Positioning - in all directions

Standard pneumatic Handling Electrical drives Servopneumatic

Characteristics of Pneumatic Systems

• Pneumatics has for some considerable time been used for

carrying out the simple mechanical tasks. Linear, swivel
and rotary motions can be easily performed with
pneumatic components. Especially pneumatic cylinders
have a significant role as near drive units due to their
relatively low cost, ease of installation, simplicity and
robust construction.
• Pneumatics is competing with two other working media:
– Electrics
– Hydraulics
Advantages of pneumatic systems:

Availability: Air is available practically everywhere in unlimited quantities

Transport: Air can be easily transported in pipelines, even over large distances

Storage: Air can be stored in a reservoir and removed as required

Temperature: Compressed air is insensitive to temperature fluctuations

Explosion proof: Compressed air offers minimal risk of explosion of fire

Cleanness: Unlubricated exhaust air is clean. Leaking pipes or components cause

no contamination to the environment.

Components: The operating components are of simple construction and relatively

inexpensive

Speed: Compressed air is a very fast working medium.

Adjustable: Speed and forces are infinitely adjustable

Overload safe: Pneumatic tools and components can be loaded to the point of stopping
without damage.
Disadvantages of pneumatic systems:

Preparation: Compressed air requires good preparation. Dirt and condensate has to be
removed.

Compressibility: Air is compressible and therefore it is not always possible to achieve uniform
motions or constant speeds.

Force: Compressed air is most economical at a working pressure of 6-7 bar. This
limits the achievable forces. (Festo’s largest cylinder DGP-320 has a thrust of
~50.000 N at 6 bar).

Noise level: Exhausting air is loud. Using sound absorbing silencer can solve the
problem.

Cost: Compressed air is a relatively expensive medium. The high energy costs are
partially compensated by inexpensive components.
Air Generation and Distribution

Equipment to be considered in the generation and preparation of compressed air

4
3 6
1 7
2
6
6
5

1 Air Compressor
2 Recooler
3 Water and oil separator
4 Air Reservoir
5 Drainage Point
6 Air Dryer
7 Air filter and pressure regulator
 PneumatPNEUMATICS
ic actuators

Linear motion Rotary motion

Single acting Cylinder Double acting cylinder Rotary Module Air motor
- pushing - with/o end cushioning - Vane type - Piston type
- pulling - with/o sensing - Racket/pinion type - Sliding vane type
- with/o sensing - special designs
- special designs
 Control chain and
Pneumatics signal flow Electrics
Cylinders Electric motor
Motors Solenoids
Actuating devices
Indicators Linear motors
Power contactors
Directional control Output driver Power transistors
valves
Semiconductors

Directional control
Contactors
valves
Relays
non-return valves
Processing elements Timers
pressure valves
Counters
Shuttle vavles
Electronic components
Dual pressure valves

Switches
Switches
Pushbuttons
Pushbuttons
Limit switches
Limit switches Input elements program generators
Pressure sequencer
proximity switches
Proximity switches
indicators
 Power Supply

These are available in various configurations with different levels of filtering and regulation of the output
voltage.

The power supply should be able to comfortably manage the total system current requirements without
overloading. Consideration should be also given to the impact of future expansion of the system.

AC AC DC DC
Full wave Rectified Unfliltered Filtered
+

24 VDC
AC
Transformer Rectifier Filter Regulator Output
Mains
0V
5/2 Way valve
5/2-way valves have 5 connecting ports and two working positions. Basically a 5/2-way valve has the same
functionality as a 4/2-way valve. The difference between the two valves is that the 5/2-way valve has a
separate exhaust port for each working port. Working port (4) exhausts through port (5) while working port
(2) exhausts through port (3). Today 4/2-way valves are generally replaced by 5/2-way valves.
4 2
5/2-way suspended disc seat valve, pilot air operated
14 12

5 3
1

The 5/2-way valve is not actuated. The supply air is connected to the working port (2) while the air from
working port (4) is exhausting to the atmosphere trough port (5).
When the valve stem is switch to the working position, the connections (1) to (2) and (4) to (5) are closed and the passages
between (1) and (4) and (2) to (3) are opened. The valve has small overlapping between the two switching positions where
all five ports are shortly connected together. In normal operation this overlapping is not recognized.

