via the AND gate G4 as an overflow, and it is reset when the monostable multi-MM pulse falls.

The output of the counter CT becomes, for example, an input to the CPU of a microcomputer, and is used to read out cloth thickness data for setting yarn unwinding and yarn tension.

This invention has the above-mentioned configuration, in which pulses are generated from the astable multi-NM in connection with the starting operation of the sewing machine pedal, and thereby the ultrasonic waves of the oscillation circuit UO oscillate while the pulses are generated from the monostable multi-MM. The signal is generated from the transmitter 2.

When the cloth W is on the throat plate 1, the path of the ultrasonic waves to the receiver 3 is shorter than when there is no cloth (the speed of the sound waves is constant), so the time until reception is shorter, and the reception The generation of the received signal from the device 3 is delayed by Δt (FIG. 3). After the output from the receiver 3 is applied to a full-wave rectification filter BF, it is passed through the output of the monostable multi-MM pulse generation filter BF by a gate circuit GI, and the detected output and the output of the multi-MM are passed through a NAND gate G2. The reference pulse is input to the counter CT between the outputs of the gate G to obtain the output of △t, and when the output of the counter CT becomes, for example, "110," the cloth W is one piece. Since the thickness of the cloth is detected, the cloth thickness data for one cloth is read out by the output of this counter CT.Also, when the cloth W moves and the cloth thickness W of the cloth step part etc. faces the detection position, , the path of the ultrasonic wave to receiver 3 becomes even shorter (Fig. 1).
The time becomes shorter, the pulse of NAND gate G2 becomes narrower, and the number of reference pulses in that pulse also decreases, and when the count value becomes, for example, "011", the value corresponds to the thickness of three pieces of cloth, so Read out the cloth thickness data for three cloth emissions from the microcomputer. When the cloth W passes the detection position, the path of the ultrasonic wave becomes longer (Fig. 1, part 2), and the time becomes longer, so that during the pulse of gate G2, △ etc. >Δt, ), the count value becomes "111r," and the cloth thickness data of zero cloth thickness is read out from the microcomputer.

In this embodiment, the time difference between transmission and reception, that is, the number of reference pulses (clock pulses) generated during the output pulse of NAND gate G2 is counted, and the cloth thickness is determined based on the count value. However, it is also possible to use a timer or the like to perform comparative measurements during the pulse, that is, during the time, and determine the cloth thickness during that time.

Further, instead of this embodiment, the fabric thickness may be determined by processing by a microcomputer and based on count values or time.

Furthermore, in this embodiment, the transmitter 2 and the receiver 3 are arranged above the needle slope so that the emitted ultrasonic waves are reflected by the throat plate or the cloth and the reflected waves are received. may be placed above the needle slope and on the top surface of the throat plate, and the fabric thickness may be determined based on the ultrasonic transmittance.

As described above, according to the present invention, the transmitter 2, UO is arranged at a distance above the needle slope and generates ultrasonic waves toward the needle plate, and the ultrasonic waves from the transmitter can be received via the cloth movement path. a receiver 3 disposed in the receiver 3 that generates an electric signal in connection with reception; and a time setting for generating a pulse corresponding to the time difference between when the transmitter generates an ultrasonic wave and when the receiver generates an electric signal. A determination circuit G that determines the thickness of the cloth in conjunction with the circuits G1, G2, MM and during the pulse of the time setting circuit.
3. With the OS and CT installed, the fabric thickness can always be detected reliably without being affected by light or dust around the sewing machine. Since these settings can be made reliably when making settings or when controlling the means for letting out the thread in advance before tying the stitches, effects such as obtaining a seam with a striped base of the thread length can be obtained.

Brief Description of the Drawings Fig. 1 is an explanatory diagram briefly showing the detection means of this embodiment, Fig. 2 is a block diagram of the electric circuit of this embodiment, and Fig. 3 is a time chart based on Fig. 2. .

Oh four 3rd figure OZ diagram

Claims (1)

[Claims] 1 A transmitter 2, UO, which is arranged at a distance above the throat plate and generates ultrasonic waves toward the throat plate; a receiver 3 that generates a signal; a time setting circuit G1, G2, MM that generates a pulse with a width corresponding to the time difference between when the transmitter generates an ultrasonic wave and when the receiver generates an electrical signal;
A cloth thickness detection device for a sewing machine, comprising a determination circuit G3, OS, and CT for determining the thickness of cloth in relation to the pulse width of a time setting circuit.