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Hydraulic system with secondary exhaust passage

  • US 5,950,519 A
  • Filed: 07/10/1997
  • Issued: 09/14/1999
  • Est. Priority Date: 11/26/1996
  • Status: Expired due to Fees
First Claim
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1. A hydraulic system for working cylinders of construction equipment, comprising an oil pump, at least one working cylinder operated by pump discharged oil, and a directional control valve for providing the oil to said cylinder and returning the oil to an oil tank, further comprising:

  • a first oil passage connecting a large chamber of said cylinder to the oil tank, said first oil passage being provided separately from the directional control valve;

    a second oil passage connecting a small chamber of said cylinder to the oil tank, said second oil passage being provided separately from the directional control valve;

    a first passage control valve disposed within said first oil passage, said first passage control valve opening the first oil passage when the pump discharged oil is fed into the small chamber of the cylinder through the directional valve but otherwise closing the first passage control valve; and

    a second passage control valve disposed within said second oil passage, said second passage control valve opening the second oil passage when the pump discharged oil is fed into the large chamber of the cylinder through the directional valve but otherwise closing the second passage control valve.

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