What is a low speed cylinder? Analysis of the structural principle of low-speed cylinder

What is a low speed cylinder?


Cylinder movement speed is an important technical parameter. What is its lowest speed without crawling? What's its top speed? This is an issue that many mechanical design engineers are very concerned about.





A common prejudice among people is that although the cylinder moves very fast, it will be unbalanced and crawling if it runs at a slow speed. At present, domestic and foreign literature stipulates that the technical index of low-speed cylinder crawling without crawling is 50mm/s. Although pneumatic professionals have been improving the cylinder structure and sealing design, the throttling characteristics of the speed control valve (one-way throttle valve) are also constantly improving. Improvement, but the negative effects of low-speed crawling of the cylinder and poor cylinder terminal buffering effect have always influenced mechanical design engineers to boldly adopt pneumatic technology. If an operating speed of less than 50mm/s is required, designers often first consider hydraulic technology, or use a combination of gas-liquid damping to achieve it.








Figure 1 Sealing form of cylinder





In recent years, the special sealing technology developed by the German company FESTO enables the cylinder to run smoothly without crawling at a speed of about 5mm/s - as shown in Figure 1, the upper part of the piston axis is the sealing form of a standard cylinder ;The lower part of the piston axis is the sealing form of the low-speed cylinder. It can be clearly seen from the figure that the seals of the standard cylinder and the seals of the low-speed cylinder are significantly different in size and shape.







Analysis of the structural principle of low-speed cylinder


It should be noted that low-speed cylinder and low-friction cylinder are two different concepts. In the past, people often regarded low-friction cylinders as low-speed cylinders, or misunderstood low-speed cylinders because of their small friction. It should be emphasized here that a low-friction cylinder can be pushed when the pressure difference on both sides of the cylinder piston is not large. Its seals, bearing bushings, etc. all have low friction characteristics. That is to say, the fact that the cylinder can push the piston and complete the entire stroke under very low pressure conditions does not mean that it can run at a constant speed during motion, or that it will not crawl.














Figure 2 Friction of cylinder


—Standard gas red ---Low speed gas red ---Low friction cylinder









The low-speed cylinder is mainly manifested in the fact that the cylinder piston can run at a very small constant speed. As long as the cylinder has the sufficient stroke length it requires, its pressure and temperature conditions can be relatively stable. The low-speed cylinder shown in Table 1 and Figure 2 does not mean that its starting working pressure must be low. On the contrary, among the φ32~φ50 cylinders, the starting pressure of the low-speed cylinder is higher than that of the conventional standard cylinder. Therefore, low-speed cylinders and low-friction cylinders are essentially two completely different concepts of cylinders.








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