A 4/2-way valve is a very commonly used control and switching valve in pneumatics and hydraulics. It has four ports (ways) and can assume two different switching positions. The most common implementation of a 4/2-way valve is as a spool valve.
Compared to spool valves, seat valves offer the following advantages:
- high tightness,
- good suitability for high pressures,
- less sensitive to contamination,
- fast switching operations.
For the implementation of a 4/2-way valve in medical technology, SVS-Automation chose the seat valve design because of these advantages and the existing FFKM seals, which allowed the use of proven components.
The realization is carried out in such a way that two 3/2-way solenoid valves are integrated into one valve manifold, and the inlets, outlets, and exhaust ports are interconnected according to the schematic shown below. The schematic additionally includes a check valve, which is also integrated into the same valve manifold.
The 3/2-way valve components used are not the standard version with one port on the guide tube, but rather a special design in which all ports are integrated into the valve body. A single valve in this special design is shown in the following illustration of a brass valve.
The actuation of the 4/2-way valve is designed so that either no solenoid coil or both solenoid coils of the 3/2-way solenoid valves are energized simultaneously, thus achieving the two different switching positions:
- No solenoid coil energized: P → A and B → T
- Both solenoid coils energized: P → B and A → T
Conclusion
With this simple design, a 4/2-way function can be realized that retains the advantages of seat valves while being compactly integrated into a valve block. In many applications, these advantages outweigh the disadvantage of requiring two solenoid coils for the two 3/2-way valves.
As with all valve manifolds, the valve function can be further expanded with additional elements such as pressure regulators or filters.
