Valve for high pressure fluid systems

A valve for use in a high pressure fluid system, said valve comprising:

• a housing having a chamber therein and an inlet and an outlet open to said chamber;
• a valve assembly mounted in said housing and movable between a position opening and a position closing fluid flow from said inlet through said chamber and to said outlet;
• said valve assembly including an inner cylindrical member coaxially mounted to an outer cylindrical member, said inner cylindrical member extending axially into an interior of said outer cylindrical member;
• said valve assembly further including a valve member mounted between said inner cylindrical member and said outer cylindrical member;
• means for selectively moving said valve assembly between said opening and closing positions;
• said moving means comprising means utilizing pressure fluid at said inlet for moving said valve assembly to said opening position, spring means for moving said valve to said closing position and means for balancing the effects of inlet pressure on said valve assembly as said valve assembly is moving to said closing position;
• said spring means including a first spring biasing said inner cylindrical member and said outer cylindrical member toward said closing position, stop means engaging said valve assembly to prevent further movement of said valve assembly by said first spring;
• said spring means further comprising a second relatively light spring biased between said outer cylindrical member and said valve member and operable, upon said inner and outer cylindrical members being prevented by said stop means from further movement by said first spring, to urge said valve member to said closing position;
• and
• a flexible seal means carried by said valve member and engageable with said housing to prevent fluid flow from said inlet to said outlet when said valve assembly is in said closing position.