View
215
Download
1
Category
Preview:
Citation preview
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
Recommended