Hydraulic system having tandem hydraulic function
First Claim
1. A hydraulic system comprising first and second hydraulic pumps, first and second actuators, a first directional control valve of closed center type connected to said first and second hydraulic pumps for controlling a flow rate of a hydraulic fluid supplied to said first actuator, and a second directional control valve of closed center type connected to at least said first hydraulic pump for controlling a flow rate of a hydraulic fluid supplied to said second actuator, wherein said hydraulic system further comprises:
- first and second feeder lines respectively connecting said first and second hydraulic pumps to a pump port of said first directional control valve; and
first and second reverse-flow preventing valves disposed respectively in said first and second feeder lines for preventing the hydraulic fluids from reversely flowing to said first and second hydraulic pumps;
wherein a first auxiliary valve with a flow cutoff function of selectively cutting off a flow of the hydraulic fluid supplied from said first hydraulic pump is disposed, in addition to said first reverse-flow preventing valve, in at least said first feeder line of said first and second feeder lines, said first auxiliary valve being operable in response to operation of said second directional control valve.
1 Assignment
0 Petitions
Accused Products
Abstract
Pump ports 9p, 10p, 11p, 13p of boom, arm, bucket and first travel directional control valves 9-11, 13 are connected to first and second hydraulic pumps 1a, 1b through feeder lines 93a, 93b; 103a, 103b; 113a, 113b; 133a, 133b. Auxiliary valves 91a, 91b; 101a, 101b; 111a, 101b; 131a, 131b controlled respectively by proportional solenoid valves 31a, 31b; 32a, 32b; 33a, 33b; 34a, 34b are disposed in those feeder lines. The auxiliary valves each have a function as a reverse-flow preventing function and a variable resisting function including a flow cutoff function, whereby a joining circuit and a preference circuit can be realized in the closed center circuit with a simple structure and further, a preference degree and metering characteristics can be set independently of each other during the combined operation of plural actuators.
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Citations
23 Claims
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1. A hydraulic system comprising first and second hydraulic pumps, first and second actuators, a first directional control valve of closed center type connected to said first and second hydraulic pumps for controlling a flow rate of a hydraulic fluid supplied to said first actuator, and a second directional control valve of closed center type connected to at least said first hydraulic pump for controlling a flow rate of a hydraulic fluid supplied to said second actuator, wherein said hydraulic system further comprises:
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first and second feeder lines respectively connecting said first and second hydraulic pumps to a pump port of said first directional control valve; and first and second reverse-flow preventing valves disposed respectively in said first and second feeder lines for preventing the hydraulic fluids from reversely flowing to said first and second hydraulic pumps; wherein a first auxiliary valve with a flow cutoff function of selectively cutting off a flow of the hydraulic fluid supplied from said first hydraulic pump is disposed, in addition to said first reverse-flow preventing valve, in at least said first feeder line of said first and second feeder lines, said first auxiliary valve being operable in response to operation of said second directional control valve.
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2. A hydraulic system comprising first and second hydraulic pumps, first and second actuators, a first directional control valve of closed center type connected to said first and second hydraulic pumps for controlling a flow rate of a hydraulic fluid supplied to said first actuator, and a second directional control valve of closed center type connected to at least said first hydraulic pump for controlling a flow rate of a hydraulic fluid supplied to said second actuator, wherein said hydraulic system further comprises:
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first and second feeder lines respectively connecting said first and second hydraulic pumps to a pump port of said first directional control valve; and first and second reverse-flow preventing valves disposed respectively in said first and second feeder lines for preventing the hydraulic fluids from reversely flowing to said first and second hydraulic pumps; wherein said second directional control valve is connected to said first and second hydraulic pumps, and said hydraulic system further comprises; third and fourth feeder lines respectively connecting said first and second hydraulic pumps to a pump port of said second directional control valve, and third and fourth reverse-flow preventing valves disposed respectively in said third and fourth feeder lines for preventing the hydraulic fluids from reversely flowing to said first and second hydraulic pumps, wherein a first auxiliary valve with a flow cutoff function of selectively cutting off a flow of the hydraulic fluid supplied from said first hydraulic pump is disposed, in addition to said first reverse-flow preventing valve, in at least said first feeder line of said first and second feeder lines, and a second auxiliary valve with a flow cutoff function of selectively cutting off a flow of the hydraulic fluid supplied from said second hydraulic pump is disposed, in addition to said fourth reverse-flow preventing valve, in at least said fourth feeder line of said third and fourth feeder lines. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9)
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10. A hydraulic system for a hydraulic excavator comprising first and second hydraulic pumps, a plurality of actuators including a boom cylinder, an arm cylinder, a bucket cylinder, a swing motor and first and second travel motors and a plurality of directional control valves of closed center type including a boom directional control valve an arm directional control valve, a bucket directional control valve, a swing directional control valve and first and second travel directional control valves for controlling respective flow rates of hydraulic fluids supplied to said boom cylinder, said arm cylinder, said bucket cylinder, said swing motor and said first and second travel motors, wherein said hydraulic system further comprises:
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first and second feeder lines and third and fourth feeder lines respectively connecting said first and second hydraulic pumps to pump ports of at least two of said plurality of directional control valves of closed center type, first and second reverse-flow preventing valves disposed respectively in said first and second feeder lines for preventing the hydraulic fluids from reversely flowing to the respective first and second hydraulic pumps, and first and second auxiliary valves disposed respectively in said first and second feeder lines having variable resisting functions of subsidiarily controlling flows of the hydraulic fluids from the respective first and second hydraulic pumps, and third and fourth reverse-flow preventing disposed respectively in said third and fourth feeder lines for preventing the hydraulic fluids from reversely flowing to the respective first and second hydraulic pumps, and third and fourth auxiliary valves disposed respectively in said third and fourth feeder lines and having variable resisting functions of subsidiarily controlling flows of the hydraulic fluids supplied from the respective first and second hydraulic pumps. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification