| 摘要 |
A valve assembly having a fluid switch and a main valve for controlling fluid pressure in a working volume in three control states wherein the main valve has three ports for fluid, flow of fluid through a first port and a second port being controlled by the fluid switch being provided with an electrical signal in a first state or a second state respectively, and flow of fluid through the third port being controlled by alternating said signal, preferably rapidly, between said first and second states.
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