The ports (12) and (14) are pilot air signals, which switch the valve stem. When pilot signal (12) is applied, the valve
switches to the position where (1) is connected to (2), while pilot signal (14) would switch the valve to the position where
(1) is connected to (4).

When both pilots are applied, the valve remains in its current switching position.
5/2-way valve with applied pilot signal (14) 5/2-way valve with applied pilot signal (12 ).
Pilot operated valves

To avoid high actuating force, mechanically controlled valves can be equipped with an internal pilot valve to assist valve
switching. This allows for example large bore valves to be operated with small actuating forces. This increases the
sensitivity of the system.

position where (1) is connected to (4). When both pilots are applied, the valve remains in its current switching position.
5/2-way valve with applied pilot signal (14) 5/2-way valve with applied pilot signal (12)

3/2-way roller lever valve, internal pilot, normally closed

1 3
Representation
From these basic the symbol for a valve is comprised. The connections are always drawn to the
box, which shows the initial position.
 ACTUATION TYPES

Mechanical

General manual operation

Push button

Stem operated

Foot pedal

Lever operated

Detent lever operated

Spring return

Spring centered

Roller lever

Roller lever with idle return

Pneumatic

Direct pneumatic actuation

Indirect pneumatic actuation (pilot)

Pressure release

Electrical

Single solenoid operation

Double solenoid operation

Permanent magnet

Combined

Double solenoid and pilot operation

with manual override
Single acting cylinder

With single acting cylinders compressed air is applied on only one side
of the piston face. Therefore the cylinder can generate work in only one
direction. The return movement of the piston is effected by a built-in
spring or by the application of an external force.
Double acting cylinder

A double acting cylinder is operated by the reciprocal input of

compressed air. When compressed air is applied to the rear port of the
cylinder while the other side is open to the atmosphere, the cylinder
starts to advance. To return the piston to its initial position the air supply
has to be connected to the front port while the rear chamber of the
cylinder has to be exhausted. The switching of air is done by means of a
directional control valve.
PNP/NPN configuration

Generally two sensor designs are distinguished, PNP (positive switching) and
NPN (negative switching).

+ 24 VDC + 24 VDC

Lo a d

Lo a d

GND GND

PNP NPN
 Pressure switch

A pressure switch senses the air pressure of the air-line and compares this with a pre-set
adjustable value. When the pressure reaches the pre-set limit the internal changeover
contacts are switched and an electrical output signal is given.
The design incorporates a diaphragm, which is linked with a stem to an adjustable spring.
When the pneumatic signal has sufficient pressure to overcome the spring force the stem is
operated and switches the changeover contacts.
 INDUCTIVE SENSORS CAPACITIVE SENSORS

OPTICAL SENSORS

Optical proximity sensors

Through beam sensors Retro-reflective sensors Diffuse sensors

Designs with fibre optic cable Designs with fibre-optic cable

Position sensing
Cylinders can be fitted with a magnet in the piston. This allows a contactless sensing of
the position of the piston with proximity switches.
 Switches and relays

Switches are primarily distinguished by their contact configuration

- normally open (path 3 to 4)
- normally closed (path 1 to 2)
- changeover contacts (path 1 to 2 or 1 to 4)

On actuation a normally open (NO) contact enables energy flow while a normally closed contact (NC) disables energy flow.
The changeover contacts (CO) can be used as either normally open or normally closed contacts or both.
Switches may consist of a single pair of contacts either normally open (NO) or normally closed (NC) or have a set of
changeover (CO) contacts. More complex configurations (multi-pole switches) are available. A range of actuation methods
is also available such as pushbutton, mechanical electrical or pneumatic actuation. The actuation method can be momentary
(non-latching) or detented (latching),

