Pilot operated spool valve

Claim 1

IN A FLOW CONTROL VALVE, A VALVE BODY HAVING A BORE THEREIN, AN INLET PORT, A PAIR OF EXHAUST PORTS AND A PAIR OF WORK PORTS COMMUNICATING WITH SAID BORE, A SPOOL VALVE RECIPROCABLE IN SAID BORE, SAID SPOOL VALVE BEING CONSTRUCTED AND ARRANGED RELATIVE TO SAID INLET PORT SO THAT SAID INLET PORT IS ALWAYS OPEN, SAID SPOOL VALVE BEING CONSTRUCTED SO AS IN ONE POSITION TO CONNECT ONE WORK PORT WITH SAID INLET PORT WHILE THE OTHER WORK PORT IS CONNCECTED TO AN EXHAUST PORT, MEANS AT ONE END OF SAID SPOOL VALVE FOR SHIFING SAID SPOOL VALVE IN ONE DIRECTION TO CONNECT SAID OTHER WORK PORT TO SAID INLET PORT AND SAID ONE WORK PORT TO THE OTHER EXHAUST PORT, SAID SPOOL VALVE HAVING A COMPRESSION CHAMBER AT THE OTHER END THEREOF AND A PLUNGER RECIPROCABLE IN SAID CHAMBER, PASSAGE MEANS ESTABLISHING CONSTANT COMMUNICATION BETWEEN THE INNER END OF SAID CHAMBER AND SAID INLET PORT IN SAID BORE, THE OUTER END OF SAID PLUNGER BEING ENGAGEABLE WITH THE END WALL OF SAID BORE WHEREBY SHIFTING OF SAID SPOOL VALVE IN SAID ONE DIRECTION CAUSES SAID PLUNGER TO RETRACT INTO SAID COMPRESSION CHAMBER WHEREBY THE PRESSURE FLUID IN SAID CHAMBER WILL SHIFT SAID SPOOL VALVE IN THE OPPOSITE DIRECTION.