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Control system for hydraulic actuator

  • US 4,367,624 A
  • Filed: 02/15/1980
  • Issued: 01/11/1983
  • Est. Priority Date: 02/20/1979
  • Status: Expired due to Term
First Claim
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1. A control system for controlling a hydraulic actuator during full stroke operations and inching operations, said control system comprising:

  • an engine;

    a first hydraulic pump with a large displacement capacity driven by said engine;

    a second hydraulic pump with a small displacement capacity driven by said engine;

    a pilot pump driven by said engine;

    first pilot operated control valve means connected at the input side thereof to said first pump, the output side thereof being selectively connected to said hydraulic actuator and a drain;

    second pilot operated control valve means connected at the input side thereof to said second pump, the output side thereof being selectively connected to said hydraulic actuator and a drain wherein said second pilot operated control valve means is actuated by a lower pilot pressure than said first pilot operated control valve means; and

    third control valve means for pilot pressure connected at the input side thereof to said pilot pump, the output side thereof being connected to said first and second pilot operated control valve means for controlling the actuation thereof, such that, during full stroke operations, said first and second pilot operated control valve means are actuated by said third control valve means such that said hydraulic actuator is operated by hydraulic fluid from said first and second hydraulic pumps and during inching operations, only said second pilot operated control valve means is operated by said third control valve means such that said hydraulic actuator is operated by hydraulic fluid from only said second hydraulic pump, wherein each of said first and second pilot operated control valve means has two pilot ports formed therein one of which is connected to said third control valve means for pilot pressure through a first conduit, the other port being connected to said third control valve means for pilot pressure through a second conduit and wherein adjustable restrictor means is provided between said first and second conduits, said restrictor means being interlocked with lever means for operating said third control valve means for pilot pressure.

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