Basic Pneumatics -...

Basic Pneumatics

Module 3: Directional control Valves

PREPARED BY

Academic Services

April 2012

© Applied Technology High Schools, 2012

ATM 1132 – Basic Pneumatics

2 Module 3: Directional control Valves

Module 3: Directional control valves

Module Objectives

After the completion of this module, the student will be able to:

Diffrentiate between the main types of directional control valves.

Explain the function of each type of directional control valves.

Demonstrate the function and uses of 3/2 way valve, (N/C) push button actuated.

Demonstrate the function and uses of 3/2 way valve, (N/O) push button actuated.

Demonstrate the function and uses of 3/2 way valve, (N/C) roller lever actuated.

Explain the function and uses of 5/2 way valve, selector valve.

Explain the function and uses of 5/2 way valve, single pilot valve.

Explain the function and uses of 5/2 way valve, double pilot valve.

Use the FluidSIM software to build and simulate a pneumatic circuits that contain DCV

Build a pnueumatic circuit using DCV on the Festo trainer and check its operation

Design simple pneumatic circuits for a given application.

Module Contents

Topic Page No.

1 Introduction 3

2 3/2 way valve (N/C), push button actuated 4

3 3/2 way valve (N/O), push button actuated 5

4 3/2 way valve (N/C), roller lever actuated 6

5 3/2 way selector valve 6

6 5/2 way valve 7

7 Valve actuators 9

8 Practical task 1 (Pressure dependent control) 7

9 Practical task 2 (Foil welding drum) 11

10 Supplementary resources and References 14

11 Worksheet 20


Module 3: Directional control valves 3

1 Introduction

Directional control valves are

devices which influence the path

taken by an air stream.

The directional control valve is

represented by two numbers.

The first number represents the

number of ports, and the second

number represents the number

of positions as shown in Fig. 3.1.

Note:

These symbols do not provide

any information about the

constructional design, but just

indicate the function of the

valve.

Fig.3.1: DCV Ports and positions

2.1 3/2 way DCV - Normally

Closed (N/C)

Way of operation:

A 3/2-way valve has 3 ports (1,

2 and 3) and 2 switching

positions (before operating and

after operating). It is

represented by the normal

position. Normally closed means

that compressed air cannot flow

through the valve as shown in

Fig. (3.2).

(a) pressure port (1) is blocked

(b) 3/2 way DCV (NC)

(before actuation)

Fig. 3.2: 3/2 way DCV (N/C) before

actuation



When the pushbutton is actuated the

valve is opened, thus allowing the air

to flow from port (1) to port (2) as

shown in Fig. 3.3.

Un-actuated

In normally closed 3/2 way valve, a

spring-loaded disk seal blocks the air

flow from the air supply port (1) to

the working port (2). The working

port (2) is connected with exhaust

port (3) as shown in Fig. (3.2).

Actuated

Actuating this valve results in allowing

the flow from port (1) to port (2) and

blocking the exhaust port (3) as

shown in Fig. (3.3).

Fig. (3.4.a) shows the ISO symbol of

3/2 way valve normally closed (N/C)

and spring reset. Fig. 3.4.b shows the

picture of the valve.

Fig. 3.3: 3/2 way DCV (N/C) after actuation

(a) ISO symbol of 3/2 way

directional control valve N/C

(b) Picture of 3/2 way directional

control valve N/C

Fig. 3.4: 3/2 DCV (N/C) symbol

and picture

2.2 3/2-DCV - Normally Open (N/O) Way of operation:

Normally open means that compressed air

flows through the valve as shown in Fig.

(3.5.a). When the pushbutton is actuated the

valve is closed, thus stopping the air to flow

from port (1) to port (2).

(a) 3/2 way directional

control valve N/O



Un-actuated

In the normally open 3/2 way valve, a spring

loaded disk blocks exhaust port (3). The air

supply port (1) is connected to the working

port (2).

