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Construction machine dual-dump hydraulic circuit with piloted arm-boom cylinder supply priority switching valves

  • US 4,875,337 A
  • Filed: 09/28/1987
  • Issued: 10/24/1989
  • Est. Priority Date: 09/27/1986
  • Status: Expired due to Term
First Claim
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1. A hydraulic circuit for a construction machine comprising:

  • an acutator for working machine;

    an actuator for working element;

    first and second hydraulic pumps;

    first and third directional control valves connected to said first hydraulic pump, said first directional control valve controlling an operation of said actuator for working machine and said third directional control valve controlling an operation of said actuator for working element;

    a second directional control valve connected to said second hydraulic pump, said second directional control valve including a neutral position at which a communication between said second hydraulic pump and a first output port of said second directional control valve is blocked and a communication between said actuator for working machine and a reservoir is blocked, one changed position at which said communication between said second hydraulic pump and said first output port is allowed and said communication between said actuator for working machine and the reservoir is blocked and another changed position at which said communication between said second hydraulic pump and said first output port is blocked and said communication between said actuator for working machine and the reservoir is allowed;

    first pilot operating means for controlling operation of said first and second directional control valves;

    second pilot operating means for controlling an operation of said third directional control valve and for shifting said second directional control valve to said one changed position;

    first hydraulic fluid joining means for joining hydraulic fluid of said second hydraulic pump with hydraulic fluid of said first hydraulic pump, said first hydraulic joining means connecting said first output port of said second directional control valve to an input side of said third directional control valve;

    second hydraulic fluid joining means for joining the hydraulic fluid of said second hydraulic pump with the hydraulic fluid of said first hydraulic pump, said second joining means connecting an input side of said second directional control valve to an input side of said first directional control valve; and

    priority control means for, when a signal of said first pilot operating means is issued, preventing a signal of said second pilot operating means from being applied to said second directional control valve, said priority control means including a first passageway for leading the signal of said second pilot operating means to said second directional control valve, a device interposed in said first passageway for closing said first passageway when the signal of said first pilot operating means is received and a second passageway interconnecting between said device and said first pilot operating means to lead to said device the signal of said first pilot operating means to close said first passageway;

    whereby said actuator for wording element is actuated by the hydraulic fluid from the first and second hydraulic pumps joined by said first hydraulic fluid joining means when only said second pilot operating means is operated andsaid actuator for working machine is actuated by the hydraulic fluid from the first and second hydraulic pumps joined by said second hydraulic fluid joining means when only said first pilot operating means is operated and also when said first and second pilot operating means are operated at the same time.

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