Pneumatics

Question 1

Why use pneumatics?

Answer 1

Pneumatics are:

Clean - Pneumatic systems are clean because they use compressed air. If a Pneumatics system develops a leak, it will be air that escapes rather than oil (which is used in hydraulics).

Safe - Pneumatic systems are very safe when compared to other systems. For example, electronics cannot be used for paint spraying mechanisms because many electronic components produce sparks.

Reliable - Pneumatic systems are very reliable and can keep working for a long time.

Economical - When compared to other systems, pneumatic systems are cheaper to run because the components used last for a long time.

Flexible - Once you have the basic components, you can set them up to carry out many different tasks.

Question 2

Provide examples of how Pneumatic systems are used in everyday technology.

Answer 2

Pneumatic systems are used in everyday technologies like:

1. Airbrushes.
2. Aerosol cans.
3. Removing objects from conveyor belts.
4. Automatic doors.
5. Robotics.
6. Lorry Brakes.
7. Dentist drills.

Question 3

Why are pneumatic systems used in lorry brakes?

Answer 3

Pneumatic systems are useful in lorry brakes because the pneumatic system pumps compressed air in between the tyre and the brake clasps. Thus stopping the brake clasps from triggering.

So when the brakes are needed the compressed air is let to escape from in between the tyre and brake clasp - thus allowing the brake clasps to function and clasp the tyres.

The advantage of using a pneumatic system is that if there is an error or if the pneumatic system breaks, the lorry brakes are activated (for the pneumatic system STOPS the brakes from functioning and when removed the clasps activate as default).

Question 4

Why are pneumatic systems used in dentist drills?

Answer 4

They are safer than electric or fluid systems because electricity can cause shocks and if there are fluid leaks the hydraulic fluid can enter the mouth.

Question 5

Describe how the compressor operates?

Answer 5

1. The compressor and power unit produces the compressed air.
2. The compressor stores compressed air so that there is a constant supply of compressed air available.
3. Conditioning the compressed air - removing dirt, dust and water vapour. The air is also lubricated at this stage.
4. Conveying the compressed air to the pneumatic components via air lines and outlets.

Question 6

How can you be safe whilst handling compressed air?

Answer 6

1. Wear safety glasses - to protect from dust and other moving parts (inside the air and being moved by air).
2. Never blow compressed air at anyone.
3. Don’t turn on the main air supply until the circuit is completely connected up. Disconnected pipes can whip around and cause injury.
4. Always turn off the main air supply before you try to alter the circuit.
5. Keep your fingers clear of moving parts such as piston rods.
6. If you notice air leaking from joints or components, turn off the air supply at once.

Question 7

Draw a 3/2 valve.

Question 8

Draw a plunger.

Question 9

Draw a roller tip.

Question 10

Draw a push button.

Question 11

Draw a lever.

Question 12

Draw the symbol for a single acting cylinder.

Question 13

Draw the symbol for a bi directional flow control valve.

Question 14

Draw the symbol for a plunger.

Question 15

Draw the symbol for a roller tip.

Question 16

Draw a symbol for a push button.

Question 17

Draw the symbol for a lever.

Question 18

Draw the symbol for an exhaust.

Question 19

Draw the symbol for the main air/pressure source.

Question 20

Draw the symbol for a single acting cylinder.

Question 21

What is a single acting cylinder? How does it work?

Answer 21

A single acting cylinder is a type of piston. The piston is forced out by the pressure of the air. When the air supply is removed and the air inside the cylinder is allowed to escape, the piston moves back, driven by the force of a spring.

Question 22

What is the manifold and regulator?

Answer 22

The Manifold provides six separate connection points for connecting components to the air supply. They are self-sealing.

The regulator controls air pressure going into the circuit and it can be adjusted.

Question 23

How do 3/2 valves work?

Answer 23

When the button (or input) of a 3/2 valve is pressed (so the 3/2 valve is turned on), the spool is moved between (thus connecting - spools are connecting blocks within valves) the main air input and the output components. When turned on, the spool connects the 1 and 2 valve.

When the 3/2 valve is off, the spool is NOT pushed in between the input and output, but between the output and exhaust. When turned off, the spool connects the 2 and 3 valve.

Question 24

Draw a uni directional speed control.

What is it used for?

Answer 24

Some applications of circuits may require specific actuation speeds from cylinders - the uni directional speed control slows down the speed of air moving in one direction. It controls the speed of the piston outsroke OR instroke.

Question 25

Draw an AND circuit. How does it work?

Answer 25

You need to turn on both 3/2 valves at the same time for the circuit to work.

Valve A and Valve B need to be on for the circuit to operate fully.

Question 26

Draw a shuttle valve.

Question 27

Draw a OR circuit. How does it work?

Answer 27

You can turn on either valve (or both at the same time) for the circuit to fully operate. But the circuit won’t fully operate if either Valve A or Valve B aren’t turned on.

Question 28

Draw a double acting cylinder? What are its features?

Answer 28

The double acting cylinder has two air connections. When you pull the piston rod out, it doesn’t automatically go back in (for there is no spring inside).

It has to be activated into instroke by using another valve or source of air.

Question 29

Draw a 5/2 valve.

Question 30

Draw an automatic piston outstroke then instroke circuit.

Draw an automatic piston outstroke then instroke then repeat circuit.

Question 31

Draw the symbol for a reservoir. What does it do?

Answer 31

It acts as a time delay in circuits.

Question 32

How do you calculate the force exerted by a cylinder?

Answer 32

Force = Area X Pressure
Force = π r² x Pressure

Pressure is in Bars - for example 3 bar is worth 0.3 N (which is the Pressure)

Question 33

What is the difference in calculation for calculating the instroke and outsroke force of a cylinder?

Answer 33

The outstroke force is calculated as normal - Area X Pressure

but the instroke force is different:

(Cylinder Area - rod area) X Pressure

Question 34

Draw a bi directional control valve.

What is it used for?

Answer 34

Some applications of circuits may require specific actuation speeds from cylinders - the bi directional speed control slows down the speed of air moving in both direction. It controls the speed of the piston outsroke and instroke.