Schematic Symbol for
2 port, 2 position valve
(more about circuit symbols)
As the name suggests a two-position directional valve has two positions, and is always in one of two states.
With a simple two-positon, two port valve (symbol shown at right) - the valve will either be open or closed.
With a two-position, five port valve, the two output ports are always in opposite modes. When one is receiving inlet air, the other is connected to the exhaust port.
Air path in position one:
Air path in position two:
Complete Schematic Symbol
When actuated, 3-position directional control valves function similarly to the above. However, a center or "neutral" position is provided that blocks all ports (center closed), or connects both output ports to the exhausts (center exhaust) when the valve is not being actuated.
Pressure held models are ideal for "inching" operations where you want the cylinder rod to move to a intermediate position and hold. Cylinder Switches can be used to sense the position of the piston/rod mid-stroke.
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