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Figure 8 shows the complete symbol for a 2-position, 2-way, solenoid-operated, spring-return directional control valve. Since the solenoid symbol is attached to the top square, the top square shows us that ports 1 and 2 are connected when the solenoid is energized. The spring symbol is attached to the bottom square. When the valve is de-energized, the spring will return it to its rest position. The bottom square shows us that ports 1 and 2 are disconnected when the valve is de-energized. Figure 9 shows the complete symbol for another 2-position 2-way valve, but this one is manually or solenoid operated and spring returned. The symbols for valves can be drawn in any position that is convenient for the diagram. In Figure 9, the valve is drawn sideways. Since the manual symbol and the solenoid symbol are attached to the right square when the valve is energized, the right square shows us how the ports are connected. The spring symbol is attached to the left square. When the valve is de-energized the spring will return it to its rest position. The left square shows us that ports 1 and 2 are disconnected when the valve is de-energized. When an actuator is attached to one of the squares, that square shows how the ports are connected or disconnected when that actuator is used to operate the valve. In the next article we will continue our discussion by explaining 3-way and 4-way directional control valves. |
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