Actuated

Actuating this valve results in allowing the

flow from port (2) to port (3) and blocking

the supply air port (1).

Fig. (3.5.b) shows the ISO symbol of 3/2 way

valve normally open (N/O) and spring reset,

And Fig. 5.5.c shows the picture of the valve.

(b) ISO symbol of 3/2 way directional control valve NO

(c) Picture of 3/2 way DCV (N/O).

Fig. 3.5: 3/2 DCV (N/O)

2.3 3/2 Way- Roller Lever Valve- Normally closed (N/C)

The roller lever actuation way is

considered to be one of the most

important types of valve actuation

that is used for automatic operation of

the pneumatic cylinders. It is

generally known as pneumatic limit

switch.

2.3.1 Symbol and Construction

Fig. (3.6.a) shows the picture of the

3/2 way valve, N/C, roller lever valve.

Fig. (3.6.b) shows the ISO symbol of

the 3/2 roller lever valve.

Fig. (3.6.c) shows the construction of

the 3/2 roller lever valve.

(a) Picture of the roller lever valve

(b) ISO symbol

(c) Construction

Fig. 3.6: 3/2 way roller lever valve



2.3.2 Function

This valve is actuated by pressing the roller lever e.g. by means of cylinder trip

cam. The valve is returned to the normal position via return spring after

releasing the roller lever.

2.4 3/2 way, selector valve

Fig. 3.7 shows the picture and the ISO

symbol of the 3/2 way, selector valve.

(a) Picture

(b) ISO symbol

Fig 3.7: 3/2 way selector valve

3. 5/2 way Directional Control Valve

This valve contains 5 ports and 2

positions. The 5/2 DCV could be

actuated manually or by using

pressure actuation (single pilot and

double pilot), or by electrical

actuation (solenoid).

3.1. Before actuated

When the 5/2-way valve is not

actuated, the flow will be from port

(1) to port (2) while the exhaust will

be from port (4) to port (5) as

illustrated in Fig. 3.8.a

(a) Initial position (before actuation)

(b) Second position (after actuation)

(c) ISO symbol of 5/2 way valve

Fig 3.8: 5/2 way valve



3.2 After actuation

After operating the valve by any method, the valve will be shifted to the

other position and in this case, the flow will be from port (1) to port (4)

while the exhaust will be from port (2) to port (3) as shown in Fig. (3.8.b).

3.3 Types of 5/2 DCV: 3.3.1 5/2 way selector valve This valve is used for manual

operation, and you can control the

valve by selector switch, and it is used

in simple applications. Fig. 3.9 shows

the picture and the ISO symbol of the

valve.

3.3.2 5/2 way single pilot valve

This valve is used for automatic


valve by a pneumatic signal and a

spring return. Fig. 3.10 shows the

picture and the ISO symbol of the

valve.

3.3.2 5/2 way double pilot valve

This valve is used for automatic


valve by two pneumatic signals and

this valve keeps the last position after

removing the applied signal, and it is

sometimes called memory valve. Fig.

3.11 shows the picture and the ISO

symbol of the valve.

Fig. 3.9: 5/2 way selector valve

Fig. 3.10: 5/2 way single pilot

valve

Fig. 3.11: 5/2 way double pilot

valve



4. Valve actuators:

The pneumatic directional control

valves can be actuated (operated) in

several ways such as follows:

4.1 Manual actuators

Fig. (3.12.a) shows (from left to

right) three manual actuation

methods: manual, push button and

foot pedal.

4.2 Mechanical actuators

Fig. (3.12.b) shows (from left to

right) two mechanical actuation

methods: roller and idle return roller.

4.3 Electrical actuators

Fig. (3.12.c) shows an example of

electrical actuation (solenoid valve).

4.4 Pneumatic actuators

Fig. (3.12.d) shows an example of

pneumatic (pressure) actuation.

