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Pneumatic control valve plays a vital role in the basic pneumatic circuit

Update:13 May 2021

In the basic pneumatic circuit of a cylinder, the pneum […]

In the basic pneumatic circuit of a cylinder, the pneumatic reversing circuit is an important link. In this circuit, the pneumatic control valve plays a vital role.

The role of two-position five-way valve, three-position five-way valve, and three-position three-way valve used in the cylinderThe effect of using two-position five-way valve:

(1) Control double-acting cylinder

Use two-position five-way single electronically controlled reversing valve to control the action of double-acting cylinders. When energized, the piston rod extends, and when the power is off, the piston rod returns. If the cylinder suddenly loses power in the extended state, the cylinder will retract immediately. Therefore, in the circuit, a circuit with a "memory" function should be designed to prevent the sudden power failure from retracting the piston rod. In this way, even in the event of a sudden power failure, the reversing valve remains in its original state. Therefore, the reversing valve is also kept in the original position, which avoids the "top cow" and current rise caused by the two solenoid coils being energized at the same time, avoids the possibility of the solenoid coil being burned, and avoids the malfunction of the cylinder. Therefore, the interlock circuit plays a safety protection role for the double electronically controlled reversing valve and the circuit. The commutation control circuit of the AC direct-acting double electronically controlled directional valve must be interlocked and protected.

The effect of using three-position three-way valve

(1) Control the role of single-acting cylinders

The three-position three-way reversing valve is used to realize the reversing control of the single-acting cylinder, and can realize simple intermediate stop of the single-acting cylinder. The function of the three-position three-way valve can be replaced by a combination of a two-position three-way valve and a two-position two-way valve.

(2) The use of two three-position three-way valves can drive a double-acting cylinder to perform a variety of actions

This valve is not a leak-free valve, so it cannot be used for long-term mid-stop and emergency stop.

(3) As a distribution valve or selection valve

Using three-position three-way reversing valve (VEX3 series), it can be used as a distribution valve or selection valve.

(4) Used for vacuum suction and vacuum destruction

The three-position three-way valve of the VEX3 series can be used for vacuum adsorption and vacuum destruction. The suction cup is connected to port A, and attention should be paid to the leakage of the vacuum suction cup and piping.

The role of three-position five-way valve

(1) The basic function of using three-position five-way valve

The use of three-position five-way reversing valve can realize that the cylinder stops in the middle of the stroke, and the middle-position closed reversing valve is used. Because the gas is compressible, and pneumatic components such as cylinders, valves and pipe joints cannot guarantee absolutely no leakage, the cylinder cannot be kept in the middle stop position for a long time, that is, the positioning accuracy of the cylinder is poor.

(2) The characteristics of the double-piston rod cylinder center pressure reversing valve:

The double-piston rod cylinder uses a circuit with a neutral pressure type directional valve. When the reversing valve is in the neutral position, because the pressure action area on both sides of the piston is equal, if the cylinder has no axial external load force, the piston maintains a balanced force and can stop at a certain position in the middle. The stopping accuracy is high, but the cylinder cannot be vertical. use.

(3) The circuit characteristics of the single-piston rod cylinder using the neutral pressure type directional valve:

Because the pressure acting area on both sides of the piston is not equal, in order to balance the forces on both sides of the piston, a pressure reducing valve with a one-way valve should be installed on the rodless side of the cylinder.

(4) Circuit characteristics of using neutral pressure relief type directional valve:

When the reversing valve is in the neutral position, the cylinder can move freely under the push of external force. This circuit is affected by the inertia of piston movement, and the stop position of the cylinder is not easy to control, so it is not suitable for occasions requiring intermediate positioning. If this circuit is assembled on the same pallet with other circuits, the center stop position may also change under the influence of back pressure from other circuits. In this case, a separate exhaust baffle should be provided. When this circuit is restarted, because there is no residual pressure on the exhaust side, the piston rod will suddenly extend out. A circuit must be installed to prevent the rapid extension of the piston rod.


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