What Is a Pneumatic Cylinder?
A pneumatic cylinder is a type of cylinder that moves in a single direction when fluid pressure is applied.
It is characterized by its unidirectional operation and is returned to its original position by an external force, such as a spring or gravity. Pneumatic cylinders are cost-effective due to their relatively simple design and low manufacturing costs. They are also more compact and lightweight compared to double-acting cylinders, making them suitable for applications with space constraints and weight considerations.
Pneumatic cylinders offer predictable unidirectional motion, making control easy and reducing the risk of accidents or machine breakdowns due to incorrect operation.
However, their unidirectional nature makes them unsuitable for applications requiring complex movement patterns. For such cases, additional control devices or systems may need to be implemented to achieve multiple stopping positions, for example.
Uses of Pneumatic Cylinders
Pneumatic cylinders find a wide range of applications. Here are a few examples of pneumatic cylinder applications:
1. Automobiles
Pneumatic cylinders are commonly used in automotive braking systems. When the brake pedal is pressed, the pneumatic cylinder applies pressure to the brake pads, pressing them against the disc or drum to generate braking force.
Pneumatic cylinders are also frequently employed in vehicle suspensions. The movement of the cylinder controls the vertical motion of the wheels, enhancing ride comfort and vehicle stability.
2. Manufacturing
Automated machines and manufacturing lines utilize pneumatic cylinders for tasks such as assembling and sorting parts. These cylinders can automate assembly processes by extending a piston to move parts.
Pneumatic cylinders are also used for material extrusion in certain plastic and metal molding machines. They apply pressure to the mold, pushing the material out to create a specific shape.
3. Chemical Plants
Pneumatic cylinders are employed to control open/close mechanisms such as valves and gates in chemical plants. The cylinder’s motion is responsible for opening and closing these devices, regulating the flow and shut-off of fluids. They play a crucial role in fluid control within pipelines and piping systems.
Principle of Pneumatic Cylinders
A pneumatic cylinder consists of a cylindrical component known as the cylinder tube and a piston that reciprocates inside the tube. The piston is designed to fit snugly within the cylinder tube.
Since pneumatic cylinders operate in a unidirectional manner, the supply and discharge of fluid are carefully controlled. Fluid is introduced into the cylinder through a designated path.
When fluid is supplied to the cylinder, the pressure within the cylinder typically increases. This rise in pressure propels the piston in one direction. The piston’s movement is a result of the change in the internal volume of the cylinder.
After being extended, a pneumatic cylinder requires an external force to return it to its initial position once the fluid supply is stopped. This external force may be provided by a spring or gravity, with spring-based products being the more common choice. The external force returns the piston to the cylinder’s starting position, preparing it for the next operation.
How to Select a Pneumatic Cylinder
When choosing a pneumatic cylinder, it’s essential to consider the following factors:
1. Inner Diameter of the Tube
The tube’s inner diameter (I.D.) refers to the size of the cylinder’s interior. While a larger tube I.D. can generate higher pressure, it often results in a larger overall size. Conversely, a smaller tube I.D. is suitable for compact designs but limits pressure capabilities. The selection of the appropriate tube I.D. should align with your application’s requirements.
2. Stroke
Stroke refers to the distance the piston travels during reciprocation. Choose a stroke length that matches your application’s needs. A too-short stroke may not cover the required range of motion, while an overly long stroke could lead to an oversized cylinder that restricts the design.
3. Push-In/Pull-Out Characteristics
Select between push-in and pull-out based on fluid inflow requirements, depending on your specific application. The push-in and pull-out speeds may vary depending on the product.
4. Position Detection
Position detection devices, such as reed switches, limit switches, and micro switches, are used to detect the cylinder’s position and send/receive control signals. Choosing a pneumatic cylinder equipped with a position detection system facilitates integration with your control system. Reed switches are commonly used due to their space-efficient design, with products incorporating reed switches featuring a built-in magnet within the cylinder.