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Hydraulic circuit for a pipelayer

  • US 3,938,669 A
  • Filed: 03/25/1974
  • Issued: 02/17/1976
  • Est. Priority Date: 03/25/1974
  • Status: Expired due to Term
First Claim
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1. A hydraulic circuit for a pipelayer machine having an extensible boom pivotally mounted to a vehicle, an extensible hoist cable extending from the outer end of said boom, and a counterweight extending from one side of said vehicle to counterbalance said boom, said circuit comprising:

  • a boom lift motor operatively connected for lifting said boom;

    a hoist motor operatively connected for extending and retracting said hoist cable;

    a first source of pressurized fluid for supplying fluid by way of first circuit means for low speed operation of said motors;

    first valve means for selectively communicating fluid from said first source of fluid to one of said motors;

    a second source of pressurized fluid for supplying fluid by way of second circuit means for high speed operation of said motors;

    second valve means for selectively communicating fluid from said second source to said one of said motors;

    control means interconnecting said first and second valve means and operative over a first range of movement for moving said first valve means into communicating position and operative over a second range of movement for moving said first valve means to a non-communicating position and simultaneously therewith move said second valve means to a communicating position.

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