Two-stage hydraulic solenoid valve

摘要

A two-stage hydraulic solenoid valve for controlling the application or release of hydraulic pressure to components of a steam turbine control system. The valve includes a primary hydraulic circuit in which a floating poppet operates between first and second valving positions to connect the valve's outlet port to either an inlet port or a drain port so that the connected control system components receive full hydraulic pressure or are provided with a pressure release path. A secondary hydraulic circuit controls the poppet position through a solenoid actuatable ball and valve seating arrangement wherein a ball is alternatively positioned between a pair of valve seats to switch fluid connections to poppet actuation chambers, one such chamber being located at each end of the poppet. The ball is positioned in sealing contact with one valve seat by the solenoid and is returned to the other seat by fluid pressure upon deactivating the solenoid. A spring is provided to urge the poppet into its first valving position although unbalanced hydraulic forces add to the spring force to firmly seat the valve; the poppet is moved to its second position entirely by unbalanced hydraulic forces.