Variable volume, shape memory actuated insulin dispensing pump

  • US 8,047,812 B2
  • Filed: 12/29/2008
  • Issued: 11/01/2011
  • Est. Priority Date: 10/09/2002
  • Status: Active Grant
First Claim
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1. A pumping system comprising:

  • a chamber;

    a first piston within the chamber;

    a shape memory element within the chamber that changes length when a current flows through the shape memory element;

    the shape memory element moving the first piston between a first physical limit defined by a first portion of the chamber and second physical limit defined by a second portion of the chamber, such that when the first piston is at the first physical limit the chamber is filled with fluid and when the first piston is at the second physical limit the chamber is discharged of fluid;

    at least a first switch disposed at the at least one of the first physical limit and the second physical limit that indicates when the first piston is in contact with the at least one of the first physical limit and the second physical limit;

    a second piston coupled to the shape memory element that moves to accommodate changes in the shape memory element and reduce stress on the pumping system; and

    a processor programmed to measure a first time period, wherein the first time period is the time it takes for the first piston to move between the first physical limit and the second physical limit, to compare the first time period to a predetermined time period, and to determine that the pumping system is not primed when the first time period is below the predetermined time period by a threshold amount of time.

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