Introduction to Pneumatics Pneumatics Symbols Air generation and distribution Table 1: Symbols use in energy conversion and preparation ITEM SYMBOL MEANING Compressor SUPPLY Pressure Source Pneumatic Pressure Source Air Reservoir Filter : separation and filtration of particles SERVICE EQUIPMENT 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 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 Symbol Development 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 SYMBOL Table 5: Pressure Valve EXPLANATION Sequence valve-in line Adjustable pressure regulating valve, relieving type Auxiliary Symbols Table 6: Auxiliary Symbol SYMBOL EXPLANATION Pressure gauge Silencer Exhaust
Plug 0 Bar 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
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. Figure 6: Circuit Diagram 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 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