Introduction to Pneumatics

Pneumatics Symbols

Air generation and distribution

Table 1: Symbols use in energy conversion and preparation

ITEM SYMBOL MEANING

SUPPLY

Compressor

Pressure Source

Pneumatic Pressure Source

Air Reservoir

SERVICE

EQUIPMENT

Filter : separation and filtration of

particles

Filter and separator (automatic)

Lubricator

Pressure regulator

COMBINED

SYMBOLS

Air Service Unit : Filter,

Regulator, Gauge, Lubricator

Simplified air service unit with

lubricator

Input Elements

Directional control valves

Table 2: Directional Control Valve Symbol Development

Explanation Of Symbol Symbol Development

Valve switching positions are represented as squares

The number of squares shows how many switching

positions the valve has

Line indicate flow paths, arrows shows the direction

of flow

Shut off positions are identified in the boxes by lines

drawn at right angles

The connections ( inlet and outlet ports ) are shown

by lines on the outside of the box

Table 3: Directional Control Valve, Ports and Positions (ways)

SYMBOL EXPLANATION

2/2 - way directional control valve, normally open

3/2 – way directional control valve normally closed

3/2 – way directional control valve, normally open

4/2 – way directional control valve

Flow from 1 to 2 and from 4 to 3

5/2 – way directional control valve

Flow from 1 to 2 and 4 to 5

5/3 – way directional control valve

Mid position closed

Figure 1: Methods of Actuation

0 Bar

Flow Control Valve

Table 4: Flow Control Valves

SYMBOL EXPLANATION

Flow control valve, adjustable

One-way flow control valve

Pressure control valves

Table 5: Pressure Valve

SYMBOL EXPLANATION

Sequence valve-in line

Adjustable pressure regulating

valve, relieving type

Auxiliary Symbols

Table 6: Auxiliary Symbol

SYMBOL EXPLANATION

Pressure gauge

Silencer

Exhaust

Plug

Visual indicator

Processing Elements

Table 7: Non-return valves and derivatives

SYMBOL EXPLANATION

Check valve

Shuttle valve

AND Valve

Quick exhaust valve

Actuator (Output)

Table 8: Actuators

SYMBOL EXPLANATION

Single acting cylinder with spring return

Double acting cylinder

Double acting cylinder with double ended

piston rod

0 Bar

Double acting 2 cushion cylinder

Air motor rotation in one direction

Rotary actuator

Development of single actuator circuit

Example 1: Direct control of a single-acting cylinder

A single acting cylinder of 25mm diameter is to advance a component when a push button is

pressed. As long as the push button is activated the cylinder is to remain in the clamped position. If

the push button released, the clamp is to retract.

Figure 2: Positional Sketch

Figure 3: Circuit Diagram

Example 2: Indirect control of a double acting cylinder

A double acting cylinder is to extend when a push button is operated. Upon release of the push

button the cylinder is to retract.

Figure 4: Circuit Diagram

Example 3: The logic AND function

The piston rod of a double acting cylinder is to advance when both push button of the 3/2 way valve

is actuated. If either of these is released, then the cylinder is to return to the initial position.

Figure 5: Circuit Diagram

Example 4: The logic OR function

A double-acting cylinder is to advance if one of two push buttons is operated. If the push button is

then released, the cylinder is to retract.

Example 5: Memory circuit and speed control of a cylinder

The piston rod of a double acting cylinder is to advance when a 3/2 way push button valve is

actuated manually. The cylinder is to remain advanced until a second valve is actuated. The signal of

the second valve can only take effect after the first valve has been released . The cylinder is to then

return to the initial position. Then cylinder is to remain in the initial position until a new start signal is

given. The speed of the cylinder is to be adjustable in both directions.

Figure 6: Circuit Diagram

Figure 7: Circuit Diagram

Combinational valves

The combined functions of various elements can produce a new function. The new component can

be constructed by the combination of individual elements or manufactured in a combined

configuration to reduce size and complexity. An example is the timer which is the combination of a

one way flow control valve, a reservoir and a 3/2 way directional control valve.

Figure 8: Time delay valve

Example 1: The timer delay valve

A double-acting cylinder is used to press together glued component. Upon operation of a push

button, the clamping cylinder extends. Once the fully advanced position is reached, the cylinder is to

remain a time of T= 6 seconds and then immediately retract to the initial position. The cylinder

retraction is to be adjustable. A new start cycle is only possible after the cylinder has fully retracted.

Figure 9: Circuit Diagram

Development of multiple actuators circuits

In case of multiple cylinder circuits, a clear definition of the problem is important. The

representation of the desired motion of all actuators described using the displacement-step

diagram. The special condition for the start of the sequence must also be defined.

Example 1: Coordinated motion

Two cylinders are used to transfer parts from a magazine onto a chute. When a push button is

pressed, the first cylinder extends, pushing part from the magazine and positions it in preparation

for transfer by the second cylinder onto the out feed chute. Once the part is transfer, the first

cylinder retracts, followed by the second. Confirmation of all extended and retracted positions are

required.

Figure 10: Displacement Step Diagram

Figure 11: Circuit Diagram