Air over oil high pressure modulating valve

An air over oil high pressure modulating valve comprising housing means having a pneumatic pressure chamber in communication with a longitudinally extending bore, piston means slidably disposed within said chamber, first poppet valve means carried by the piston means and extending into the bore, second poppet valve means slidably disposed within the bore and engageable by said first poppet valve means, valve seat means provided on said second poppet valve means for providing alternate closed and open positions for the first poppet valve means, vent port means provided in the housing in the proximity of the first poppet valve means for venting fluid pressure during opening and closing of said first poppet valve means, valve seat means provided on the inner periphery of the bore for providing alternate open and closed positions for the second poppet valve means, fluid passageway means extending through said second poppet valve means, pneumatic pressure inlet port means provided in communication with said chamber for applying pneumatic pilot pressure to one side of the piston means for selectively controlling the movement thereof within said chamber, hydraulic fluid inlet port means provided in said housing means and in communication with the bore, hydraulic fluid return port means provided in said housing means in communication with the bore for recirculation of hydraulic fluid through the housing, fluid trapping sealing means carried by the second poppet valve means and in sealing engagement with the bore and interposed between the hydraulic fluid input port means and hydraulic fluid outlet port means, hydraulic fluid outlet port means for controlled discharge of hydraulic fluid, said piston means being responsive to the pilot pressure and to pressure differentials acting thereon for closing the first poppet valve in one position of the piston and to preclude return of fluid pressure through the fluid pressure return outlet and for closing the first poppet valve means and simultaneously opening the second poppet valve means in another position of the piston means for providing said controlled discharge of hydraulic fluid through the outlet port means and for simultaneously closing both the first and second poppet valve means in another position of the piston means for trapping controlled hydraulic fluid pressure at the discharge port means, said fluid trapping sealing means cooperating with the trapped fluid pressure for increasing the sealing efficiency of the second poppet valve means in the closed position thereof, and wherein said fluid trapping sealing means comprises an outwardly extending annular shoulder provided on the outer periphery of the second poppet valve means and interposed between the hydraulic fluid inlet port means and hydraulic fluid return port means, and an annular seal being disposed around the outer periphery of the second poppet valve means and in engagement with the shoulder whereby one face of the seal ring is open at the hydraulic pressure surrounding the poppet valve in the proximity thereof.