Patent ID: 6405529
Filing Date: 2002-06-18
Classification: F15B

Abstract:
A hydraulic system comprising:a pump that is adapted to generate a flow of pressurized hydraulic fluid in an outlet line; an unloading valve that communicates with said outlet line of said pump; a primary control valve that selectively provides communication between said outlet line of said pump and a primary hydraulic actuator; an auxiliary control valve that selectively provides communication between said outlet line of said pump and an auxiliary hydraulic actuator; a first restriction that communicates with said outlet line of said pump; a second restriction that communicates through a line with said first restriction; a first two-way valve that communicates with said second restriction; a second two-way valve that communicates with said first two-way valve; and a shuttle valve having input lines that communicates with said primary and auxiliary control valves and an output line that communicates with said second two-way valve; wherein said second two-way valve is responsive to the magnitude of the load pressure of said auxiliary hydraulic actuator for selectively providing communication between said first two-way valve and said output line of said shuttle valve; said first two-way valve is responsive to the magnitude of the load pressure of said primary hydraulic actuator and to the magnitude of the load pressure of said auxiliary hydraulic actuator for selectively providing communication between said second restriction and said second two-way valve; and said unloading valve is responsive to the magnitude of the pressure of the hydraulic fluid in said outlet line of said shuttle valve and to the magnitude of the pressure of the hydraulic fluid in said line providing communication between said first restriction and said second restriction for selectively providing communication between said output line of said pump and a reservoir.