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Hydraulic control for earth working machines

  • US 4,833,798 A
  • Filed: 06/13/1988
  • Issued: 05/30/1989
  • Est. Priority Date: 06/11/1987
  • Status: Expired due to Term
First Claim
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1. Hydraulic control system for a heavy-duty earth-working machine, such as a hydraulic excavator, hydraulic power shovel or the like, the machine having a structure and mechanism for turning on a vertical axis, as well as a plurality of hydraulically-operated users, comprising:

  • a plurality of pivotally mounted pressure pumps operating similarly and being respectively associated with said mechanism of said users;

    a plurality of spring means, each of the pumps being held by a spring-means of the plurality to a relatively small pivot angle but permitting deflection out of that angle upon application of pressure to the respective pump for pivoting the pump, a first one of said pumps being associatable with said turning mechanism;

    a load-limit valve producing a particular control pressure;

    a pilot pump operating as a measuring or metering pump for providing pressure to the load limit valve, such that a pressure increase or decrease in a controlled fashion obtains, as derivable through the load-limit valve;

    a first valve means for individually connecting the load-limit valve to respective pressure pumps of the plurality such that the pilot pump pressure can be made effective in the respective pump of the plurality causing the respective pump to pivot more with increasing pressure;

    the respective connections by the valve means obtains when the working pressure of the respective pump as connected to the respective user exceeds the said maximum working pressure whereupon the respective spring means associated with the respective pump retracts the respective pump in order to reduce the amount of fluid conveyed by the respective pump until the working pressure drops below said maximum pressure value;

    means for causing said first pump to be selectively connected to or separated from the said loadlimit valve, further causing, on separation, to have a particular pressure applied to the first pump such that maximum pivot angle and maximum fluid pumping obtain;

    a particular valve of said first valve means causing the first pump to feed pressure fluid to the turning mechanism; and

    means for rendering power and pressurized fluid from said first pump available for augmenting the power as provided by the other pumps of the plurality and to augment the amount of pressurized fluid that is being used by at least one of said additional users.

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