| 摘要 |
A sealed control valve assembly is provided for use in connection with a fluid valve having an inlet, an outlet and a flow control orifice hydraulically interposed therebetween for controlling the flow through the fluid valve. The valve assembly includes a sealed cylindrical isolator cap sealingly mounted to the fluid valve so that the chamber defined by the isolator cap is in hydraulic communication with the fluid valve. In one embodiment, an armature composed of a magnetic material is reciprocatably disposed within the isolator cap. A modulating plug is connected to a lower end of the armature to extend outside the isolator cap into the fluid valve adjacent the flow control orifice. A magnetic pole piece assembly, including a magnetic sandwiched between a pair of pole pieces, is reciprocatably disposed outside and adjacent to the isolator cap. A diaphragm assembly is provided to move the pole piece assembly down in response to fluid pressure exerted against the diaphragm. The pressure against the diaphragm can be varied in relation to a condition of the fluid flowing through the fluid valve. The pole piece assembly and the armature form a magnetic circuit so that the armature follows the movement of the pole piece assembly in order to maintain the continuity of the magnetic circuit. The modulating plug moves with the armature to modulate the fluid flowing through the flow control orifice in the fluid valve. A biasing spring may be provided to react against the downward action of the diaphragm and provide a return stroke for the pole piece assembly and armature. Rotary actuated and rotary-linear actuated sealed valve assemblies are also disclosed.
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