 |
|
|
The Fundamentals of
Pneumatics This is the seventh in a series of articles covering the basic principles of pneumatics. In this article, air cylinders will be covered. An air cylinder is a device which converts pneumatic energy into mechanical energy. At this time we are concerned with two basic types of air cylinders: single- acting and double-acting cylinders. Figure 1 shows the symbol for a typical single-acting, single-rod spring-return air cylinder. It is single-acting because the air can only enter in one end; single-rod because the rod only extends out one end of the cylinder; and spring-return because a spring inside the cylinder will return the rod to its normal position when high pressure air to the cylinder is shut off. It should be noted that when the cylinder is activated the air in the spring side of the piston must be allowed to escape from the cylinder. For this reason a small hole is usually drilled through the side of the cylinder near the end to allow air to escape. Figure 2 shows a typical single-acting air cylinder. Figure 3 shows the internal components of a single-acting, single-rod, spring-return air cylinder. Figure 4 shows the symbol for a double-acting, single- rod air cylinder. When high pressure air enters port B it will push the piston to the left, which will pull the cylinder rod into the cylinder. When the high pressure air is removed from port B and enters port A the piston will push the cylinder rod to the right, extending it. Figure 5 shows a typical double-acting, single-rod, air cylinder. Figure 6 shows the internal construction of a typical double-acting, single-rod air cylinder. |
|
