Cage valve with pilot and mechanical operating means

Claim 1

In a fluid valve of the type having a cylindrical cage, a cylindrical piston disposed within said cage, an outlet, a main port between one end of said cage and said outlet, a main seal attached to one end of said piston and aligned with said main port for engagement thereof, the diameter of said main port being substantially smaller than the diameter of said cage, said piston being a loose, sliding fit for moving longitudinally within said cage between a closed position in said one end of said cage and an open position toward the other end of said cage, said seal engaging said main port in said closed position to close completely said main port, a cage port through the wall of said cage near said one end thereof, the cylindrical wall of said piston being opposite said cage port while said piston is in said one end of said cage, the flow of fluid through said valve being gradually decreased through said cage port to a relatively small amount as said piston is moved from said open position through positions where said cylindrical wall increasingly overlaps said cage port as said cylinder approaches said closed position, a housing surrounding the cylindrical wall of said cage to form an inlet chamber about said cage, and an inlet of said valve communicating with said inlet chamber, a combination of pilot means and direct mechanical means for moving said piston between said closed position and said open position, said pilot means including fluid bleeding means communicating between said inlet chamber and the interior portion of said cage at said other end thereof for all positions of said piston between said closed position and said open position, said interior portion at said other end of said cage being closed except for said bleeding means, a pilot conduit coaxially disposed through said piston, the end of said conduit facing said main port being within the periphery of said main seal and communicating with said main port, a pilot sealiNg surface encircling the other end of said pilot conduit on that end surface of said piston opposite said main seal thereof, a pilot sealing member, said direct mechanical means comprising a solenoid assembly including a plunger coaxially aligned with said pilot conduit and said pilot sealing member being attached to the end of said plunger adjacent said pilot sealing surface of said piston, a spring connected to said plunger to urge said pilot sealing member against said pilot sealing surface, those portions of said pilot sealing member outside said pilot sealing surface always being surrounded by fluid at the pressure existing within said interior portion of said cage between said piston and said other end of said cage, a lost-motion coupling between said plunger and said piston, said solenoid assembly in response to being energized operable to move said pilot sealing member sufficiently to open said pilot conduit and subsequently operating through said lost-motion coupling for moving said piston from said closed position to said open position, said pilot conduit while open having sufficient capacity to prevent within said interior portion of said cage pressure resulting from continuous flow of fluid through said bleeding means, said spring immediately upon deenergization of said solenoid assembly moving said pilot sealing member to close said pilot conduit and to urge said piston to said closed position, the movement of said piston toward said closed position being namely controlled by moderate force from said spring and the existing fluid pressures on said piston including the pressure of fluid in that portion of said cage between said piston and said other end resulting from continuous passageway provided by said bleeding means.