Pneumatics

Pneumatics

1. What is it?

   • Pneumatic systems use the energy in compressed air to work, by controlling the release of air to pneumatic cylinders we can turn that energy into movement
   • Input components: 3/2 valve + plunger, roller trip, push button or lever
     • Process Components: Unidirectional flow restrictor, shuttle valve
       • Output components: Single Acting Cylinder (SAC)

2. When is it used

   • Everyday life: tyres, road drills, vehicle doors, wheel and tyre changing equipment and dentist drills
   • Industry: Spray painting, Moving components in factories, pressing and punching

3. SAC

   • Cylinders convert the energy in the compressed air into a linear motion by allowing the air to enter the cylinder and pushes a piston from one end to another
   • When a piston rod is actuated it is in a positive state
   • When compressed air is supplied to the cylinder the piston rod extends (outstroke) and when it is switched of its called the instroke
   • Normally used with a three port valve

4. Three port valves (3/2 valves)

   • Can have different actuators which when activated will allow air to flow from the pressure source, through the 3/2 valve to the output component, when the switch is not pressed air will flow out the exhaust

5. Actuators

   • Plungers
     • Activated by pushing. Sometimes a SAC will activate a plunger 3//2 valve to activate another circuit, this is used in sequential circuits
   • Roller trips
     • Usually used as a follow up after an initial circuit and is activated by a SAC in another circuit used in sequential circuits
   • Push button
     • Can be used to start a pneumatics circuit and is the main method of actuation used to start processes in industry
   • Lever
     • Used as a follow up after an initial circuit, used in sequential circuits like factories that need constant processes to occur

6. Shuttle Valve/Or valve

   • 2 inlets with 1 outlet where only 1 inlet can be active
   • Selects the higher of the 2 pressures through a small ball inside that gets moved side to side by the compressed air sealing the other inlet
   • I.e. pneumatic based emergency stop button

7. Logic OR

   • The SAC will extend when EITHER valves are pressed as the shuttle valve provides the OR control ensuring the piston rod extends
   • I.e. sliding door
   • The air from the activated 3/2 valve can escape through the other 3/2 valve

8. AND Logic

   • Both valves will need to be pressed for the piston rod in the SAC will outstroke
   • Valve B will have no air supply unless Valve A is open as valve B contols the air supply towards the SAC
   • Used as a safety feature in industry

9. Speed control

   • Controls the speed of a SAC by restricting the flow of compressed air
   • Symbol is made from a restrictor and a check valve showing the air will free flow only from left to right

10. Safety

    • 1. never blow compressed air at someone 2. Wear safety glasses 3. keep fingers clear of piston rod 4. if air is leaking from joint turn it off 5. always turm air off before altering circuit