Fuel shut-off valve

A valve comprising:

• a. a body having a cylindrical bore;
• b. a radially inwardly extending annular seat dividing said bore into first and second sections;
• c. a first inlet passage communicating with said first bore section for connection to a fuel tank;
• d. a second inlet passage communicating with said second bore section for connection to a source of oil having a predetermined normal operating pressure;
• e. an outlet passage communicating with said second bore section for connection to a fuel pump for transmitting fuel from said valve to said pump;
• f. a first piston slidably positioned in said cylindrical bore, said piston including
• 1. a pressure-receiving face positioned between said second inlet and said outlet for subjection to the pressure of said oil;
• 2. a fuel face positioned within said first bore section for subjection to the pressure of said fuel;
• and
• 3. a reduced diameter portion positioned between said fuel face and said pressure-receiving face to permit fuel to flow through said second bore section;
• g. a first annular sealing means positioned in said second bore section between said pressure-receiving face and said outlet to prevent oil from passing said face to said outlet;
• h. a second annular sealing means positioned in said first bore section and movable in said bore with said piston to a position engaging said annular seat to prevent passage of fuel from said first bore section to said second bore section;
• i. a biasing spring mounted in said bore urging said piston to a sealed position wherein said second annular sealing means engages said annular seat, said biasing spring exerting a force on said piston in a direction opposite to, but less than, the force exerted on said piston by said normal operating pressure;
• j. mechanical override means extending through said body and contacting said first piston for urging said first piston against the force of said biasing spring to disengage said second annular sealing means from said annular seat to permit fuel to flow from said first inlet passage to said outlet passage comprising
• 1. a second bore in said body
• 2. a second piston slidably positioned in said second bore, said second piston having an annular groove with an O-ring therein sealingly engaging said second bore;
• and
• k. retaining means for limiting the travel of said second piston to limit the distance said second annular sealing means may be moved from said annular seat, whereby removal of said retaining wears permits said second piston to travel beyond the limit to a position interrupting the sealing engagement between said second bore and the O-ring in the annular groove of said second piston, thereby permitting oil to exit said body via said second bore.