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Method and apparatus for reducing free flow risk

  • US 7,628,590 B2
  • Filed: 02/16/2005
  • Issued: 12/08/2009
  • Est. Priority Date: 02/16/2005
  • Status: Expired due to Fees
First Claim
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1. A method for reducing a risk of external pressure-induced free flow through a pump having an inlet and an outlet comprising:

  • establishing a fluid communication between the pump inlet to a first side of a pressure responsive member;

    establishing a fluid communication between the pump outlet and a second side of the pressure responsive member independent of a pump outlet line;

    continuously sensing a pressure difference between an inlet pressure and an outlet pressure with the pressure responsive member;

    mechanically communicating the pressure difference to a flow restricting element associated with the pump outlet line, wherein the flow restricting element does not inhibit the fluid communication between the pump outlet and the pressure responsive member; and

    activating the flow restricting element when the inlet pressure exceeds the outlet pressure to increase a resistance to a fluid flow through the pump outlet line in proportion to the pressure difference between the inlet pressure and the outlet pressure.

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