The working principle of the Pneumatic cylinder throttle valve
The throttling effect is produced by the valve stem clamping the flexible rubber hose, and the gas pressure can also be used to replace the valve stem, compressing the rubber hose. The flexible throttle valve has a simple structure, low-pressure drop, and high operational reliability. It is not sensitive to pollution and usually operates within a pressure range of 0.3 to 0.63 MPa.
It is more difficult to adjust the speed of pneumatic actuators by using pneumatic flow control valves than by using hydraulic flow control valves because gas is compressible. Therefore, when using a pneumatic flow control valve for speed regulation, the following points should be noted to prevent crawling:
(1) There must be no air leakage on the pipeline.
(2) The lubrication condition between the Pneumatic cylinder and the piston should be good.
(3) The flow control valve should be installed around the Pneumatic cylinder or pneumatic motor as much as possible.
(4) Try to adopt the outlet throttling speed regulation method as much as possible;
(5) The additional load should be stable. If the external load varies greatly, hydraulic or mechanical devices (such as pneumatic-hydraulic linkage) should be used to compensate for the speed changes caused by the load variations.
The working principle of the Pneumatic cylinderone-way throttle valve is A combined flow control valve composed of a one-way valve and a throttle valve in parallel, as shown in the following figure. When the airflow flows in one direction, such as from P to A, as indicated by the flow direction, it is throttled through the throttle valve. When the airflow flows in the opposite direction from A to P, the check valve opens without throttling. One-way throttle valves are often used in the speed regulation and delay circuits of cylinders.
The working principle of the Pneumatic cylinder exhaust throttle valve is to be installed at the exhaust port of the actuator (such as a pneumatic motor), and it is a control valve that regulates the flow of gas entering the atmosphere. It can not only adjust the movement speed of the actuator, but also often has a muffler component, so it can also reduce the exhaust noise.
The following figure shows the working principle of the exhaust throttle valve. Its working principle is similar to that of a throttle valve. It regulates the exhaust flow by adjusting the flow area out of the throttle port 1 and reduces the exhaust noise through the sound-absorbing sleeve 2.
Characteristics and Selection of Pneumatic Cylinder Throttle Valves
The throttle valve of the Pneumatic cylinder is an indispensable accessory for the cylinder. Most people seldom pay attention to this standard part. When selecting a model, they only care about choosing ø4 or ø6, or if the Pneumatic cylinder diameter is too large, they might as well choose ø8. Are there any other things to pay attention to?
Throttle valves are divided into intake throttling and exhaust throttling. As the names suggest, one throttles when intake and the other throttles when exhaust. If the airflow is from the threaded end to the air pipe end and the adjusting nut has a significant effect after adjustment, it is an exhaust throttle valve. Conversely, it is an intake throttle valve (many people do not know how to adjust the Pneumatic cylinder speed when they go to the site).
When the intake throttling occurs, the pressure in the exhaust chamber is small (connected to the atmospheric pressure), and the intake chamber is filled with gas after flow restriction. The gas flow rate is small, and the initial pressure is low. When the Pneumatic cylinder load is large, there will be a crawling and then surging phenomenon. When the exhaust gas is throttled, due to the effect of the flow-limiting valve, the pressure in the exhaust chamber will not suddenly drop to zero. Meanwhile, the pressure in the intake chamber is the same as that of the gas source, which can form a relatively stable pressure difference and achieve a better speed regulation effect. For common single-acting cylinders or blowers, when using exhaust throttling, the throttling valve is completely ineffective (this is very common; those in assembly are not mentioned, but those in engineering are unaware of it), because the flow is limited by the return stroke of the cylinder, and the return stroke of the Pneumatic cylinder is generally unloaded.
| Characteristics | Intake throttle valve | Exhaust throttle valve |
| The proportional relationship between the opening size of the valve and the speed | no | have |
| Low-speed smoothness | It is prone to low-speed crawling |
good |
| The influence of load inertia | It has an impact on the speed regulation characteristics |
small |
| Startup delay | Very small | It is proportional to the load rate |
| Starting acceleration | small | big |
| Speed at the end of the journey | big | Approximately the average speed |
| Buffering capacity | poor | good |
| Applicable occasions | Blowing air, single-acting cylinders, blocking cylinders (generally single-acting cylinders), or other cylinders that move in one direction relying on the load force (such as tension cylinders that control tension), etc |
Suitable for general double-acting cylinders |
Pressure-regulating cap locking function
This might be familiar to everyone. As shown in the picture at the beginning, some brands have a pressure-regulating cap locking function. After the Pneumatic cylinder speed is adjusted properly, in some places with high speed requirements, to prevent vibration changes over time or accidental touches by other personnel, this type of speed control valve is used. Of course, the cost is relatively high. In general situations, ordinary ones can be used.
Selection of the diameter of the throttle valve
The thread specification of the throttle valve is selected based on the cylinder, while the pipe diameter of the speed control valve is chosen according to the corresponding Pneumatic cylinder diameter. Generally, the recommended diameters are provided at the beginning of the brand manual, which can be referred to for selection. Avoid choosing an air pipe diameter that is too small, which may cause the Pneumatic cylinder to fail to operate or have a crawling phenomenon.
Above is the working principle of Pneumatic cylinder throttle valves, characteristics, and selection of Pneumatic cylinder throttle valves. To learn more related information, visit https://www.joosungauto.com/.
