The solenoid valve used for our pneumatic actuators is a four-way, on/off, electrically controlled valve. An electrical signal to the solenoid's coil switches the compressed air supply to the actuator cavities as follows: The solenoid valve is used with the actuator, and simultaneously pressurizes port A while exhausting the end cap cavities through port B, or vice versa. The solenoids are furnished with mufflers and speed controls. The muffler reduces the sound of the exhausting air, and the speed control determines the cycle time of the actuator. The speed controls are manually set needle valves that can be adjusted. The cycle time can be slowed by restricting the flow of the exhausting air, thus maintaining back pressure on the opposite side of the pressured actuator cavity. Solenoids are available in Type 4X and Type 7 ratings, and in all voltages. The 115 Vac model has a 6.2 watt coil. Upon electrical failure, actuators with single-coil solenoids will return to the de-energized position. This position can be either actuator position depending upon how the plumbing is connected from the solenoid block to the air connection of the actuator, port A or port B.
Solenoids can be either close-coupled to the actuator (as shown), or they can be remotely installed, always considering that pneumatic air looses pressure over distance. During the absence of electric power, the actuator can be cycled by operating the manual override on the solenoid, providing that supply air is still available.
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