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Pneumatic System

Page history last edited by pbworks 5 years, 2 months ago

What is a Pneumatic Actuator?

 

A pneumatic actuator converts energy (typically in the form of compressed air) into mechanical motion. The motion can be rotary or linear, depending on the type of actuator.

A pneumatic actuator mainly consists of a piston, a cylinder, and valves or ports. The piston is covered by a diaphragm, or seal, which keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm downward, moving the piston underneath, which in turn moves the valve stem, which is linked to the internal parts of the actuator. Pneumatic actuators may only have one spot for a signal input, top or bottom, depending on action required. Valves require little pressure to operate and usually double or triple the input force. The larger the size of the piston, the larger the output pressure can be. Having a larger piston can also be good if air supply is low, allowing the same forces with less input.

This pressure is transferred to the valve stem, which is hooked up to either the valve plug, butterfly valve etc. Larger forces are required in high pressure or high flow pipelines to allow the valve to overcome these forces, and allow it to move the valves moving parts to control the material flowing inside.

Pneumatic actuators range from as low as $15 on up to tens of thousands of dollars depending on quality, size, application etc.

  

Linear systems

 

The first and most simple version is the single-acting cylinder, where a piston-oriented system forces compressed air through a solenoid valve into the back of the piston. This highly-compressed air seeks the easiest way to exit, and exerts a large amount of force on the piston face. The surface area of the piston face, or the bore size, directly affects how easily the air will manage to push the piston. The larger the bore size, the more easily the air will move it--until weight itself becomes a significant factor. As the piston is pushed out, the air exits through escape valves that are carefully position further down the cylinder. The piston falls back naturally in place until another burst of compressed air is fired into the cylinder.

The single-acting cylinder can also be modified with a compressed spring mechanism, inserted between the end of the cylinder and the side of the piston opposite where the compressed air enters. This system works in a similar fashion to the standard, but after the compressed air is released, the piston is forced back down to its original position at the end of the cylinder by the spring. This system is used for repeated, linear motion involving heavy loads, and requires a greater force of compressed air to complete its task.

 

Other cylinder systems are double-acting, or systems that use valves to inject two different streams of compressed air, alternating on either side of the piston. One burst of compressed air pushes the piston out, and another burst pushes it back it to the starting position. More compressed air is needed in this system, and like the others the pressure of the air used needs to be carefully controlled.

 

 

Rotary systems

  

Rotary pneumatic motors work when the energy from the compressed air is stored up and then routed to the motor chamber, which is sealed. The pressure gets blown out, and makes the rotor turn quickly. When the rotors begin to turn quickly, the motion is similar to that of a windmill. The engine's flywheel is turned by the air starter or the pinion gear when high torque levels are created by the reduction gears.

 

 

Applications

 

  • Tie rod cylinders
  • Rotary actuators
  • Grippers
  • Rod-less actuators with magnetic linkage or rotary cylinders
  • Rod-less actuators with mechanical linkage
  • pneumatic artificial muscles
  • Specialty actuators that combine rotary and linear motion—frequently used for clamping operations
  • Vacuum generators
  • Industry Use
  • Custom Machinery 

 

 

 

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