(a) Manual actuation

(b) Mechanical actuation

(c) Electrical actuators

(d) Pneumatic actuation

Fig. 3.12: Valve actuators



5. Pneumatic actuators

They are used to produce the required forces in

the pneumatic systems. Pneumatic actuators will

be covered in more details in modules 4 and 5

5.1 Single acting cylinder

Single acting cylinder (SAC) is an output device.

The function of the SAC is to convert the pressure

energy to mechanical energy (linear motion).

Fig. (3.13.a) shows a picture of the single acting

cylinder.

Figure (3.13.b) shows the ISO symbol of the

single acting cylinder.

5.2 Double acting cylinder

Double acting cylinder (DAC) is an output device.

The function of the DAC is to convert the pressure

energy to mechanical energy (linear motion).

Fig. (3.14.a) shows a picture of the double acting

cylinder.

Figure (3.14.b) shows the ISO symbol of the

double acting cylinder.

Note:

Single acting cylinder is used to produce linear

force in one direction only. Whereas, double

acting cylinder is used to produce linear force in

two directions.

(a) Single acting

Cylinder

(b) ISO symbol of

Single acting cylinder.

Fig. 3.13: Single acting

Cylinder

(a) Double acting cylinder

(b) ISO symbol of

double acting cylinder

Fig. 3.14: Double acting

Cylinder



6- Practical Task 1: Gravity feed magazine

6.1 Learning objectives:

Upon the completion of this task, the student will be

• Familiar with indirect actuation of a double acting cylinder by using a double pilot valve.

• Using the 3/2 way roller valve for automatic return of the cylinder.

6.2 Task description:

Wooden planks are to be pushed along from a gravity feed magazine to a

clamping device as shown in Fig.3.15. By pressing a pushbutton valve one

plank is pushed by the slide out of the gravity feed magazine. After the

slide has reached the forward end position it returns to its start position.

Fig. 3.15: Positional sketch



6.3 Task requirements:

1. Draw pneumatic circuit diagram to control the movement of the

slide.

2. Simulate the circuit using Fluid SIM software.

3. Assemble the circuit practically and check its operation.

Draw the pneumatic circuit here



7- Practical Task 2: Diverting device

7.1 Learning objectives:

Upon the completion of this task, the student will be

• Familiar with indirect actuation of a double acting cylinder by using a double pilot valve.

• Familiar with using different types of directional control valves.

7.2 Task description:

Using a diverting device, parts are to be moved from one conveyor track

onto the other in a linear sequence as illustrated in Fig. 3.17. By

operating a selector valve the oscillating piston rod of a cylinder pushes

the turntable via a pawl in stepped sequence. The parts are diverted and

transported onwards in the opposite direction. By returning the selector

valve back to the normal position the drive unit is switched off.

Fig. 3.17: Positional sketch



7.3 Task requirements:

1. Draw a pneumatic circuit diagram to control the operation of the

piston.

2. Simulate the circuit using FluidSIM software.

3. Assemble the circuit practically and check its operation.

Draw the pneumatic circuit here



8. For further reading, you can use the following links:

1- www.Fest-didactic.com

2- http://www.eng2all.com/vb/t28932.html

3- http://www.logiclab.hu/lesson.php?fe=2

9. Supplementary recourses

1. Pneumatics video from Festo.

2. FluidSIM software.

10. References

1- Festo manuals and workbook TP101

2- Festo manuals and textbook TP101

http://www.fest-didactic.com/�

http://www.eng2all.com/vb/t28932.html�

http://www.logiclab.hu/lesson.php?fe=2�



Student’s notes

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Worksheet 1 Draw the symbol of 3/2 way (N/C), roller lever valve ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… Draw the symbol of 5/2 way, double pilot valve …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. Draw the symbol of 3/2 way, selector valve …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. What is the difference between 5/2 single pilot and 5/2 double pilot? ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… What is the function of directional control valves? …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

What is the difference between N/O and N/C valves? …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

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