Actuators

Before we can determine which square indicates the energized state and which square indicates the de-energized state, we must know the symbols for actuators. An actuator is the means by which the valve is energized and de-energized. Actuators are represented by symbols that are added to the ends of the directional control valve's symbol.

Figure 3 shows some actuator symbols which represent manual operation. Figure 3A shows the symbol that is used to indicate that a pushbutton is depressed to energize the valve. Figure 3B shows the symbol that is used to indicate that a lever is operated to energize the valve. Figure 3C shows the widely used universal symbol to indicate manual operation. While this symbol indicates that the valve can be manually energized, it does not indicate the specific means such as, pushbutton, lever, foot pedal, etc.

Figure 4A and 4B show some actuator symbols which represent mechanical operation. When a mechanical arm contacts the roller cam it pushes it down energizing the valve.
Figure 4C shows the symbol used to indicate a spring. Springs are normally used to return a valve to its rest position, after it has been energized by another means.

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