Soft ventable relief valve

1. A pilot operated pressure valve comprising:

a main section, an elongated cylindrical hollow outer housing sealingly connected at one end thereof to and longitudinally extending from said main section, an elongated pilot section having a pilot chamber and being mounted within a cylindrical interior of said outer housing and longitudinally extending at one end thereof from said main section, and a pressure adjust section adjustably sealingly connected to another end of said outer housing at another end of said pilot section and defining a loading chamber between said pilot section and said pressure adjust section;

said main section including an inlet port at one end thereof, an outlet port, a retainer sealingly connected to another end of said main section, a main piston slidably mounted within said main section, and a main spring positioned within and extending longitudinally along a main chamber formed centrally between said retainer and said main piston;

a head of said main piston defining one end of said main chamber and including a main orifice adjacent said inlet port which allows a relatively small quantity of pressurized fluid at said inlet port to be metered into and to fill said main chamber;

said retainer including a longitudinally extending passage having a pilot seat at one end and a damping orifice at another end thereof, said damping orifice in fluid communication with said main chamber for allowing a relatively small quantity of pressurized fluid in said main chamber to be metered into said pilot chamber from said main chamber;

said main spring biasingly urging said main piston into sealing engagement against said inlet port until a predetermined inlet pressure is reached equal to a threshold pressure of said valve whereupon said main piston is opened by axial movement thereof against said main spring to allow pressurized fluid to enter said inlet port and to exit said valve directly from said outlet port;

said pilot section including an elongated pilot spring acting at one end thereof within an elongated pilot sleeve of said pilot section against a pilot piston held for sliding translation within said pilot sleeve and supporting a pilot ball held from said pilot seat by a return spring acting between said pilot piston and said one end of said retainer, said pilot piston moving said pilot into a partially sealed position against said pilot seat when pressure in said pilot chamber exceeds a predetermined minimum pressure wherein inlet pressure increases to the operating pressure;

said pilot sleeve longitudinally positionable by said pressure adjust section within said outer housing to vary a length of said pilot spring and thus to vary operating pressure;

said pilot sleeve including a crosshole closed to fluid communication with said pilot chamber by a relief ball held biasingly, longitudinally slidably positionable within said pilot chamber, one end of said pilot sleeve including a control orifice which allows a relatively small quantity of pressurized fluid in said pilot chamber to be metered therefrom into fill said loading chamber;

said loading chamber having a net surface area greater than that of said retainer whereby said pilot sleeve is moveably urged against said pilot spring to vary the valve operating pressure between the threshold pressure and a maximum valve operating pressure.

2. A pilot operated pressure valve as set forth in claim 1 , further comprising:

said retainer including a cross passage in sealed alignment with a pilot bypass port formed through said outer housing, said cross passage in fluid communication with said pilot chamber and inlet downstream of said damping orifice for allowing pressurized fluid to exit said valve from said pilot bypass port wherein the operating pressure of said valve is reduced.

3. A pilot operated pressure valve comprising:

a main section, an elongated cylindrical hollow outer housing sealingly connected at one end thereof to and longitudinally extending from said main section, an elongated pilot section having a pilot chamber and being mounted within a cylindrical interior of said outer housing and longitudinally extending at one end thereof from said main section, and a pressure adjust section adjustably sealingly connected to another end of said outer housing at another end of said pilot section and defining a loading chamber between said pilot section and said pressure adjust section;

said main section including an inlet port at one end thereof, an outlet port, a retainer sealingly connected to another end of said main section, a main piston slidably mounted within said main section, and a main spring positioned within and extending longitudinally along a main chamber formed centrally between said retainer and said main piston;

a head of said main piston defining one end of said main chamber and including a main orifice adjacent said inlet port which allows a relatively small quantity of pressurized fluid at said inlet port to be metered into and to fill said main chamber;

said retainer including a longitudinally extending passage having a pilot seat at one end and a damping orifice at another end thereof, said damping orifice in fluid communication with said main chamber for allowing a relatively small quantity of pressurized fluid in said main chamber to be metered into said pilot chamber from said main chamber;

said main spring biasingly urging said main piston into sealing engagement against said inlet port until a predetermined inlet pressure is reached equal to a threshold pressure of said valve whereupon said main piston is opened by axial movement thereof against said main spring to allow pressurized fluid to enter said inlet port and to exit said valve directly from said outlet port;

said pilot section including an elongated pilot spring acting at one end thereof within an elongated pilot sleeve of said pilot section against a pilot piston held for sliding translation within said pilot sleeve and supporting a pilot ball held from said pilot seat by a return spring acting between said pilot piston and said one end of said retainer, said pilot piston moving said pilot into a partially sealed position against said pilot seat when pressure in said pilot chamber exceeds a predetermined minimum pressure wherein inlet pressure increases to the operating pressure;

said pilot sleeve longitudinally positionable by said pressure adjust section within said outer housing to vary a length of said pilot spring and thus to vary operating pressure.

4. A pilot operated pressure valve as set forth in claim 3 , further comprising:

said retainer including a cross passage in sealed alignment with a pilot bypass port formed through said outer housing, said cross passage in fluid communication with said pilot chamber and inlet downstream of said damping orifice for allowing pressurized fluid to exit said valve from said pilot bypass port wherein the operating pressure of said valve is reduced.

5. In a pilot operated pressure valve comprising an elongated main section, an elongated cylindrical hollow outer housing sealingly connected at one end thereof to and longitudinally extending from said main section, an elongated pilot section having a pilot chamber and being mounted within a cylindrical interior of said outer housing and longitudinally extending at one end thereof from said main section, and a pressure adjust section adjustably sealingly connected to another end of said outer housing at another end of said pilot section, said main section including an inlet port at one end thereof, an outlet port, a retainer sealingly connected to another end of said main section, a main piston slidably mounted within said main section, and a main spring positioned within and extending longitudinally along a main chamber formed centrally between said retainer and said main piston, a head of said main piston defining one end of said main chamber and including a main orifice adjacent said inlet port which allows a relatively small quantity of pressurized fluid at said inlet port to be metered into and fill said main chamber, said retainer including a longitudinally extending damping orifice in fluid communication with said main chamber which allows a relatively small quantity of pressurized fluid in said main chamber to be metered into said pilot chamber from said main chamber, said main spring biasingly urging said main piston into sealing engagement against said inlet port until a predetermined inlet pressure equal to a maximum operating pressure of said valve is reached whereupon said main piston is opened by axial movement thereof against said main spring to allow pressurized fluid to enter said inlet port and to exit said valve directly from said outlet port, said pilot section including an elongated pilot spring acting at one end thereof within an elongated pilot sleeve of said pilot chamber member, the improvement comprising:

said pilot section including an elongated pilot spring acting at one end thereof within an elongated pilot sleeve of said pilot section against a pilot piston held for sliding translation within said pilot sleeve and supporting a pilot ball held from said pilot seat by a return spring acting between said pilot piston and said one end of said retainer, said pilot piston moving said pilot into a partially sealed position against said pilot seat when pressure in said pilot chamber exceeds a predetermined minimum pressure wherein inlet pressure increases to the operating pressure;

said pilot sleeve longitudinally positionable by said pressure adjust section within said outer housing to vary a length of said pilot spring and thus to vary operating pressure.

6. The improvement of claim 5 , further comprising:

said retainer including a cross passage in sealed alignment with a pilot bypass port formed through said outer housing, said cross passage in fluid communication with said pilot chamber and inlet downstream of said damping orifice for allowing pressurized fluid to exit said valve from said pilot bypass port wherein the operating pressure of said valve is reduced.