Patent ID: 7296406

Claim:
A system comprising: a controlled piston slidably mounted in a controlled piston sleeve and having a first end; a spool movably mounted in a spool sleeve; a first fluid passage from said spool to said controlled piston first end, the position of said spool affecting the fluid pressure applied to said controlled piston first end and a position of said controlled piston; an FFV in an FFV sleeve in said first fluid passage having a first end section having a first diameter, a second end section having a second diameter and a central section having a third diameter less than said first and second diameters, said FFV being shiftable between a first position blocking said first fluid passage and a second position allowing fluid flow past said central section to said controlled piston; and a second fluid passage from said spool to said FFV first end section; whereby shifting said spool to a failsafe position shifts said FFV to said FFV first position to seal a fixed volume of fluid between said FFV and said controlled piston first end.