Control system weft detection
The weft detection of water-jet looms, commonly known as “weft detection device”, mainly has the following three forms, and the latter two forms are widely adopted.
(1) Mechanical weft detector: Its working principle is the same as the “chicken peck” type weft detector of shuttle looms. It uses the process contacts of its spring and lever for detection. It is mainly used in Czech water-jet weaving. machine.
(2) Touch-type weft detection device: Its working principle is to use the high-voltage DC generated by the weft detection unit to supply the weft finder touch finger; when the touch finger comes into contact with the water-containing weft wire, the water and the weft wire will detect When the weft circuit is connected, a signal with weft wire is generated; if there is no weft wire, there will be no such electrical signal, that is, the weft stop signal is output.
According to the installation and structure of the finger-type weft finder, it is divided into two types: “top-mounted weft finder” and “bottom-mounted weft finder”.
The top-mounted weft detector is directly installed on the top of the reed and can be easily installed, adjusted and replaced; due to its split structure, it can be partially replaced and the maintenance cost is low. Its disadvantage is that it is not suitable for high-speed operation, so it has been gradually eliminated in recent years.
The bottom-mounted weft detector has an integral structure and is directly installed on the beat-up shaft. Its probe and lead cable are sealed with engineering plastics. Because it has no mechanical connection with the reed, it has good rigidity and high reliability in weft detection. In recent years, due to the application of electric weft detection, the scope of use of the bottom-mounted weft detection has gradually narrowed.
(3) Electrical weft detection device: Its working principle is to detect the presence or absence of the weft by changing the level of the electrical signal when the weft interrupts the source. Usually, a gallium arsenide infrared source and a power tube are used to form a power detection circuit. During weaving, the weft is sprayed to a predetermined position. When it enters the power detection area, the power source is cut off, causing “weft” in the detection circuit. signal; if there is no weft, the source is not interrupted, and a “no weft” signal appears in the detection circuit.
The main features of the fully electric weft detection device are that it is suitable for a wide range of varieties, is not affected by water quality, and has strong anti-interference ability.
The fully electric weft detection device consists of fully electric sensors and leads, control units and installation brackets.
When installing the electric weft detection device, make sure that its bottom and left and right sides do not collide with the reed and the reed holder, and that the upper part of its detection port and the warp wire are on the same plane. It is necessary to ensure that the weft wire can accurately enter the detection port of the fully electric weft detection device when flying. The adjustment method is to adjust the handwheel of the loom to 0° and check whether the weft yarn at the cloth fell enters the detection point of the completion detection device.
The adjustment method for the front and rear position of the complete electric weft detection device is: make the distance between the weft line and the completion detection point about 15mm, and make the weft line enter the detection point of the completion detection device at 310°~340° on the hand wheel.
To complete the adjustment of the electric weft detection device, you must first adjust the weft insertion of the loom to the best state and the scissors to the best state. Make sure that after the scissors cut the weft yarn, 2 to 3 strands are left uncut.
The fully electric weft detection device consists of a probe and a control unit.
The probe is composed of conductive fiber, infrared electric transmitting tube, electric tube and circuit. When the loom is working, the weft enters the detection point. In the process, the electric signal is converted into an electrical signal and sent to control unit. The control unit processes and amplifies the weft detection signal to infer whether the weft insertion is correct, and then sends the corresponding weft signal to the main control board of the loom.
Probe leads: power (positive), power (negative), signal.
Control unit leads: +12V, weft signal output (F), synchronization signal input (FtIR) (PS), synchronization signal output (Ft or PS′), stop signal output (STOP), power supply OV.
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