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Volumetric pump with spring-biased cracking valves

  • US 5,158,437 A
  • Filed: 08/08/1991
  • Issued: 10/27/1992
  • Est. Priority Date: 03/15/1990
  • Status: Expired due to Term
First Claim
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1. A method for preventing variations in fluid supply pressure from affecting a fluid delivery rate of a pump, said pump including an inlet valve and an outlet valve, and operative to displace fluid from a pumping chamber, said chamber being defined by a flexible member, the method comprising the sequential steps of:

  • (a) substantially filling the pumping chamber with fluid from a source by opening the inlet valve;

    (b) blocking fluid flow from the pump through the outlet valve while biasing the inlet valve closed with a first force;

    (c) with the inlet and outlet valves in a back-flow condition as defined in part (b), forcing fluid from the pumping chamber back through the inlet valve toward the source as fluid pressure in the pumping chamber exceeds that necessary to open the inlet valve, in opposition to the first force;

    (d) closing the inlet valve with a second force substantially greater than the first force while biasing the outlet valve closed with a third force; and

    (e) with the inlet and outlet valves in a pumping condition as defined in part (d), displacing fluid from the pumping chamber through the outlet valve as fluid pressure in the pumping chamber exceeds that necessary to open the outlet valve, in opposition to the third force, whereby the pressure of fluid delivered by the pump through the outlet valve is substantially independent of variations in supply pressure.

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