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Hydraulic circuitry for an excavator

  • US 3,922,855 A
  • Filed: 09/03/1974
  • Issued: 12/02/1975
  • Est. Priority Date: 12/13/1971
  • Status: Expired due to Term
First Claim
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1. A hydraulic circuit for a hydraulic excavator comprising:

  • a first and a second variable displacement pump for supplying pressurized fluid to said circuit;

    a first series of series-connected distributor valves operatively connected for directing fluid from said first pump to a translation motor and to a first pair of implement control motors;

    a second series of series-connected distributor valves operatively connected for directing fluid from said second pump to said translation motor and at least another implement control motor;

    pilot control means for shifting said distributor valves for said translation motor in sequence;

    said pilot control means including a source of pressurized pilot control fluid;

    drive control means including pilot valve means operative to direct said pilot fluid for shifting said distributor valves controlling said translation motor and operative to vary the pressure of said pilot pressure over a wide range of pressures;

    anD, the first of said distributor valves being operative to shift progressively over a first range of pilot fluid pressures and the second of said distributor valves being operative to progressively shift over a second range of pilot fluid pressures so that the first pump is operative to supply fluid for low speed operation and fluid from said second pump is added to said first pump fluid for high speed operation.

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