Combined sequence and check valve

Claim 1

A SEQUENCE AND CHECK VALVE COMPRISING IN COMBINATION, A VALVE BODY HAVING A BORE THEREIN AND A PAIR OF PRIMARY FLUID PASSAGES FOR SUPPLYING FLUID UNDER VARYING PRESSURE TO SAID VALVE BODY BORE AND FOR REMOVING FLUID UNDER PRESSURE THEREFROM, A CONTROL PLUNGER RECEIVED IN SAID VALVE BODY BORE AND SLIDABLE BETWEEN A BLOCKED POSITION AND AN OPEN POSITION FOR ALTERNATELY ISOLATING SAID PRIMARY PASSAGES FROM ONE ANOTHER AND CONNECTING SAID PRIMARY PASSAGES TO ONE ANOTHER RESPECTIVELY IN SAID VALVE BODY BORE, SAID CONTROL PLUNGER HAVING A BORE THEREIN AND A PAIR OF SPACED FLUID PORTS TO CONNECT SAID CONTROL PLUNGER BORE TO SAID PAIR OF PRIMARY FLUID PASSAGES RESPECTIVELY, MEANS TO PRODUCE A BIAS FORCE TENDING TO HOLD SAID CONTROL PLUNGER IN THE BLOCKED POSITION, MEANS DEFINING A PAIR OF CONTROL FLUID PASSAGES IN SAID BODY OPERABLE TO CONNECT SAID VALVE BODY BORE AT EACH END OF SAID CONTROL PLUNGER TO ONE OF SAID PRIMARY FLUID PASSAGES TENDING TO PRODUCE BALANCED OPPOSING HYDRAULIC FORCES THEREON, MEANS TO HOLD THE HYDRAULIC FORCE AT ONE END OF SAID PLUNGER SUBSTANTIALLY AT A PREDETERMINED FLUID PRESSURED LEVEL TO EFFECT AN UNBALANCE OF SAID OPPOSING HYDRAULIC FORCES, SAID HYDRAULIC FORCES WHEN UNBALANCED OVERCOMING SAID BIAS FORCE AND SHIFTING SAID CONTROL PLUNGER TO THE OPEN POSITION, A CHECK PLUNGER RECEIVED IN SAID CONTROL PLUNGER BORE AND SLIDABLE THEREIN BETWEEN A CHECKED POSITION AND AN OPEN POSITION, SAID FLUID PORTS ISOLATED FROM ONE ANOTHER WHEN SAID CHECK PLUNGER IS SAID CONTROL POSITION AND CONNECTED TO ONE ANOTHER IN SAID CONTROL PLUNGER BORE WHEN SAID CHECK PLUNGER IS IN SAID OPEN POSITION THEREOF, AND MEANS TO PRODUCE A BIAS FORCE ON SAID CHECK PLUNGER TENDING TO HOLD SAID CHECK PLUNGER IN SAID CHECKED POSITION, SAID BIAS FORCE YIELDABLY WHEN THE FLUID PRESSURE IN THE OTHER OF SAID PRIMARY PASTHAN THE FLUID PRESSURE IN THE OTHER OF SAID PRIMARY PASSAGES BY A PREDETERMINED AMOUNT WHEREBY SAID CHECK PLUNGER IS SHIFTED TO THE OPEN POSITION THEREOF.