4-Way, 2-position pilot valve

A 4-way, 2-position pilot valve, said valve comprising:

• a housing, first and second exhaust passages in said housing;
• a cylinder;
• a main piston slidable in said cylinder;
• first and second cylinder ports in communication with said cylinder on opposite sides of said main piston, respectively;
• an inlet port in said housing;
• first, second and third annular valve seats in said housing;
• a first valve stem slidable in said housing;
• first and second ball valves movably supported in said housing;
• a first spring supported in said housing in a manner to bias said first ball valve against said first seat, reciprocation of said first valve stem in one direction causing said first ball valve to be pushed off of said first seat, said first valve stem being located between said first and second ball valves, said first valve stem having a length less than the distance between said first and second ball valves when said first and second ball valves engage said first and third valve seats, respectively, said inlet port being in communication with said second ball valve to enter through one of said second and third valve seats, the pressure in said inlet port causing said second ball valve, when in one position to seal against said third seat;
• a second valve stem including a cylindrical pilot piston fixed therewith slidable in said housing, said housing having a cylindrical portion with a cylindrical wall and a hole through said wall, said hole being vented externally of said housing, said pilot piston being slideable contiguously within said cylindrical wall in one direction to open said hole to the interior of said housing cylindrical portion, and slidable in the opposite direction, said pilot piston, when in one position, sealing said hole shut, said pilot piston having means connected therewith to push said second ball valve from said one position in engagement with said third seat to another position in engagement with said second seat, said first ball valve being pushed to a position spaced from said first seat by engagement of said second ball valve with said first valve stem and by engagement of said first valve stem with said first ball valve;
• a spring to bias said second valve stem out of engagement with said second ball valve when said second ball valve engages said third seat;
• and selectively operable reciprocatory means to move said second valve stem to an extent to cause said hole to be sealed and to cause said second ball valve to engage said second valve seat.