The circuit principle of the disconnection control sensor of the electronic pattern sewing machine:
The sensor consists of a body 2, and a top cover 3 on the top cover with two additional suture tension regulators 4 and a photodiode 8 with lead wires, which are insulated from the metal top cover by means of a rubber cloth bushing. In the area between the thread clamps 4 of the upper thread 5, there is the sensitive element of the sensor, that is, the disc 1 with a radial groove, which is mounted on the shaft of the thread passing wheel 6. The upper thread 5 is set on the thread passing wheel, and the incandescent lamp 10 and the photodiode are placed on both sides of the disc.
When the electronic pattern sewing machine is powered on, the needle thread is forming stitches while rotating the thread passing wheel with disc 1. The latter interrupts the light from the light source to the photodiode intermittently, and the photodiode simultaneously converts pulses into electrical pulses. The electric pulse enters the base of the control circuit, and T1 is cut off when the photodiode is shielded. Here the negative bias enters T3, and T3 is turned on. T2 is turned on due to the adaptation of the resistance value, and T4 is turned off due to the positive bias from T2. When the photodiode φd receives light, TI turns on, T3 turns off, T2 turns off, and T4 turns on. The collector circuits of T3 and T4 connect the coils of the magnetic relays P1 and P2. The coil current is connected in parallel by capacitors C1 and C2. When T3 and T4 are turned on, current flows in the coils of P1 and P2, which is enough to make P1 and P2 work.
If the electronic pattern sewing machine is running, and the displacement of the suture occurs (thread consumption), that is, the rotation of the disc and an electronic signal of a certain frequency occurs, then T3 and T4 are disconnected in turn. Due to the parallel capacitance of CI and C2, P1 and P2 are too late to be powered off, so they are always connected. When the thread is broken, the disc rotated by the suture stops in one of the following two positions; the photodiode is shaded or illuminated. Therefore, T3 or T4 cuts off PI or P2 and is disconnected, and at the same time, there is no current in P1 or P2 in the contactor actuator circuit. In this way, the above-mentioned sensor can detect the thread breakage of buttonholes, buttons and other semi-automatic sewing machines according to the displacement of the suture. The circuit principle of the sensor is the pulse frequency that matches the standard seam. When the upper thread is broken, the pulse transmission stops, and when the bottom thread is broken or used up, because the consumption of the upper thread is reduced at this time, and the continuous pulse frequency is reduced, the control circuit issues a stop command.
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