Important considerations when selecting switches include

- Current and voltage rating of contacts
- Level of electrical insulation of the switch housing
- Number and configuration of contacts
- Method of actuation and switch design

CONTACT CONFIGURATION

3 1 1

4 2 2 4
No rm a lly o p e n No rm a lly c lo s e d Ch a n g e o ve r
Relays

In electropneumatics relay are generally used as signal processors. Rather than switching a solenoid directly via a limit
switch or electric sensor, the relay contacts act as a buffer, carrying the larger amount of current.

Relay characteristics
A small amount of energy applied to the relay coil can control a larger energy flow through the relay contact
Relays are able to switch a number of independent circuit paths
Isolate the input signal (relay coil) from the output signal (relay contacts). This is refereed to be a potential free
contact.
High operating speed, i.e. short switching times

13 23 31 41

K1

14 24 32 42
Solenoid valve

Solenoid principle
If a conductor is formed into the shape of a coil and current is passing through the conductor, an electromotive force is
generated. By adding turns to the conductor, the magnetic field is strengthened and adding turns to the conductor increases
the force. Adding an iron core to the solenoid further increases the force.

DC solenoid

When current is applied to the solenoid head, a magnetic field is generated which influences the valve stem and the soft iron
core at the end of the stem housing. The divers polarities at the soft iron core and the valve stem initiates a force of
attraction, which causes the stem to be pulled up. When the current is switched off, the magnetic field collapses and the
spring pushes back the stem into its initial position.

+ + N

- -

When the solenoid is switched on, the current rises slowly. During development of the magnetic field the inductance of the
coil generates a force which opposes the applied voltage. This explains the slightly slow energising action of DC solenoid
 System Development

Each electropneumatic circuit can be divided in two distinctive parts

- pneumatics
- electrical

There exists an interface between the pneumatic and electrical elements. These elements will appear on
both the pneumatic and electrical circuit diagrams.

The steps in development of a basic circuit

- Describe operation of circuit
- Develop a displacement step diagram for the pneumatic actuators
- Draw the pneumatic circuit
- Specify the pneumatic/electric interface
- Draw the electrical diagram
- Document maintenance information (numbering and designation of elements)
- Document type of components and technical data

Development guide for pneumatics

- circuit layout should follow the signal flow through the control chain from bottom to top
- cylinders and directional control valves are drawn horizontally with the cylinders operating
from left to right.
Development guide for pneumatics

Circuit layout should follow the signal flow through the control chain from bottom to top cylinders
and directional control valves are drawn horizontally with the cylinders operating from left to
right.

Components are represented by symbols, which indicate the function. The symbols are placed in
accordance with the level of the system. Pneumatic signal flow is from bottom to top.

Numbering of pneumatic circuit elements is done the following way.

a0 a1 b0 b1
1.0 2.0

A 2.02
P R
1.01 1.02 2.01

1.1 4 2 2.1 4 2
Y1 Y2 Y3
14 12 14

0.1 5
1
3 5
1
3
Development guide for electrical layout

layout should follow the signal flow through the control chain (input,
processing, output) from top to bottom
circuits with relay control can be further divided into a control section and a
power section
components should be placed from left to right according to the sequence of
operation

0V

K0 K3 K3 K4 K2

S1 K0 A1

B0 B1 A0

K1

S2 S2

K4

K0 K1 K2 K4 K3 Y1 Y2 Y3
+24V
 Electrical drives product range

click
Electro mechanical
Linear axes 2nd quarter
2003

Coupling elements

1nd quarter
2003
Motors & gearboxes

Controllers/drivers
 Standard configuration
Pneumatic Linear drive
DGP(L)-...
Sensor Sensor Shock absorber
YSR-...

PPV PPV
cushioning cushioning

Flow control valves

GRLA-...

Double Solenoid valve

JMFH-...