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Electronically controlled hydraulic system for lowering a boom in an emergency

  • US 6,647,718 B2
  • Filed: 10/04/2001
  • Issued: 11/18/2003
  • Est. Priority Date: 10/04/2001
  • Status: Expired due to Fees
First Claim
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1. In a machine having a boom, that is moved by a first hydraulic actuator, and a load carrier, that is coupled to the boom and moved with respect thereto by a second hydraulic actuator;

  • a method for moving the boom when pressurized fluid from a source is not available, said method comprising;

    sensing a first position of the boom;

    draining hydraulic fluid under pressure from the first hydraulic actuator without applying pressurized fluid from the source to the first hydraulic actuator;

    conveying the hydraulic fluid from the first hydraulic actuator to the second hydraulic actuator without employing pressurized fluid from the source; and

    controlling flow of the hydraulic fluid into the second hydraulic actuator in response to the first position of the boom to produce movement of the load carrier with respect to the boom, wherein as the boom moves, an angular relationship of the load carrier with respect to a surface on which the machine is supported is maintained substantially constant.

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